Clinical Vision Tests Research Articles

Assessing the impact of glazing and window shade systems on view clarity

Windows provide access to daylight and outdoor views, influencing building design. Various glazing and window shade materials are used to mitigate glare, overheating and privacy issues, and they affect view clarity. Among them, we evaluated the effect of window films, electrochromic (EC) glass, and fabric shades on view clarity. We conducted an experiment with 50 participants using visual tests adapted from clinical vision tests (visual acuity, contrast sensitivity, color sensitivity) and images displayed on a computer monitor in a controlled laboratory. Window films and EC glass tints outperformed fabric shades in visual acuity, contrast sensitivity and view satisfaction with the exception of the darkest EC tint state and dark grey VLT 3% shade for color sensitivity and view satisfaction. The EC tints pose internal reflection issues and fabric shades are preferred for visual privacy. Window films and EC glass hinder participants’ blue–green color discrimination while fabric shades also decrease red–yellow color discrimination. Visual acuity predicts view satisfaction and contrast sensitivity is the strongest predictor for visual privacy. Generally, higher visible light transmittance and lower solar reflectance (darker color) enhance human visual performance. The proposed workflow provides an experimental procedure, identifies the primary variables and establishes a predictive framework for assessing view clarity of fenestration.

The Assessment of Vision in Children with Severe Learning Difficulties: A Systematic Review

The Assessment of Vision in Children with Severe Learning Difficulties: A Systematic Review

A novel tool for quantitative measurement of distortion in keratoconus.

BackgroundKeratoconus is associated with thinning and anterior protrusion of the cornea resulting in the symptoms of blurry and distorted vision. The commonly used clinical vision tests such as visual acuity and contrast sensitivity may not reflect the symptoms experienced in keratoconus and there are no quantitative tools to measure visual distortion. In this study, we used a quantitative test based on vernier alignment and field matching techniques to quantify visual distortion in keratoconus and assess its relation to corneal structural changes.MethodsA total of 50 participants (25 keratoconus and 25 visually normal) completed the experiment where they aligned supra-threshold white target circles in opposite field in reference to guidelines and circles to complete a square structure monocularly. The task was repeated five times and the global distortion index (GDI) and global uncertainty index (GUI) were calculated as the mean and standard deviation respectively of local perceived misalignment of target circles over five trials.ResultsBoth GDI and GUI were higher in participants with keratoconus compared to controls (p < 0.01). Both parameters correlated with the best corrected visual acuity, maximum corneal curvature (Kmax), topographical keratoconus classification (TKC) and central corneal thickness (CCT).ConclusionOur findings show that the quantitative measure of distortion could be a useful tool for behavioural assessment of progressive keratoconus.

Testing Vision Is Not Testing For Vision.

Visual prostheses aim to restore, at least to some extent, vision that leads to the type of perception available for sighted patients. Their effectiveness is almost always evaluated using clinical tests of vision. Clinical vision tests are designed to measure the limits of parameters of a functioning visual system. I argue here that these tests are rarely suited to determine the ability of prosthetic devices and other therapies to restore vision. This paper describes and explains many limitations of these evaluations.Prosthetic vision testing often makes use of multiple-alternative forced-choice (MAFC) procedures. Although these paradigms are suitable for many studies, they are frequently problematic in vision restoration evaluation. Two main types of problems are identified: (1) where nuisance variables provide spurious cues that can be learned in repeated training, which is common in prosthetic vision, and thus defeat the purpose of the test; and (2) even though a test is properly designed and performed, it may not actually measure what the researchers believe, and thus the interpretation of results is wrong. Examples for both types of problems are presented. Additional problems arise from confounding factors in the administration of tests are pointed as limitations of current device evaluation. For example, head tracing of magnified objects enlarged to compensate for the system's low resolution, in distinction from the scanning head (camera) movements with which users of prosthetic devices expand the limited field of view. Because of these problems, the ability to perform satisfactorily on the clinical tests is necessary but insufficient to prove vision restoration, therefore, additional tests are needed. I propose some directions to pursue in such testing.Translational RelevanceNumerous prosthetic devices are being developed and introduced to the market. Proving the utility of these devices is crucial for regulatory and even for post market acceptance, which so far has largely failed, in my opinion. Potential reasons for the failures despite success in regulatory testing and directions for designing improved testing are provided. It is hoped that improved testing will guide improved designs of future prosthetic systems and other vision restoration approaches.

