Structure and composition of Bowman's membrane. Study by frozen resin cracking.
Jacobsen I E,Jensen O A,Prause J U
Bowman's membrane, seen as a homogeneous layer in light microscopy, is demonstrated by transmission electron microscopy as a layer with fibrils in random distribution, for which reason the term used at present is Bowman's layer. Frozen resin cracking demonstrates that the fibrils of the layer run in certain patterns and lie in 3 or 4 strata in the central areas of the cornea. In the periphery, stratification is scarcely demonstrable. The fibrils consist of collagen inseparable by histochemical methods from the collagen in the stroma, but the diameter is only half or two-thirds of the diameter of the stromal fibrils. The authors discuss the possibility that artifacts are responsible for the findings. However, an explanation of the results may be that Bowman's layer is a condensation of the superficial layers of the stroma resulting from the development of the layer. The fibrils are presumed to break in different ways, but apparently in layers in which the breaking strengths are identical.
[Treatment of recurrent corneal erosion by puncture of Bowman's membrane].
Tritten J J,Herbort C P
Klinische Monatsblatter fur Augenheilkunde
16 patients (18 eyes) with a recurrent corneal erosion have been treated with anterior stromal punctures. The pain disappeared in 15 patients and remained unchanged for one patient. No recurrence was observed over a 18 months follow-up period (maximum 39 months) and no patient was complaining of glare. The technique is simple, effective, cheap and easily performed without special instrumentation.
Corneal clouding with increased acid mucopolysaccharide accumulation in Bowman's membrane.
Rodrigues M M,Calhoun J,Harley R D
American journal of ophthalmology
Two infants had bilateral congenital corneal clouding and abnormal acid mucopolysaccharide accumulation in a thickened Bowman's membrane. This unusual entity was not associated with acid mucopolysaccharide deposits in the skin and visceral tissues or with increased levels of acid mucopolysaccharide in the urine. The similarity and differences have been compared to the systemic mucopolysaccharidosis and macular corneal dystrophy.
[Consequences of different ablation rates in Bowman's membrane and corneal stroma for photorefractive keratectomy].
Fortschritte der Ophthalmologie : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft
If photorefractive keratectomy (PRK) is performed with an ArF-excimer-laser, the existence of different ablation rates in Bowman's membrane and corneal stroma is of crucial importance, as ablation rates are considered to be constant in PRK. Consequently, if photoablation cannot be confined to Bowman's layer alone, at least two new surfaces with different refractive powers would result. For the correction of myopia with PRK, different ablation rates would mean that: (1) the central corneal surface with the desired refractive power is smaller than the total ablation zone. The lower the ablation rate in Bowman's layer compared to that of stroma, the smaller the area of desired refraction. (2) the maximum attainable refractive change will also be smaller, the lower ablation rate in Bowman's layer is compared to that of stroma. (3) Enlargement of the central zone of desired refraction is limited by the maximum acceptable ablation depth.
Corneal dystrophies. I. Dystrophies of the epithelium, Bowman's layer and stroma.
Waring G O,Rodrigues M M,Laibson P R
Survey of ophthalmology
Most corneal dystrophies are autosomal dominant, bilateral disorders that primarily affect one layer of an otherwise normal cornea, progress slowly after their appearance in the first or second decade, and are not associated with a systemic disease. Epithelial basement membrane dystrophy and Fuchs' endothelial dystrophy are seen commonly by the general ophthalmologist; fleck, posterior polymorphous, granular or lattice dystrophies are seen more rarely, and others may never be seen in general office practice. While the distinctive clinical appearance of most corneal dystrophies allows accurate diagnosis, the integration of slitlamp findings with histopathologic and biochemical findings aids in the understanding of the clinical observations and provides a more rational basis for therapy. Transmission electtron microscopy is the most accurate method of histopathologic diagnosis. Epithelial dystrophies usually manifest intraepithelial cysts and abnormal basement membrane. In stromal dystrophies, an abnormal substance accumulates within the keratocytes or among the collagen fibrils; it may be an excess normal metabolite (like glycosaminoglycans in macular dystrophy), a material not usually present (like amyloid in lattice dystrophy), or a substance of unknown composition (like hyaline in granular dystrophy). Each dystrophy is illustrated with a composite drawing. Endothelial dystrophies will be reviewed separately in a second article.
Congenital corneal opacification secondary to Bowman's layer dysgenesis.
Apple D J,Olson R J,Jones G R,Carey J C,Van Norman D K,Ohrloff C,Philippart M
American journal of ophthalmology
Progressive, bilateral corneal clouding was noted at birth in an otherwise healthy infant. There was no evidence of an infectious or hereditary cause. A trial of corticosteroids was unsuccessful, and the opacification in both corneas increased during the course of a few months, necessitating penetrating keratoplasty. However, reopacification of both grafts ensued within two to four months, and a second graft was done on the right eye. Histologic examination of both the original corneal buttons and the failed graft from the right eye showed a thickening of Bowman's layer that was three to four times greater than that of normal controls. This was associated with an increased number of keratocytes producing pools of collagen bundles within Bowman's layer. This report documents a unique form of corneal opacification unassociated with other ocular or systemic diseases. This process may be interpreted as a phenomenon in which the cells that contribute to the intrauterine formation of Bowman's layer continue to proliferate in an abnormal and exuberant fashion beyond fetal life, leading to corneal opacification.
Agenesis of Bowman's layer. A histopathological study of four cases.
Kasner L,Mietz H,Green W R
Congenital absence of Bowman's layer has been described in Peters' anomaly, sclerocornea, and osteogenesis imperfecta type II. More commonly, Bowman's layer is absent secondary to inflammatory or degenerative processes of the cornea. We present three cases of bilateral absence of Bowman's layer in otherwise unremarkable corneas that were unassociated with other ocular or systemic abnormalities. In a fourth case, similar absence of Bowman's layer was present in a patient with osteogenesis imperfecta type III. In all four cases, the absence of Bowman's layer was unassociated with any evidence of scarring or inflammation. By electron microscopy, the stroma was composed of regularly arranged collagen fibers with a uniform fiber diameter throughout. In the case of osteogenesis imperfecta type III, there was mild irregularity of the anteriormost stroma. The lack of inflammation or scarring in these four cases lead us to conclude that they represent a true congenital absence, or agenesis, of Bowman's layer.
Does Bowman's layer determine the biomechanical properties of the cornea?
Seiler T,Matallana M,Sendler S,Bende T
Refractive & corneal surgery
BACKGROUND:Bowman's layer is believed to be the stabilizing element of corneal curvature due to its assumed mechanical stiffness. METHODS:Uniaxial stress-strain analysis was performed in paired corneal strips to compare the contribution from Bowman's layer. Two central strips were taken from each cornea and Bowman's layer was removed from one of them with the excimer laser. RESULTS:Pairwise comparison yielded no statistical difference in elastic or viscoelastic properties according to presence or absence of Bowman's layer. At a strain of 2%, the stress was measured to be (5.06 +/- 2.01) x 10(3) N/m2 with Bowman's layer and (4.72 +/- 1.3) x 10(3) N/m2 without Bowman's layer. Also, the two relaxation times did not differ significantly. CONCLUSIONS:These findings imply that Bowman's layer does not contribute significantly to mechanical stability within the cornea.
Reevaluation of corneal dystrophies of Bowman's layer and the anterior stroma (Reis-Bücklers and Thiel-Behnke types): a light and electron microscopic study of eight corneas and a review of the literature.
Küchle M,Green W R,Völcker H E,Barraquer J
To clarify whether Reis-Bücklers' and Thiel-Behnke's corneal dystrophies are one entity or whether two distinct corneal dystrophies of Bowman's layer and the superficial stroma (CDB) exist, 28 corneal specimens with clinically suspected diagnosis of CDB were examined by light and electron microscopy, and the literature was reviewed. Eight specimens came from patients with a honeycomb-shaped pattern of opacities at the level of Bowman's layer. Study of those eight specimens disclosed destruction of Bowman's layer, a subepithelial fibrocellular tissue with an undulant configuration, absence of the epithelial basement membrane in many areas and the presence of "curly" collagen fibers with a diameter of 9-15 nm. We concluded that two distinct autosomal dominant CDB exist and propose the designations CDB type I (synonyms: geographic or "true" Reis-Bücklers' dystrophy) and CDB type II (synonyms: honeycomb-shaped or Thiel-Behnke's dystrophy). The eight corneas of our series were characterized as CDB type II. CDB I is clinically characterized by confluent geographic opacities at the level of Bowman's layer, histopathologically by bandshaped granular Masson-positive subepithelial deposits, and ultrastructurally by the presence of "rod-shaped bodies" and may be a superficial variant of granular dystrophy. Visual loss is significantly greater in CDB I, and recurrences after keratoplasty or keratectomy seem to be earlier and more extensive in CDB I. Most cases reported thus far in the literature as "Reis-Bücklers' dystrophy" are CDB II (honeycomb-shaped or Thiel-Behnke's dystrophy).
