Evolution of operating microscopes and development of 3D visualization systems for intraocular surgery.

The recent development of high-resolution, heads-up, 3D visualization microscopy systems has provided new technical and visualization options for ophthalmic surgeons. In this review, we explore the evolution of microscope technologies, the science behind modern 3D visualization microscopy systems, and the practical benefits (as well as disadvantages) that these systems provide over conventional microscopes for intraocular surgical practice. Overall, modern 3D visualization systems reduce the requirements for artificial illumination and provide enhanced visualization and resolution of ocular structures, improving ergonomics, and facilitating a superior educational experience. Even when considering their disadvantages, such as those related to technical feasibility, 3D visualization systems have an overall positive benefit/risk ratio. It is hoped these systems will be adopted into routine clinical practice, pending further clinical evidence on the benefits they may provide on clinical outcomes.

Defocus curves: focusing on factors influencing assessment.

Defocus curve assessment is used to emulate defocus over a range of distances and is a valuable tool that is used to differentiate the performance of presbyopia-correcting intraocular lenses. However, defocus curves are limited by a lack of standardization, and multiple factors can affect their generation and interpretation. This review discusses key factors that influence the assessment of defocus curves, including pupil size, level of contrast, sphere vs cylinder defocus, viewing distance, monocular vs binocular assessment, use of Snellen vs logMAR charts, and diopter range and step size. Moreover, different methods to analyze defocus curves, including the direct comparison method, range-of-focus analysis, and area under the curve analysis, can affect result interpretation. A good understanding of these factors and standardization of the methodology are important to ensure optimal cross-study comparisons.

Refractive Outcomes after Cataract Surgery.

A post-operative manifest refractive error as close as possible to target is key when performing cataract surgery with intraocular lens (IOL) implantation, given that residual astigmatism and refractive errors negatively impact patients' vision and satisfaction. This review explores refractive outcomes prior to modern biometry; advances in biometry and its impact on patients' vision and refractive outcomes after cataract surgery; key factors that affect prediction accuracy; and residual refractive errors and the impact on visual outcomes. There are numerous pre-, intra-, and post-operative factors that can influence refractive outcomes after cataract surgery, leaving surgeons with a small "error budget" (i.e., the source and sum of all influencing factors). To mitigate these factors, precise measurement and correct application of ocular biometric data are required. With advances in optical biometry, prediction of patient post-operative refractory status has become more accurate, leading to an increased proportion of patients achieving their target refraction. Alongside improvements in biometry, advancements in microsurgical techniques, new IOL technologies, and enhancements to IOL power calculations have also positively impacted patients' refractory status after cataract surgery.

Biometric assessment of pseudophakic subjects during objective accommodative stimulation: a prospective observational study.

CLINICAL RELEVANCE: Ultrasound biomicroscopy is an objective method for assessing changes in anterior segment biometry. There is a paucity of data on the reliability of this method. A reliable method for assessing anterior segment changes during physiologically driven accommodation can be a useful tool for clinicians, researchers, and industry. BACKGROUND: To assess the test-retest reliability of ultrasound biomicroscopy for measurements of change in anterior chamber depth during a distance to near fixation task in pseudophakic subjects. METHODS: Subjects were adults with monofocal intraocular lenses implanted in both eyes who completed a 6-month post-operative period and had monocular uncorrected distance visual acuity of 6/15 (0.4 logMAR) or better. The change in anterior chamber depth during a distance to near fixation task was measured with a 35-MHz VuMAX HD ultrasound biomicroscopy device (Sonomed Escalon, New Hyde Park, NY) during two separate visits. An asymmetrical vergence paradigm allowed evaluation of anterior segment biometry at 22-µm axial resolution in one eye, while the fellow eye fixated on the target. To assess the test-retest reliability, 2-sided 95% CI from a paired t test was calculated for the difference in anterior chamber depth change from distance to near between visits. RESULTS: The mean (standard deviation) near-focused anterior chamber depth measured by ultrasound biomicroscopy was 4.331 (0.237) and 4.333 (0.241) mm at visits 1 and 2, respectively. In response to a change in fixation from distance (4 m) to near (40 cm), the mean anterior chamber depth change was -0.012 (0.038) and 0.003 (0.039) mm at visits 1 and 2, respectively. Analysis of the difference in the change in anterior chamber depth between visits was -0.015 mm (95% CI, -0.035 to 0.003). CONCLUSION: Ultrasound biomicroscopy is a repeatable, objective method for assessing change in anterior segment biometry during physiological changes in fixation from distance to near.

