Freiburg Visual Acuity Test Research Articles

Effect of nystagmus on VEP-based objective visual acuity estimates

In order to determine the effect of nystagmus on objective visual acuity (VA) estimates, we compared subjective (VApsych) and objective (VEP, VAVEP) VA estimates in participants with nystagmus. For this purpose, 20 participants with nystagmus (NY) caused by idiopathic infantile nystagmus, albinism, achiasma or acquired nystagmus were recruited in this study. Estimates of BCVA (best corrected visual acuity) were determined psychophysically (VApsych; FrACT, Freiburg visual acuity test) and electrophysiologically (VAVEP; EP2000) according to ISCEV (International Society of Clinical Electrophysiology of Vision) guidelines. For each participant the eye with the stronger fixation instability [Nidek microperimeter (MP-1), Nidek Instruments] was included for further analysis. VApsych vs VAVEP were compared via paired t-tests and the correlation of the difference between VApsych and VAVEP (∆VA) vs the degree of fixation instability was tested with Pearson correlation (r). We found VAVEP to be better than VApsych [by 0.12 Logarithm of the Minimum Angle of Resolution (logMAR); mean ± standard error (SE) of VAVEP vs VApsych: 0.176 ± 0.06 vs. 0.299 ± 0.06, P = 0.017] and ∆VA to be correlated linearly with the degree of fixation instability (r2 = 0.21,p = 0.048). In conclusion, on average we report a small VA overestimation, around 1 line, for VAVEP compared to VApsych in NY. This overestimation depended on the magnitude of the fixation instability. As a rule of thumb, a reduction of the fixation probability in the central 4° from 100 to 50% leads on average to a VAVEP overestimation of around 0.25 logMAR, i.e. 2.5 lines.

Evaluation of the effects of blue-enriched white light on cognitive performance, arousal, and overall appreciation of lighting.

Light's non-visual effects on the biological clock, cognitive performance, alertness, and mental health are getting more recognized. These are primarily driven by blue light, which triggers specific retinal cells containing melanopsin. Traditionally, research on light has relied on correlated color temperature (CCT) as a metric of its biological influence, given that bluer light corresponds to higher Kelvin values. However, CCT proves to be an inadequate proxy of light's biological effects. A more precise metric is melanopic Equivalent Daylight Illuminance (mel-EDI), which aligns with melanopsin spectrum. Studies have reported positive cognitive impacts of blue-enriched white light. It's unclear if the mixed results are due to different mel-EDI levels since this factor wasn't assessed. Given recent recommendations from experts to aim for at least 250 mel-EDI exposure daily for cognitive benefits, our aim was to assess if a 50-minute exposure to LED light with 250 mel-EDI could enhance concentration and alertness, without affecting visual performance or comfort compared to conventional lighting producing around 150 mel-EDI. To ensure mel-EDI's impact, photopic lux levels were kept constant across conditions. Conditions were counterbalanced, parameters included subjective sleepiness (KSS; Karolinska Sleepiness Scale), concentration (d2-R test), visual performance (FrACT; Freiburg Visual Acuity and Contrast Test), general appreciation (VAS; Visual Analogous Scale), preferences and comfort (modified OLS; Office Lighting Survey). The experimental light significantly reduced sleepiness (p = 0.03, Cohen's d = 0.42) and also decreased contrast sensitivity (p = 0.01, Cohen's d = 0.50). The conventional light was found to be more comfortable (p = 0.002, Cohen's d = 0.62), cheerful (p = 0.02, Cohen's d = 0.46) and pleasant (p = 0.005, Cohen's d = 0.55) while the experimental light was perceived as brighter (p = 0.004, Cohen's d = 0.58) and tended to be more stimulating (p = 0.10). Notably, there was a preference for conventional lighting (p = 0.004, Cohen's d=0.56) and concentration was equally improved in both conditions. Despite the lack of further improvement in concentration from exposure to blue-enriched light, given the observed benefits in terms of vigilance, further research over an extended period would be justified. These findings could subsequently motivate cognitive optimization through lighting for workers that would benefit from artificial lighting such as in northern regions.

Scotopic and Photopic Conventional Visual Acuity and Hyperacuity - Binocular Summation.