The shape of Bowman's layer in the human cornea.
Patel S,Reinstein D Z,Silverman R H,Coleman D J
Journal of refractive surgery (Thorofare, N.J. : 1995)
PURPOSE:The aim of this investigation was to derive a mathematical model for Bowman's layer, the interface between the epithelium and stroma, in the human cornea. METHODS:The central epithelial thickness distribution within 14 normal human corneas was measured in vivo using high frequency ultrasonic digital signal processing with a measurement precision of 2 microns. The results per eye were averaged and incorporated into existing algorithms for the estimation of the shape of the anterior surface of Bowman's layer using terminology in accordance with Baker's equation. RESULTS:The average radius of Bowman's layer was 7.34 mm (SE +/- 0.17 mm). Descriptions of this boundary ranged from a steepening or prolate ellipse to a hyperbola. However, the typical Bowman's layer is hyperbolic with a shape factor, p = -0.22 (SE +/- 1.81). CONCLUSION:The results support previous cadaver studies where Bowman's layer was found to be steeper than the anterior corneal surface but disagree with the concept that the average Bowman's layer is akin to a prolate ellipse. The hyperbolic nature of the average Bowman's layer has the potential to influence the optical performance of the eye.
Three-dimensional appearance of Bowman's layer after radial keratotomy.
Yamamoto S,Sawaguchi S,Fukuchi T,Kanazawa H,Hashizume H,Abe H
Journal of cataract and refractive surgery
PURPOSE:To examine the 3-dimensional collagen fibrillar architecture of Bowman's layer after radial keratotomy (RK). SETTING:Department of Ophthalmology, Niigata University School of Medicine, Niigata, Japan. METHODS:This study used monkey eyes in which 0.3 mm deep radial incisions were made on the cornea 2 weeks and 1, 6, and 12 months before the animals were killed. Corneal buttons were immersed in a fixative and the cells macerated with sodium hydroxide 10%. Scanning electron microscopy (SEM) was performed according to standard procedures. A part of the specimens was embedded in epoxy resin for light microscopic (LM) observation for comparison. RESULTS:The 3-dimensional collagen fibrillar architecture of Bowman's layer was revealed by SEM. The rupture of Bowman's layer could be seen 12 months after surgery and there was no continuity of collagen fibrils in the ruptured area. In LM observations, the width of the stromal incisions gradually became narrower near 12 months after surgery. CONCLUSION:Our cell-maceration/SEM method showed that the rupture of Bowman's layer remained up to 12 months after RK. This suggests that discontinuity of Bowman's layer may be responsible for globe rupture after RK.
Bowman's layer structure and function: critical or dispensable to corneal function? A hypothesis.
Wilson S E,Hong J W
PURPOSE:The purpose of this article is to review available information regarding development, structure, and function of Bowman's layer in the cornea. Disease-related abnormalities of Bowman's layer are described. A hypothesis is advanced to explain the development and maintenance of Bowman's layer. METHODS:Literature review and hypothesis formulation based on previous studies. RESULTS:Information is presented that supports the hypothesis that Bowman's layer forms as a result of cytokine-mediated interactions occurring between corneal epithelial cells and keratocytes that include chemotactic and apoptotic effects on the keratocytes. This hypothesis suggests that Bowman's layer results from such interactions beginning in early development and continuing into adulthood in humans and other animals, such as chickens. CONCLUSIONS:Bowman's layer may be a visible indicator of ongoing stromal-epithelial interactions in the human and have no critical function in corneal physiology. Bowman's layer is commonly destroyed in diseases such as advanced bullous keratopathy where stromal-epithelial interactions may be interrupted. Bowman's-like layers often form in response to epithelium, for example when epithelial plugs extend into the stroma in corneas with radial keratotomy incisions.
Ultrastructural and molecular analysis of Bowman's layer corneal dystrophies: an epithelial origin?
Ridgway A E,Akhtar S,Munier F L,Schorderet D F,Stewart H,Perveen R,Bonshek R E,Odenthal M T,Dixon M,Barraquer R,Escoto R,Black G C
Investigative ophthalmology & visual science
PURPOSE:Two mutations (R555Q and R124L) in the BIGH3 gene have been described in anterior or Bowman's layer dystrophies (CDB). The clinical, molecular, and ultrastructural findings of five families with CDB was reviewed to determine whether there is a consistent genotype:phenotype correlation. METHODS:Keratoplasty tissue from each patient was examined by light and electron microscopy (LM and EM). DNA was obtained, and exons 4 and 12 of BIGH3 were analyzed by polymerase chain reaction and single-stranded conformation polymorphism/heteroduplex analysis. Abnormally migrating products were analyzed by direct sequencing. RESULTS:In two families with type I CDB (CDBI), the R124L mutation was defined. There were light and ultrastructural features of superficial granular dystrophy and atypical banding of the "rod-shaped bodies" ultrastructurally. Patients from three families with "honeycomb" dystrophy were found to carry the R555Q mutation and had characteristic features of Bowman's dystrophy type II (CDBII). CONCLUSIONS:There is a strong genotype:phenotype correlation among CBDI (R124L) and CDBII (R555Q). LM and EM findings suggest that epithelial abnormalities may underlie the pathology of both conditions. The findings clarify the confusion over classification of the Bowman's layer dystrophies.
Phototherapeutic keratectomy versus diamond burr polishing of Bowman's membrane in the treatment of recurrent corneal erosions associated with anterior basement membrane dystrophy.
Sridhar M S,Rapuano Christopher J,Cosar C Banu,Cohen Elisabeth J,Laibson Peter R
PURPOSE:To compare the efficacy of phototherapeutic keratectomy (PTK) to epithelial debridement and polishing of Bowman's membrane using a diamond burr (DB) in the treatment of recurrent corneal erosions associated with anterior basement membrane (ABM) dystrophy. DESIGN:Retrospective nonrandomized comparative trial. METHODS:Medical records of 39 patients (42 eyes) who underwent a PTK or DB procedure for recurrent corneal erosions associated with ABM dystrophy between March 1992 and June 2000 were reviewed. History of injury, prior treatment received, and the corneal slit-lamp findings were noted in all patients. In both procedures, all loose epithelium was completely removed. In PTK patients, 5 microm of Bowman's membrane was ablated with the excimer laser. In patients who underwent DB treatment, a hand-held battery-driven diamond dusted burr was used to gently and uniformly polish Bowman's membrane in the area of the epithelial defect. MAIN OUTCOME MEASURES:Symptomatic improvement, recurrence of painful erosions, development of haze, and change in the visual acuity. Statistical analysis was performed for comparison of data between the two groups. RESULTS:Fifteen eyes of 14 patients underwent PTK, and 27 eyes of 25 patients underwent epithelial debridement and DB treatment. In the PTK group, mild haze was seen in five (35.7%) eyes. Recurrence of painful erosions was seen in four eyes (26.7%). The mean follow-up was 17.6 +/- 5.7 months (range, 0.7-81.9 months). Best-corrected visual acuity was better in five eyes (35.7%) after the procedure and the same in nine eyes (64.3%). In the DB group, mild haze was seen in seven eyes (25.9%). Recurrence of painful erosions was seen in three eyes (11.1%). The mean duration of follow-up was 6.7 months (range, 1-24.2 months). Best-corrected visual acuity was better in 3 eyes (14.3%), the same in 17 eyes (81%), and worse in 1 eye (4.8%) after the procedure. Final visual acuity was not available for one eye in the PTK group and 6 eyes in the DB group. There was no statistically significant difference in haze (Fisher's exact test, P = 0.38), recurrence of erosions (Kaplan-Meier analysis with log rank, P = 0.73), and vision being better or the same (Fisher's exact test, P = 0.6) between the PTK and DB groups. CONCLUSIONS:Both PTK and DB treatment are effective methods of treating recurrent corneal erosions associated with ABM dystrophy. Diamond burr treatment, being a simpler, less expensive office procedure with a tendency toward lesser incidence of haze and recurrence in this study, seems to have advantages over PTK in the treatment of recurrent corneal erosions. Further prospective studies are required to confirm the long-term efficacy of DB treatment in the management of recurrent corneal erosions associated with ABM dystrophy.
Cellular incursion into Bowman's membrane in the peripheral cone of the keratoconic cornea.