New methodology for measuring intraocular lens performance using acuity reserve.

PURPOSE: To validate a new methodology of intraocular lens (IOL) assessment using acuity reserve analysis via area under the curve (AUC) to assess intermediate vision. SETTING: Study 1 was conducted at 17 sites in Australia, Chile, and Europe. Study 2 was conducted at 15 sites in Australia, Brazil, and Europe. DESIGN: Post hoc analyses of defocus curve results from 2 clinical trials (study 1: single-arm investigation of the AcrySof IQ PanOptix Trifocal IOL [model TFNT00; Alcon Research LLC]; study 2: comparative investigation of AcrySof PanOptix Trifocal IOL vs the AT LISA Trifocal IOL [model 839MP; Carl Zeiss Meditec AG]). METHODS: Acuity reserve was calculated using AUC compared with visual demand (logMAR) at various distances. Study 1 validated the model; study 2 compared acuity reserve, for a range of defocus levels, for the 2 IOLs. RESULTS: The defocus curve (study 1 [149 patients; 298 eyes]) showed good visual acuity (ie, >20/25) at all defocus levels; the AUC estimate showed 2 lines or more of reserve at -2.50 diopters. Comparative post hoc analysis (study 2 [182 patients]) demonstrated significantly improved acuity reserve with PanOptix IOL vs AT LISA IOL at 20 to 40 days postoperatively (P < .001) and 120 to 180 days postoperatively (P < .001). CONCLUSIONS: Acuity reserve analysis using AUC represents a new methodology for comparative IOL assessment, providing additional detail beyond defocus curve analysis. This method demonstrated that the PanOptix Trifocal IOL was superior to the AT LISA Trifocal IOL (model 839MP) for visual acuity at near to intermediate distances with visual acuity reserve analysis.

Measures of visual disturbance in patients receiving extended depth-of-focus or trifocal intraocular lenses.

The degree of visual disturbance associated with a particular model of intraocular lens (IOL) depends on several factors, including IOL optic, material, and mechanics. Characterization of visual disturbance profiles is paramount for informing clinical IOL selection. Although many studies evaluating presbyopia-correcting IOLs include subjective assessment of visual symptoms, the types of patient-reported outcome measures (PROMs) used to capture these outcomes are inconsistent across studies, complicating data contextualization. Furthermore, some tools produce more meaningful results than others. This review presents a discussion on the scientific literature published on the subjective and semiobjective (halo and glare simulator, light-distortion analyzer, vision monitor, and halometers) methods used to assess visual disturbances in patients implanted with trifocal or extended depth-of-focus IOLs, highlighting their advantages and limitations. It underscores the importance of between-study comparisons and the need for standardized PROMs in clinical IOL research to provide more accurate information for IOL selection.

Visual Demand and Acuity Reserve of Chinese versus English Newspapers.

SIGNIFICANCE: This study suggests that Chinese newspaper characters are more legible than English newspaper letters. Characters in Chinese newspapers have higher acuity reserve than English newspapers. PURPOSE: The purpose of this study was to evaluate visual demand and acuity reserve for Chinese newspapers in comparison with published data on U.S. newspapers. METHODS: The test distances for visual acuity in Chinese clinical studies were reviewed systematically. Characters from different sections of newspapers printed in simplified Chinese were evaluated. The character height, frequency, and visual demand and acuity reserve of each newspaper section were determined for Chinese characters of the six different levels of complexity. RESULTS: More than 70% of Chinese clinical studies measure near visual acuity at either 33 or 40 cm. The height of Chinese characters ranged from 1.95 to 3.28 mm across different sections of five newspapers compared with 1.0 to 2.0 mm for English letters. The frequency of Chinese characters from least to most complex ranged from 7 to 34% across 12 sections of one Chinese newspaper. The angular threshold across the six complexity levels of Chinese characters ranged from 4.62 to 5.93 arcmin (0.54 to 0.69 mm at 40-cm reading distance) with a weighted angular threshold of 5.18 arcmin compared with 3.37 arcmin (0.39 mm) for the English letters. For Chinese newspapers, at 40-cm reading distance, the acuity reserve for the smallest and largest median size was 3.55 and 4.61, respectively. CONCLUSIONS: Chinese characters are larger than English characters in all newspaper sections newspapers by a factor of 1.60 to 2.34. Given that Chinese characters need to be 1.54 times larger than English letters to provide the same acuity reserve, on average, Chinese newspapers are more legible than U.S. English newspapers.