The purpose of this study was to determine and compare binocular summation (BiS) of conventional visual acuity (cVA) versus hyperacuity (hVA) for photopic and scotopic luminance conditions as a potential biomarker to assess the outcome of interventions on binocular function. Sixteen young adults (age range [years] = 21-31; 8 women; cVA logMAR < 0.0) participated in this study. The Freiburg Visual Acuity Test (FrACT) was used for VA testing and retested on another day. Both cVA and hVA were determined for dark grey optotypes on light grey background. Participants underwent 40minutes of dark adaptation prior to scotopic VA testing. Binocular and monocular VA testing was performed. The eye with better VA over the 2 days of testing was selected, the BiS was quantified (binocular VA - better monocular VA) and repeated measures ANOVAs were performed. Binocular VA exceeded monocular VA for all luminance conditions, VA-types, and sessions. We report BiS estimates for photopic and scotopic cVA and hVA, (logMAR BiS ± SEM [decimal BiS]): photopic = -0.01 ± 0.01 [1.03] and -0.06 ± 0.03 [1.15]; and scotopic = -0.05 ± 0.01 [1.12] and -0.11 ± 0.04 [1.28], respectively). Improvement for binocular vision estimates ranged from 0.01 to 0.11 logMAR. A repeated-measures ANOVA (RM ANOVA) did not reveal significant effects of LUMINANCE or VA TYPE on BiS, albeit a trend for strongest BiS for scotopic hVA (15% vs. 28%, photopic versus scotopic, respectively) and weakest for photopic cVA (3% vs. 12%, photopic versus scotopic conditions, respectively). Our results indicate that BiS of VA is relevant to scotopic and photopic hVA and cVA. It appears therefore a plausible candidate biomarker to assess the outcome of retinal therapies restoring rod or cone function on binocular vision. Binocular summation of visual acuity might serve as a clinical biomarker to monitor therapy outcome on binocular rod and cone-mediated vision.

The Freiburg Acuity Test in Preschool Children: Testability, Test-Retest Variability, and Comparison With LEA Symbols.

To determine the testability, performance, and test-retest variability (TRV) of visual acuity (VA) assessment using the Freiburg Visual Acuity Test (FrACT) compared to the LEA Symbols Test (LEA) in preschool children. In 134 preschool children aged 3.0 to 6.8years, monocular VA of each eye was measured twice with a four-orientation Landolt C version of the FrACT and once with the LEA. FrACT runs were preceded by a binocular run for explanatory purposes. Test order alternated between subjects. Optotypes were presented on a computer monitor (FrACT) or on cards (LEA) at a distance of 3 m. Overall, 68% completed the FrACT (91/134 children) and 88% completed the LEA (118/134 children). Testability depended on age: FrACT, 19% (<4years) and 87% (≥4years); LEA, 70% (<4years) and 95% (≥4years). Mean ± SD VA difference between tests was 0.11 ± 0.19 logarithm of the minimum angle of resolution [logMAR], with LEA reporting better acuity. The difference depended on age (0.27 ± 0.23 logMAR [<4years], 0.09 ± 0.18 logMAR [≥4years], P<0.001) and on test sequence (higher age dependence of FrACT VAs for LEA first, P<0.001). The 95% limits of agreement for the FrACT TRV were ±0.298 logMAR. The examiner-independent FrACT, using international reference Landolt C optotypes, can be used to assess VA in preschool children aged ≥4years, with reliability comparable to other pediatric VA tests. Use of the automated FrACT for VA assessment in preschool children may benefit objectivity and validity as it is a computerized test and employs the international reference Landolt C optotype.

Visual acuity testing in preschool children: Freiburg acuity test (FrACT) vs LEA symbols test

