Photopic Acuity Research Articles

Development and Validation of a Novel Night-Time Hazard Visibility Test.

Night-time driving is dangerous, with increased crash rates, particularly involving vulnerable road users. A Night-Time Hazard Visibility Test (NHVT) was developed and validated by exploring the effects of refractive and cataract blur on performance. The NHVT comprised video clips of night-time roads from the driver's perspective, including different hazards (pedestrians, cyclists, and vehicles). Participants responded when they first recognized hazards requiring them to take evasive action to avoid a collision. In experiment 1, there were 16 young visually normal drivers (mean age = 22.3, standard deviation [SD] = 2.2 years) who completed 2 NHVT sets, viewed separately through best-correction and refractive blur (+1.00 diopter sphere [DS]). In experiment 2, a refined version of the NHVT was administered to an additional 16 young visually normal drivers (mean age = 21.1, SD = 1.2 years) with best-correction and cataract blur. The order of visual conditions and NHVT sets were counterbalanced. In experiment 1, refractive blur significantly reduced photopic visual acuity (VA) compared to best-corrected vision (+0.09 vs. -0.21 logMAR, P < 0.001) and delayed response times by 0.69 seconds (3.10 vs. 2.41 seconds, P < 0.001) compared to best-corrected vision. In experiment 2, cataract blur reduced VA compared to best-corrected vision (+0.03 vs. -0.17 logMAR, P < 0.001) and delayed response times by 0.63 seconds (2.92 vs. 2.29 seconds, P < 0.001). The NHVT was sensitive to refractive and cataract blur, providing preliminary support of its validity as a measure of night-time hazard visibility performance. The NHVT has potential as an off-road assessment of visibility for night driving and application for assessment of drivers with different refractive corrections and ocular diseases.

Visual Function and Driving Performance Under Different Lighting Conditions in Older Drivers: Preliminary Results From an Observational Study.

Age-related vision changes significantly contribute to fatal crashes at night among older drivers. However, the effects of lighting conditions on age-related vision changes and associated driving performance remain unclear. This pilot study examined the associations between visual function and driving performance assessed by a high-fidelity driving simulator among drivers 60 and older across 3 lighting conditions: daytime (photopic), nighttime (mesopic), and nighttime with glare. Active drivers aged 60 years or older participated in visual function assessments and simulated driving on a high-fidelity driving simulator. Visual acuity (VA), contrast sensitivity function (CSF), and visual field map (VFM) were measured using quantitative VA, quantitative CSF, and quantitative VFM procedures under photopic and mesopic conditions. VA and CSF were also obtained in the presence of glare in the mesopic condition. Two summary metrics, the area under the log CSF (AULCSF) and volume under the surface of VFM (VUSVFM), quantified CSF and VFM. Driving performance measures (average speed, SD of speed [SDspeed], SD of lane position (SDLP), and reaction time) were assessed under daytime, nighttime, and nighttime with glare conditions. Pearson correlations determined the associations between visual function and driving performance across the 3 lighting conditions. Of the 20 drivers included, the average age was 70.3 years; 55% were male. Poor photopic VA was significantly correlated with greater SDspeed (r=0.26; P<.001) and greater SDLP (r=0.31; P<.001). Poor photopic AULCSF was correlated with greater SDLP (r=-0.22; P=.01). Poor mesopic VUSFVM was significantly correlated with slower average speed (r=-0.24; P=.007), larger SDspeed (r=-0.19; P=.04), greater SDLP (r=-0.22; P=.007), and longer reaction times (r=-0.22; P=.04) while driving at night. For functional vision in the mesopic condition with glare, poor VA was significantly correlated with longer reaction times (r=0.21; P=.046) while driving at night with glare; poor AULCSF was significantly correlated with slower speed (r=-0.32; P<.001), greater SDLP (r=-0.26; P=.001) and longer reaction times (r=-0.2; P=.04) while driving at night with glare. No other significant correlations were observed between visual function and driving performance under the same lighting conditions. Visual functions differentially affect driving performance in different lighting conditions among older drivers, with more substantial impacts on driving during nighttime, especially in glare. Additional research with larger sample sizes is needed to confirm these results.

