Vision with different presbyopia corrections simulated with a portable binocular visual simulator

Head-mounted adaptive optics visual simulator

Adaptive optics visual simulation is a powerful tool for vision testing and evaluation. However, the existing instruments either have fixed tabletop configurations or, being wearable, only offer the correction of defocus. This paper proposes a novel head-mounted adaptive optics visual simulator that can measure and modify complex ocular aberrations in real-time. The prototype is composed of two optical modules, one for the objective assessment of aberrations and the second for wavefront modulation, all of which are integrated into a wearable headset. The device incorporates a microdisplay for stimulus generation, a liquid crystal on silicon (LCoS) spatial light modulator for wavefront manipulation, and a Hartmann-Shack wavefront sensor. Miniature optical components and optical path folding structures, together with in-house 3D printed mounts and housing, were adapted to realize the compact size. The system was calibrated by characterizing and compensating the internal aberrations of the visual relay. The performance of the prototype was analyzed by evaluating the measurement and compensation of low-order and higher-order aberrations induced through trial lenses and phase masks in an artificial eye. The defocus curves for a simulated bifocal diffractive lens were evaluated in real eyes. The results show high accuracy while measuring and compensating for the induced defocus, astigmatism, and higher-order aberrations, whereas the MTF analysis shows post-correction resolution of up to 37.5 cycles/degree (VA 1.25). Moreover, the subjective test results show the defocus curves closely matched to a commercial desktop visual simulator.

Defocus flicker of chromatic stimuli deactivates accommodation

Tunable lenses, optical elements able to change their optical power within milliseconds, constitute an emerging technology increasingly used in ophthalmic applications. In this study, 25 subjects looked through tunable lenses at a chromatic stimulus to evaluate the perceptual response of the human visual system to periodic changes in defocus of 0.25D of amplitude and 15 Hz of temporal frequency. These defocus changes produce flicker and chromatic distortions that change with the overall level of defocus. The task in this study was to minimize the flicker by varying the average optical power, and it was performed for different myopic and hyperopic starting points. Subjects also performed a blur-minimization task in a black-and-white stimulus of the same geometry. The flicker-minimization task is more repeatable than the blur-minimization task (standard deviations ±0.17D and ±0.49D). The time per repetition of the flicker-minimization task is only 38s. Cycloplegia severely affects the blur-minimization, but not the flicker-minimization task, confirming that defocus flicker deactivates the accommodative system. This discovery can be used to develop new methods for measuring the refractive error of the eye that does not require supervision and can potentially improve existing subjective methods in terms of accuracy, precision, and measurement time.

Monovision Correction Preference and Eye Dominance Measurements

Purpose

To propose new methods for eye selection in presbyopic monovision corrections.

Methods

Twenty subjects with presbyopia performed two standard methods of binary eye dominance identification (sensory with +1.50 diopters [D ]and +0.50 D and sighting with "hole-in-the-card") and two psychophysical methods of perceived visual quality: (1) the Preferential test, 26 natural images were judged with the near addition in one eye or in the other in a 2-interval forced-choice task, and the Eye Dominance Strength (EDS) defined as the proportion of trials where one monovision is preferred over the other; (2) the Multifocal Acceptance Score (MAS-2EV) test, the perceived quality of a natural images set (for 2 luminance levels and distances) was scored and EDS defined as the score difference between monovision in one eye or the other. Left-eye and right-eye dominance are indicated with negative and positive values, respectively. Tests were performed using a Simultaneous Vision Simulator, which allows rapid changes between corrections.

Results

Standard sensory and sighting dominances matched in only 55% of subjects. The Preferential EDS (ranging from -0.7 to +0.9) and MAS-2EV EDS (ranging from -0.6 to +0.4) were highly correlated. Selecting the eye for far in monovision with the MAS-2EV, sensory, or sighting tests would have resulted in 79%, 64%, and 43% success considering the Preferential test as the gold standard.

Conclusions

Tests based on perceptual preference allow selection of the preferred monovision correction and measurement of dominance strength.

Translational Relevance

The binocular visual simulator allows efficient implementation of eye preference tests for monovision in clinical use.

Adaptive optics visual simulators: a review of recent optical designs and applications [Invited]

In their pioneering work demonstrating measurement and full correction of the eye's optical aberrations, Liang, Williams and Miller, [JOSA A14, 2884 (1997)10.1364/JOSAA.14.002884] showed improvement in visual performance using adaptive optics (AO). Since then, AO visual simulators have been developed to explore the spatial limits to human vision and as platforms to test non-invasively optical corrections for presbyopia, myopia, or corneal irregularities. These applications have allowed new psychophysics bypassing the optics of the eye, ranging from studying the impact of the interactions of monochromatic and chromatic aberrations on vision to neural adaptation. Other applications address new paradigms of lens designs and corrections of ocular errors. The current paper describes a series of AO visual simulators developed in laboratories around the world, key applications, and current trends and challenges. As the field moves into its second quarter century, new available technologies and a solid reception by the clinical community promise a vigorous and expanding use of AO simulation in years to come.