Aims/Purpose: Cross‐sectional study to compare testability and performance of the Freiburg Visual Acuity Test (FrACT) and LEA Symbols Test (LEA) and to determine test–retest variability of visual acuities (VAs) achieved with the FrACT in preschool children.Methods: Monocular VA of both eyes was measured in 136 preschool children (268 eyes) aged 3.0 to 6.8 years – once with the LEA and twice with a 4‐orientation Landolt C version of the FrACT. The monocular FrACT runs were preceded by a binocular run for explanatory purposes. The test order alternated between subjects. Optotypes were presented either on a computer monitor (FrACT) or on cards (Lighthouse Single Symbol Book; LEA) at a distance of 3 m.Results: The overall testability of children was 70.1% for FrACT (188 of 268 eyes) and 90.3% for LEA (242 of 268 eyes). Testability depended markedly on age, with children aged &lt;4 years at 23.0% (FrACT), 73.0% (LEA); ≥ 4 years: 88.1% (FrACT), 96.9% (LEA). The mean VA difference between FrACT and LEA was 0.11 LogMAR, with LEA reporting better acuity. The difference depended on age, with children aged &lt;4 years exhibiting greater VA differences (0.27 LogMAR) while differences were smaller in children aged ≥4 years (0.09 LogMAR); in an additional adult control group the VA values of LEA and FrACT were even closer with 0.02 LogMAR mean difference. The 95% limits of agreement of test–retest‐variability of VAs in the FrACT were ± 0.29 LogMAR with a bias of 0.017 LogMAR (better acuity for the first test run).Conclusions: The FrACT, as an examiner‐independent tool using international reference Landolt C optotypes, can be reliably used to assess VA in preschool children aged 4 years and older. We confirm that the LEA Symbols Test reports better acuity than tests based on Landolt rings.

Visual acuity and reading print size requirements in children with vision impairment

ABSTRACT Clinical Relevance The support of students with a vision impairment throughout education could be enhanced by assessing the functional reading ability of the individual. This visual assessment could inform educators of individualised student needs and potentially improve the academic achievement for these students. Background Support for children with a vision impairment within a classroom is typically based on clinical findings of distance visual acuity and visual fields. Therefore, determining optimal print size for reading is essential to ensure best academic outcomes. Secondary aims were to investigate the possible impact of underlying pathology on reading ability. Methods Forty-seven participants were recruited from a state-wide support service for children with a vision impairment in South Australia. Three visual acuity groups were formed based on World Health Organisation definitions of mild, moderate, and severe vision impairment. Correlation between clinical measures of distance visual acuity using the Freiburg Visual Acuity Test, were compared with reading acuity and critical print size (smallest font before reading speed reduced) using Minnesota low vision reading chart (MNREAD). Results No significant correlations were found for mild (0.20–0.49 logMAR) and severe (1.00–1.52 logMAR) vision impairment groups between distance visual acuity and reading acuity read (p = .64, CI [−.585, .395]/p = .82, CI [−.48, .58]) or critical print size (p = .78, CI [−.57, .45]/p = .43, CI [−.34, .68]. A significant correlation was found for the moderate vision impairment group: 0.50–0.99 logMAR for minimum reading acuity (p < .001, CI [.44, .91]) and critical print size (p = .03, CI [.05, .80]). Conclusions Standard clinical measures of distance visual acuity are an unpredictable estimate of reading ability in children with mild and severe vision impairment. Additional measures of functional near reading ability could provide a more meaningful indicator of reading ability and help provide optimum support to students through education.

Blue-light stimulation of the blind-spot constricts the pupil and enhances contrast sensitivity.

Short- and long-wavelength light can alter pupillary responses differently, allowing inferences to be made about the contribution of different photoreceptors on pupillary constriction. In addition to classical retinal photoreceptors, the pupillary light response is formed by the activity of melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGC). It has been shown in rodents that melanopsin is expressed in the axons of ipRGCs that bundle at the optic nerve head, which forms the perceptual blind-spot. Hence, the first aim of this study was to investigate if blind-spot stimulation induces a pupillary response. The second aim was to investigate the effect of blind-spot stimulation by using the contrast sensitivity tests. Fifteen individuals participated in the pupil response experiment and thirty-two individuals in the contrast sensitivity experiment. The pupillary change was quantified using the post-illumination pupil response (PIPR) amplitudes after blue-light (experimental condition) and red-light (control condition) pulses in the time window between 2 s and 6 s post-illumination. The contrast sensitivity was assessed using two different tests: the Freiburg Visual Acuity Test and Contrast Test and the Tuebingen Contrast Sensitivity Test, respectively. Contrast sensitivity was measured before and 20 minutes after binocular blue-light stimulation of the blind-spot at spatial frequencies higher than or equal to 3 cycles per degree (cpd) and at spatial frequencies lower than 3 cpd (control condition). Blue-light blind-spot stimulation induced a significantly larger PIPR compared to red-light, confirming a melanopsin-mediated pupil-response in the blind-spot. Furthermore, contrast sensitivity was increased after blind-spot stimulation, confirmed by both contrast sensitivity tests. Only spatial frequencies of at least 3 cpd were enhanced. This study demonstrates that stimulating the blind-spot with blue-light constricts the pupil and increases the contrast sensitivity at higher spatial frequencies.