Functional and morphological characterization of ocular phenotype in C3H/HeOuJ (Pde6b‐rd1) mice

Aims: C3H/HeOuJ mice (The Jackson Laboratory strain #000635) are homozygous for the retinal degeneration 1 mutation Pde6brd1 (rd1) causing severe visual deficits. The purpose of this study was to characterize the ocular phenotype of male and female mice with the rd1 mutation.Methods: The ophthalmic phenotype of mixed sex rd1 and aged‐matched C57BL/6J wild type (WT) mice (6 females and 4 males for rd1 group, 6 females and 5 males for WT group) was assessed at 3 months of age. Retinal photoreceptor function was quantified using scotopic flash electroretinography (fERG) with six different light intensities: 0.003, 0.01, 0.1, 1, 3 and 10 cd.s/m2 (Celeris, Diagnosys LLC). Retinal morphology was evaluated with spectral domain optical coherence tomography (SD‐OCT) (Envisu R2200, Bioptigen Inc./Leica Microsystems). Retinal thickness was measured from SD‐OCT images using a proprietary convolutional neural network. Optomotor reflex (OMR) was measured as photopic visual acuity and contrast sensitivity at 0.019 and 0.06 cyc/° (OptoDrum Plus, Striatech GmbH). Data were analysed by unpaired t‐test or Mann–Whitney test.Results: At 3 months of age, the rd1 mutation resulted in significant impairment of visual function in both male and female mice compared to age‐matched WT. fERG a and b‐wave amplitudes were decreased by 90% in both sexes (p &lt; 0.001). The rd1 mice had only minimal visual acuity and contrast sensitivity assessed by OMR. Functional decline correlated with structural changes, notably the significant thinning of the retina (p &lt; 0.001).Conclusions: The Pde6brd1 mutation resulted in severe functional and structural changes at 3 months of age. The mice presented significantly decreased but detectable fERG amplitudes, however, they had no functional vision as assessed by OMR. Combining fERG and OMR offers longitudinal in‐life quantification of retinal circuitry and functional vision with great utility for evaluation of novel therapeutic approaches for regeneration of the visual system.

MNREAD Reading Vision in Adults With Glaucoma Under Mesopic and Photopic Conditions.

Despite good photopic visual acuity, glaucoma patients report difficulty performing daily activities under dim light such as reading. Here we investigated the impact of mesopic lighting conditions on reading vision of glaucoma patients. The study design included 39 patients with glaucoma and 40 healthy controls. Reading vision was assessed with MNREAD charts under mesopic (2 cd/m2) and photopic (220 cd/m2) conditions. Four reading indexes: maximum reading speed (MRS), critical print size (CPS), reading acuity (RA), and reading accessibility index (ACC) were obtained from the MNREAD test yielding a plot of reading speed versus print size. Compared to photopic conditions, reading vision of both healthy controls and glaucoma patients significantly decreased under mesopic conditions (P < 0.05). For glaucoma patients (85% with mild or moderate glaucoma), MRS and ACC decreased by six words per minute and 0.1, respectively under mesopic conditions; CPS and RA increased by 0.25 and 0.18 logMAR, respectively. Moreover, under both photopic and mesopic conditions, reading vision of glaucoma patients was significantly worse than that of healthy controls, but the difference was greater under mesopic conditions (P < 0.05) even after controlling for age and visual acuity. Mesopic conditions make reading more challenging for both healthy controls and glaucoma patients. However, reading in dim light appears to be more burdensome for glaucoma patients. Mesopic reading tests mediated by both cone and rod photoreceptor systems likely provide a more sensitive and comprehensive assessment of a patient's reading impairment than testing under photopic conditions.

Reading Vision in Adults With Early and Intermediate Age-Related Macular Degeneration Under Mesopic and Photopic Conditions.