A Novel Intraocular Lens Simulator that Allows Patients to Experience the World Through Multifocal Intraocular Lenses Before Surgeries

Purpose

The purpose of this study was to investigate whether the intraocular lens (IOL) simulator can simulate how the world appears to patients with multifocal IOLs by allowing the patients to see far and near objects through the IOL simulator.

Methods

Twenty eyes from 20 patients (age = 50-70 years old) were included in the study. The IOL simulator we developed consists of a trial lens frame adapter, a lens tube, a concave lens, a spacer, a wet cell, and an IOL. We used two IOLs: Tecnis monofocal and Tecnis bifocal IOL (add +3.25 diopter [D]). Patients wore a trial lens frame with an IOL simulator on distant corrected trial lenses and underwent the following tests: defocus curve, satisfaction with distance and near vision, halo around the light, and near point accommodation (NPA). To check how the world appears to the patients through this simulator, a machine vision lens and a scientific camera were attached to the simulator, and far and near objects were photographed.

Results

In the defocus curve of multifocal IOL, the visual acuity showed the second peak at -4 D. Compared to monofocal IOL, satisfaction with distant vision was slightly worse, more halos were felt, satisfaction with near vision was higher, and the NPA was shorter in multifocal IOL. In the scientific camera test, through the multifocal IOL, the waiting room was blurry, the halo around the ceiling light was prominent, and the characteristics on the near visual acuity chart were clear.

Conclusion

Subjects could experience the functions of multifocal IOLs with our newly developed IOL simulator.

Translational Relevance

This IOL simulator using geometric optics allows patients to experience the function of multifocal IOLs before cataract surgery.

In Vitro Optical Performance of Multifocal and Extended Depth-of-Focus Intraocular Lenses in Spherical Aberration Conditions

ABSTRACT

PurposeTo evaluate and compare the optical performances of 4 different types of intraocular lenses (IOLs) in various spherical aberration (SA) conditions.SettingPOSTECH, Pohang, Republic of Korea.DesignIn vitro laboratory study.MethodsA custom optical bench system with adaptive optics (AO) was used. A monofocal IOL, a bifocal IOL, a trifocal IOL, and an extended depth-of-focus (EDOF) IOL from the Zeiss were evaluated by measuring through-focus modulation transfer function (MTF) as a function of vergence. MTF changes with SA from -0.1μm to +0.1μm with 0.05μm step size were analyzed and compared.ResultsIn aberration free condition, the 4 IOLs showed different MTF curves consistent with their designs In SA conditions, all the IOLs showed MTF value decreases and the decrease rates at the far focus varied from 28% to 38% per 0.1μm SAs. The trifocal IOL had low MTF values at the intermediate focus in the noise level with ±0.1μm SAs.ConclusionsAll the tested IOLs showed MTF decreases with SA in different levels. The trifocal and EDOF IOLs were the most and least sensitive to SA among the evaluated IOLs. The study results might be useful in the selection of IOLs for cataract patients with SAs.

Simulating Outcomes of Cataract Surgery: Important Advances in Ophthalmology

As the human eye ages, the crystalline lens stiffens (presbyopia) and opacifies (cataract), requiring its replacement with an artificial lens [intraocular lens (IOL)]. Cataract surgery is the most frequently performed surgical procedure in the world. The increase in IOL designs has not been paralleled in practice by a sophistication in IOL selection methods, which rely on limited anatomical measurements of the eye and the surgeon's interpretation of the patient's needs and expectations. We propose that the future of IOL selection will be guided by 3D quantitative imaging of the crystalline lens to map lens opacities, anticipate IOL position, and develop fully customized eye models for ray-tracing-based IOL selection. Conversely, visual simulators (in which IOL designs are programmed in active elements) allow patients to experience prospective vision before surgery and to make more informed decisions about which IOL to choose. Quantitative imaging and optical and visual simulations of postsurgery outcomes will allow optimal treatments to be selected for a patient undergoing modern cataract surgery.

How does the world appear to patients with multifocal intraocular lenses?: a mobile model eye experiment

Background

To show how the world appear to patients with multifocal intraocular lens (IOL) using a novel mobile model eye.

Methods

The mobile model eye was composed of an artificial cornea, IOL, IOL chamber, and a camera. A monofocal IOL (Tecnis monofocal IOL) and two diffractive multifocal IOL (ReSTOR, Tecnis multifocal IOL) were used in the study. We went outside to take a picture of the scenery. At night, we stood on a road and took pictures to see how the traffic lights and headlights of cars looked. For an indoor analysis, we approached the Early Treatment Diabetic Retinopathy Study (ETDRS) chart to the model eye from a distance of 95 cm to check the multifocal function of the lenses. In the car, we took pictures of the street and a cell phone in turn to check the multifocal function of the lenses.

Results

Two multifocal IOLs showed definite multifocal function. Far objects appeared either similarly clear or slightly hazier (depending on the IOL model) than those with the monofocal IOL. In the night vision, there was a mild or severe halo around light sources compared to those with the monofocal IOL.

Conclusion

We believe that this mobile model eye can be used to evaluate how the real world appear to a patient with a multifocal IOL, to explain multifocal function of the IOLs, and possible complications in the patients, before performing a surgery.