Contrast Sensitivity and Night Driving in Older People: Quantifying the Relationship Between Visual Acuity, Contrast Sensitivity, and Hazard Detection Distance in a Night-Time Driving Simulator.

Purpose(i) To assess how well contrast sensitivity (CS) predicts night-time hazard detection distance (a key component of night driving ability), in normally sighted older drivers, relative to a conventional measure of high contrast visual acuity (VA); (ii) To evaluate whether CS can be accurately quantified within a night driving simulator.Materials and MethodsParticipants were 15 (five female) ophthalmologically healthy adults, aged 55–81 years. CS was measured in a driving simulator using Landolt Cs, presented under static or dynamic driving conditions, and with or without glare. In the dynamic driving conditions, the participant was asked to simultaneously maintain a (virtual) speed of 60 km/h on a country road. In the with glare conditions, two calibrated LED arrays, moved by cable robots, simulated the trajectories and luminance characteristics of the (low beam) headlights of an approaching car. For comparison, CS was also measured clinically (with and without glare) using a Optovist I instrument (Vistec Inc., Olching, Germany). Visual acuity (VA) thresholds were also assessed at high and low contrast using the Freiburg Visual Acuity Test (FrACT) under photopic conditions. As a measure of driving performance, median hazard detection distance (MHDD) was computed, in meters, across three kinds of simulated obstacles of varying contrast.ResultsContrast sensitivity and low contrast VA were both significantly associated with driving performance (both P < 0.01), whereas conventional high contrast acuity was not (P = 0.10). There was good correlation (P < 0.01) between CS measured in the driving simulator and a conventional clinical instrument (Optovist I). As expected, CS was shown to decrease in the presence of glare, in dynamic driving conditions, and as a function of age (all P < 0.01).ConclusionContrast sensitivity and low contrast VA predict night-time hazard detection ability in a manner that conventional high contrast VA does not. Either may therefore provide a useful metric for assessing fitness to drive at night, particularly in older individuals. CS measurements can be made within a driving simulator, and the data are in good agreement with conventional clinical methods (Optovist I).

Real-time, precise, rapid and objective visual acuity assessment by self-adaptive step SSVEPs

Objective. This study aimed to explore an online, real-time, and precise method to assess steady-state visual evoked potential (SSVEP)-based visual acuity more rapidly and objectively with self-adaptive spatial frequency steps. Approach. Taking the vertical sinusoidal reversal gratings with different spatial frequencies and temporal frequencies as the visual stimuli, according to the psychometric function for visual acuity assessment, a self-adaptive procedure, the best parameter estimation by sequential testing algorithm, was used to calculate the spatial frequency sequence based on all the previous spatial frequencies and their significance of the SSVEP response. Simultaneously, the canonical correlation analysis (CCA) method with a signal-to-noise ratio (SNR) significance detection criterion was used to judge the significance of the SSVEP response. Main results. After 18 iterative trails, the spatial frequency to be presented converged to a value, which was exactly defined as the SSVEP visual acuity threshold. Our results indicated that this SSVEP acuity had a good agreement and correlation with subjective Freiburg Visual Acuity and Contrast Test acuity, and the test–retest repeatability was also good. Significance. The self-adaptive step SSVEP procedure combined with the CCA method and SNR significance detection criterion appears to be an alternative method in the real-time SSVEP acuity test to obtain objective visual acuity more rapidly and precisely.