Reading is involved in various daily activities that operate under a wide range of luminance levels. Rod- and cone-mediated mesopic visual function is known to be impaired even in early/intermediate age-related macular degeneration (AMD). It remains unclear whether and to what extent mesopic reading is impaired in early/intermediate AMD. Here, we assessed differences in reading vision between photopic and mesopic conditions in early/intermediate AMD and compared their performance to those in older adults with normal macular health. The study included 30 patients with early/intermediate AMD and 30 healthy controls. Reading performance was tested on the MNREAD iPad app under mesopic (2cd/m2 with a neural-density filter) and photopic (220 cd/m2) conditions. Four reading indices-maximum reading speed (MRS), critical print size (CPS), reading acuity (RA), and reading accessibility index (ACC)-were obtained from the MNREAD test, yielding a function representing reading speed versus print size. Compared to photopic conditions, patients with AMD and healthy controls both exhibited noticeable decreases in reading vision under mesopic conditions (P < 0.001) despite normal photopic visual acuity. This decrease was more pronounced in AMD even after adjusting for age (P < 0.001): Under mesopic conditions, MRS and ACC decreased by 8 words per minute and 0.1, respectively; CPS and RA were enlarged by 0.27 and 0.24 logMAR, respectively. Reading vision deteriorates under mesopic conditions compared to photopic conditions in early/intermediate AMD and is accentuated compared to this difference in healthy controls. A mesopic reading test may provide a more sensitive and comprehensive assessment of a patient's reading impairment.

Effect of low luminance on face recognition in adults with central and peripheral vision loss.

To investigate the effect of low luminance on face recognition, specifically facial identity discrimination (FID) and facial expression recognition (FER), in adults with central vision loss (CVL) and peripheral vision loss (PVL) and to explore the association between clinical vision measures and low luminance FID and FER. Participants included 33 adults with CVL, 17 with PVL and 20 controls. FID and FER were assessed under photopic and low luminance conditions. For the FID task, 12 sets of three faces with neutral expressions were presented and participants asked to indicate the odd-face-out. For FER, 12 single faces were presented and participants asked to name the expression (neutral, happy or angry). Photopic and low luminance visual acuity (VA) and contrast sensitivity (CS) were recorded for all participants and for the PVL group, Humphrey Field Analyzer (HFA) 24-2 mean deviation (MD). FID accuracy in CVL, and to a lesser extent PVL, was reduced under low compared with photopic luminance (mean reduction 20% and 8% respectively; p < 0.001). FER accuracy was reduced only in CVL (mean reduction 25%; p < 0.001). For both CVL and PVL, low luminance and photopic VA and CS were moderately to strongly correlated with low luminance FID (ρ = 0.61-0.77, p < 0.05). For PVL, better eye HFA 24-2 MD was moderately correlated with low luminance FID (ρ = 0.54, p = 0.02). Results were similar for low luminance FER. Together, photopic VA and CS explained 75% of the variance in low luminance FID, and photopic VA explained 61% of the variance in low luminance FER. Low luminance vision measures explained little additional variance. Low luminance significantly reduced face recognition, particularly for adults with CVL. Worse VA and CS were associated with reduced face recognition. Clinically, photopic VA is a good predictor of face recognition under low luminance conditions.

Retinal Responses to Visual Stimuli in Interphotoreceptor Retinoid Binding-Protein Knock-Out Mice.

Interphotoreceptor retinoid-binding protein (IRBP) is an abundant glycoprotein in the subretinal space bound by the photoreceptor (PR) outer segments and the processes of the retinal pigmented epithelium (RPE). IRBP binds retinoids, including 11-cis-retinal and all-trans-retinol. In this study, visual function for demanding visual tasks was assessed in IRBP knock-out (KO) mice. Surprisingly, IRBP KO mice showed no differences in scotopic critical flicker frequency (CFF) compared to wildtype (WT). However, they did have lower photopic CFF than WT. IRBP KO mice had reduced scotopic and photopic acuity and contrast sensitivity compared to WT. IRBP KO mice had a significant reduction in outer nuclear layer (ONL) thickness, PR outer and inner segment, and full retinal thickness (FRT) compared to WT. There were fewer cones in IRBP KO mice. Overall, these results confirm substantial loss of rods and significant loss of cones within 30 days. Absence of IRBP resulted in cone circuit damage, reducing photopic flicker, contrast sensitivity, and spatial frequency sensitivity. The c-wave was reduced and accelerated in response to bright steps of light. This result also suggests altered retinal pigment epithelium activity. There appears to be a compensatory mechanism such as higher synaptic gain between PRs and bipolar cells since the loss of the b-wave did not linearly follow the loss of rods, or the a-wave. Scotopic CFF is normal despite thinning of ONL and reduced scotopic electroretinogram (ERG) in IRBP KO mice, suggesting either a redundancy or plasticity in circuits detecting (encoding) scotopic flicker at threshold even with substantial rod loss.

