Effects of spherical aberration on visual acuity at different contrasts

Intraindividual Comparison of an Enhanced Monofocal and an Aspheric Monofocal Intraocular Lens of the Same Platform

PURPOSE

To compare intraindividual differences in visual performance of a monofocal and enhanced monofocal intraocular lens (IOL) of the same platform.

DESIGN

Prospective, interventional, fellow-eye comparison clinical study.

METHODS

In total, 55 patients (110 eyes) with bilateral age-related cataract were enrolled. All patients received a monofocal ZCB00 IOL in the dominant and an enhanced monofocal Eyhance ICB00 IOL in the nondominant eye. After 2 to 4 months, monocular best-corrected distant visual acuity (BCDVA), distance-corrected intermediate visual acuity (DCIVA), distance-corrected near visual acuity (DCNVA), contrast visual acuity, monocular defocus curves, internal higher-order aberrations (HOAs) and spherical aberrations (SA), decentration, and tilt were compared.

RESULTS

The monocular mean BCDVA, DCIVA at 80 cm and 66 cm, and DCNVA were -0.03 ± 0.07, 0.24 ± 0.12, 0.32 ± 0.13, and 0.50 ± 0.13 logarithm of the minimum angle of resolution for the enhanced ICB00 and -0.06 ± 0.06 (P = .014), 0.30 ± 0.11 (P = .005), 0.38 ± 0.12 (P = .004), and 0.55 ± 0.14 (P = .034) logarithm of the minimum angle of resolution for the ZCB00, respectively. Internal HOAs (P = .001) and negative SA (P < .001) were increased with the ICB00 at 3 mm and comparable at 5 mm (P > .05). Contrast acuity, tilt, and decentration were similar (P > .05).

CONCLUSIONS

Significantly increased monocular DCIVA at 80 cm and 66 cm and DCNVA at 40 cm were observed with the enhanced ICB00 IOL, and the ZCB00 IOL demonstrated better BCDVA. This would result in a mean gain of 2 to 3 Early Treatment of Diabetic Retinopathy Study letters at near and intermediate distance. Monocular defocus curves displayed highest differences of 5 Early Treatment of Diabetic Retinopathy Study letters at -1.25 diopters (D) and -1.50 D levels of defocus and a depth of focus of 1.23 D for the ICB00 IOL and 0.94 D for the ZCB00 IOL. Decentration, tilt, and HOAs were generally low.

Characteristics and Related Parameters of Quick Contrast Sensitivity Function in Chinese Ametropia Children

PURPOSE

To investigate the characteristics of quick contrast sensitivity function (qCSF) and its related parameters in Chinese ametropia children.

METHODS

This case series study enrolled 106 eyes of 53 children (male/female=29/24, age: 9.04±2.06 years). Examinations included manifest refraction, axial length, corneal curvature, and monocular and binocular qCSF readings without refractive correction (area under log CSF [AULCSF], CSF acuity, and contrast sensitivity [CS] at 1.0 to 18.0 cpd). The subjects were divided into groups according to age and refractive parameters for analysis.

RESULTS

The mean spherical equivalent (SE), AULCSF, and CSF acuity of the test eyes were -0.94±1.53 D, 0.44±0.33, and 8.50±5.97 cpd, respectively. In the monocular qCSF comparison, the refraction sphere (RS) was the major factor correlated with qCSF readings (B=0.186, P =0.009 for AULCSF; B=0.543, P =0.019 for CSF acuity; generalized linear model). The three groups stratified by RS/SE (<-1.00D, -1.00D to 0D, and >0D) showed significant differences in CS at medium spatial frequencies (3.0 and 6.0 cpd; all P <0.05). In the low RS/SE group (within -1 to 0 D), the CS at 12.0 cpd was significantly lower than that in the hyperopia group (all P <0.05). Binocular qCSF readings were significantly correlated with those of the eyes with lower RS (all P <0.05).

CONCLUSION

RS and SE are the major contributing factors of qCSF without refractive correction in children. The CS at medium spatial frequencies decrease significantly as the RS/SE increase. In low myopia children, the CS at medium and high spatial frequencies are significantly decreased, providing practical value in visual function screening in children.