Association of Patterns of Glaucomatous Macular Damage With Contrast Sensitivity and Facial Recognition in Patients With Glaucoma

Facial recognition is a critical activity of daily living that relies on macular function. Glaucomatous macular damage may result in impaired facial recognition that may negatively affect patient quality of life. To evaluate the association of patterns of glaucomatous macular damage with contrast sensitivity and facial recognition among patients with glaucoma. In this prospective cohort study at a single tertiary care center, 144 eyes of 72 consecutive patients with glaucoma with good visual acuity (20/40 or better in each eye) were studied. Data were collected from March to April 2019. Eyes with macular damage were categorized as having focal, diffuse, or mixed (focal and diffuse) damage based on optic disc and macular spectral-domain optical coherence tomography and 10-2 visual field (VF) damage. Only eyes with focal or diffuse damage were included. Higher-acuity and lower-acuity eyes were determined by 10-2 VF mean deviation (MD). Facial disability was defined as facial recognition scores at the 2% level of normal participants. (1) Monocular contrast threshold as measured by the Freiburg Visual Acuity and Contrast Test and (2) binocular facial recognition as measured by the Cambridge Face Memory Test. Of the 72 included patients, 49 (68%) were White and 41 (57%) were female, and the mean (SD) age was 67.0 (11.6) years. Eyes with diffuse damage had greater contrast impairment compared with eyes with focal damage (β = -0.5; 95% CI, -0.6 to -0.4; P < .001) after adjusting for 10-2 VF MD, 24-2 VF MD, age, presence of an early cataract, and number of drops. Similarly, Cambridge Face Memory Test scores were significantly lower in patients with diffuse rather than focal macular damage, regardless of eye (better-seeing eye: β = 10.0; 95% CI, 2.0 to 18.2; P = .001; worse-seeing eye: β = 5.5; 95% CI, 0.8 to 10.0; P = .23). Relative risk of facial disability was greater for patients with diffuse but not focal macular damage in the better-seeing eye (relative risk, 86.2; 95% CI, 2.7 to 2783.3; P = .01). In this cohort study, diffuse rather than focal glaucomatous macular damage was associated with diminished facial recognition and contrast sensitivity. Evaluation of macular optical coherence tomography and 10-2 VF and resultant detection of diffuse macular damage may help minimize glaucoma-related visual disability.

Accident Vulnerability and Vision for Action: A Pilot Investigation.

Many accidents, such as those involving collisions or trips, appear to involve failures of vision, but the association between accident risk and vision as conventionally assessed is weak or absent. We addressed this conundrum by embracing the distinction inspired by neuroscientific research, between vision for perception and vision for action. A dual-process perspective predicts that accident vulnerability will be associated more strongly with vision for action than vision for perception. In this preliminary investigation, older and younger adults, with relatively high and relatively low self-reported accident vulnerability (Accident Proneness Questionnaire), completed three behavioural assessments targeting vision for perception (Freiburg Visual Acuity Test); vision for action (Vision for Action Test—VAT); and the ability to perform physical actions involving balance, walking and standing (Short Physical Performance Battery). Accident vulnerability was not associated with visual acuity or with performance of physical actions but was associated with VAT performance. VAT assesses the ability to link visual input with a specific action—launching a saccadic eye movement as rapidly as possible, in response to shapes presented in peripheral vision. The predictive relationship between VAT performance and accident vulnerability was independent of age, visual acuity and physical performance scores. Applied implications of these findings are considered.

Threshold Determination Criterion in Steady-State Visual Evoked Potential-Based Acuity Assessment: A Comparison of Four Common Methods

The steady-state visual evoked potential (SSVEP) visual acuity is usually defined by extrapolating a straight line regressed through significant SSVEP amplitudes plotted versus spatial frequencies to 0 μV or a noise level floor, or the finest spatial frequency evoking a significant SSVEP. This study aimed to compare the performance of the commonly used threshold determination criteria of the extrapolation technique and the finest spatial frequency technique. Visual acuity was measured both by the Freiburg Visual Acuity Test (FrACT) and SSVEP with vertical sinusoidal reversal gratings in ten adults. The extrapolation technique including three methods of linear extrapolation to zero (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ), linear extrapolation to noise level baseline (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and linear extrapolation to zero versus log spatial frequency (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ), and the finest spatial frequency technique with significance determination by canonical correlation analysis (CCA) and “OR”operation (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) were used to determine the SSVEP visual acuity. Bland-Altman method found a pretty good agreement between the SSVEP and FrACT acuity obtained by all the four threshold estimation criteria. One-way repeated-measures ANOVA and Bonferroni post-hoc analysis found that there was no significant difference among visual acuities measured by FrACT and all the four criteria, except for the visual acuity estimated by C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> slightly higher than that of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , demonstrating that these visual acuity estimating methods had a similar performance in evaluating the visual function. The correlation and agreement between subjective FrACT acuity and objective SSVEP acuity measured by four criteria respectively were all pretty good, demonstrating that all of these four threshold estimation criteria had a good performance in SSVEP visual acuity assessment.