Vision-Based Concussion/Mild Traumatic Brain Injury Diagnostic Tests/Biomarkers: An Update and Reappraisal

Detection and diagnosis of concussion/mild traumatic brain injury (C/mTBI) has a multitude of general vocational and avocational, as well as public health and educational, implications. A relatively short, focused, updated, highyield set of subjective and objective clinical vision tests are proposed that we and others have found to be assistive in the process. These vision tests are of a sensory, motor, and/or perceptual nature, many of which are relatively easy to implement in the standard, clinical environment.

Testing Vision is Not Testing For Vision

Visual prostheses aim to restore, at least to some extent, vision that leads to the type of perception available for sighted patients. Their effectiveness is almost always evaluated using clinical tests of vision. Clinical vision tests are designed to measure the limits of parameters of a functioning visual system. I argue here that these tests are rarely suited to determine the ability of prosthetic devices and other therapies to restore vision. This paper describes and explains many limitations of these evaluations. Prosthetic vision testing often makes use of multiple-alternative forced-choice (MAFC) procedures. Although these paradigms are suitable for many studies, they are frequently problematic in vision restoration evaluation. Two main types of problems are identified: (1) where nuisance variables provide spurious cues that can be learned in repeated training, which is common in prosthetic vision, and thus defeat the purpose of the test; and (2) even though a test is properly designed and performed, it may not actually measure what the researchers believe, and thus the interpretation of results is wrong. Examples for both types of problems are presented. Additional problems arise from confounding factors in the administration of tests are pointed as limitations of current device evaluation. For example, head tracing of magnified objects enlarged to compensate for the system's low resolution, in distinction from the scanning head (camera) movements with which users of prosthetic devices expand the limited field of view. Because of these problems, the ability to perform satisfactorily on the clinical tests is necessary but insufficient to prove vision restoration, therefore, additional tests are needed. I propose some directions to pursue in such testing. Translational relevance Numerous prosthetic devices are being developed and introduced to the market. Proving the utility of these devices is crucial for regulatory and even for post market acceptance, which so far has largely failed, in my opinion. Potential reasons for the failures despite success in regulatory testing and directions for designing improved testing are provided. It is hoped that improved testing will guide improved designs of future prosthetic systems and other vision restoration approaches.

Lost in the Lights: The Effects of Glare on Catching Performance

It has long been observed that glare produced by bright external light sources can impair sports performance, however, empirical research on this topic is limited. The goals of the present study were to investigate the effects of glare on catching performance and to determine to what extent these effects could be predicted by clinical tests of vision. College baseball players caught balls varying in both speed and direction. Glare was produced by a spotlight above the ball with glare magnitude varied by changing the angle subtended by the ball and the glare source. Three glare angles (12, 15 and 18 deg) were compared to a no glare condition. At 12 deg, the presence of glare produced both delayed reaction times and spatial and temporal errors in catching, while only the errors occurred for larger glare angles. Glare susceptibility assessed using a low contrast visual acuity test significantly correlated with catching performance in only 3 out of 7 conditions in which significant effects of glare on catching were found. The presence of glare can produce problems both in detecting an approaching object and in judging its trajectory and time of arrival. Clinical vision tests will have limited effectiveness for evaluating glare interventions. Meeting abstract presented at VSS 2015. Language: en

Optimisation and assessment of three modern touch screen tablet computers for clinical vision testing.