Spherical aberration for expanding depth of focus

The increase in the depth of focus (DoF) for the treatment of presbyopia or cataracts is a topic of great interest for anterior segment surgeons who have seen how new surgical possibilities to achieve DoF enlargement have emerged. Nowadays, several technologies to extend the DoF are available, from corneal laser refractive surgery procedures in presbyopia to intraocular lens (IOL) implantation in cataract or refractive lens exchange. Some of these procedures are based on aspheric profiles, either in the cornea or in the IOL, which modulate the spherical aberration (SA) and, therefore, extend the light energy on different focal planes. The aim of this narrative review was to give an overall picture about the reasons why there is not a general solution persistent along time of SA induction to extend DoF, especially considering that SA depends on pupil diameter and this decreases with age.

Single-step transepithelial photorefractive keratectomy in high myopia: qualitative and quantitative visual functions

AIM

To investigate quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy (TransPRK) in high myopia.

METHODS

In a prospective interventional case-series, 30 eyes with high myopia (-6.00 to -8.75 D) with (up to -3.00 D) or without astigmatism were enrolled from Bina Eye Hospital, Tehran, Iran. One-step TransPRK was performed with aberration-free aspherical optimized profile and SCHWIND AMARIS 500 laser. One-year follow-up results for refraction, visual acuities, vector analysis, ocular wave-front (OWF) and corneal wave-front (CWF) higher order aberrations (HOA), contrast sensitivity (CS), and post-operative haze were assessed.

RESULTS

After the surgery, both photopic and mesopic CSs significantly improved (both P<0.001). We detected significant induction of OWF coma and trefoil (P<0.001 for both) HOAs; CWF coma (P=0.002), spherical (P<0.001), and tetrafoil (P=0.003) HOAs in 6 mm analysis diameter; and CWF trefoil (P=0.04) HOA in 4 mm analysis diameter. The range of mean induction observed for various HOAs was 0.005-0.11 µm. The 86.7% of eyes reached an uncorrected distance visual acuity of 20/20 or better; 96.7% of eyes were within ±0.5 D of targeted spherical refraction. In vector analysis, mean correction index value was 1.03 and mean index of success was 0.22. By 12mo after the operation, no eye lost any number of corrected distance visual acuity lines. We detected no corneal haze greater than 1⁺ throughout the follow-up.

CONCLUSION

Our findings show promising effects of single-step TransPRK on quality of vision in high myopic eyes. It also improves refraction and visual acuity.

Image Quality Analysis of Eyes Undergoing LASER Refractive Surgery

Laser refractive surgery for myopia increases the eye’s higher-order wavefront aberrations (HOA’s). However, little is known about the impact of such optical degradation on post-operative image quality (IQ) of these eyes. This study determined the relation between HOA’s and IQ parameters (peak IQ, dioptric focus that maximized IQ and depth of focus) derived from psychophysical (logMAR acuity) and computational (logVSOTF) through-focus curves in 45 subjects (18 to 31yrs) before and 1-month after refractive surgery and in 40 age-matched emmetropic controls. Computationally derived peak IQ and its best focus were negatively correlated with the RMS deviation of all HOA’s (HORMS) (r≥-0.5; p<0.001 for all). Computational depth of focus was positively correlated with HORMS (r≥0.55; p<0.001 for all) and negatively correlated with peak IQ (r≥-0.8; p<0.001 for all). All IQ parameters related to logMAR acuity were poorly correlated with HORMS (r≤|0.16|; p>0.16 for all). Increase in HOA’s after refractive surgery is therefore associated with a decline in peak IQ and a persistence of this sub-standard IQ over a larger dioptric range, vis-à-vis, before surgery and in age-matched controls. This optical deterioration however does not appear to significantly alter psychophysical IQ, suggesting minimal impact of refractive surgery on the subject’s ability to resolve spatial details and their tolerance to blur.

Simulated prototype of posterior chamber phakic intraocular lens for presbyopia correction

PURPOSE

To evaluate the visual impact of adding different spherical aberration values to an Implantable Collamer Lens phakic intraocular lens (pIOL) to increase the depth of focus using an adaptive optics visual simulator.

SETTING

University of Valencia, Valencia, Spain.

DESIGN

Experimental study.

METHODS

Wavefront aberrations in -3.00 D and -6.00 diopter (D) pIOLs were measured in vitro. Afterward, different simulated pIOL experimental prototypes were created along with variances in the spherical aberration. An adaptive optics visual simulator was used to simulate vision after the implantation of the different pIOL prototypes from their wavefront aberrations. The corrected distance visual acuity (CDVA) and depth of focus were measured in 3.0 and 4.5 mm pupils.