Objective assessment of visual acuity: a refined model for analyzing the sweep VEP.

The aim of this study was to develop a simple and reliable method for the objective assessment of visual acuity by optimizing the stimulus used in commercially available systems and by improving the methods of evaluation using a nonlinear function, the modified Ricker model. Subjective visual acuity in the normal subjects was measured with Snellen targets, best-corrected, and in some cases also uncorrected and with plus lenses (+ 1D, + 2D, + 3D). In patients, subjective visual acuity was measured best-corrected using the Freiburg Visual Acuity Test. Sweep VEP recordings to 11 spatial frequencies, with check sizes in logarithmically equidistant steps (0.6, 0.9, 1.4, 2.1, 3.3, 4.9, 7.3, 10.4, 18.2, 24.4, and 36.5cpd), were obtained from 56 healthy subjects aged between 17 and 69years (mean 42.5 ± 15.3SD years) and 20 patients with diseases of the lens (n = 6), retina (n = 8) or optic nerve (n = 6). The results were fit by a multiple linear regression (2nd-order polynomial) or a nonlinear regression (modified Ricker model) and parameters compared (limiting spatial frequency (sflimiting) and the spatial frequency of the vertex (sfvertex) of the parabola for the 2nd-order polynomial fitting, and the maximal spatial frequency (sfmax), and the spatial frequency where the amplitude is 2dB higher than the level of noise (sfthreshold) for the modified Ricker model. Recording with 11 spatial frequencies allows a more accurate determination of acuities above 1.0 logMAR. Tuning curves fitted to the results show that compared to the normal 2nd-order polynomial analysis, the modified Ricker model is able to describe closely the amplitudes of the sweep VEP in relation to the spatial frequencies of the presented checkerboards. In patients with a visual acuity better than about 0.5 (decimal), the predicted acuities based on the different parameters show a good match of the predicted visual acuities based on the models established in healthy volunteers to the subjective visual acuities. However, for lower visual acuities, both models tend to overestimate the visual acuity (up to ~ 0.4 logMAR), especially in patients suffering from AMD. Both models, the 2nd-order polynomial and the modified Ricker model performed equally well in the prediction of the visual acuity based on the amplitudes recorded using the sweep VEP. However, the modified Ricker model does not require the exclusion of data points from the fit, as necessary when fitting the 2nd-order polynomial model making it more reliable and robust against outliers, and, in addition, provides a measure for the noise of the recorded results.

The effect of increasing the illumination on operators\u2019 visual performance in the control-room of a combined cycle power plant

BackgroundLighting is one of the environmental factors affecting the performance of the control room operators. Therefore, the aim of this study was to compare the control room operators’ visual performance in two different illumination conditions at a combined cycle power plant through field-work.MethodsSixteen operators in day shift were evaluated with the Freiburg Visual Acuity test (FrACT) software at two lighting systems with different intensities. It includes the first phase with fluorescent illumination system (Power: 40 W, Color Temperature: 4000 Kelvin, Luminous Flux: 2780 Lumen and Model: Pars Shahab) and the second phase with a combined illumination system includes fluorescent and LED (Power: 48 W, Color Temperature: 4000 Kelvin, Luminous Flux: 5400 Lumen and Model: Mazinoor).ResultsBased on the results, visual performance index and visual acuity significantly increased after the intervention (p < 0.001). As to contrast, more lighting significantly reduced the percentage of recognized contrast (p < 0.001) and increased the contrast performance index (p < 0.001).ConclusionsThe results of this study showed that increasing the intensity of light from the values below the allowable limit to the values above the allowable limit would increase the visual indicators in individuals.