Technological advances have led to the development of powerful yet portable tablet computers whose touch-screen resolutions now permit the presentation of targets small enough to test the limits of normal visual acuity. Such devices have become ubiquitous in daily life and are moving into the clinical space. However, in order to produce clinically valid tests, it is important to identify the limits imposed by the screen characteristics, such as resolution, brightness uniformity, contrast linearity and the effect of viewing angle. Previously we have conducted such tests on the iPad 3. Here we extend our investigations to 2 other devices and outline a protocol for calibrating such screens, using standardised methods to measure the gamma function, warm up time, screen uniformity and the effects of viewing angle and screen reflections. We demonstrate that all three devices manifest typical gamma functions for voltage and luminance with warm up times of approximately 15 minutes. However, there were differences in homogeneity and reflectance among the displays. We suggest practical means to optimise quality of display for vision testing including screen calibration.

The effect of duration post-migraine on visual electrophysiology and visual field performance in people with migraine

In between migraine attacks, some people show visual field defects that are worse when measured closer to the end of a migraine event. In this cohort study, we consider whether electrophysiological responses correlate with visual field performance at different times post-migraine, and explore evidence for cortical versus retinal origin. Twenty-six non-headache controls and 17 people with migraine performed three types of perimetry (static, flicker and blue-on-yellow) to assess different aspects of visual function at two visits conducted at different durations post-migraine. On the same days, the pattern electroretinogram (PERG) and visual evoked response (PVER) were recorded. Migraine participants showed persistent, interictal, localised visual field loss, with greater deficits at the visit nearer to migraine offset. Spatial patterns of visual field defect consistent with retinal and cortical dysfunction were identified. The PERG was normal, whereas the PVER abnormality found did not change with time post-migraine and did not correlate with abnormal visual field performance. Dysfunction on clinical tests of vision is common in between migraine attacks; however, the nature of the defect varies between individuals and can change with time. People with migraine show markers of both retinal and/or cortical dysfunction. Abnormal visual field sensitivity does not predict abnormality on electrophysiological testing.

Testing vision: From laboratory psychophysical tests to clinical evaluation

®. ® Accurate and reliable evaluation of the visual function of patients is a critical factor both in diagnosing visual problems and in evaluating the outcome of clinical intervention. The scientific basis for measuring visual function in the laboratory is largely based on the details of signal detection theory and our knowledge of visual physiology. To be clinically useful, however, vision tests need to satisfy stringent requirements including high specificity and sensitivity, good test–retest reliability, robustness to individual variations in anatomical and physiological factors, as well as small variations in the testing environment (such as fluctuations in luminance), and still be quick and easy to administer. This Feature Issue contains reviews covering the historical background, the theoretical basis, and practical considerations for achieving useful measures of the most commonly tested visual functions in the clinic or in the laboratory. Each of the nine articles in this Feature Issue focuses on a different but equally important aspect of human vision. Starting from the monocular assessment of visual function (although binocular assessment is also possible), the first four papers deal with the measurement of visual acuity (Bailey & Lovie-Kitchin, 2013) and contrast sensitivity (Pelli & Bex, 2013), the calibration by a novel method of electronic displays for clinical vision tests, especially those related to contrast manipulation (To et al., 2013), and perim

An assessment of a modern touch-screen tablet computer with reference to core physical characteristics necessary for clinical vision testing

There are a multitude of applications using modern tablet computers for vision testing that are accessible to ophthalmology patients. While these may be of potential future benefit, they are often unsupported by scientific assessment. This report investigates the pertinent physical characteristics behind one of the most common highest specification tablet computers with regard to its capacity for vision testing. We demonstrate through plotting of a gamma curve that it is feasible to produce a precise programmable range of central luminance levels on the device, even with varying background luminance levels. It may not be possible to display very low levels of contrast, but carefully using the gamma curve information allows a reasonable range of contrast sensitivity to be tested. When the screen is first powered on, it may require up to 15 min for the luminance values to stabilize. Finally, luminance of objects varies towards the edge of the screen and when viewed at an angle. However, the resulting effective contrast of objects is less variable. Details of our assessments are important to developers, users and prescribers of tablet clinical vision tests. Without awareness of such findings, these tests may never reach satisfactory levels of clinical validity and reliability.

Psychophysical contrast calibration.

