Strategic filtering of high-energy visible light expands neural correlates of functional vision particularly in older participants.

In this study we assessed the neural correlates of functional vision while varying patterns of light filtration. Four filter conditions used relatively flat filtering across the visible spectrum while one filter was a step filter that selectively absorbed violet light (wavelengths below about 415 nm). Neural effects were quantified by measuring the BOLD response ((T2*-based fMRI) while subjects performed a challenging visual task (judging gap direction in Landolt Cs that randomly varied in size). In general (based on p < 0.01 directional criterion not corrected for aggregated error), as filtering increased (less interference by bright light), brain activity associated with the task also increased. This effect, even using the most conservative statistics, was most evident when using the violet filter (especially for the older subjects) despite only reducing the very highest energy portion of the visible spectrum. This finding suggests that filtering can increase neural activity associated with functional vision; such effects might be achievable through filtering just the highest visible energy (violet).

Tear film dynamics of a new soft contact lens.

PURPOSE: To present the objective metrics from a study that evaluated the clinical performance of a senofilcon A contact lens, both with and without a new manufacturing technique. METHODS: This was a single-site, five-visit, controlled, randomised, subject-masked, 2 × 2 crossover study (May-August 2021) with a 2-week lens dispensing period (bilateral wear) and weekly follow-up visits. Healthy adult (18-39 years), habitual spherical silicone hydrogel contact lens wearers were included. The High-definition (HD) Analyzer™ was used to objectively measure the lens-on-eye optical system resulting from the study lenses at 1-week follow-up. Measurements assessed were vision break-up time (VBUT), modulation transfer function (MTF) cutoff, Strehl ratio (SR), potential visual acuity (PVA) for 100% contrast and objective scatter index (OSI). RESULTS: Of the 50 enrolled participants, 47 (94.0%) were randomly assigned to one of the two possible lens wear sequences (test/control or control/test) and dispensed at least one study lens. The estimated odds ratio of VBUT > 10 s was 1.582 (95% confidence interval [CI]: 1.009 to 2.482) in test versus control lens. The least squares mean difference estimates of MTF cutoff, SR and PVA for 100% contrast between test versus control lens were 2.243 (95% CI: 0.012 to 4.475), 0.011 (95% CI: -0.002 to 0.023) and 0.073 (95% CI: -0.001 to 0.147), respectively. The estimated ratio of median OSI between test versus control lens was 0.887 (95% CI: 0.727 to 1.081). The test lens demonstrated superiority over the control lens with respect to VBUT and MTF cutoff. No serious adverse events were reported; eight adverse events (three ocular, five non-ocular) were indicated by six participants during the study. CONCLUSION: The test lens demonstrated an increased probability of having a longer VBUT (>10 s). Future studies may be designed to assess the efficacy and long-term use of the test lens in a larger population.

Unexpected vision performance with photochromic contact lenses in normal and low light conditions: An analysis of two randomized trials / Rendimiento visual inesperado con lentes de contacto fotocromáticos en condiciones normales y de poca luz: un análisis de dos ensayos aleatorios

Purpose: Evaluate the performance of a photochromic contact lens in various lighting conditions throughout the day, including those indoor and outdoor environments where the photochromic contact lens is in a less active or inactive state. Methods: Data from two clinical trials of a photochromic contact lens were analyzed to evaluate its performance in various light environments. Both studies involved a photochromic test lens (ACUVUE® OASYS with Transitions™ Light Intelligent Technology™) and a similar non-photochromic control lens (ACUVUE® OASYS 2-week with HYDRACLEAR® PLUS). The studies were both multi-visit, multi-site, 2-treatment by 3-period randomized crossover (i.e., Test/Control/Control or Control/Test/Test) dispensing studies, with follow-up visits after each 2-week dispensing period. Results: A total of 250 subjects were dispensed lenses across both studies, of which 237 total subjects completed. In situations where exposure to an activating light source is common (e.g., outdoors), the Test lens was preferred nearly 6:1 over the control lens. In situations where exposure to an activating light source is less common – indoors, driving at night, using digital devices –, the Test lens was still preferred over the control lens by margins of 4:1, nearly 4:1, and over 3:1 respectively. The Test lens was superior with respect to quality of vision, ability to see comfortably, clarity of vision, reduction of squinting while using computers and reduction of bright light while driving at night. Conclusion: The photochromic test contact lens was rated superior to a non-photochromic control lens in environmental situations where the lens is in a less active or inactive state.(AU)

The effect of a short-wave filtering contact lens on color appearance.