RESULTS

In a 3.0 mm pupil, the CDVA achieved with -3.00 and -6.00 D pIOLs and all pIOL prototypes evaluated was above 20/20 except for a -6.00 D pIOL + spherical aberration 4 at 50% CDVA contrast, which decreased to 20/25. However, in a 4.5 mm pupil, the CDVA obtained with the pIOL prototypes decreased significantly and was more pronounced when the spherical aberration induced was negative. The depth of focus increment was larger with the highest spherical aberration added and with a small pupil. Nevertheless, it was independent of the sign of the added spherical aberration.

CONCLUSIONS

The outcomes show that residual negative spherical aberration after pIOL implantation will disrupt the CDVA. However, some residual positive spherical aberration after pIOL implantation increased the depth of focus with excellent CDVA, providing a possible pIOL design for young presbyopic patients.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Adaptive optics vision simulation and perceptual learning system based on a 35-element bimorph deformable mirror

An adaptive optics visual simulation combined with a perceptual learning (PL) system based on a 35-element bimorph deformable mirror (DM) was established. The larger stroke and smaller size of the bimorph DM made the system have larger aberration correction or superposition ability and be more compact. By simply modifying the control matrix or the reference matrix, select correction or superposition of aberrations was realized in real time similar to a conventional adaptive optics closed-loop correction. PL function was first integrated in addition to conventional adaptive optics visual simulation. PL training undertaken with high-order aberrations correction obviously improved the visual function of adult anisometropic amblyopia. The preliminary application of high-order aberrations correction with PL training on amblyopia treatment was being validated with a large scale population, which might have great potential in amblyopia treatment and visual performance maintenance.

In vitro optical performance of a new aberration-free intraocular lens

PURPOSE

To assess the optical performance of the new EnVista intraocular lens (IOL).

MATERIALS AND METHODS

Four aspheric IOLs were evaluated; the new EnVista is one amoung them. This IOL, similarly to the Z-Flex HB and the Bi-Flex 1.8 667AB ones, has a neutral aspheric design, whereas the fourth IOL under test (AcrySof IQ IOL SN60WF) presents a negative spherical aberration (SA). The IOL's aberration patterns were measured in vitro, by setting them up on an optical bench. From these aberration-pattern data, the modulation transfer function (MTF), the average modulation values, and the points spread function (PSF) were calculated. Furthermore, in order to assess the potential optical quality that these IOLs would yield once they are implanted, an average corneal-aberration pattern was juxtaposed to the in-vitro profiles and the same parameters were calculated again.

RESULTS

For the IOL-only scenario (ie, without including the corneal factor), it was the EnVista IOL, which is aberration-free that showed the higher MTF, PSF values. This was followed by the other two aberration-free IOL models. However, when the effect of an average corneal pattern was also taken into consideration, the AcrySof IQ IOL SN60WF always outperformed the other neutral-asphericity IOLs.

CONCLUSIONS

The in-vitro optical performance of the EnVista IOL was good, but it decreases substantially in a whole-eye scenario, when the wavefront profile of an average cornea is added. Other designs with different degrees of SA should be considered for this IOL in order to surpass these results.

Visual simulation through an aspheric aberration-correcting intraocular lens in subjects with different corneal profiles using adaptive optics

BACKGROUND

The aim of this study was to analyse the visual quality of the AcrySof IQ SN60WF(®) intraocular lens (IOL) when combined with different corneal profiles.

METHODS

Ten eyes of 10 participants with no prior history of refractive or cataract surgery were evaluated. An adaptive optics visual simulator was used to simulate the wavefront aberration pattern of an aspheric aberration-correcting IOL (AcrySof IQ SN60WF(®)). Normal corneas (group A), low and high myopic corneal ablations (groups B and C, respectively) and low and high hyperopic corneal ablations (groups D and E, respectively) were also simulated. Monocular distance visual acuities at 100, 50 and 10 per cent of contrast were measured.

RESULTS

At 100, 50 and 10 per cent contrast, no differences were found between groups A and B (p > 0.06 for all contrasts). Group A obtained better values than groups C, D and E for all contrasts (p = 0.031, p = 0.038, p = 0.032 at 100, 50 and 10 per cent of contrast, respectively). At the same time, group B obtained better values than groups C, D and E (p = 0.041, p = 0.042, p = 0.036 at 100, 50 and 10 per cent of contrast, respectively). Within the five groups, the worst results were always obtained for group E (p = 0.017, p = 0.021 and p = 0.025 at 100, 50 and 10 per cent of contrast, respectively).