Electronic displays and computer systems offer numerous advantages for clinical vision testing. Laboratory and clinical measurements of various functions and in particular of (letter) contrast sensitivity require accurately calibrated display contrast. In the laboratory this is achieved using expensive light meters. We developed and evaluated a novel method that uses only psychophysical responses of a person with normal vision to calibrate the luminance contrast of displays for experimental and clinical applications. Our method combines psychophysical techniques (1) for detection (and thus elimination or reduction) of display saturating non-linearities; (2) for luminance (gamma function) estimation and linearization without use of a photometer; and (3) to measure without a photometer the luminance ratios of the display's three color channels that are used in a bit-stealing procedure to expand the luminance resolution of the display. Using a photometer we verified that the calibration achieved with this procedure is accurate for both LCD and CRT displays enabling testing of letter contrast sensitivity to 0.5%. Our visual calibration procedure enables clinical, internet and home implementation and calibration verification of electronic contrast testing.

Relationships in Glaucoma Patients Between Standard Vision Tests, Quality of Life, and Ability to Perform Daily Activities

Purpose: To determine the relationships among three methods of assessing visual loss caused by glaucoma: (1) standard clinical tests of vision, (2) self-reported quality of life, and (3) the ability to perform activities of daily living.Methods: One hundred and ninety two glaucoma patients with a full range of glaucomatous visual loss were selected from the Glaucoma Service of Wills Eye Institute. Subjects were evaluated clinically by visual acuity, contrast sensitivity, visual field, stereopsis, the Disc Damage Likelihood Scale, and intraocular pressure. Subjects were evaluated subjectively by the 25-item National Eye Institute’s Visual Functioning Questionnaire (NEI-VFQ-25) and objectively by a performance-based measure of visual function, the Assessment of Disability Related to Vision (ADREV). Statistical analysis, including Spearman coefficients, was performed on the data from the clinical measures, NEI-VFQ-25, and ADREV.Results: The clinical tests had higher correlations with ADREV than with the NEI-VFQ-25. There was a moderate, but not strong, connection between how patients rated their own visual ability with how they performed when objectively tested.Conclusions: ADREV provides valid estimates of how visual loss due to glaucoma affects the ability to perform activities of daily living. Performance-based testing and quality of life evaluations are both independently important measures of health, which are related, but by no means the same.

Useful Field of View as a Reliable Screening Measure of Driving Performance in People With Parkinson's Disease: Results of a Pilot Study

Purpose: To determine the correlations of the Useful Field of View (UFOV), compared to other clinical tests of Parkinson's disease (PD); vision; and cognition with measures of on-road driving assessments and to quantify the UFOV's ability to indicate passing/failing an on-road test in people with PD. Methods: Nineteen randomly selected people with idiopathic PD, mean age = 74.8 (6.1), 14 (73.7%) men, 18 (94.7%) Caucasians, were age-matched to 104 controls without PD. The controls had a mean age of 75.4 (6.4), 59 (56.7%) men, 96 (92.3%) Caucasians. Both groups were referred for a driving evaluation after institutional review board approval. Results: Compared to neuropsychological and clinical tests of vision and cognition, the UFOV showed the strongest correlations (r > .75, p < 0.05) with measures of failing a standardized road test and number of driving errors. Among PD patients, the UFOV Risk Index score of 3 (range 1–5) was established as the optimal cutoff value for passing the on-road test, with sensitivity 87 percent and specificity 82 percent, AUC = 92 percent (SE 0.61, p = .002). Similarly, the UFOV 2 (divided attention) optimum cutoff value is 223 ms (range 16–500 ms), sensitivity 87.5 percent, specificity 81.8 percent, AUC = 91 percent (SE 0.73, p = .003). The UFOV 3 (selected attention) optimal cutoff value is 273 ms (range 16–500 ms), sensitivity 75 percent, specificity 72.7 percent, AUC = 87 percent (SE 0.81, p = .007). Conclusion: In this pilot study among PD patients, the UFOV may be a superior screening measure (compared to other measures of disease, cognition, and vision) for predicting on-road driving performance but its rigor must be verified in a larger sample of people with PD.