Sherwin T,Brookes N H,Loh I-P,Poole C A,Clover G M
Experimental eye research
Analysis of corneal tissue from normal and keratoconic donors has revealed differences which may represent early signs in the pathogenesis of keratoconus. Peripheral areas of keratoconic tissue obtained from transplant surgery were targeted to ascertain cellular disposition and morphological changes which may be masked within the extensive damage of the central keratoconic cone. Peripheral keratoconic corneae exhibited discrete incursion of fine cellular processes into Bowman's membrane. These processes originated from keratocytes and were often observed in conjunction with a defined indentation from the basal epithelium. Comparison of the lysosomal enzymes cathepsin B and G with constitutively expressed cytoplasmic esterase determined that both cathepsins were elevated within keratocytes of keratoconic tissue compared with normal tissue. Some clusters of keratoconic keratocytes had elevated levels of cathepsin exceeding all others. Cathepsin-rich keratocytes localized with morphologically compromised regions of Bowman's membrane. The presence of cell nests deeper within the stroma indicated that the catabolic changes, which are visible within the acellular Bowman's membrane, are probably also occurring deeper within the stroma, but are masked and not readily detectable.
Experimental anterior lens capsule transplantation for chronic corneal ulcers-Bowman's layer replacement?
Kozák Igor,Trbolová Alexandra,Kolodzieyski Lev,Juhás Tomás,Ledecký Valent
PURPOSE:This study was designed to measure the value of allografted anterior lens capsule in the reepithelialization of recurrent corneal ulcers. METHODS:Mechanical ulcers of uniform size were created with a 6-mm corneal trephine in both eyes of four Chinchilla male rabbits at one-third corneal depth. Following initial epithelial regrowth, an identical injury was created in the same area of each cornea a second time. In four eyes (treated group), an anterior lens capsule from a healthy donor rabbit was sutured into the ulcer bed followed by antibiotic/steroid drops three times daily for 1 week. The remaining four control eyes were allowed to heal without surgical intervention using the same antibiotic/steroid drops only. Slit-lamp examination and histopathology findings were recorded over a 6-month follow-up period. RESULTS:The four treated eyes reepithelialized after the second injury at a faster rate than the control group eyes and had a lower percentage of corneal opacification at all follow-up exam dates. Histopathology revealed normal epithelium overlying the transplanted anterior lens capsule and no infiltration of inflammatory cells in the subepithelial stroma. CONCLUSIONS:In experimental conditions, allotransplantation of anterior lens capsule speeds up reepithelialization after repeated mechanical trauma to the cornea. To our knowledge, this is the first experimental transplantation of an anterior lens capsule to create an artificial Bowman's layer in recurrent corneal ulcerations to aid reepithelialization and minimize corneal scarring.
In vivo laser confocal microscopy of Bowman's layer of the cornea.
Kobayashi Akira,Yokogawa Hideaki,Sugiyama Kazuhisa
PURPOSE:To investigate in vivo microstructures of Bowman's layer in normal human subjects using a cornea-specific in vivo laser scanning confocal microscope (Heidelberg Retina Tomograph 2 Rostock Cornea Module, HRT2-RCM). DESIGN:Single-center, prospective, observational case series. PARTICIPANTS:Nineteen normal volunteers (10 male, 9 female; mean age, 46.2+/-21.7 years [range, 18-77]). METHODS:The central and peripheral cornea, specifically the epithelium, Bowman's layer, and its subjacent stroma, were examined using the HRT2-RCM. MAIN OUTCOME MEASURES:Selected images of the corneal layers were evaluated qualitatively for the shape and degree of light reflection of the microstructures. RESULTS:In all subjects, normal epithelial (superficial, wing, basal) cells, subbasal nerve plexus, Bowman's layer, and its subjacent stoma were observed clearly. However, in all subjects, polymorphic structures composed of fibrillar materials with less reflectivity than corneal nerves were observed beneath Bowman's layer. After application of pressure by a Tomo-cap, we observed numerous ridges that protruded into the epithelial basal and wing cell layers. Superficial stromal striae were also observed. These ridges and striae corresponded exactly to the orientation of the fibrous structures located beneath the epithelial cells. CONCLUSION:We report for the first time, the presence of polymorphic structures composed of fibrillar materials (K-structures) beneath Bowman's layer in normal human subjects, detected by HRT2-RCM. We surmise that these microstructures may correspond to the modified and condensed anterior stromal collagen fibers/lamellae that merge into Bowman's layer and that these fibrillar materials may be responsible for the formation of the anterior corneal mosaic. Further investigation of these microstructures in diseased eyes may provide insights into their pathophysiologic role in Bowman's layer.
In vivo laser confocal microscopy findings for Bowman's layer dystrophies (Thiel-Behnke and Reis-Bücklers corneal dystrophies).
Kobayashi Akira,Sugiyama Kazuhisa
OBJECTIVE:To investigate microstructures in patients with genetically confirmed Bowman's layer dystrophies (Thiel-Behnke or Reis-Bücklers corneal dystrophy) using an in vivo laser scanning confocal microscope. DESIGN:Single-center, prospective, comparative small case series. PARTICIPANTS:Two patients from one pedigree (a 29-year-old woman and 58-year-old man) with Thiel-Behnke corneal dystrophy (Arg555Gln [R555Q] heterozygous missense mutation of human transforming growth factor beta-induced [TGFBI] gene) and 3 patients from one pedigree (a 70-year-old woman, 58-year-old man, and 14-year old man) with Reis-Bücklers corneal dystrophy (Arg124Leu [R124L] heterozygous missense mutation of the TGFBI gene) were examined. Two patients with Reis-Bücklers corneal dystrophy exhibited recurrence after corneal transplantation. TESTING:All patients were examined by slit-lamp biomicroscopy. The center and the peripheral cornea of both eyes also were examined by in vivo laser scanning confocal microscopey. Image analysis was used to identify the corneal epithelial and stromal deposits correlated with each disorder. MAIN OUTCOME MEASURES:Selected images of the corneal layers were evaluated qualitatively for the shape and degree of light reflection of the deposits. RESULTS:In each dystrophy, distinct characteristic deposits were observed in the epithelium and Bowman's layer, respectively, by in vivo laser scanning confocal microscopy. In Thiel-Behnke corneal dystrophy, the deposits in the epithelial basal cell layer showed homogeneous reflectivity with round edges accompanying dark shadows. In contrast, deposits in Reis-Bücklers corneal dystrophy in the same cell layer showed extremely high reflectivity from small granular materials without any shadows in all cases. In each dystrophy, Bowman's layer was replaced totally with pathological materials; the reflectivity of those materials is much higher in Reis-Bücklers corneal dystrophy than in Thiel-Behnke corneal dystrophy. CONCLUSIONS:In vivo laser scanning confocal microscopy is capable of identifying in vivo corneal microstructural changes related to Thiel-Behnke and Reis-Bückler corneal dystrophy with a higher resolution than is available with slit-lamp biomicroscopy or in vivo white-light confocal microscopy. As a result, this device may enable differentiation of Thiel-Behnke and Reis-Bücklers corneal dystrophy in vivo. In vivo laser scanning confocal microscopy also may be a valuable tool for further research into the corneal dystrophies, especially to follow the natural course.
[In vivo laser confocal microscopic analysis of the interface between Bowman's layer and the stroma of the cornea].
Nippon Ganka Gakkai zasshi
Recently, cornea-specific in vivo laser confocal microscopy (Heidelberg Retina Tomograph 2 Rostock Cornea Module (HRT2-RCM), Heidelberg Engineering GmbH, Dossenheim, Germany) has become available, are now possible detailed in vivo observation of corneal and conjunctival microstructure. Using HRT2-RCM, we have demonstrated the presence of "polymorphic structures composed of fibrillar material" beneath Bowman's layer in normal volunteer eyes. We surmise that these microstructures may correspond to the modified and condensed anterior stromal collagen fibers/lamellae that merge into Bowman's layer. We also observed numerous ridges protruding into the epithelial basal and wing cell layers after application of pressure with a Tomo-cap. These ridges corresponded exactly to the orientation of the K-structures beneath the epithelial cells, suggesting that these ridge formations correspond to the pattern of the anterior mosaic formation. The potential association of these microstructures with anterior corneal mosaic formation is also discussed in this review.
The role of Bowman's layer in corneal regeneration after phototherapeutic keratectomy: a prospective study using in vivo confocal microscopy.