Extended depth-of-focus technology in intraocular lenses.

The extended depth-of-focus (EDOF) intraocular lens (IOL) is an emerging technology that is designed to improve range of vision, especially at intermediate distances. In this review, we describe the clinical performance of 4 emerging EDOF IOL technologies; that is, small aperture, bioanalogic, diffractive optics, and nondiffractive optical manipulations. The American Academy of Ophthalmology generated a consensus statement for EDOF IOLs that provided benchmarks and recommendations for classifying an implant as an EDOF IOL as well as standardized testing criteria for evaluating performance. Although many types of EDOF technologies are being developed, there are important differences in their performance that require further testing and evaluation.

Metric-Based Visual Acuity and Defocus Curve Simulation of Two Multifocal Intraocular Lens Models.

PURPOSE: To predict clinical defocus curve performance of the PanOptix intraocular lens (IOL) model TFNT00, a population-based image quality metric was applied to a pseudophakic eye model. METHODS: Visual acuity (VA) was simulated using a 2-surface reduced eye model. For each virtual eye, the derived corneal surface was combined with scaled IOL surface. Corneal power and aberration, anterior chamber depth, and pupil size were iterated using a Monte-Carlo approach. Image quality of the IOLs was assessed using the total aberration map to compute the amplitude point spread function. A diffraction-normalized light-in-the-bucket metric was calculated for each virtual eye for defocuses from -3.5 D to +1.0 D (step size 0.25 D) and transformed to VAs and defocus curves. Simulated VA for the ReSTOR +3.0 D lens was used to generate a calibration function by linear regression correlation of simulated data with clinical VA data. Simulated TFNT00 VA was then validated by comparing defocus curves to clinical TFNT00 data. RESULTS: From -3.5 D to +1.0 D, the simulated defocus curve was generally consistent with the defocus curve from the TFNT00 clinical trial. The mean absolute difference was 0.022 logMAR (~1 letter) for simulated VA versus clinical trial VA. CONCLUSION: IOL image quality can be assessed using a population-based virtual eye model to simulate VA and predict clinical performance. Computational modeling and simulation can be applied to future IOL development before clinical trials are conducted.

The Effects of Blue Light-Filtering Intraocular Lenses on the Protection and Function of the Visual System.

Filtration of high-energy short-wave visible light (blue light) to improve vision and protect against damage has evolved both in aquatic animals and terrestrial species. In humans, pigments in the inner layer of the macula absorb wavelengths between 400 and 520 nm and function to improve visual performance. In patients who undergo cataract surgery, replacing cataractous lenses with artificial intraocular lenses (IOLs) that do not mimic normal healthy adult lenses could result in preventable negative visual effects, including glare disability. Blue light-filtering (BLF) IOLs were designed to filter short-wave light in addition to ultraviolet light and mimic the natural crystalline lens. Current studies indicate that BLF IOLs may provide protection from blue light-induced retinal damage and slow the development and progression of age-related macular degeneration. Additionally, BLF IOLs have been shown to improve chromatic contrast, reduce photostress recovery time, reduce glare disability and discomfort, and generally improve visual performance under glare conditions. Although a number of concerns have been raised about the relative risks versus the benefits of BLF IOLs, recent studies reported no adverse effects on visual function or contrast under photopic conditions, no long-term effects on color vision, and no detrimental effects on circadian rhythms with BLF IOLs. Based on the current understanding of the field, evidence suggests that BLF IOLs would be returning the eye to a more natural state compared with non-BLF lenses.

Long-term effectiveness and safety of a three-piece acrylic hydrophobic intraocular lens modified with hydroxyethyl-methacrylate: an open-label, 3-year follow-up study.

