Modulation transfer function and pupil size in multifocal and monofocal intraocular lenses in vitro.
Kawamorita Takushi,Uozato Hiroshi
Journal of cataract and refractive surgery
PURPOSE:To investigate the relationship between pupil size and the modulation transfer function (MTF) of a multifocal intraocular lens (IOL) in vitro and to predict the visual effects in vivo. SETTING:Department of Ophthalmology and Visual Science, Kitasato University Graduate School of Medical Sciences, Kitasato, Japan. METHODS:A refractive multifocal IOL (Array SA-40N, Allergan) and a monofocal IOL (PhacoFlex SI-40NB, AMO) were evaluated using the OPAL Vector system and a model eye with a variable effective aperture. With effective pupil diameters of 2.1, 3.0, 3.4, 3.9, 4.6, 5.1, and 5.5 mm, the in-focus and defocus MTFs were measured in the multifocal and monofocal IOLs. RESULTS:With increases in effective pupil diameter, the far MTF progressively decreased at all spatial frequencies. In contrast, the near MTF began to increase at effective pupil diameter 2.1 mm, showed a peak at 3.4 mm, and decreased at diameters greater than 3.4 mm. The ratio of near MTF to far MTF showed an increase with larger effective pupil diameters and at lower spatial frequencies. CONCLUSIONS:With a zonal progressive multifocal IOL, the pupil size effected a trade-off between the far and near MTFs: The near MTF increased at the expense of the far MTF at large pupil sizes (effective pupil diameter >3.4 mm). To enhance near vision with a multifocal IOL, the desirable effective pupil diameter should be 3.4 mm or larger.
Double-pass system assessing the optical quality of pseudophakic eyes.
Lee Hun,Lee Kwanghyun,Ahn Ji Min,Kim Eung Kweon,Sgrignoli Bradford,Kim Tae-Im
Optometry and vision science : official publication of the American Academy of Optometry
PURPOSE:To compare the optical quality measurements obtained from the double-pass system and ocular aberrations, subjective visual acuity, and contrast sensitivity score in pseudophakic eyes. METHODS:Three months after cataract surgery, modulation transfer function (MTF) cutoff frequency, Strehl ratio, objective scatter index, and objective pseudoaccommodation obtained from the double-pass system were compared with total aberration, higher-order aberration, and spherical aberration obtained from ray-tracing aberrometer. In addition, parameters of the double-pass system were compared with subjective visual acuity and the contrast sensitivity score. RESULTS:Forty eyes of 40 patients were included. The MTF cutoff frequency and Strehl ratio were negatively correlated with total aberration (r = -0.503, p = 0.003; r = -0.509, p = 0.003, respectively) and subjective visual acuity (r = -0.453, p = 0.007; r = -0.354, p = 0.040, respectively). The objective scatter index was positively correlated with total aberration (r = 0.451, p = 0.024) and subjective visual acuity (r = 0.516, p = 0.008). The MTF cutoff frequency showed a correlation with contrast sensitivity score under photopic and mesopic conditions. CONCLUSIONS:Optical quality parameters obtained from the double-pass system were correlated with ocular aberrations, subjective visual acuity, and contrast sensitivity score in pseudophakic eyes.
Subjective Visual Performance and Objective Optical Quality With Intraocular Lens Glistening and Surface Light Scattering.
Luo Furong,Bao Xuan,Qin Yingyan,Hou Min,Wu Mingxing
Journal of refractive surgery (Thorofare, N.J. : 1995)
PURPOSE:To evaluate the long-term effect of glistenings and surface light scattering of intraocular lenses (IOLs) on visual and optical performance after cataract surgery. METHODS:Pseudophakic eyes that underwent standard phacoemulsification and two types of hydrophobic acrylic spherical IOL implantation without complications for at least 5 years were included in this retrospective study. Participants were divided into the glistenings, surface light scattering, and control groups according to the current condition of the IOLs. Then participants received a follow-up examination including uncorrected and corrected distance visual acuity (UDVA and CDVA), contrast sensitivity, straylight, and intraocular higher order aberrations, as well as point spread function (PSF) and modulation transfer function (MTF). RESULTS:A total of 140 eyes were included in the study. UDVA, CDVA, and glare sensitivity were not significantly different among the three groups (P > .05). However, compared with the control group, the IOLs of the glistenings and surface light scattering groups were associated with significantly lower contrast sensitivity under no glare conditions. Furthermore, eye with glistenings exhibited the highest straylight value (P < .05), whereas no difference was found between the surface light scattering and control groups. In contrast to the control group, the spherical aberration increased and the mean values of PSF and MTF decreased in the glistenings and surface light scattering groups. CONCLUSIONS:Both glistenings and surface light scattering tend to impair subjective visual performance, such as contrast sensitivity, and potentially affect objective optical quality, including straylight, spherical aberration, PSF, and MTF. [J Refract Surg. 2018;34(6):372-378.].