Lagali Neil,Germundsson Johan,Fagerholm Per
Investigative ophthalmology & visual science
PURPOSE:To examine the role of Bowman's layer (BL) on the nature of anterior corneal regeneration after excimer laser phototherapeutic keratectomy (PTK). METHODS:A cohort of 13 patients underwent PTK to remove either 7 mum of BL for treatment of primary recurrent corneal erosions (RCE; six patients) or complete BL removal (15-mum ablation) to treat RCE or poor vision secondary to map-dot-fingerprint (MDF) dystrophy (seven patients). Clinical examinations and laser-scanning in vivo confocal microscopy (IVCM) were conducted before surgery and at a mean of 4 and 8 months after surgery. RESULTS:Total BL removal resulted in a significant decline in subbasal nerve density at 4 months (P = 0.007) that barely recovered to preoperative levels at 8 months (P = 0.055). With BL partially present, subbasal nerve density did not significantly change from preoperative levels. Superficial, wing, and basal epithelial cell density recovered to preoperative levels within 4 months after PTK, regardless of the presence of BL. Subepithelial keratocytes, however, were more densely distributed in corneas without BL relative to those with a partial BL present (P = 0.005), and increased anterior keratocyte reflectivity was noted in all eyes without BL and in no eye with a partial BL present. CONCLUSIONS:Subbasal nerve regeneration is delayed and subepithelial keratocyte density and reflectivity remain elevated up to 10 months after total BL removal by PTK. The results provide initial evidence for a possible role of BL in facilitating rapid stromal wound healing and an associated recovery of anterior corneal transparency and the restoration of epithelial innervation after epithelial trauma.
Epithelial debridement and Bowman's layer polishing for visually significant epithelial irregularity and recurrent corneal erosions.
Aldave Anthony J,Kamal Khairidzan M,Vo Rosalind C,Yu Fei
PURPOSE:To report the utility of epithelial debridement and diamond burr polishing of Bowman's layer (ED + DBP) in the management of recurrent corneal erosions and visually significant epithelial irregularity associated with epithelial basement membrane dystrophy (EBMD). DESIGN:Retrospective interventional consecutive case series. PARTICIPANTS:All patients who underwent ED + DBP by a single surgeon between November 1, 2002 and November 1, 2008. METHODS:Data were collected regarding the frequency and severity of symptoms associated with EBMD as well as previous treatments. Details regarding the procedure and the postoperative course were recorded as well. The significance of the improvement in visual acuity after treatment was determined using Wilcoxon signed rank test. MAIN OUTCOME MEASURES:Change in visual acuity and recurrent corneal erosions after treatment. RESULTS:ED + DBP was performed on 56 eyes (42 patients) during the 72-month period under review. Of the 56 eyes, 37 (66%) were treated for recurrent corneal erosions and 22 (39%) were treated for visually significant epithelial irregularity (3 eyes were treated for both conditions). EBMD was diagnosed in 46 eyes (82%), and a history of corneal trauma was elicited in 9 eyes (16%). Visual acuity improved significantly (P = 0.016), and recurrent corneal erosions resolved after treatment in 24 (96%) of the 25 eyes with a history of corneal erosions before treatment with more than 3 months of follow-up (average, 18.9 months; range, 3.5-66.5 months). Visual acuity improved significantly (P = 0.004), and visual aberrations related to epithelial irregularity resolved in all 14 eyes treated for visually significant EBMD with more than 3 months of follow-up (average, 14.2 months; range, 3.4-50.8 months). Mild, central subepithelial corneal haze developed in 12 (26%) of the 47 eyes that did not demonstrate subepithelial haze before ED + DBP, although it was not associated with decreased vision at the last follow-up visit in any patient. CONCLUSIONS:ED + DBP is a safe and effective technique in the management of recurrent corneal erosions and visually significant epithelial irregularity associated with EBMD.
Topographic thickness of Bowman's layer determined by ultra-high resolution spectral domain-optical coherence tomography.
Tao Aizhu,Wang Jianhua,Chen Qi,Shen Meixiao,Lu Fan,Dubovy Sander R,Shousha Mohamed Abou
Investigative ophthalmology & visual science
PURPOSE:To characterize the thickness profile of the corneal epithelium and the Bowman's layer across the horizontal meridian. METHODS:Forty-four eyes of 22 healthy subjects were investigated in this study. Ultra-high resolution anterior segment spectral domain-optical coherence tomography (SD-OCT) was used to assess the topographic thickness of the epithelium and the Bowman's layer across the cornea. Thicknesses at five locations, including the center, midperiphery, and periphery close to the limbus, on both the nasal and the temporal sides along the horizontal meridian, were analyzed. RESULTS:Mean epithelial thickness at the central cornea was 52.5 ± 2.4 μm. It increased gradually from the center to the periphery (P < 0.001). There was no significant difference between the nasal side and the temporal side for epithelial thickness. The central Bowman's layer thickness was 17.7 ± 1.6 μm, and it remained constant from the center to the midperiphery (P > 0.05). However, thicknesses at the nasal and temporal periphery, 20.0 ± 1.9 μm and 19.8 ± 2.2 μm, respectively, were significantly greater than the central and midperipheral thicknesses (P < 0.001). Nasal and temporal thicknesses were similar on either side of the center. CONCLUSIONS:The epithelium and the Bowman's layer were not evenly distributed across the horizontal meridian of the cornea. SD-OCT provided useful information about topographic thickness of the different corneal layers in vivo.
Bowman's layer encystment in cases of persistent Acanthamoeba keratitis.
Yokogawa Hideaki,Kobayashi Akira,Yamazaki Natsuko,Ishibashi Yasuhisa,Oikawa Yosaburo,Tokoro Masaharu,Sugiyama Kazuhisa
Clinical ophthalmology (Auckland, N.Z.)
BACKGROUND:The purpose of this study was to report Acanthamoeba encystment in Bowman's layer in Japanese cases of persistent Acanthamoeba keratitis (AK). METHODS:Laser confocal microscopic images of the cornea were obtained in vivo from 18 consecutive eyes from 17 confirmed AK patients. Retrospectively, 14 cases treated over 4 months were categorized as a nonpersistent group and three cases that required prolonged therapy for more than 6 months were categorized as a persistent group. Clinical outcomes based on final best-corrected visual acuity were retrospectively analyzed, and selected confocal images were evaluated qualitatively for abnormal findings. RESULTS:The final best-corrected visual acuity was significantly lower (P < 0.01) for patients in the persistent group compared with that in the nonpersistent group. At the initial visit, in vivo confocal microscopy demonstrated Acanthamoeba cysts exclusively in the epithelial layer in both the nonpersistent group (80%) and the persistent group (100%). At a subsequent follow-up visit, numerous Acanthamoeba cysts were observed in the epithelial cell layer and in Bowman's layer in all patients with persistent AK, but Acanthamoeba cysts were undetectable in all cases with nonpersistent AK tested. CONCLUSION:Invasion of cysts into Bowman's layer was characteristically observed in patients with persistence of AK. This finding suggests that invasion of Acanthamoeba cysts into Bowman's layer may be a useful predictor for a persistent clinical course.
An accurate method to determine Bowman's layer thickness in vivo in the human cornea.
Germundsson Johan,Fagerholm Per,Koulikovska Marina,Lagali Neil S
Investigative ophthalmology & visual science
PURPOSE:To determine an accurate value for Bowman's layer (BL) thickness in vivo in humans. METHODS:Seventeen corneal transplant patients were examined preoperatively by laser-scanning in vivo confocal microscopy (IVCM), and corneal buttons were removed postoperatively and sectioned for light microscopy (LM). Nine corneas with uniformly thick BL by LM were used for thickness measurement. In the uniformly thick samples, probable overestimation of BL thickness in vivo by a first in vivo method (Method 1) led to the development of a revised in vivo method (Method 2). Method 2 was used to measure BL thickness in 20 healthy volunteers. RESULTS:In nine patients, mean BL thickness prior to transplantation was 13.7 ± 1.6 μm by IVCM (Method 1) while BL thickness of the removed corneal button was 9.7 ± 1.7 μm by LM (P < 0.001). The correlation of BL thickness between IVCM (Method 1) and LM was poor (P = 0.226). In 20 right eyes of 20 normal corneas, both in vivo methods were used to determine BL thickness. Mean BL thickness by Method 1 was 13.2 ± 1.6 μm and by Method 2 was 9.1 ± 1.4 μm (P < 0.001). BL thickness measurements by both in vivo methods were highly correlated (P < 0.001). CONCLUSION:BL thickness by a revised in vivo method was close to LM values in this study and to values reported in fixed tissue in other studies. The authors believe this revised method provides the most accurate estimates of BL thickness in vivo to date.
Precise thickness measurements of Bowman's layer, epithelium, and tear film.