We assessed the effect of a contact lens that filters short-wavelength (SW) visible light on color appearance. These effects were modeled and measured by direct comparison to a clear contact lens. Sixty-one subjects were enrolled, and 58 completed as cohort; 31 were 18 to 39 years old (mean ± SD, 29.6 ± 5.6), 27 were 40 to 65 years old (50.1 ± 8.1). A double-masked contralateral design was used; participants randomly wore a SW-filtering contact lens on one eye and a clear control lens on the other eye. Subjects then mixed three primaries (including a short-wave primary, strongly within the absorbance of the test lens) until a perceived perfect neutral white was achieved with each eye. Color appearance was quantified using chromaticity coordinates measured with a spectral radiometer within a custom-built tricolorimeter. Color vision in natural scenes was simulated using hyperspectral images and cone fundamentals based on a standard observer. Overall, the chromaticity coordinates of matches that were set using the SW-filtering contact lens (n = 58; x = 0.345, y = 0.325, u' = 0.222, v' = 0.470) and clear contact lens (n = 58; x = 0.344, y = 0.325, u' = 0.223, v' = 0.471) were not significantly different, regardless of age group. Simulations indicated that, for natural scenes, the SW-filtering contact lens that was evaluated changes L/(L+M) and S/(L+M) chromatic contrast by no more than -1.4% to +1.1% and -36.9% to +5.0%, respectively. Tricolorimetry was used to measure color appearance in subjects wearing a SW-filtering lens in one eye and a clear lens in the other, and the results indicate that imparting a subtle tint to a contact lens, as in the SW-filtering lens that was evaluated, does not alter color appearance for younger or older subjects. A model of color vision predicted little effect of the lens on chromatic contrast for natural scenes.

Unexpected vision performance with photochromic contact lenses in normal and low light conditions: An analysis of two randomized trials.

PURPOSE: Evaluate the performance of a photochromic contact lens in various lighting conditions throughout the day, including those indoor and outdoor environments where the photochromic contact lens is in a less active or inactive state. METHODS: Data from two clinical trials of a photochromic contact lens were analyzed to evaluate its performance in various light environments. Both studies involved a photochromic test lens (ACUVUE® OASYS with Transitions™ Light Intelligent Technology™) and a similar non-photochromic control lens (ACUVUE® OASYS 2-week with HYDRACLEAR® PLUS). The studies were both multi-visit, multi-site, 2-treatment by 3-period randomized crossover (i.e., Test/Control/Control or Control/Test/Test) dispensing studies, with follow-up visits after each 2-week dispensing period. RESULTS: A total of 250 subjects were dispensed lenses across both studies, of which 237 total subjects completed. In situations where exposure to an activating light source is common (e.g., outdoors), the Test lens was preferred nearly 6:1 over the control lens. In situations where exposure to an activating light source is less common - indoors, driving at night, using digital devices -, the Test lens was still preferred over the control lens by margins of 4:1, nearly 4:1, and over 3:1 respectively. The Test lens was superior with respect to quality of vision, ability to see comfortably, clarity of vision, reduction of squinting while using computers and reduction of bright light while driving at night. CONCLUSION: The photochromic test contact lens was rated superior to a non-photochromic control lens in environmental situations where the lens is in a less active or inactive state.

The Influence of HEV-Filtering Contact Lenses on Behavioral Indices of Glare.