The effect of simulated normal and amblyopic higher-order aberrations on visual performance.
Domínguez-Vicent Alberto,Pérez-Vives Cari,Ferrer-Blasco Teresa,García-Lázaro Santiago,Montés-Micó Robert
Journal of AAPOS : the official publication of the American Association for Pediatric Ophthalmology and Strabismus
PURPOSE:To study the effect of simulated amblyopic and normal higher-order aberrations on visual performance of normal eyes. METHODS:To assess visual function, an adaptive optics visual simulator was used to compensate volunteers' ocular aberrations and simulate the wavefront aberration patterns found in healthy and amblyopic eyes in 7 healthy individuals. Visual acuity for high (100%), medium (50%), and low (10%) contrast and contrast sensitivity at 10, 20, and 25 cycles per degree (cpd) were measured after simulation of both pattern aberrations. The modulation transfer function and the point spread function were computed based on the aberration data. All measures were taken for 3 and 5.5 mm pupil sizes. RESULTS:No statistically significant differences in visual acuity and contrast sensitivity were found between both groups for any analyzed contrast level, spatial frequency, and pupil size values. Mean logMAR visual acuity for a 3 mm pupil was -0.11 ± 0.04 for 100% contrast levels, -0.06 ± 0.06 for 50%, and 0.17 ± 0.07 for 10%. For a 5.5 mm pupil, the values were -0.06 ± 0.04 (100%), 0.00 ± 0.05 (50%), and 0.21 ± 0.06 (10%). Mean contrast sensitivity for a 3 mm pupil was 1.9 ± 0.2 for 10 cpd, 1.2 ± 0.15 for 20 cpd, and 0.9 ± 0.1 for 25 cpd. For a 5.5 mm pupil, contrast sensitivity was 1.4 ± 0.2 (10 cpd), 0.9 ± 0.2 (20 cpd), and 0.6 ± 0.2 (25 cpd). MTFs and PSFs were comparable in the two groups for both pupils. CONCLUSIONS:The higher-order aberrations seen in idiopathic amblyopic eyes alone do not appear to contribute to the decreased visual function.
Training to improve contrast sensitivity in amblyopia: correction of high-order aberrations.
Liao Meng,Zhao Haoxing,Liu Longqian,Li Qian,Dai Yun,Zhang Yudong,Zhou Yifeng
Perceptual learning is considered a potential treatment for amblyopia even in adult patients who have progressed beyond the critical period of visual development because adult amblyopes retain sufficient visual plasticity. When perceptual learning is performed with the correction of high-order aberrations (HOAs), a greater degree of neural plasticity is present in normal adults and those with highly aberrated keratoconic eyes. Because amblyopic eyes show more severe HOAs than normal eyes, it is interesting to study the effects of HOA-corrected visual perceptual learning in amblyopia. In the present study, we trained twenty-six older child and adult anisometropic amblyopes while their HOAs were corrected using a real-time closed-loop adaptive optics perceptual learning system (AOPL). We found that adaptive optics (AO) correction improved the modulation transfer functions (MTFs) and contrast sensitivity functions (CSFs) of older children and adults with anisometropic amblyopia. When perceptual learning was performed with AO correction of the ocular HOAs, the improvements in visual function were not only demonstrated in the condition with AO correction but were also maintained in the condition without AO correction. Additionally, the learning effect with AO correction was transferred to the untrained visual acuity and fellow eyes in the condition without AO correction.
Wavefront aberrations, depth of focus, and contrast sensitivity with aspheric and spherical intraocular lenses: fellow-eye study.
Nanavaty Mayank A,Spalton David J,Boyce James,Saha Shouvik,Marshall John
Journal of cataract and refractive surgery
PURPOSE:To compare wavefront aberration, depth of focus, contrast sensitivity, and in vivo modulation transfer function (MTF) after fellow-eye implantation of aspheric and spherical intraocular lenses (IOLs). SETTINGS:Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom. METHODS:This prospective randomized controlled study comprised patients with bilateral cataract who received an aspheric AcrySof SN60WF IOL or a spherical AcrySof SN60AT IOL in the first eye and the other IOL in the second eye. Assessments at 3 and 6 months included 100% and 9% logMAR best corrected visual acuity (BCVA) and photopic and mesopic functional acuity contrast testing. Total internal and corneal aberrations and depth of focus were computed. Distance-corrected near logMAR acuity was available at 12 months. RESULTS:At 3 and 6 months, there was no significant difference in 100% and 9% BCVA or photopic contrast sensitivity. Mesopic contrast sensitivity was better and total and internal spherical aberrations were significantly less with the aspheric IOL. Total and internal eye vertical coma was reduced with aspheric IOL. Total MTF was not significantly different between groups. The aspheric IOL group had 0.46 diopter less depth of focus than the spherical IOL group at 6 months (P<.05). Distance-corrected near acuity was significantly better with the spherical IOL. CONCLUSIONS:Aspheric IOLs significantly reduced spherical aberration, improving mesopic contrast sensitivity. Vertical coma was reduced with aspheric IOLs. Reduction of aberrations may be responsible for reduced depth of focus with aspheric IOLs. This may be disadvantageous for near vision and reading ability.