Schmoll Tilman,Unterhuber Angelika,Kolbitsch Christoph,Le Tuan,Stingl Andreas,Leitgeb Rainer
Optometry and vision science : official publication of the American Academy of Optometry
PURPOSE:To visualize corneal microstructure such as tear film, epithelium, and Bowman's layer in three dimensions with spectral domain optical coherence tomography (SDOCT) exhibiting 1.3 μm axial resolution at 100,000 A-scans/s. This enables measurement of epithelial and Bowman layer thickness across an area of 8.4 mm × 8.4 mm and measuring the tear film thickness at the central cornea. METHODS:We designed a high-performance SDOCT system, which uses a broad bandwidth TiSapph Laser and a high-speed complementary metal-oxide-semiconductor detector technology, providing a resolution in tissue of 1.3 μm and an acquisition speed of 100,000 A-scans/s. Such speed and resolution is a prerequisite if precise anatomy is to be determined. The high resolution gives access to corneal microstructure such as the epithelium layer as well as the boundaries of Bowman's layer and stroma. Even more interestingly, the tear film can be distinguished on the surface of the cornea. The Bowman's layer and epithelial thickness for both eyes of nine subjects have been measured out of which two subjects underwent photorefractive keratectomy treatment. RESULTS:Three-dimensional volumes of the human cornea have been recorded in vivo at an A-scan rate of 100,000 scans/s. Epithelial thickness was measured to be 55.8 ± 3.3 μm and Bowman's layer thickness 18.7 ± 2.5 μm in normal eyes. Epithelial thickness in the eyes after refractive surgery was measured to be 68.2 ± 5.0 μm. The Bowman layer was degenerated in these eyes. The average tear film thickness of four eyes was 5.1 ± 0.5 μm. CONCLUSIONS:Using a high-performance SDOCT system with high-imaging speed and ultrahigh resolution, we produced precise thickness maps of the epithelium and for the first time of the Bowman's layer. Such a system will give insight into high-fidelity three-dimensional corneal microstructure helping to precisely plan refractive surgery. It may furthermore yield new perspectives on studying and understanding tear film dynamics.
Corneal Collagen Cross-Linking Mushroom Shape Demarcation Line Profile After Limited Bowman's Membrane Removal by Phototherapeutic Keratectomy.
Kymionis George D,Grentzelos Michael A,Klados Nektarios E,Xanthopoulou Niki A,Paraskevopoulos Theodore A,Detorakis Efstathios T
The open ophthalmology journal
PURPOSE:To report a corneal collagen cross-linking (CXL) mushroom shape demarcation line profile after limited Bowman's membrane removal by phototherapeutic keratectomy (PTK). METHODS:Case report. RESULTS:A twenty-one-year-old male with progressive keratoconus underwent mechanical epithelial debridement (at an 8.5 mm zone) followed by PTK (at a 5.0 mm zone and in a 10 μm depth) and CXL. No intra- or early postoperative complications were found. Evaluation of the corneal stromal demarcation line depth using anterior segment optical coherence tomography revealed a mushroom shape profile. CONCLUSION:It seems that removal of the Bowman's layer leads to greater depth of the corneal stromal demarcation line.
Epithelium and Bowman's layer thickness and light scatter in keratoconic cornea evaluated using ultrahigh resolution optical coherence tomography.
Yadav Rahul,Kottaiyan Ranjini,Ahmad Kamran,Yoon Geunyoung
Journal of biomedical optics
A custom-developed ultrahigh resolution optical coherence tomography with an axial resolution of 1.1 μm in corneal tissue was used to characterize thickness and light scatter of the epithelium and Bowman's layer in keratoconic (KC) cornea noninvasively. A 4-mm wide vertical corneal section around the apex in nine KC and eight normal eyes was imaged in vivo. The epithelium and Bowman's layer were visualized and their thickness profiles were quantified. Scatter was quantified based on the sensitivity normalized mean signal intensity distribution. Average mean thickness of the epithelium and Bowman's layer in KC eyes was significantly smaller (p<0.05) than the normal eyes. The epithelium thickness variation across a central 3-mm cornea was significantly larger in KC eyes than in normal eyes. The scatter in KC eyes was significantly increased only for Bowman's layer. The changes observed in this study could improve our understanding of the underlying disease mechanism of KC and can provide new indications for early disease diagnosis.
Fractal analysis of AFM images of the surface of Bowman's membrane of the human cornea.
Ţălu Ştefan,Stach Sebastian,Sueiras Vivian,Ziebarth Noël Marysa
Annals of biomedical engineering
The objective of this study is to further investigate the ultrastructural details of the surface of Bowman's membrane of the human cornea, using atomic force microscopy (AFM) images. One representative image acquired of Bowman's membrane of a human cornea was investigated. The three-dimensional (3-D) surface of the sample was imaged using AFM in contact mode, while the sample was completely submerged in optisol solution. Height and deflection images were acquired at multiple scan lengths using the MFP-3D AFM system software (Asylum Research, Santa Barbara, CA), based in IGOR Pro (WaveMetrics, Lake Oswego, OR). A novel approach, based on computational algorithms for fractal analysis of surfaces applied for AFM data, was utilized to analyze the surface structure. The surfaces revealed a fractal structure at the nanometer scale. The fractal dimension, D, provided quantitative values that characterize the scale properties of surface geometry. Detailed characterization of the surface topography was obtained using statistical parameters, in accordance with ISO 25178-2: 2012. Results obtained by fractal analysis confirm the relationship between the value of the fractal dimension and the statistical surface roughness parameters. The surface structure of Bowman's membrane of the human cornea is complex. The analyzed AFM images confirm a fractal nature of the surface, which is not taken into account by classical surface statistical parameters. Surface fractal dimension could be useful in ophthalmology to quantify corneal architectural changes associated with different disease states to further our understanding of disease evolution.
Vertical and horizontal thickness profiles of the corneal epithelium and Bowman's layer after orthokeratology.
Lian Yan,Shen Meixiao,Jiang Jun,Mao Xinjie,Lu Ping,Zhu Dexi,Chen Qi,Wang Jianhua,Lu Fan
Investigative ophthalmology & visual science
PURPOSE:To investigate thickness profile changes of the corneal epithelium and Bowman's layer at the vertical and horizontal meridians with overnight myopia orthokeratology (OK) lenses. METHODS:Twenty subjects (age range: 19-33 years) wore reverse-geometry rigid gas-permeable OK lenses in both eyes for 30 days. Before lens wear and after 1, 7, and 30 days of overnight lens wear, evaluation of lens fitting, visual acuity examination, corneal topography, and ultra-high resolution optical coherence tomography (UHR-OCT) were performed. The central, midperipheral, and peripheral cornea were imaged in both the horizontal and vertical meridians. Custom software was produced to acquire the thickness profiles of the epithelium and Bowman's layer. RESULTS:Unaided visual acuity and refraction were improved significantly after OK lens wear. The central corneal epithelium thinned in the horizontal and vertical meridians after one night of lens wear (P < 0.05). In the horizontal meridian, the epithelium thickened at the temporal and nasal midperipheries (P < 0.05), while the superior midperipheral epithelium thinned in the vertical meridian. There were no changes in the thickness profile of Bowman's layer during the study period. CONCLUSIONS:Overnight wear of OK lenses caused the central corneal epithelium to thin in both the vertical and horizontal meridians, while the midperipheral nasal and temporal epithelium became thicker and the superior midperipheral epithelium became thinner. The thickness of the central or midperipheral Bowman's layer in either meridian did not change. Improved vision acuity after overnight OK lens wear can be attributed to changes in the corneal epithelium and not Bowman's layer.
Age-related thinning of Bowman's layer in the human cornea in vivo.
Germundsson Johan,Karanis Georgios,Fagerholm Per,Lagali Neil
Investigative ophthalmology & visual science
PURPOSE:To determine the thickness of Bowman's layer (BL) in vivo in a healthy population and to determine its variation with age. METHODS:Eighty-two subjects aged 15 to 88 years with clear, healthy corneas were examined bilaterally with laser scanning in vivo confocal microscopy (IVCM). Bowman's layer thickness was determined from IVCM images of anterior and posterior BL boundaries. For a given eye, BL thickness was averaged across four central locations by two independent observers. In addition, central corneal thickness was measured by time-domain optical coherence tomography. RESULTS:A significant negative correlation of BL thickness with age was found in right eyes (Pearson r = -0.579, P < 0.0001) and in left eyes (r = -0.558, P < 0.0001). Linear regression analysis yielded a decline in BL thickness of 0.06 μm per year. In 41 older subjects (mean age, 64.4 years), BL thickness was significantly thinner (mean ± SD, 8.6 ± 1.7 μm in right eyes) than that in 41 younger subjects (mean age, 31.6 years) (mean ± SD, 10.7 ± 1.6 μm in right eyes) (P < 0.001). No correlation of corneal thickness with age or of BL thickness with corneal thickness was observed. Strong intereye correlations in BL thickness (r = 0.771, P < 0.0001) and corneal thickness (r = 0.969, P < 0.001) were found. CONCLUSIONS:Bowman's layer thins with age in the normal cornea, losing one-third of its thickness between the ages of 20 and 80 years. In vivo measurement of BL thickness by IVCM could aid in clinical assessment and planned treatments of the anterior cornea.