Visual Performance, Satisfaction, and Spectacle Independence after Implantation of a New Hydrophobic Trifocal Intraocular Lens.

The main objective was to evaluate distance, intermediate, and near vision in patients who have undergone cataract extraction with bilateral implantation of a new trifocal diffractive intraocular lens (IOL), along with patient-reported outcomes (PRO). A total of 50 eyes from 25 patients after AsqelioTM Trifocal IOL (AST Products, Inc., Billerica MA, USA) implantation were assessed in this study. At 3 months after surgery, the photopic visual acuity (VA) at distance, intermediate, and near distances was measured. Binocular photopic defocus curves were also obtained. Three questionnaires to assess patients’ visual satisfaction and spectacle dependence, among other items, were completed: the Catquest-9SF, the patient-reported spectacle independence questionnaire (PRSIQ), and the patient-reported visual symptoms questionnaire (PRVSQ). The average spherical equivalent was 0.21 ± 0.37 D at 3 months post-operation, and the average absolute tolerance to defocus was 3.64 ± 0.70 D. The mean binocular uncorrected VAs for distance, intermediate, and near vision were −0.02 ± 0.09, 0.06 ± 0.08, and 0.11 ± 0.07 logMAR, respectively. The best-corrected VA was better than 0.1 logMAR for the whole range from distance to near. PROs revealed spectacle independence and general satisfaction with vision, and the incidence of photic phenomena were low. This study shows that the new bi-aspheric diffractive trifocal IOL provides a good visual performance at different distances under photopic conditions, accompanied by patient satisfaction and spectacle independence.

Treatment of age-related visual impairment with a peptide acting on mitochondria.

ABSTRACTAge-related visual decline and disease due to neural dysfunction are major sources of disability that have resisted effective treatment. In light of evidence that visual impairment and mitochondrial dysfunction advance with age, we characterized age-related decline of spatial visual function in mice and investigated whether treatment of aged mice with the mitochondrion-penetrating peptide elamipretide that has been reported to improve mitochondrial function, would improve it. Impaired photopic acuity measured by using a virtual optokinetic system emerged near 18 months and declined to ∼40% below normal by 34 months. Daily application of the synthetic peptide elamipretide, which has high selectivity for mitochondrial membranes that contain cardiolipin and promotes efficient electron transfer, was able to mitigate visual decline from 18 months onwards. Daily application from 24 months onwards, i.e. when acuity had reduced by ∼16%, reversed visual decline and normalized function within 2 months. Recovered function persisted for at least 3 months after treatment was withdrawn and a single treatment at 24 months delayed subsequent visual decline. Elamipretide applied daily from 32 months onwards took longer to take effect, but substantial improvement was found within 2 months. The effects of age and elamipretide treatment on contrast sensitivity were similar to those on acuity, systemic and eye drop applications of elamipretide had comparable effects, scotopic spatial visual function was largely unaffected by age or treatment, and altered function was independent of variation in optical clarity. These data indicate that elamipretide treatment adaptively alters the aging visual system. They also provide a rationale to investigate whether mitochondrial dysfunction is a treatable pathophysiology of human visual aging and age-related visual disease.

Mesopic Disability Glare in Stage-Two Dysfunctional Lens Syndrome.