Opacificación capsular posterior en lentes intraoculares hidrofílicos en comparación con lentes intraoculares hidrofóbicos usando imágenes de Scheimpflug

PurposeTo determine the visual outcomes and posterior capsule opacification in acrylic intraocular lenses (IOL). MethodsProspective analysis of 38 eyes of 19 patients who had uneventful phacoemulsification with implantation of a IOL Akreos MI60 or a IOL Acrysof IQ from February 2013 to January 2014. Patients from a single surgeon, the protocol included the determination logMAR best corrected visual acuity, spherical equivalent, contrast sensitivity assessed by the freiburg visual acuity test and posterior capsule opacification scoring using the evaluation of posterior capsular opacification system (EPCO2000) by digital retroillumination photography and high resolution tomograms from Scheimpflug reconstructions analyzed using ImageJ freeware. ResultsThe mean follow up was 6.2 months±1.4 (SD). Contrast sensitivity and best corrected visual acuity were similar between the lenses. Mean pixel intensity value using EPCO2000 software for Akreos MI60 was 1.08U and 1.08U for Acrysof IQ (P=.785). Using ImageJ mean value in pixels for Akreos MI60 was 1.76U and for Acrysof IQ was 2.56U (P=.027). There were no significant correlationship between EPCO2000 and Scheimpflug images (r=.141, P=.412). ConclusionsThis study found that the results of visual function were comparable between both lenses. The posterior capsular opacification was seen to be lesser extent with the Akreos MI60 IOL when measured by Scheimpflug images, probably due to the very design of the lens which showed no correlation compared to the digital retroillumination photoghaphy.

Visual evoked potential-based acuity assessment: overestimation in amblyopia

When visual acuity (VA) is assessed with spatially repetitive stimuli (e.g., gratings) in amblyopes, VA can be markedly overestimated. We evaluated to what extent this also applies to VEP-based objective acuity assessment, which typically uses gratings or checkerboards. Seventeen subjects with amblyopia (anisometropic and strabismic) participated in the study; decimal VA range of their amblyopic eye covered 0.03-1.0 (1.5-0.0 logMAR). Using the Freiburg Acuity VEP (FrAVEP) method, checkerboard stimuli with six check sizes covering 0.02°-0.4° were presented in brief-onset mode (40 ms on, 93 ms off) at 7.5 Hz. All VEPs were recorded with a Laplacian montage. Fourier analysis yielded the amplitude and significance at the stimulus frequency. Psychophysical VA was assessed with the Landolt-C-based automated Freiburg Visual Acuity Test (FrACT). Test-retest limits of agreement for both FrACT and FrAVEP were ±0.20 logMAR. In all but two dominant eyes and high-acuity amblyopic eyes (VA<0.3 logMAR), FrACT and FrAVEP agreed within the expected limits of ±0.3 logMAR. However, the VEP-based acuity procedure overestimated single Landolt-C acuity by more than 0.3 logMAR in 9 of 17 (53%) of the amblyopic eyes, up to 1 logMAR. While all subjects had a psychophysical acuity difference>0.2 logMAR between the dominant and amblyopic eye, only three of them showed such difference with the FrAVEP. Both measurements of visual acuity with the VEP and FrACT were highly reproducible. However, as expected, in amblyopia, acuity can be markedly overestimated using the VEP. We attribute this to the use of repetitive stimulus patterns (checkerboards), which also lead to overestimation in psychophysical measures. The VEP-based objective assessment never underestimated visual acuity, but needs to be interpreted with appropriate caution in amblyopia.

Nonretinotopic Exogenous Attention

Attention is crucial for visual perception because it allows the visual system to effectively use its limited resources by selecting behaviorally and cognitively relevant stimuli from the large amount of information impinging on the eyes. Reflexive, stimulus-driven attention is essential for successful interactions with the environment because it can, for example, speed up responses to life-threatening events. It is commonly believed that exogenous attention operates in the retinotopic coordinates of the early visual system. Here, using a novel experimental paradigm [1], we show that a nonretinotopic cue improves both accuracy and reaction times in a visual search task. Furthermore, the influence of the cue is limited both in space and time, a characteristic typical of exogenous cueing. These and other recent findings show that many more aspects of vision are processed nonretinotopically than previously thought.