The use of Bowman's layer vertical topographic thickness map in the diagnosis of keratoconus.
Abou Shousha Mohamed,Perez Victor L,Fraga Santini Canto Ana Paula,Vaddavalli Pravin K,Sayyad Fouad E,Cabot Florence,Feuer William J,Wang Jianhua,Yoo Sonia H
PURPOSE:To evaluate the use of Bowman's layer (BL) vertical topographic thickness maps in diagnosing keratoconus (KC). DESIGN:Prospective, case control, interventional case series. PARTICIPANTS:A total of 42 eyes: 22 eyes of 15 normal subjects and 20 eyes of 15 patients with KC. INTERVENTION:Bowman's layer 2-dimensional 9-mm vertical topographic thickness maps were created using custom-made ultra high-resolution optical coherence tomography. MAIN OUTCOME MEASURES:Bowman's layer average and minimum thicknesses of the inferior half of the cornea, Bowman's ectasia index (BEI; defined as BL minimum thickness of the inferior half of the cornea divided by BL average thickness of the superior half of the cornea multiplied by 100), BEI-Max (defined as BL minimum thickness of the inferior half of the cornea divided by BL maximum thickness of the superior half of the cornea multiplied by 100), keratometric astigmatism (Ast-K) of patients with KC, and average keratometric (Avg-K) readings. RESULTS:In patients with KC, BL vertical thickness maps disclosed localized relative inferior thinning of the BL. Inferior BL average thickness (normal = 15±2, KC = 12±3 μm), inferior BL minimum thickness (normal = 13±2, KC = 7±3 μm), BEI (normal = 91±7, KC = 48±14), and BEI-Max (normal = 75±8; KC = 40±13) all showed highly significant differences in KC compared with normal subjects (P< 0.001). Receiver operating characteristic (ROC) curve analysis showed excellent predictive accuracy for BEI and BEI-Max with 100% sensitivity and specificity (area under the curve [AUC] of 1) with cutoff values of 80 and 60, respectively. The AUC of inferior BL average thickness and minimum thickness were 0.87 and 0.96 with a sensitivity of 80% and 93%, respectively, and a specificity of 93% and 93%, respectively. Inferior BL average thickness, inferior BL minimum thickness, BEI, and BEI-Max correlated highly to Ast-K (R = -0.72, -0.82, -0.84, and -0.82, respectively; P< 0.001) and to Avg-K (R = -0.62, P< 0.001; R = -0.59, P = 0.001; R = -0.60, P< 0.001; and R = -0.59, P = 0.001, respectively). CONCLUSIONS:Bowman's layer vertical topographic thickness maps of patients with KC disclose characteristic localized relative inferior thinning. Inferior BL average thickness, inferior BL minimum thickness, BEI, and BEI-Max are qualitative and quantitative indices for the diagnosis of KC that accurately correlate with the severity of KC. In our pilot study, BEI and BEI-Max showed excellent accuracy, sensitivity, and specificity in the diagnosis of KC.
The Impact of Flap Creation Methods for Sub-Bowman's Keratomileusis (SBK) on the Central Thickness of Bowman's Layer.
Xu Zhe,Shen Meixiao,Hu Liang,Zhuang Xiran,Peng Mei,Hu Di,Liu Jing,Wang Jianhua,Qu Jia,Lu Fan
PURPOSE:To determine the impact of flap creation methods for sub-Bowman's keratomileusis (SBK) on central Bowman's layer thickness. METHODS:SBK flaps were made by Moria microkeratome for 20 subjects and by femtosecond (FEMTO) laser for 21 subjects. Corneal sublayer thicknesses were measured by ultra-high resolution optical coherence tomography before SBK and at 1 day, 1 week, 2 weeks, and 1 month afterwards. Each subject was imaged twice on each visit. Thicknesses of central epithelium, Bowman's layer, flap, and total cornea were calculated using a custom-made automated image processing algorithm. The repeatability of sublayer thickness measurements was tested by the intraclass correlation coefficient (ICC) and by the coefficient of repeatability (CoR) at 1 week post-SBK. RESULTS:ICCs of the Moria and FEMTO groups were ≥ 0.959 and ≥ 0.961 respectively for all sublayer measurements. The segmentation CoRs were less than 6.78% and 5.63% respectively. For both groups, microdistortions were present in the epithelium and Bowman's layer after SKB. The flap thickness of the Moria group was 9.8 μm (95% confidence interval: 4.8 - 14.8 μm) thinner than the FEMTO group one day after SBK (independent samples t-test, P < 0.05). Bowman's layer became thicker by 1.6 ± 1.1 μm and 1.7 ± 1.6 μm one day post-SBK for the Moria and FEMTO groups (repeated ANOVA, P < 0.05) and then remained stable. Corneal and sublayer thickness were similar between the two groups. CONCLUSIONS:Central Bowman's layer thickness increased 1 day post-SBK. Flap creation by Moria microkeratome and femtosecond laser did not have significantly different impacts on Bowman's layer thickness following SBK. TRIAL REGISTRATION:Chinese Clinical Trial Registry (ChiCTR) NO: ChiCTR-OCH-14004525.
[Polishing of Bowman's membrane with diamond burr in the treatment of recurrent corneal erosion syndrome].
Mamikonyan V R,Trufanov S V,Tekeeva L Yu,Malozhen S A,Subbot A M,Fyodorov A A
PURPOSE:To study the effectiveness of polishing Bowman's membrane with a diamond burr (DBPBM) in the treatment of recurrent corneal erosion syndrome (RCES). MATERIAL AND METHODS:The study included 22 patients (22 eyes) with RCES aged 20-56 years who underwent our original modification of DBPBM. All patients had keratotopography examined, endothelial cell density measured, and optical coherence tomography (OCT) of the cornea taken before and after the procedure. Additionally, conjunctival scraping, blood test for types I and II herpes (fluorescent antibody method) were performed before the surgery. Post-operative treatment included 1-2 weeks of anti-inflammatory and anti-bacterial steroid therapy, and 6 months of artificial tear Cationorm usage. RESULTS:Rehabilitation of all patients after the procedure went quickly, and no relapses were noted during the follow-up. Complete epithelialization of the area of surgical intervention under soft contact lens occurred over 2-3 days. Epithelial thickness was measured with OCT including epithelial mapping; after the surgery, it was almost even over the entire corneal surface. No complications such as induced post-operative refractive error or corneal haze were registered during the course of the study. Disruption of basal epithelial layer and epithelial basal membrane in the area of erosion relapse detected with scanning electron microscopy confirmed the need for their removal in the course of the surgery. CONCLUSION:Conservative treatment of RCES rarely yields results. Removal of inadequate epithelium and following DBPBM using our original method is a highly effective and accessible procedure for RCES treatment with low risk of complications and relapse.
[Morphological changes in the cornea of patients with recurrent corneal erosion after diamond burr polishing of Bowman's membrane].
Trufanov S V,Tekeeva L Yu,Surnina Z V,Malozhen S A
PURPOSE:To evaluate morphological changes in the cornea of patients with recurrent corneal erosion (RCE) using laser confocal microscopy before and after abrasive polishing of Bowman's membrane with a diamond burr (APBMDB). MATERIAL AND METHODS:The study included 17 patients (20 eyes) with established RCE diagnosis; they underwent laser confocal microscopy on HRT III device with Rostock Cornea module (Heidelberg Engineering GmbH, Germany). Morphological analysis of epithelial cells, nerve fibers, stroma and corneal endothelium was conducted. After that, all patients underwent APBMDB. Patient examination was repeated after 1, 3, 6, and 12 months. RESULTS:Superficial epithelium was intact before treatment in almost all cases. Islets of hyper-reflective cells, drop-shaped arrangements and stripes characterizing abnormal basal membrane were found in basal epithelium layer. Activated keratocytes and anomalous extracellular matrix were observed in the anterior stroma. No changes could be found in the posterior stroma or endothelium. Subbasal nerve plexus had changes in the form of short and atypically formed corneal nerve fiber funiculi, reduced amount of long corneal nerve fiber funiculi, as well as their tendency for forming closed round shapes. Increase in the amount of Langerhans cells was observed. One month after the procedure, pathological changes in the epithelium and basal membrane were absent, reduction in the amount of Langerhans cells and activated keratocytes was observed. Three months after the polishing, continued reduction of the amount of Langerhans cells was noted. Regeneration of nerves partially restored after 6 months; after 12 months, confocal microscopy results were comparable to healthy volunteers. CONCLUSION:Confocal laser microscopy of the cornea of patients with RCE showed presence of changes in basal epitheliocytes, basal membrane, anterior stroma and corneal nerve fibers, as well as positive dynamics of these changes after abrasive polishing of Bowman's membrane with a diamond burr.