CONCLUSIONS

The results suggest that the aspheric aberration-correcting IOL studied provides comparable results, when it is combined with normal corneas and with corneas with simulated low myopic ablations. When negative amounts of residual spherical aberration after cataract surgery are expected to be achieved, IOLs with more positive spherical aberration should be considered.

Adaptive Optics for Visual Simulation

A revision of the current state-of-the-art adaptive optics technology for visual sciences is provided. The human eye, as an optical system able to generate images onto the retina, exhibits optical aberrations. Those are continuously changing with time, and they are different for every subject. Adaptive optics is the technology permitting the manipulation of the aberrations, and eventually their correction. Across the different applications of adaptive optics, the current paper focuses on visual simulation. These systems are capable of manipulating the ocular aberrations and simultaneous visual testing though the modified aberrations on real eyes. Some applications of the visual simulators presented in this work are the study of the neural adaptation to the aberrations, the influence of aberrations on accommodation, and the recent development of binocular adaptive optics visual simulators allowing the study of stereopsis.

Depth of focus through different intraocular lenses in patients with different corneal profiles using adaptive optics visual simulation

PURPOSE

To evaluate the depth of focus with monofocal intraocular lenses (IOLs) in patients with different corneal profiles using adaptive optics (AO) visual simulation.

METHODS

An AO visual simulator (crx1, Imagine Eyes) was used to simulate the aberration pattern of three monofocal IOLs (Acrysof IQ SN60WF [Alcon Laboratories Inc]; Akreos Adapt AO [Bausch & Lomb]; and Triplato [AJL Ophthalmic]) of different optic designs. Five groups were considered: patients without any corneal refractive surgery (normal cornea group) and with prior low and high myopic and hyperopic ablations (low myopic ablation, high myopic ablation, low hyperopic ablation, and high hyperopic ablation groups). Defocus curves for all situations were measured, with the target being moved from -5.00 to +2.50 diopters (D) in 0.25-D steps, and visual acuity was measured at all vergences.

RESULTS

Ten eyes from 10 patients were evaluated. The higher residual spherical aberration (SA) for all IOLs was obtained for the high myopic ablation group and the most negative residual SA was obtained for the high hyperopic ablation group. The best compromise between distance visual and depth of focus for the normal cornea, low myopic ablation, and high myopic ablation groups was obtained with the aspheric designs, whereas the best results for the low hyperopic and high hyperopic ablation groups were obtained with the spherical IOL.

CONCLUSIONS

The results of this study suggest that the better compromise between distance visual acuity and depth of focus with the three IOLs and the different corneal profiles relies on a certain amount of positive SA. Above a certain limit of residual SA (positive or negative), visual acuity decreases at all vergences, worsening the depth of focus.

Adaptive optics for studying visual function: a comprehensive review

Compared to most ophthalmic technologies, adaptive optics, or AO, is relatively young. The first working systems were presented in 1997 and, owing in part to its complexity, the development of AO systems has been relatively slow. Nevertheless, AO for vision science is coming of age and the scope of applications continues to increase. Applications of AO can be broadly split along two lines; for retinal imaging and for testing visual function. This review will focus on the applications of adaptive optics for testing visual function. Since this represents only a subset of the field of AO for ophthalmoscopy, it is possible to cite virtually every paper that has been published in the field to date. As such, this is a comprehensive review whose intent is to get all readers up to speed on the state of the art. More importantly, perhaps, this review will focus on the types of science that can be accomplished with AO with a view to future applications. The reference list alone is informative, since the reader will quickly discover that the community that is using AO for vision science is rather small. Looking at the dates for the cited papers, the reader will also discover that the field is rapidly expanding.

Imaging single cells in the living retina

A quarter century ago, we were limited to a macroscopic view of the retina inside the living eye. Since then, new imaging technologies, including confocal scanning laser ophthalmoscopy, optical coherence tomography, and adaptive optics fundus imaging, transformed the eye into a microscope in which individual cells can now be resolved noninvasively. These technologies have enabled a wide range of studies of the retina that were previously impossible.