Spatial Localization in Visual Impairment

To investigate self-reported difficulties experienced by visually impaired subjects in real-world tasks requiring judgment of space and distance and to determine whether laboratory measures of spatial localization predict self-reported difficulty with spatial tasks better than traditional measures of visual function, such as visual acuity and contrast sensitivity. Forty-two subjects with visual impairment participated. The Spatial Localization Questionnaire (SLQ) was developed to investigate self-reported spatial localization difficulties, and subjects answered the questionnaire as part of the study. Subjects also completed a variety of clinical vision tests (visual acuity, contrast sensitivity, stereo acuity, and reading speed) and laboratory vision tests (vernier acuity, bisection acuity, and visual direction). The SLQ was found to have good validity. Several significant correlations were found between the Rasch analysis ability scores for the questionnaire and the clinical and laboratory vision tests. Using stepwise regression analysis, we found that vernier acuity and contrast sensitivity accounted for 42% of the variance in the Rasch scores (P < 0.001). The findings indicate that certain subjects with visual impairment have difficulty with real-world spatial tasks, as indicated by the SLQ. Of note, these difficulties were better predicted by vernier acuity (a resolution test) and contrast sensitivity, rather than vernier or bisection bias, which measure localization.

Evaluation of a reading rehabilitation programme for patients with age-related macular degeneration (AMD-READ Project)

Low-vision patients with AMD often have difficulty reading, even when text is magnified to compensate for loss of central visual acuity (VA). The goal of this study is to evaluate the benefits of a reading rehabilitation programme to improve reading speed in patients with advanced AMD. Forty-eight patients with AMD were recruited from the low-vision service at Moorfields Eye Hospital. Each patient was given a battery of clinical vision tests, including near and distance VA, contrast sensitivity and reading speed evaluation. Patients were randomly assigned to a reading rehabilitation programme or standard low-vision services. Patients in the rehabilitation programme completed the “Learn to Use Your Vision for Reading Workbook” at home over a 6-week period. At baseline, reading speeds for standardised magnified text averaged 54 words/min. Following training, reading speeds improved less than 1 word/min in the trained group and 5 words/min in the control group. There was no significant difference in improvement in the two groups. The reading rehabilitation programme was not shown to be effective. This may reflect limitations in the implementation of the training; however, we are more inclined to interpret these results as an indication of the success of conventional low-vision services in the absence of extended training.

Standard Measures of Visual Acuity Do Not Predict Drivers??? Recognition Performance Under Day or Night Conditions

This study investigated whether visual acuity or contrast sensitivity, measured under a range of luminance conditions, could predict drivers' recognition performance under real-world day and night road conditions. Twenty-four participants, comprising three age groups (younger, mean = 21.5 years; middle-aged, mean = 46.6 years; and older, mean = 71.9 years), drove around a 1.8-km closed road circuit under day and nighttime conditions. At night, headlight intensity was varied over 1.5 log-units by ND filters mounted on the headlights. Participants drove around the circuit under five light conditions (daytime and four at night) and were asked to report relevant targets, including road signs, large low-contrast road obstacles, and pedestrians who wore retroreflective markings on either the torso or the limb joints (creating "biological motion"). Real-world recognition performance was measured as percent correct recognition and, in the case of low-contrast road obstacles, avoided. Clinical vision tests included high-contrast visual acuity and Pelli-Robson letter contrast sensitivity measured at four luminance levels. Real-world recognition performance of all age groups was significantly degraded under low light conditions, and this impairment was greater for the older participants. These changes in drivers' recognition performance were more strongly predicted by contrast sensitivity than visual acuity measured under standard photopic conditions. Interestingly, contrast sensitivity was highly correlated with visual acuity measured under low-luminance conditions. Further analyses showed that recognition performance while driving is better predicted by combinations of two tests: either 1) photopic visual acuity and photopic contrast sensitivity, or 2) photopic and mesopic visual acuity. These findings confirm that visibility is seriously degraded during night driving and that the problem is greater for older drivers. These changes in real-world recognition performance were better predicted by a standard test of contrast sensitivity than by visual acuity. Still better predictions can be obtained by the use of two vision tests. The implications of these findings for driver licensing standards are discussed.