The effect of optotype presentation duration on acuity estimates revisited

A high reproducibility of visual acuity estimates is important when monitoring disease progression or treatment success. One factor that may affect the result of an acuity measurement is the duration of optotype presentation. For times below 1 s, previous studies have convincingly shown that acuity estimates increase with presentation duration. For durations above 1 s, the situation is less clear. We have reassessed this issue using the Freiburg Visual Acuity Test with normal subjects. Presentation durations of 0.1 s, 1 s, and 10 s were assessed. Confirming previous findings, in all subjects acuity estimates in the 1-s condition were higher than those in the 0.1-s condition, on average nearly by a factor of 2, equivalent to 3 lines. However, in 12 out of 14 subjects, acuity estimates increased further with a presentation duration of 10 s, on average by 23% (P=0.002), or roughly 1 line. Test-retest variability improved by 49% (P=0.003). These findings can be explained by a simple statistical model of acuity fluctuations. Cognitive processing may also be a relevant factor. Interestingly, most observers subjectively felt that they could perceive the optotypes best in the 1-s condition. The results highlight the importance of standardizing presentation durations when high reproducibility is required.

Enhanced Visual Acuity and Image Perception Following Correction of Highly Aberrated Eyes Using an Adaptive Optics Visual Simulator

To evaluate the changes in visual acuity and visual perception generated by correcting higher order aberrations in highly aberrated eyes using a large-stroke adaptive optics visual simulator. A crx1 Adaptive Optics Visual Simulator (Imagine Eyes) was used to correct and modify the wavefront aberrations in 12 keratoconic eyes and 8 symptomatic postoperative refractive surgery (LASIK) eyes. After measuring ocular aberrations, the device was programmed to compensate for the eye's wavefront error from the second order to the fifth order (6-mm pupil). Visual acuity was assessed through the adaptive optics system using computer-generated ETDRS opto-types and the Freiburg Visual Acuity and Contrast Test. Mean higher order aberration root-mean-square (RMS) errors in the keratoconus and symptomatic LASIK eyes were 1.88+/-0.99 microm and 1.62+/-0.79 microm (6-mm pupil), respectively. The visual simulator correction of the higher order aberrations present in the keratoconus eyes improved their visual acuity by a mean of 2 lines when compared to their best spherocylinder correction (mean decimal visual acuity with spherocylindrical correction was 0.31+/-0.18 and improved to 0.44+/-0.23 with higher order aberration correction). In the symptomatic LASIK eyes, the mean decimal visual acuity with spherocylindrical correction improved from 0.54+/-0.16 to 0.71+/-0.13 with higher order aberration correction. The visual perception of ETDRS letters was improved when correcting higher order aberrations. The adaptive optics visual simulator can effectively measure and compensate for higher order aberrations (second to fifth order), which are associated with diminished visual acuity and perception in highly aberrated eyes. The adaptive optics technology may be of clinical benefit when counseling patients with highly aberrated eyes regarding their maximum subjective potential for vision correction.

Validation of Modified Grating Test as a visual acuity test in low vision patients with retinitis pigmentosa

Abstract Purpose The Modified Grating Test is a newly designed test for visual acuity (VA) measurement in patients with retinitis pigmentosa (RP) with low vision. Freiburg Visual Acuity Test (FrACT) is a validated test for low vision, but no patients with RP were tested. In our study we tested RP patients investigating the consistency of the Modified Grating Test by comparing the results with those of the FrACT and the ETDRS charts. Methods 16 eyes of 8 patients were tested and divided into 3 groups depending on their VA. Group 1 had a VA of hand motion (HM, n= 6), group 2 counting fingers (CF, n=6) and group 3 better than CF (n=4). The Modified Grating Test consists of a circle with black and white bars of the same width in a decreasing logarithmic order covering the range from 2.7 to 0.3 logMAR. The FrACT is a computerized test with Landoldt C in different directions and in decreasing order. ETDRS charts were used at a distance of 0.5m. Each test was performed 4‐5 times. The data were normally distributed. To compare the values we used the paired samples t‐test. Results The mean VA in group 1 as measured by the Modified Grating Test was 1.3 logMAR and by FrACT 1.21 logMAR (p=0.21). In the group 2 the patients reached a mean VA of 0.7 logMAR with the Modified Grating Test and 0.6 logMAR with FrACT. 0.68 logMAR was measured with ETDRS charts (p=0.13). Conclusion Our preliminary data suggest that the Modified Grating Test is a suitable test for the low vision range and might be beneficial for the follow up in patients undergoing a retinal prosthesis implantation.