BACKGROUND: Clareon® is a new hydrophobic acrylic optic biomaterial designed for enhanced clarity and greater resistance to glistening. The present study evaluated the effectiveness and safety of a three-piece hydrophobic, monofocal intraocular lens (IOL) Model MA60NM, made of this new optic material. METHODS: In this prospective, multicenter, open-label study, eligible patients aged ≥60 years, underwent a unilateral implantation with IOL Model MA60NM following phacoemulsification. Patients were followed-up for up to 3 years after implantation. Visual outcome and serious adverse events (SAEs, cumulative and persistent) were compared to ISO grid rates (BS EN ISO 11979-7:2006). The primary effectiveness variable was Best Spectacle-Corrected Visual Acuity (BSCVA) at 1-year postoperative follow-up. In addition, posterior capsular opacification (PCO) was assessed qualitatively and graded by slit lamp exam on a 5-point scale at all visits. RESULTS: Overall, 179 and 138 patients completed the 1-year and 3-year postoperative follow-up, respectively. The BSCVA outcomes were better with IOL Model MA60NM than the ISO grid rates with 95.5% of patients at 1 year and 94.2% of patients at 3 years having achieved a BSCVA of 20/40 or better vs 92.5% in ISO grid. The incidence of cumulative or persistent SAEs was lower after Model MA60NM implantation than the ISO grid reference. The incidence of clinically significant PCO was 1.1% at the 1-year and 2.2% at the 3-year visit. Posterior capsulotomy rate was 1.1% at 1 year and 1.4% at 3 years. CONCLUSION: The three-piece hydrophobic, monofocal IOL Model MA60NM was effective for the visual correction of aphakia and successfully met all the safety parameters as defined by the ISO criteria. PCO and posterior capsulotomy rates were low over the 3-year follow-up period. This study provides evidence and supports the long-term safety and effectiveness of the new optic biomaterial Clareon®.

Accommodation and pupil responses to random-dot stereograms / Respuestas acomodativa y pupilar a los estereogramas de puntos aleatorios

We investigated the dynamics of accommodative and pupillary responses to random-dot stereograms presented in crossed and uncrossed disparity in six visually normal young adult subjects (mean age=25.8±3.1 years). Accommodation and pupil measures were monitored monocularly with a custom built photorefraction system while subjects fixated at the center of a random-dot stereogram. On each trial, the stereogram initially depicted a flat plane and then changed to depict a sinusoidal corrugation in depth while fixation remained constant. Increase in disparity specified depth resulted in pupil constriction during both crossed and uncrossed disparity presentations. The change in pupil size between crossed and uncrossed disparity conditions was not significantly different (p>0.05). The change in pupil size was also accompanied by a small concomitant increase in accommodation. In addition, the dynamic properties of pupil responses varied as a function of their initial (starting) diameter. The finding that accommodation and pupil responses increased with disparity regardless of the sign of retinal disparity suggests that these responses were driven by apparent depth rather than shifts in mean simulated distance of the stimulus. Presumably the need for the increased depth of focus when viewing stimuli extended in depth results in pupil constriction which also results in a concomitant change in accommodation. Starting position effects in pupil response confirm the non-linearity in the operating range of the pupil (AU)

Investigamos la dinámica de las respuestas acomodativa y pupilar a los estereogramas de puntos aleatorios (RDS) que se presentaron en disparidad cruzada y no cruzada en seis sujetos jóvenes adultos con visión normal (edad media= 25,8±3,1 años). Se supervisaron monocularmente las respuestas acomodativa y pupilar con un sistema de foto-refracción desarrollado para tal fin, mientras los sujetos fijaban la vista en el centro de un estereograma de puntos aleatorios. En cada prueba, el estereograma representaba inicialmente un plano liso, representando a continuación una ondulación sinusoidal en profundidad, mientras que la fijación permanecía constante. El incremento de la profundidad debido a la disparidad dio lugar a una constricción de la pupila durante las presentaciones de disparidad cruzada y no cruzada. El cambio del tamaño pupilar en las situaciones de disparidad cruzada y no cruzada no resultó significativamente diferente (p>0,05). El cambio del tamaño pupilar se vio también acompañado de un pequeño incremento acomodativo concomitante. Además, las propiedades dinámicas de las respuestas pupilares variaron en función de su diámetro inicial (de partida). El hallazgo del incremento de las respuestas acomodativa y pupilar con la disparidad, independientemente del signo de la disparidad retiniana, sugiere que dichas respuestas fueron impulsadas por la profundidad aparente, en lugar de deberse a los cambios en la distancia simulada media del estímulo. Presumiblemente, la necesidad de un incremento de enfoque al visionar los estímulos ampliados en profundidad deriva en una constricción pupilar, que deriva a su vez en un cambio acomodativo concomitante. Los efectos de la posición de partida sobre la respuesta pupilar confirman la no linealidad del rango operativo de la pupila (AU)

Accommodation and pupil responses to random-dot stereograms.