OBJECTIVES: We assessed the effects of a HEV-filtering contact lens on positive dysphotopsia (halos and starbursts) and a behavioral index of scatter measured using two-point light thresholds. These effects were assessed by direct comparison to a clear (i.e., non-HEV filtering) contact lens tested in the fellow eye. METHODS: Sixty-one subjects were randomized and fit with study lenses and 58 subjects completed the study. A double-masked contralateral design was used. Subjects were randomized to test lens-OD, control lens-OS, or vice versa. Participants were exposed to a point source of broadband simulated sunlight (a 403-nm condition was also tested) that created the appearance of halos/starbursts. The degree of dysphotopsia was measured as the diameter of broadband and violet-induced halos, and broadband light-induced starbursts. Two-point thresholds were assessed as the minimum resolvable distance between two pinpoints of light. RESULTS: The HEV-filtering lens was statistically superior ( P <0.0001) to the clear lens in all the conditions tested. The HEV-filtering lens significantly reduced halo diameter by 30%, starburst diameter by 23%, and resolvable distance in the two-point condition by 18% (white) and 30% (violet). CONCLUSIONS: HEV-filtering contact lenses can reduce some deleterious effects of bright broadband light by decreasing light scatter, halos, and starbursts.

Reduction of Glare Discomfort and Photostress Recovery Time Through the Use of a High-Energy Visible-Filtering Contact Lens.

OBJECTIVES: Glare discomfort (GDC) is the slight pain (discomfort) that arises when exposed to light that exceeds one's adaptive state. Such light can also cause a temporary loss in visual function (photostress, PS). We tested the hypothesis that filtering with a high-energy visible (HEV) light-filtering contact lens can reduce GDC and speed PS recovery time. METHODS: Sixty-one subjects were randomized and fit with study lenses and 58 subjects completed as cohort (20-65 years of age). A double-masked, randomized, contralateral design was used (HEV filter on one eye; control lens on the other). Participants were given a 5-s exposure to a broadband white photostressor. Video images were analyzed, and palpebral fissure size during exposure was measured, as was PS recovery time to a 2-degree mid-wave target. RESULTS: The HEV-filtering test lens was statistically superior ( P <0.0001) to the clear comparison contact lens with respect to the magnitude of squint (44.9% squint reduction) and photostress recovery time (24.3% faster recovery). CONCLUSIONS: High-energy visible light-filtering contacts can reduce GDC and speed PS recovery. Filtering HEV light before it is incident upon the retina is a natural strategy (e.g., by the lens and macular pigment) for attenuating some of the deleterious effects of bright broadband light.

The Effects of a Senofilcon A Contact Lens With and Without a Photochromic Additive on Positive Dysphotopsia Across Age.

OBJECTIVE: The visual effects of wearing a photochromic contact lens (test) were directly compared with a nonphotochromic contact lens (control). Positive dysphotopsia (halos, starbursts) and intraocular scatter (behaviorally determined) were assessed. Both younger and middle-aged subjects were evaluated to examine the influence of age. METHODS: Fifty-four subjects (18-62 years) were tested using a contralateral design. Subjects were fit with a photochromic contact lens on one eye and a nonphotochromic contact lens on the other eye, randomly assigned. Testing occurred with and without photochromic activation (darkened) by use of a violet activator (365 nm, half-bandwidth 20 nm). The extent of dysphotopsia (halos and spokes) was measured using an aperture (∼4 mm) that created a bright point source of light 45 inches from the plane of the eye. Between the point source and subject, a centering precision caliper was used to measure lateral spread. Two-point thresholds were determined by measuring the minimum distance between two points of broadband xenon light. RESULTS: The photochromic contact lens produced smaller halo diameters than the control contact lens, both activated (41% on average) and inactivated (21% on average), and age strata was a significant factor (P<0.001) with the older group showing a greater reduction. The photochromic contact lens produced smaller starburst diameters than the control contact lens, both activated (37% on average) and inactivated (23% on average), and age strata was a significant factor (P=0.001) with the older group showing a greater reduction. The two-point thresholds were reduced (25% activated, 9% inactivated) on average but the age effect was not significant (P<0.10). CONCLUSIONS: The senofilcon A lens with photochromic additive reduced the extent of positive dysphotopsia compared with the same lens without the additive, regardless whether the lens was activated or not. The visual benefit was greatest with the older subjects.

CLEAR - Contact lens technologies of the future.