Value of corneal epithelial and Bowman's layer vertical thickness profiles generated by UHR-OCT for sub-clinical keratoconus diagnosis.
Xu Zhe,Jiang Jun,Yang Chun,Huang Shenghai,Peng Mei,Li Weibo,Cui Lele,Wang Jianhua,Lu Fan,Shen Meixiao
Ultra-high resolution optical coherence tomography (UHR-OCT) can image the corneal epithelium and Bowman's layer and measurement the thicknesses. The purpose of this study was to validate the diagnostic power of vertical thickness profiles of the corneal epithelium and Bowman's layer imaged by UHR-OCT in the diagnosis of sub-clinical keratoconus (KC). Each eye of 37 KC patients, asymptomatic fellow eyes of 32 KC patients, and each eye of 81 normal subjects were enrolled. Vertical thickness profiles of the corneal epithelium and Bowman's layer were measured by UHR-OCT. Diagnostic indices were calculated from vertical thickness profiles of each layer and output values of discriminant functions based on individual indices. Receiver operating characteristic curves were determined, and the accuracy of the diagnostic indices were assessed as the area under the curves (AUC). Among all of the individual indices, the maximum ectasia index for epithelium had the highest ability to discriminate sub-clinical KC from normal corneas (AUC = 0.939). The discriminant function containing maximum ectasia indices of epithelium and Bowman's layer further increased the AUC value (AUC = 0.970) for sub-clinical KC diagnosis. UHR-OCT-derived thickness indices from the entire vertical thickness profiles of the corneal epithelium and Bowman's layer can provide valuable diagnostic references to detect sub-clinical KC.
Noncontact Quantification of Topography of Anterior Corneal Surface and Bowman's Layer With High-Speed OCT.
Matalia Himanshu,Francis Mathew,Gangil Tarun,Chandapura Rachana S,Kurian Mathew,Shetty Rohit,Nelson Everette Jacob Remington,Sinha Roy Abhijit
Journal of refractive surgery (Thorofare, N.J. : 1995)
PURPOSE:To quantify keratometry and wavefront aberration of the anterior corneal surface and epithelium-Bowman's layer interface using anterior segment optical coherence tomography (OCT). METHODS:Twenty-five normal eyes and 25 eyes with keratoconus were retrospectively analyzed. The anterior corneal edge and epithelium-Bowman's layer interface were segmented from 12 distortion-corrected OCT B-scans. Axial tangential curvatures and wavefront aberration were calculated by ray tracing and 6th order Zernike analyses. All eyes underwent simultaneous imaging with Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany). The Pentacam elevation data were used for aberration analyses using the same ray-tracing method. The paired t test was used to compare the variables. RESULTS:In normal eyes, mean steep axis and maximum keratometry of OCT of the anterior corneal surface and epithelium-Bowman's layer interface were significantly greater than the same of the Pentacam anterior corneal surface (P < .05). Mean root mean square of higher order aberrations of the OCT surfaces was greater than the same of the Pentacam surface by a factor of 4. In eyes with keratoconus, mean steep axis and maximum keratometry of the OCT epithelium-Bowman's layer interface was the greatest (P < .05). Mean root mean square of the higher order aberrations and vertical coma of the OCT epithelium-Bowman's layer interface was the greatest (P < .05). In general, the aberrations of the OCT epithelium-Bowman's layer interface were significantly greater than those of the Pentacam anterior corneal surface. CONCLUSIONS:A noncontact method to quantify the topography and aberrations of corneal surfaces with OCT was presented. OCT measurements yielded greater curvature and aberrations than Pentacam in both normal and keratoconic eyes. [J Refract Surg. 2017;33(5):330-336.].
Application of high resolution OCT to evaluate irregularity of Bowman's layer in asymmetric keratoconus.
Pahuja Natasha,Shroff Rushad,Pahanpate Pratik,Francis Mathew,Veeboy Leio,Shetty Rohit,Nuijts Rudy M M A,Sinha Roy Abhijit
Journal of biophotonics
Irregularity of the Bowman's layer (BL) in keratoconus (KC, sample size (n) = 28) and forme fruste keratoconus (FFKC, n = 18) eyes was evaluated. Subjects underwent high resolution OCT imaging (Bioptigen Inc., USA) and corneal tomography (Pentacam v1.20r41, OCULUS Optikgeräte GmbH, Germany). Anterior edge of the BL was segmented. A Bowman's roughness index (BRI) was defined as the sum of the enclosed areas between segmented edge and a smooth 3 order polynomial fit to the edge. BRI was compared with corneal aberrations, Keratoconus percentage index (KISA), Cone location magnitude index (CLMI) and Belin-Ambrosio enhanced ectasia display overall deviation index (BAD-D). Area under the curve (AUC) was determined with logistic regression (LR). Mean BRI (×10 ) was 2.12 mm , 1.81 mm and 1.7 mm in normal (n = 26), FFKC and KC eyes, respectively (p < 0.001). BAD-D (0.79) and BRI (0.74) had the best AUC for FFKC. By combining BAD-D and BRI, the AUC improved to 0.85 (p = 0.01). For KC eyes, KISA (0.94), CLMI (0.88), BAD-D (0.96) and aberrations had comparable AUC (p > 0.05). However, LR with BRI and other indices didn't improve the AUC in KC eyes (p > 0.05). BRI was significantly reduced in FFKC and KC eyes. It improved the detection of FFKC but not KC eyes.
Multifunctional synthetic Bowman's membrane-stromal biomimetic for corneal reconstruction.
Wang Xiaokun,Majumdar Shoumyo,Soiberman Uri,Webb Joshua N,Chung Liam,Scarcelli Giuliano,Elisseeff Jennifer H
As the outermost layer of the eye, the cornea is vulnerable to physical and chemical trauma, which can result in loss of transparency and lead to corneal blindness. Given the global corneal donor shortage, there is an unmet need for biocompatible corneal substitutes that have high transparency, mechanical integrity and regenerative potentials. Herein we engineered a dual-layered collagen vitrigel containing biomimetic synthetic Bowman's membrane (sBM) and stromal layer (sSL). The sBM supported rapid epithelial cell migration, maturation and multilayer formation, and the sSL containing tissue-derived extracellular matrix (ECM) microparticles presented a biomimetic lamellar ultrastructure mimicking the native corneal stroma. The incorporation of tissue-derived microparticles in sSL layer significantly enhanced the mechanical properties and suturability of the implant without compromising the transparency after vitrification. In vivo performance of the vitrigel in a rabbit anterior lamellar keratoplasty model showed full re-epithelialization within 14 days and integration of the vitrigel with the host tissue stroma by day 30. The migrated epithelial cells formed functional multilayer with limbal stem cell marker p63 K14 expressed in the lower layer, epithelial marker K3 and K12 expressed through the layers and tight junction protein ZO-1 expressed by the multilayers. Corneal fibroblasts migrated into the implants to facilitate host/implant integration and corneal stromal regeneration. In summary, these results suggest that the multi-functional layers of this novel collagen vitrigel exhibited significantly improved biological performance as corneal substitute by harnessing a fast re-epithelialization and stromal regeneration potential.
Bowman's layer transplantation: evidence to date.
Sharma Bhavana,Dubey Aditi,Prakash Gaurav,Vajpayee Rasik B
Clinical ophthalmology (Auckland, N.Z.)
Surgical management of keratoconus (KC) has undergone a paradigm shift in the last two decades and component corneal transplantation technique of deep anterior lamellar keratoplasty has established itself as a modality of choice for management of advanced cases of KC. Every now and then, new minimalist modalities are being innovated for the management of KC. On the same lines, a new technique, Bowman's layer transplantation, for surgical management of moderate to advanced KC has been reported in recent years. The procedure has shown to be beneficial in reducing ectasia in advanced KC with minimal intraoperative and postoperative complications. In this review, we intend to describe available information and literature with reference to this new surgical technique - Bowman's layer transplantation.
Thickness changes in the corneal epithelium and Bowman's layer after overnight wear of silicone hydrogel contact lenses.