We investigated the dynamics of accommodative and pupillary responses to random-dot stereograms presented in crossed and uncrossed disparity in six visually normal young adult subjects (mean age=25.8±3.1 years). Accommodation and pupil measures were monitored monocularly with a custom built photorefraction system while subjects fixated at the center of a random-dot stereogram. On each trial, the stereogram initially depicted a flat plane and then changed to depict a sinusoidal corrugation in depth while fixation remained constant. Increase in disparity specified depth resulted in pupil constriction during both crossed and uncrossed disparity presentations. The change in pupil size between crossed and uncrossed disparity conditions was not significantly different (p>0.05). The change in pupil size was also accompanied by a small concomitant increase in accommodation. In addition, the dynamic properties of pupil responses varied as a function of their initial (starting) diameter. The finding that accommodation and pupil responses increased with disparity regardless of the sign of retinal disparity suggests that these responses were driven by apparent depth rather than shifts in mean simulated distance of the stimulus. Presumably the need for the increased depth of focus when viewing stimuli extended in depth results in pupil constriction which also results in a concomitant change in accommodation. Starting position effects in pupil response confirm the non-linearity in the operating range of the pupil.

Reduced effect of glare disability on driving performance in patients with blue light-filtering intraocular lenses.

PURPOSE: To compare the effects of glare on driving performance in patients who had implantation of a blue light-filtering acrylic intraocular lens (IOL) and those who had implantation of an acrylic IOL with no blue-light filter. SETTING: Department of Applied Psychology, Arizona State University, Mesa, Arizona, USA. DESIGN: Cross-sectional study. METHODS: Patients with a blue light-filtering AcrySof Natural SN60AT IOL (study group) and patients with an AcrySof SA60AT IOL with no blue-light filter (control group) who had good visual acuity and a valid driver's license performed left-turn maneuvers in a driving simulator in front of oncoming traffic. The safety margin (time to collision minus time taken to turn at intersection with oncoming traffic) was calculated. The measurements were repeated with a glare source simulating low-angle sun conditions (daytime driving). RESULTS: With glare, the safety margin was statistically significantly greater in the study group (n = 17) than in the control group (n = 17) (mean 2.534 seconds ± 0.488 [SD] and 2.116 ± 0.511 seconds, respectively) (P < .05). Comparing no-glare conditions and glare conditions, the study group had significantly lower glare susceptibility, fewer collisions with the oncoming car, and a lower impact on intersection approach speed than the control group. CONCLUSIONS: The IOL incorporating blue light-filtering technology significantly reduced glare disability and improved the driver's ability to safely execute a left turn with oncoming traffic in the presence of glare simulating low-angle sun conditions. The real-world benefit of this technology is presumably mediated by a stronger signal to detect approaching objects (motion-in-depth) as a result of a reduction in glare disability. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

Dynamic photorefraction system: an offline application for the dynamic analysis of ocular focus and pupil size from photorefraction images.

Eccentric photorefraction is an optical technique used to assess static and/or dynamic changes in ocular focus (accommodation), ocular alignment (vergence) and pupil size. In this paper, we have developed and tested an offline application namely the dynamic photorefraction system (DPRS) which allows an accurate analysis of accommodation and pupil size from eccentric photorefraction images. The application uses the Microsoft componentized technology known as the Component Object Model (COM), includes distinct libraries for importing photorefraction videos and provides an accurate analysis and output of pupil size and accommodation. In addition, the system can interface with any custom built photorefractor allowing a widespread application in vision science experiments involving simultaneous measures of ocular focus and pupil size.

Vergence accommodation and monocular closed loop blur accommodation have similar dynamic characteristics.

Retinal blur and disparity are two different sensory signals known to cause a change in accommodative response. These inputs have differing neurological correlates that feed into a final common pathway. The purpose of this study was to investigate the dynamic properties of monocular blur driven accommodation and binocular disparity driven vergence-accommodation (VA) in human subjects. The results show that when response amplitudes are matched, blur accommodation and VA share similar dynamic properties.

Application of video-based technology for the simultaneous measurement of accommodation and vergence.

Accommodation and vergence are two ocular motor systems that interact during binocular vision. Independent measurement of the response dynamics of each system has been achieved by the application of optometers and eye trackers. However, relatively few devices, typically earlier model optometers, allow the simultaneous assessment of accommodation and vergence. In this study we describe the development and application of a custom designed high-speed digital photorefractor that allows for rapid measures of accommodation (up to 75Hz). In addition the photorefractor was also synchronized with a video-based stereo eye tracker to allow a simultaneous measurement of accommodation and vergence. Analysis of accommodation and vergence could then be conducted offline. The new instrumentation is suitable for investigation of young children and could be potentially used for clinical populations.