Comparison of ocular modulation transfer function determined by a ray-tracing aberrometer and a double-pass system in early cataract patients.
Qiao Liya,Wan Xiuhua,Cai Xiaogu,Vasudevan Balamurali,Xiong Ying,Tan Jiaxuan,Guan Zheng,Atchison David A,Wang Ningli
Chinese medical journal
BACKGROUND:The evaluation of retinal image quality in cataract eyes has gained importance and the clinical modulation transfer functions (MTF) can obtained by aberrometer and double pass (DP) system. This study aimed to compare MTF derived from a ray tracing aberrometer and a DP system in early cataractous and normal eyes. METHODS:There were 128 subjects with 61 control eyes and 67 eyes with early cataract defined according to the Lens Opacities Classification System III. A laser ray-tracing wavefront aberrometer (iTrace) and a double pass (DP) system (OQAS) assessed ocular MTF for 6.0 mm pupil diameters following dilation. Areas under the MTF (AUMTF) and their correlations were analyzed. Stepwise multiple regression analysis assessed factors affecting the differences between iTrace- and OQAS-derived AUMTF for the early cataract group. RESULTS:For both early cataract and control groups, iTrace-derived MTFs were higher than OQAS-derived MTFs across a range of spatial frequencies (P < 0.01). No significant difference between the two groups occurred for iTrace-derived AUMTF, but the early cataract group had significantly smaller OQAS-derived AUMTF than did the control group (P < 0.01). AUMTF determined from both the techniques demonstrated significant correlations with nuclear opacities, higher-order aberrations (HOAs), visual acuity, and contrast sensitivity functions, while the OQAS-derived AUMTF also demonstrated significant correlations with age and cortical opacity grade. The factors significantly affecting the difference between iTrace and OQAS AUMTF were root-mean-squared HOAs (standardized beta coefficient = -0.63, P < 0.01) and age (standardized beta coefficient = 0.26, P < 0.01). CONCLUSIONS:MTFs determined from a iTrace and a DP system (OQAS) differ significantly in early cataractous and normal subjects. Correlations with visual performance were higher for the DP system. OQAS-derived MTF may be useful as an indicator of visual performance in early cataract eyes.
Assessment of straylight and the modulation transfer function of intraocular lenses with centrally localized opacification associated with the intraocular injection of gas.
Łabuz Grzegorz,Yildirim Timur M,van den Berg Thomas J T P,Khoramnia Ramin,Auffarth Gerd U
Journal of cataract and refractive surgery
PURPOSE:To assess the optical quality of intraocular lenses (IOLs) explanted because of opacification after the intraocular injection of gas. SETTING:David J. Apple Laboratory, Heidelberg, Germany. DESIGN:Experimental study. METHODS:Four hydrophilic acrylic IOLs were studied, each with a centrally localized round opacification pattern associated with the intraocular use of gas. Laboratory analysis included gross examination with a light microscope, followed by alizarin and von Kossa staining. Optical quality was assessed by examining the modulation transfer function (MTF) and straylight. Results were compared with those of a control IOL and normative data for straylight of the crystalline lens. The following parameters were derived from image analysis: opacified surface fraction, light loss in the opacified surface, and the area and number of granules. The relationship between straylight increase and those parameters was studied. RESULTS:Fine granules were identified on the IOL surface and subsurface. The granules stained positive for calcium, and the MTF levels of 2 IOLs dropped markedly. The other 2 showed relatively minor changes. The straylight was extremely increased in 3 IOLs up to (and above) a level of that of a cataractous lens. A proportional relationship was found between straylight and the morphological parameters from image analysis. CONCLUSIONS:Intraocular lenses with centrally localized opacification have a strong potential for deteriorating optical performance. However, the optical quality might differ depending on the morphology of opacification. A serious straylight increase was found in most of these IOLs, suggesting that affected patients may suffer from glare-related symptoms.