Contact lenses in the future will likely have functions other than correction of refractive error. Lenses designed to control the development of myopia are already commercially available. Contact lenses as drug delivery devices and powered through advancements in nanotechnology will open up further opportunities for unique uses of contact lenses. This review examines the use, or potential use, of contact lenses aside from their role to correct refractive error. Contact lenses can be used to detect systemic and ocular surface diseases, treat and manage various ocular conditions and as devices that can correct presbyopia, control the development of myopia or be used for augmented vision. There is also discussion of new developments in contact lens packaging and storage cases. The use of contact lenses as devices to detect systemic disease has mostly focussed on detecting changes to glucose levels in tears for monitoring diabetic control. Glucose can be detected using changes in colour, fluorescence or generation of electric signals by embedded sensors such as boronic acid, concanavalin A or glucose oxidase. Contact lenses that have gained regulatory approval can measure changes in intraocular pressure to monitor glaucoma by measuring small changes in corneal shape. Challenges include integrating sensors into contact lenses and detecting the signals generated. Various techniques are used to optimise uptake and release of the drugs to the ocular surface to treat diseases such as dry eye, glaucoma, infection and allergy. Contact lenses that either mechanically or electronically change their shape are being investigated for the management of presbyopia. Contact lenses that slow the development of myopia are based upon incorporating concentric rings of plus power, peripheral optical zone(s) with add power or non-monotonic variations in power. Various forms of these lenses have shown a reduction in myopia in clinical trials and are available in various markets.

Lens fitting and subjective acceptance of senofilcon A with photochromic additive on a neophyte population.

PURPOSE: To determine the proportion of contact lens neophytes that can be successfully fitted with a photochromic contact lens, and to survey subjective performance outcomes compared to habitual spectacles. It was hypothesized that at least 50 % of lens fits would be successful. METHODS: Eleven sites enrolled contact lens neophytes with up-to-date spectacles. Subjects were fitted bilaterally with a photochromic Test contact lens (ACUVUE® OASYS with Transitions™) for one month of daily, reusable wear. Follow-up visits occurred at 1 week, 2 weeks (lenses replaced), and at 4 weeks after initial dispensing. The investigator judged lens fitting success based on overall assessment of physiology, mechanical fitting, comfort, vision, and handling at the 4-week visit. Following this visit, subjects returned to wearing habitual spectacles for one week and evaluated the performance of the study lens compared to their spectacles. RESULTS: From a total of 127 subjects who were dispensed contact lenses, 105 completed the study per protocol (mean age: 25.5 ± 5.9 years; 57 % female; 80.0 % Caucasian; 71 % with dark iris color). Investigators judged that 97 % of the contact lenses were fitted successfully after 4 weeks of wear; thus, the primary hypothesis was met. Among per-protocol subjects, 60 % reported better vision outdoors, 53 % better vision in changing lighting conditions, 62 % less squinting, and 66 % being less often bothered by bright light. Additionally, 95 % would recommend the lens to others, and 71 % would recommend their eye care practitioner if offered the lens. CONCLUSION: Greater than 95 % of subjects were successfully fitted with the photochromic contact lens based on professional judgement of physiology, mechanical fitting, comfort, vision, and handling. Subjects new to contact lens wear expressed positive opinions for the study contact lenses compared to their up-to-date spectacles.

The effects of light scatter when using a photochromic vs. non-photochromic contact lens / Efectos de la dispersión luminosas al utilizar lentes de contacto fotocromáticas vs. no fotocromáticas