IntroductionThere is a lack of evidence about the exact deterioration of visual function associated with the age-related natural changes in the lens, particularly in intermediate (stage-2) dysfunctional lens syndrome (DLS). Standard photopic visual acuity and contrast sensitivity tests may not show the visual worsening in daily life activities, such as oncoming vehicle headlights at night. The purpose of this study was to analyze visual function under different conditions and glare sources in stage-2 DLS.MethodsForty patients over 49 years of age with initial bilateral lens opacification (Lens Opacities Classification System III [LOCS-III] scores up to 3), best-corrected visual acuity of 20/25 or better, and no ocular disease were evaluated. Binocular photopic and mesopic contrast sensitivity (CS) with/without halogen and xenon increasing glare sources were analyzed. Mesopic disability glare (MDG) was calculated as the difference between mesopic CS with/without the glare source.ResultsThe median logarithmic CS (logCS) values were lower under mesopic conditions (1.05) than under photopic illumination (1.65; P < 0.001). Halogen and xenon glare further decreased mesopic CS (both, median logCS 0.75, P < 0.001). The mean MDG was 0.31 ± 0.10 log units for halogen glare and 0.33 ± 0.09 log units for xenon glare. The mesopic CS and MDG were not associated with any photopic test. The mesopic CS with glare but not photopic CS or mesopic CS was correlated with the LOCS-III scores. The best association was provided by MDG, which showed a pooled correlation with LOCS-III nuclear opalescence (r = 0.411, P < 0.001) and cortical scores (r = 0.226, P = 0.04).ConclusionThe mesopic CS under a glare source is an independent early indicator of visual impairment in stage-2 DLS patients, and appears to be substantial. Furthermore, the MDG is more sensitive than photopic and mesopic CS for evaluating patients with initial phacosclerosis. Surgeons should consider this in the decision-making process of the correct timing for lens surgery.

Development of a Method to Potentially Substitute Direct Evaluation of Mesopic Visual Acuity in Drivers

(1) Background: In mesopic lighting conditions, or under adverse environmental circumstances, visual information is reduced, which increases the risk of traffic accidents. This effect could be reduced with a precise evaluation of the visual function under mesopic conditions, but it is difficult to replicate in clinics. This study aims to develop an easy-to-adopt method to evaluate mesopic visual acuity (VA) in drivers. (2) Methods: Prospective and observational study in drivers. logMAR mesopic VA was compared with photopic VA measured under different combinations of contrast charts and filters to find the combination that responds best to mesopic conditions. (3) Results: Fifty-six drivers were examined. The best correlation was found with an 80% density filter and a Weber contrast chart of 20%. The logMAR VA for this combination was 0.01 ± 0.11, which was close to the mesopic VA values (0.01 ± 0.12). The difference between both logMAR VA was 0.00 ± 0.06 (R = 0.86; p ≤ 0.001; ICC = 0.86). (4) Conclusions: The use of 20% contrast optotypes and the interposition of an 80% filter under photopic conditions provide VA values similar to those measured under mesopic lighting conditions, making this simple system a good predictor of mesopic VA values.

The acute effect of cocoa and red-berries on visual acuity and cone-mediated dark adaptation in healthy eyes

• This study examines the acute effect of cocoa and red-berries polyphenols on retinal functions such as visual acuity (VA) and cone-mediated dark adaptation in healthy eyes. • Photopic visual acuity improved significantly after cocoa ingestion. • Mesopic or low luminance VA and dark adaptation was not affected by any of the two polyphenol diets. • The improvement in photopic visual acuity could be attributed to flavanols and Theobromine. The retina is a highly vascularized tissue with a high metabolic and oxygen demand responsible for human vision. Considering that the polyphenolic flavanols and anthocyanins have been shown to be beneficial for endothelial function and cerebral blood-flow, an acute randomized and controlled crossover trial with two different sources of polyphenols, anthocyanins from red-berries and flavanols from cocoa, was designed to better understand the effect of polyphenols on visual acuity (VA) and cone-mediated dark adaptation (DA). Thirty-seven healthy subjects (22.1 ± 2.0 years old) participated in the acute intervention for three times (red-berries, cocoa or vehicle-control) with a washout period of two weeks in-between. VA under photopic and low luminance (mesopic) conditions, DA or dynamic of recovery of contrast threshold (CT) following near-total photopigment bleach for 5 min, urine total polyphenols, theobromine and antioxidant power were measured in the three study-arms after 2-hours ingestion of the study-food. 3-hours postprandial urine showed higher levels of total polyphenols after ingestion of cocoa flavanols or red-berries anthocyanins in comparison with the vehicle-control and higher levels of theobromine only for the cocoa group. There was an increase in photopic VA with cocoa flavanols that with red-berries anthocyanins did not reach statistical significance. Both, cocoa and red berries, failed to improve mesopic VA and the cone time constant for contrast recovery and final CT of DA.