Lu Fan,Tao Aizhu,Tao Weiwei,Zhuang Xiran,Shen Meixiao
BACKGROUND:To investigate thickness changes in the corneal epithelium and Bowman's layer after overnight silicone hydrogel contact lens (CL) wear by using ultra-high resolution optical coherence tomography (UHROCT). METHODS:Eleven subjects without CL wearing history were recruited for this study. An UHROCT was used to measure the thickness of the epithelium (ET), Bowman's layer (BT), stroma (ST), and total cornea (CCT) at the center of both eyes. A silicone hydrogel CL was inserted in the right eye of each subject, and the fellow non-CL wearing left eye served as the control. The lens was inserted at 9:30 pm and removed at 8:00 am the next morning. The subjects were evaluated at 9:00 pm (baseline), 9:30 pm (lens insertion), 10:00 pm (before sleep), 7:00 am (waking), 7:30 am, and 8:00 am (lens removal). RESULTS:Compared to the lens insertion level, the ET of the lens-wearing eye increased by 5.73% at eye opening (P = 0.001). The ET of the non-CL wearing eye and the BT in both eyes did not change after overnight CL wear. Compared to baseline, the CCT of the lens-wearing eye increased by 2.87% upon waking (P = 0.003) and recovered 30 min later (P = 0.555). In contrast, compared to baseline, the CCT of the non-CL wearing eye did not increase upon waking (P = 0.105). CONCLUSIONS:By using UHROCT, we found that overnight CL wear induced different swelling responses in the various sublayers of the cornea. TRIAL REGISTRATION:Retrospectively registered. Registration number: ChiCTR1800015115 . Registered 07 March 2018.
Large Field of View Corneal Epithelium and Bowman's Layer Thickness Maps in Keratoconic and Healthy Eyes.
Pircher Niklas,Beer Florian,Holzer Stephan,Gschließer Andreas,Donner Ruth,Pircher Michael,Hitzenberger Christoph K,Schmidinger Gerald,Lammer Jan
American journal of ophthalmology
PURPOSE:To assess differences between epithelium thickness (ET) and Bowman's layer thickness (BLT) maps in keratoconic eyes and healthy eyes. DESIGN:Cross-sectional study. METHODS:Setting: institutional. STUDY POPULATION:47 patients (1 eye) with keratoconus (KC) and 20 healthy subjects (1 eye). OBSERVATION PROCEDURE:epithelium and Bowman's layer measurements were performed by using custom-designed polarization-sensitive optical coherence tomography (PS-OCT) with a conical scanning optics design. En face corneal ET and BLT maps with a diameter of 11 mm were computed. Main outcome measurements were mean ET and BLT of 25 sectors; the thinnest (minET, minBLT) and thickest sectors (maxET, maxBLT) were assessed. Ratios between thinnest/thickest sectors (R1) and between mean ET and BLT of the inferior temporal quadrant/superior nasal quadrant (R2) were calculated (R1ET, R1BLT; R2ET, R2BLT). Receiver operator characteristic (ROC) curve analysis was used to assess the diagnostic power of statistically different parameters. RESULTS:In healthy eyes, smooth ET maps were observed. KC eyes showed a "doughnut pattern." The BLT maps of healthy eyes had a smooth appearance, but highly irregular "moth"-like damage pattern could be observed in keratoconic eyes. Highest area under the curve values were found for the thinnest sector of the BLT map, the R1ET, and the thinnest sector of the ET map. CONCLUSIONS:PS-OCT imaging enables the visualization of significant differences of the corneal epithelium and the Bowman's layer in en face maps covering almost the entire cornea. ET and BLT profiles could clearly show their diagnostic importance for the distinguishing of keratoconic eyes and healthy eyes.
Accuracy of OCT Curvature and Aberrations of Bowman's Layer: A Prospective Comparison With Physical Removal of Epithelium.
Khamar Pooja,Shetty Rohit,Ahuja Prerna,Chandapura Rachana,Narasimhan Raghav,Nuijts Rudy M M A,Sinha Roy Abhijit
Journal of refractive surgery (Thorofare, N.J. : 1995)
PURPOSE:To compare optical coherence tomography (OCT) and Scheimpflug curvature and aberrations of the Bowman's layer before and after removal of the epithelium. METHODS:Bowman's layer was mapped with OCT (Optovue Inc., Irvine, CA) before and after removal of the epithelium in normal eyes undergoing photorefractive keratectomy (n = 14) and keratoconic eyes undergoing corneal cross-linking (n = 25). The anterior corneal surface before removal and the underlying Bowman's layer after removal of the epithelium were also mapped with Pentacam (Oculus Optikgeräte, Wetzlar, Germany), and the surface aberrations with ray tracing were computed. RESULTS:The agreement of OCT curvatures before and after removal of the epithelium was excellent (intraclass correlation coefficient [ICC] = 0.9). A similar trend was seen between OCT and Pentacam after removal of the epithelium. The agreement of surface wavefront aberrations of the Bowman's layer before and after removal of the epithelium was excellent (ICC = 0.9) between the devices for keratoconic eyes. However, this agreement was relatively inferior in normal eyes (ICC < 0.5). CONCLUSIONS:The virtual OCT curvature and aberrations of the Bowman's layer agreed well with its actual magnitudes on removal of the epithelium in the keratoconic eyes. In normal eyes, the agreement was inferior for aberrations but not for curvature. [J Refract Surg. 2020;36(3):193-198.].
In-vivo Three-dimensional Characteristics of Bowman's Layer and Endothelium/Descemet's Complex Using Corneal Microlayer Tomography in Healthy Subjects.
Eleiwa Taher K,Elsawy Amr,Syed Zeba A,Roongpoovapatr Vatookarn,Sayed Ahmed M,Yoo Sonia H,Abou Shousha Mohamed
Current eye research
: To characterize the three-dimensional (3D) thickness profile and age-related changes of Bowman's layer (BL), and endothelium/Descemet's membrane (En/DM) complex among healthy individuals using Corneal Microlayer Tomography (CML-T), and to describe its repeatability and accuracy.: Sixty-six eyes of 41 healthy volunteers; 27 eyes (< 40 years old), and 39 eyes (>40 years old) were imaged using HD-OCT. Automatic and manual segmentation of the corneal layers was performed, and 3D thickness maps were generated, using custom-built CML-T software. A regional analysis of mean thickness parameters between the 2 age groups was performed. A regression analysis was used to assess the correlation between age, and thickness maps. Intraclass Correlation Coefficients (ICC), Coefficients of Variation (COV), and Bland-Altman plots were used to assess the reliability of the repeated measurements in 198 locations.: CML-T successfully mapped the BL and En/DM in all included eyes. Thickness maps showed a significant increase in corneal thickness (CT), BL thickness (BMT), and En/DM complex thickness (DMT) toward the periphery with a mean difference 28 µm ( < .001), 1.1 µm ( < .001), and 1.4 µm ( < .001), respectively. There was a strong correlation between age and central DMT (r = 0.61; < .001), while there was no correlation between age and both CT, and BMT. ICC values ranged from 0.9 (BMT) to 0.997 (DMT), and from 0.808 (BMT) to 0.979 (CT) for intraoperator repeatability of manual measurements, and the accuracy of auto matic measurements, respectively. COV values were lower than 7.5% in all cases.: CML-T is a novel tool that can generate 3D-thickness maps of both BL and En/DM. CT, BMT, and DMT increase toward the periphery in healthy corneas. DMT increases with aging, while BMT does not. We also report excellent repeatability, accuracy and good agreement between automatic and manual measurements.
Bowman's layer in the cornea- structure and function and regeneration.
Wilson Steven E
Experimental eye research
Bowman's layer lies immediately posterior to the epithelial basement membrane (EBM) and anterior to the stroma proper in humans, chickens, quail, zebra fish, deer, giraffe, antelope, California sea lions, guinea pig and several other species. It is not found in dog, wolf, cat, tiger, lions, rabbit, pigs, cows, goats, or horses. Developmental anomalies of Bowman's layer are rare, but acquired damage to Bowman's layer, or even complete destruction, is frequently seen in advanced bullous keratopathy or Fuchs' endothelial dystrophy. No detrimental effects of removal of Bowman's layer over the central 6-7 mm of central cornea have been noted in millions of patients who've had photorefractive keratectomy (PRK). Recent studies have suggested the randomly-oriented collagen fibrils that make up Bowman's layer do not have a significant barrier function in modulating the passage of moderate- to large-sized proteins. It is hypothesized that Bowman's layer develops in the corneas of those species that have one because of cytokine-mediated interactions occurring between corneal epithelial cells and underlying keratocytes, including negative chemotactic and apoptotic effects on the keratocytes by low levels of cytokines such as interleukin-1α that are gradually released as epithelial cells die and slough during their normal development. A "Bowman's like layer" can generate around stromal epithelial plugs after radial keratotomy, and possibly beneath the central corneal epithelial basement membrane many years after PRK.