PURPOSE: To assess the visual effects of wearing both an activated and an inactivated photochromic contact lens, with a direct comparison to a non-photochromic contact lens worn in the fellow eye. This study focused on the visual effects of scatter quantified as the minimum distance between two points of light, and the diameter of the halo and starbursts that surround a bright white point source. METHODS: 60 subjects (aged 18-65 years) were measured in a contralateral design where lens type was randomly assigned, one type to each eye. During activated testing, all visual measures of both study lenses were made while each eye was illuminated by a violet (Lambdamax = 365, half bandwidth 20 nm) activator, which caused steady-state activation of the photochromic lens during the period of testing. Two-point thresholds were determined by measuring the minimum distance between two points of broadband xenon light. Glare geometry was measured using an aperture (∼ 4 mm) that created a bright point source of light 45 inches from the plane of the eye. Between the point source and subject, a centering precision caliper was used to measure lateral spread of halos (diffusion around the source) and visual spokes. The head was stabilized using an adjustable head-rest assembly and the eye was aligned and monitored with a bore camera. RESULTS: Compared to the non-photochromic lens, and based on the stimulus conditions used in these measurements, the activated and inactivated photochromic lens reduced the light spread using the two-point threshold technique by 32% and 19% respectively; the diameter of the halos were reduced by 44% and 16% respectively; and the spokes were narrowed by 39% and 20% respectively. Based on 95% confidence interval testing, these effects were all statistically significant (p < 0.05). CONCLUSIONS: These results are consistent with previous data showing that soft contact lenses with a photochromic additive can improve many aspects of visual function, consistent with their level or activation. Our past data focused on visual function under bright light conditions (e.g., glare disability, discomfort, photostress recovery and chromatic contrast) with an activated photochromic. In this study, we found differences even in the inactivated state, using less intense stimuli (10cd/m2 at the source). This suggests that the photochromic lens improves the effects of light scatter even at lower luminance

OBJETIVO: Evaluar los efectos visuales del uso de lentes de contacto con activación e inactivación fotocromática, mediante comparación directa con el uso de lentes de contacto no fotocromáticas en el ojo contralateral. Este estudio se centró en los efectos visuales de la dispersión, cuantificada mediante la distancia mínima entre dos puntos luminosos, y el diámetro del halo y los destellos que rodean a una fuente fija blanca brillante. MÉTODOS: Se realizaron mediciones a 60 sujetos (de edades comprendidas entre 18 y 65 años) en un diseño contralateral en el que se asignó aleatoriamente un tipo a cada ojo. Durante la prueba con activación, se realizaron todas las medidas visuales de ambas lentes en estudio, mientras se iluminaba cada ojo con un activador violeta (lambdamáx.=365, ancho de banda medio 20 nm), que causó una activación del estado de equilibrio de las lentes fotocromáticas durante el periodo de prueba. Se determinaron los umbrales de dos puntos, midiendo la distancia mínima entre dos puntos de luz de xenón de banda ancha. Se midió la geometría del reflejo utilizando una apertura (∼ 4 mm) que creó una fuente fija brillante de luz a 45 pulgadas del plano del ojo. Entre la fuente fija y el sujeto se utilizó un calibrador de precisión de centrado para medir la expansión lateral de los halos (difusión alrededor de la fuente) y los destellos. La cabeza se estabilizó utilizando un reposacabezas, alineándose y supervisándose el ojo con una cámara. RESULTADOS: Realizando una comparación con las lentes no fotocromáticas, y sobre la base de las condiciones de estímulo utilizadas en estas medidas, las lentes con activación y desactivación fotocromática redujeron la expansión de la luz utilizando la técnica del umbral de dos puntos en un 32% y un 19% respectivamente; el diámetro de los halos se redujo en un 44% y 16% respectivamente; y los brillos se estrecharon en un 39% y 20% respectivamente. Basándonos en la prueba del intervalo de confianza del 95%, todos estos efectos fueron estadísticamente significativos (p < 0,05). CONCLUSIONES: Estos resultados son consistentes con los datos previos, que reflejan que las lentes de contacto fotocromáticas pueden mejorar muchos aspectos de la función visual, en consistencia con su nivel de activación. Nuestros datos anteriores se centraron en la función visual en condiciones de luz brillante (ej.: incapacidad por deslumbramiento, incomodidad, recuperación de foto-estrés y contraste cromático) con activación de adición fotocromática. En este estudio, encontramos diferencias incluso en el estado de inactivación, utilizando estímulos menos intensos (10 cd/m2 en la fuente), lo cual sugiere que las lentes fotocromáticas mejoran los efectos de la dispersión luminosa incluso con una luminancia menor

Photobiomodulation of the Visual System and Human Health.