The \u201cspeed\u201d of acuity in scotopic vs. photopic vision

PurposeThe effect of duration of optotype presentation on visual acuity measures has been extensively studied under photopic conditions. However, systematic data on duration dependence of acuity values under mesopic and scotopic conditions is scarce, despite being highly relevant for many visual tasks including night driving, and for clinical diagnostic applications. The present study aims to address this void.MethodsWe measured Landolt C acuity under photopic (90 cd/m2), mesopic (0.7 cd/m2), and scotopic (0.009 cd/m2) conditions for several optotype presentation durations ranging from 0.1 to 10 s using the Freiburg Acuity and Contrast Test. Two age groups were tested (young, 18–29 years, and older, 61–74 years).ResultsAs expected, under all luminance conditions, better acuity values were found for longer presentation durations. Photopic acuity in young participants decreased by about 0.25 log units from 0.1 to 10 s; mesopic vision mimicked the photopic visual behavior. Scotopic acuities depended more strongly on presentation duration (difference > 0.78 log units) than photopic values. There was no consistent pattern of correlation between luminance conditions across participants. We found a qualitative similarity between younger and older participants, despite higher variability among the latter and differences in absolute acuity: Photopic acuity difference (0.1 vs. 10 s) for the older participants was 0.19 log units, and scotopic difference was > 0.62 log units.ConclusionScotopic acuity is more susceptible to changes in stimulus duration than photopic vision, with considerable interindividual variability. The latter may reflect differences in aging and sub-clinical pathophysiological processes and might have consequences for visual performance during nocturnal activities such as driving at night. Acuity testing with briefly presented scotopic stimuli might increase the usefulness of acuity assessment for tracking of the health state of the visual system.

Pharmacological Strategies for Presbyopia Correction.

To summarize the pharmacological strategies that are being explored for presbyopia correction. The review concentrates on pharmacologically induced pupillary miosis to increase depth-of-focus and lens softening or other measures to restore active accommodation. Several studies suggest that near vision improves and distance vision is unaffected for many hours after either monocular or binocular instillation of any one of several drug combinations that cause miosis. Unfortunately, in most studies, measurements were limited to photopic visual acuity for near and distance vision, whereas it is anticipated that pupil constriction may have adverse effects on mesopic and scotopic vision. It is not clear whether improved near vision was due entirely to increased depth-of-focus, or whether, for example, a drug-induced myopic shift in refraction was also involved. Currently, no study has provided direct evidence for drug-induced restoration/enhancement of true accommodation involving an ocular power change. Although it is possible that, in the future, pharmacological drops may offer a safe and reliable solution for presbyopia correction, more evidence of their effectiveness and limitations is required. [J Refract Surg. 2019;35(12):803-814.].

Older drivers' self-reported vision-related night-driving difficulties and night-driving performance.

To investigate associations between older drivers' perceived vision-related night-driving difficulties and night-time driving performance measured on a closed-road circuit. Participants included 26 older drivers (71.8±6.3years) who reported vision-related night-driving difficulties assessed with the vision and night driving questionnaire (VND-Q). High-contrast, photopic visual acuity (VA) and ratings of discomfort glare (de Boer scale) were also assessed. Night-time driving performance was measured on a closed-road circuit that involved recognition, hazard avoidance and lane-keeping tasks in the absence and presence of intermittent glare. Generalized linear mixed models investigated the relationship between VND-Q scores and overall driving performance scores, as well as with discomfort glare ratings and VA. Greater levels of vision-related night-driving difficulties (VND-Q scores) were significantly associated with poorer night-driving performance (p=0.003); the association was even stronger for driving performance in the presence of intermittent glare (p=0.001). Reduced VA was associated with poorer night-driving performance (p=0.022) but the association was weaker than for the VND-Q scores. In contrast, ratings of discomfort glare were not significantly associated with driving performance (p=0.14). The VND-Q was significantly associated with night-time driving performance and provides a useful instrument for assessing vision-related night-driving difficulties which can be incorporated into clinical vision assessments.