Humans express an expansive and detailed response to wavelength differences within the electromagnetic (EM) spectrum. This is most clearly manifest, and most studied, with respect to a relatively small range of electromagnetic radiation that includes the visible wavelengths with abutting ultraviolet and infrared, and mostly with respect to the visual system. Many aspects of our biology, however, respond to wavelength differences over a wide range of the EM spectrum. Further, humans are now exposed to a variety of modern lighting situations that has, effectively, increased our exposure to wavelengths that were once likely minimal (e.g., "blue" light from devices at night). This paper reviews some of those biological effects with a focus on visual function and to a lesser extent, other body systems.

Individual differences in visual function.

A significant proportion of research on the visual system focuses on general principles that apply to samples and/or populations. Many questions, however, are more suited to the specific characteristics of an individual. The visual system, like most systems of the body, is extremely variable with respect to function and susceptibility to disease. Understanding this variation is an important avenue to better measurement, disease prevention and treatment.

The Effect of a Photochromic Contact Lens on Visual Function Indoors: A Randomized, Controlled Trial.

SIGNIFICANCE: Photochromic soft contact lenses contain light-sensitive additives that allow them to darken when exposed to ultraviolet or violet light. One question, however, is whether the lenses influence vision indoors (minimally activated). In this study, we found that the minimally activated lenses improved many aspects of visual function under bright light. PURPOSE: Photochromic contact lenses were designed to darken when exposed to outdoor sunlight. The filtering that results improves visual function under bright light conditions. Not all bright light exposures occur outdoors. In this study, we tested whether a photochromic contact lens improved visual function under conditions where the lens was minimally activated (i.e., no more than it normally would be in an indoor environment). METHODS: A subject-masked contralateral design was used comparing a photochromic contact lens randomized to one eye against a nonphotochromic contact in the other eye of the same subject. Sixty subjects (mean = 34.90 ± 11.24 years) were tested. The primary endpoints consisted of four visual function outcomes: photostress recovery, glare disability, glare discomfort, and chromatic contrast. Photostress recovery was quantified by measuring the time needed to recover visual acquisition of a grating target after 5 seconds of an intense xenon white flash exposure; glare disability was evaluated as the energy in a surrounding xenon white annulus necessary to veil a central grating target; and glare discomfort was assessed using bioimaging of the squint response. Chromatic contrast was measured as thresholds for a green-yellow (580 nm) grating target superposed on a blue (460 nm) background. RESULTS: The minimally activated photochromic contact demonstrated improved visual performance compared with the nonphotochromic control across all visual functions tested (P < .01). CONCLUSIONS: Even under conditions of exiguous activation (e.g., as would be expected indoors or while driving at night), a photochromic contact will improve many of the more deleterious aspects of bright light.

The effects of light scatter when using a photochromic vs. non-photochromic contact lens.

PURPOSE: To assess the visual effects of wearing both an activated and an inactivated photochromic contact lens, with a direct comparison to a non-photochromic contact lens worn in the fellow eye. This study focused on the visual effects of scatter quantified as the minimum distance between two points of light, and the diameter of the halo and starbursts that surround a bright white point source. METHODS: 60 subjects (aged 18-65 years) were measured in a contralateral design where lens type was randomly assigned, one type to each eye. During activated testing, all visual measures of both study lenses were made while each eye was illuminated by a violet (λmax=365, half bandwidth 20nm) activator, which caused steady-state activation of the photochromic lens during the period of testing. Two-point thresholds were determined by measuring the minimum distance between two points of broadband xenon light. Glare geometry was measured using an aperture (∼4mm) that created a bright point source of light 45 inches from the plane of the eye. Between the point source and subject, a centering precision caliper was used to measure lateral spread of halos (diffusion around the source) and visual spokes. The head was stabilized using an adjustable head-rest assembly and the eye was aligned and monitored with a bore camera. RESULTS: Compared to the non-photochromic lens, and based on the stimulus conditions used in these measurements, the activated and inactivated photochromic lens reduced the light spread using the two-point threshold technique by 32% and 19% respectively; the diameter of the halos were reduced by 44% and 16% respectively; and the spokes were narrowed by 39% and 20% respectively. Based on 95% confidence interval testing, these effects were all statistically significant (p<0.05). CONCLUSIONS: These results are consistent with previous data showing that soft contact lenses with a photochromic additive can improve many aspects of visual function, consistent with their level or activation. Our past data focused on visual function under bright light conditions (e.g., glare disability, discomfort, photostress recovery and chromatic contrast) with an activated photochromic. In this study, we found differences even in the inactivated state, using less intense stimuli (10cd/m2 at the source). This suggests that the photochromic lens improves the effects of light scatter even at lower luminance.

Randomized Crossover Trial Evaluating the Impact of Senofilcon A Photochromic Lens on Driving Performance.

SIGNIFICANCE: The first contact lens to incorporate a photochromic additive was cleared by the U.S. Food and Drug Administration last year. Because any ophthalmic lens that absorbs visible wavelengths will reduce retinal illuminance, it is important to understand the impact of this new photochromic contact lens on vision and both daytime and nighttime driving performance. PURPOSE: The purpose of this study was to evaluate the effect of senofilcon A photochromic contact lens wear on vision and driving performance under real-world conditions by comparison with a nonphotochromic contact lens and plano photochromic spectacles. METHODS: In this randomized four-visit bilateral crossover study, 24 licensed regular drivers and established wearers of soft contact lenses were enrolled. Subjects wore in random order each of three study lens types: the investigational photochromic soft contact lens (test), a nonphotochromic soft contact lens (control 1), and plano photochromic spectacle lenses (control 2). Driver performance was assessed on a closed-circuit driving track under challenging controlled conditions. The primary endpoint was overall driving performance score calculated as a composite Z score of six objective metrics. RESULTS: All 24 subjects (mean age, 29.8 years) completed the study. For nighttime driving, the adjusted mean differences in Z score (95% confidence interval) between test and control 1 and between test and control 2 were 0.069 (-0.045 to +0.183) and 0.117 (0.003 to 0.231), respectively. For daytime driving, mean differences were 0.101 (-0.013 to +0.216) between test and control 1 and 0.044 (-0.070 to +0.158) between test and control 2. Results demonstrated noninferiority of the test lens relative to controls for nighttime and daytime driving performance using a noninferiority margin of -0.25 Z score. Noninferiority was also demonstrated on all logMAR and contrast threshold testing. No adverse events were reported during the study. CONCLUSIONS: Study results revealed no evidence of concerns with either driving performance or vision while wearing photochromic contact lenses.

A contra-lateral comparison of the visual effects of a photochromic vs. non-photochromic contact lens.

PURPOSE: To compare the effects of a photochromic contact lens vs. a non-photochromic control lens on visual function. METHODS: A subject-masked, prospective contralateral eye design was used. Sixty-one subjects were enroled based on age (using a 2:1 allocation ratio for ages 18-39 and 40-65 years, respectively). The study lenses were senofilcon A with photochromic additive (Test) that filtered over the entire lens, compared to a non-photochromic Control with no tint. The Test lens was partially activated during testing with a steady-state transmittance of approximately 62%. Eligible subjects were tested using both study lenses, with Test and Control lens randomized by eye. Five visual function outcomes were tested: photostress recovery (PSR), glare disability (GD), glare discomfort (GDC), chromatic contrast (CC) and vernier acuity (VA). Iris colour and macular pigment density were assessed as control variables. PSR was measured as the time needed to recover sight of a target after an intense xenon flash exposure; GD was evaluated as the energy needed to veil a central target by a surrounding xenon annulus; GDC was measured using bio-imaging of the squint response and by self-report using a 9-item Likert scale; CC was measured as thresholds for a yellow grating target superposed on a 460-nm background; VA was determined by measuring vernier offsets of light lines through apertures. RESULTS: Based on our stimulus conditions, PSR was 43% faster using the Test vs. the Control. The eye wearing the Test had 38% less squint (GDC) compared to the Control. GD was improved by 36% in the Test vs. Control and CC was enhanced by 48% with the Test. There was no significant difference in VA. CONCLUSIONS: There was a beneficial influence on visual function when comparing the photochromic with the non-photochromic contact lens. This benefit was seen specifically with respect to PRT, GDC, GD and CC thresholds.