Determination of scotopic and photopic conventional visual acuity and hyperacuity.

Visual acuity (VA) is an important determinant of visual function. Here we establish procedures and recommendations for VA testing extending beyond the classical VA and thus make them available for future studies of visual function in health and disease. Specifically, we provide reference values for photopic and scotopic conventional uncrowded visual acuity (cVA) and Vernier-hyperacuity (hVA) and assess their reproducibility and dependence on contrast polarity. For ten observers with normal vision, we determined photopic ("p"; maximal luminance 220 cd/m2) and scotopic ("s"; maximal luminance 0.004 cd/m2; 40 min of dark adaptation) cVA and hVA, for two contrast polarities i.e. black optotypes on white background and vice versa. To assess intersession effects, two sets of measurements were obtained on different days. Compared to pcVA (1.32 decimal VA; - 0.12 ± 0.02 LogMAR), the phVA (14.45 decimal VA; - 1.16 ± 0.04 LogMAR) scaled (in terms of decimal visual acuity) on average with a factor 11.0, the scVA (0.12 decimal VA; 0.91 ± 0.03 LogMAR) with a factor of 0.1, and the shVA (1.47 decimal VA; - 0.17 ± 0.02 LogMAR) with a factor of 1.1. There were neither significant effects of contrast polarity (p > 0.12), nor of session (p > 0.28). Our approach optimises integrated photopic and scotopic cVA and hVA measurements for general use and thus encourages the integration of these important measures of scotopic visual function in future studies. The absence of strong intersession effects demonstrates that no dedicated training session is needed to obtain scotopic and hVA measurements. The combined measures of scotopic and photopic VAs open a field of applications to study interplay and plasticity of the retinal photoreceptor systems and cortical processing in health and visual disease. As a rule of thumb, hyperacuity is 10× higher both in the photopic and scotopic range than conventional acuity. Thus, scotopic hyperacuity is close to photopic conventional acuity.

The impact of uncorrected astigmatism on night driving performance.

To investigate the effect of uncorrected astigmatism on night driving performance on a closed-road circuit. Participants included 10 drivers (mean age 24.4±7.0years), with low to moderate bilateral astigmatism (0.75-1.50 DC), who were regular contact lens (CL) wearers. Vision and night driving performance were assessed in a cross-over design with a toric CL and a best-sphere spherical CL. Binocular visual function measures included photopic and mesopic visual acuity (VA), contrast sensitivity (CS), mesopic motion sensitivity and glare tests (Mesotest® II and Halometer). Night-time driving performance was assessed on a closed-road circuit, which included measures of sign recognition, hazard detection and avoidance, pedestrian recognition distances, lane keeping, speed and overall driving score. Correction of astigmatism with toric CL significantly improved mesopic VA, photopic and mesopic CS, mesopic motion sensitivity, and reduced glare (p<0.05), compared to the spherical CL; there were no significant effects of visual correction type on photopic VA. Correction of astigmatism using toric CL resulted in significant improvements in night driving performance, compared to driving with spherical CL, particularly for sign recognition, avoidance of low contrast hazards, increased pedestrian recognition distances and overall driving score (p<0.05). Correction of low to moderate levels of astigmatism had significant positive effects on night-time driving performance and related tests of visual performance. This has important implications for optical corrections to improve night road safety of drivers with astigmatism.

Macular Thickness and Mesopic Visual Acuity in Healthy Older Subjects

ABSTRACTPurpose/Aim: Impaired mesopic visual acuity (VA) is a risk factor for incident early age-related macular degeneration (AMD) This study examines relationships between macular thickness measurements and photopic or mesopic VA in healthy eyes.Materials and Methods: In 38 young and 39 older healthy individuals, total, inner, and outer retinal layer (IRL and ORL) thicknesses were measured in the macula region through spectral-domain optical coherence tomography (SD-OCT). Measurements were made across three subfields centered at the fovea: central foveal, pericentral, and peripheral. Best-corrected distance high-contrast (HC) and low-contrast (LC) VA were measured using Bailey-Lovie logMAR letter charts under photopic and mesopic luminance conditions. In addition, the low luminance deficit in VA (LLD, difference between photopic and mesopic VA) was calculated. Relationships were examined through Spearman correlation in each age group and through multiple linear regressions across all eyes.Results: No significant correlations were detected between photopic VA (HC-VA and LC-VA) and macular thickness measurements in each age group. In mesopic conditions, age and pupil size were independent predictors of HC-VA (p = 0.001) and age and pericentral ORL thickness predictors of LC-VA (p = 0.001). Central foveal thickness emerged as the unique independent predictor of LLD (HC-VA, p = 0.013 and LC-VA, p = 0.005). Only in the older age group, was central foveal thicknesses correlated with LLD (HC-VA, r = + 0.45; p = 0.004 and LC-VA, r = + 0.33, p = 0.038).Conclusions: Greater macular thicknesses were related to worse mesopic VA and low luminance deficit in healthy subjects.

Early Changes in Visual Quality and Corneal Structure after DMEK: Does DMEK Approach Optical Quality of a Healthy Cornea?

Purpose To evaluate early changes in visual function and visual quality parameters after Descemet membrane endothelial keratoplasty (DMEK) and to compare the outcomes with healthy controls. Methods Thirteen patients who underwent DMEK and 14 controls were evaluated. All subjects underwent visual function evaluation, including visual acuity under photopic and mesopic lighting conditions and contrast sensitivity (CSV) tests CSV 1000 and Pelli-Robson. Corneal parameters were assessed with Oculus Pentacam. Corneal mean keratometry (Km), corneal densitometry values, and low and high order aberrations (LOA and HOA) were recorded. In DMEK patients, all tests were performed before surgery and 1 and 6 months after surgery. Results In patients who underwent DMEK, photopic visual acuity improved from 0.59 to 0.31 at 1 month (p=0.013) and 0.13 at 6 months (p=0.008); mesopic visual acuity and all contrast sensitivity values (both CSV and Pelli-Robson test) improved significantly in the first month (p < 0.005). A significant decrease was observed in corneal density in the 0–2 mm ring (from 43.83 to 35.60, p=0.043) and mean posterior Km (from −5.84 to −6.80, p=0.005) in the first month. Corneal HOAs and all corneal densities improved at 6 months after DMEK (p < 0.05). All visual function parameters and corneal aberrations remained lower and higher, respectively, compared with healthy controls (p < 0.05). Corneal densities were comparable with controls at 6 months after DMEK (p > 0.05). Conclusions Patients undergoing DMEK present visual function improvement and a decrease in corneal density at 1 month after surgery. Decrease in corneal posterior HOAs can be observed at 6 months. However, visual function outcomes and corneal aberrations remained worse compared with healthy controls.

Binocular visual function of myopic pseudophakic monovision.

To compare binocular visual function of myopic pseudophakic patients with myopic monovision to patients without monovision. Randomized comparative study METHODS: Sixty patients were randomized to one of two groups: patients whose refraction was targeted to -2.75 diopters (D) in the dominant eye and -1.75D in the nondominant eye (myopic monovision group), and patients whose refraction was targeted to -2.75D bilaterally (non-monovision group). Binocular uncorrected and corrected visual acuity at various distances was measured using an all-distance vision tester, and contrast visual acuity and near stereoacuity were examined. In the myopic monovision group mean refraction was -2.74D in the dominant eyes and -1.94D in the nondominant eyes, and in the non-monovision group it was -2.96D bilaterally. Mean binocular uncorrected distance (UDVA) and intermediate visual acuity (UIVA) from 0.5 m to 5.0 m were significantly better in the myopic monovision group than in the non-monovision group (P≤ 0.0134), while binocular uncorrected near visual acuity (UNVA) at 0.3 m did not differ significantly between groups. The distribution of UIVA and UDVA was significantly better in the myopic monovision group (P≤ 0.0035). Corrected visual acuity at any distance, photopic and mesopic contrast visual acuity, and stereoacuity did not differ significantly between groups. Patients with myopic monovision exhibited significantly better binocular UIVA and UDVA than those without monovision, while UNVA, corrected visual acuity, contrast sensitivity, and stereoacuity were comparable between groups, suggesting that this method is useful for patients who want to see near and intermediate distances without spectacles.