Modified attentional fields in ageing

Purpose: Clinical vision testing tends to underestimate age‐related visual decline. We have modified an automated perimeter by adding a second task at fixation and have investigated visual fields in conditions of focused (FA) and divided attention (DA).Methods: Two lasers were mounted on a Humphrey Visual Field Analyzer (Carl Zeiss, Jena, Germany). They projected red targets 2 mm either side of the standard fixation target. Fifteen young (mean age: 20 ± 1.4 years; range: 18–23) and 15 healthy old subjects (72 ± 5.1 years; range: 65–80) were assessed under FA using Fastpac 30–2 program (sequence 1). Subjects then repeated the test twice under DA (sequences 2 and 3), in which they were instructed to press a second handheld button in response to an asynchronously presented central laser target. They also responded to continuing laser targets after the threshold program finished.Results: For old subjects under DA, the mean threshold increased by 2.87 cd m−2 (sequence 2) and 0.8 cd m−2 (sequence 3) compared with FA (sequence 1). By comparison young subjects increased by 0.03 cd m−2 (sequence 2) and decreased by 0.55 cd m−2 (sequence 3). Compared with young subjects, mean threshold for old subjects was 8.44 cd m−2 (sequence 2) and 6.89 cd m−2 (sequence 3) greater. Mean reaction times for the fixation task alone were comparable (young: 353 ± 46 ms vs old: 352 ± 52 ms). However, when combined with the threshold field task, reaction times increased by much more in the old group (e.g. 497 ± 46 ms vs 557 ± 50 ms sequence 2).Conclusion: The visual fields of old subjects were only slightly reduced in DA conditions although the reduction was clearly greater than for the young group. There were marked increases in the reaction times of the older group to targets presented at fixation. Continuing studies will assess impact of DA on patients with ocular and cerebral disease.

Glaucoma patients' assessment of their visual function and quality of life.

To determine how glaucoma and glaucoma suspect patients' rating of their vision correlates with Esterman binocular visual field testing and other visual function tests. One hundred ninety-one glaucoma patients and 46 glaucoma suspect patients underwent binocular visual field testing and evaluated their vision using the linear rating scale and time-tradeoff utility tests, the National Eye Institute Visual Functional Questionnaire (NEI VFQ-25), and the Short Form 36 (SF-36) quality-of-life instruments. The mean Esterman score was 88.2 +/- 17.4 for the glaucoma subjects and 95.2 + 6.9 for glaucoma suspect subjects (maximum score 100). On a scale from 0 (blind) to 100 (ideal), the mean rating of vision for glaucoma patients and glaucoma suspect patients was 74.8 +/- 17.3 and 78.9 +/- 18.5, respectively. The Esterman test correlated moderately with the overall NEI VFQ-25 score (partial correlation coefficient (PCC) = 0.32, P = 0.001), but only weakly with the linear rating scale (PCC = 0.17, P = 0.02), and the time-tradeoff (PCC = 0.14, P = 0.06). Utility values that glaucoma and glaucoma suspect patients assign to their vision do not correlate well with Esterman results. A challenge for the future is the design of clinical tests of vision that better correlate with patient perceptions.

Perceived and actual performance of daily tasks: relationship to visual function tests in individuals with retinitis pigmentosa

Purpose To investigate the functioning in daily task performance of individuals with retinitis pigmentosa (RP). Goals were (1) to quantify the relationships among clinical tests of vision, self-reports, and evaluations of actual task performance to predict difficulty in these tasks; and (2) to validate self-report questionnaire data about daily task performance with observations and measurements of actual task performance conducted by a certified low-vision specialist. Design A cross-sectional study and survey. Participants Sixty-two individuals with RP (mean age, 37 years) participated in the study. Methods We obtained data about task performance from subjects’ reports about their daily performance as assessed by a 53-item questionnaire and from a specialist’s rating about actual ability on a 64-item battery of tasks, including ones similar to those assessed with the questionnaire. Main outcome measures Clinical measures of vision included visual acuity, visual fields using Goldmann perimetry, letter contrast sensitivity, and cone and rod electroretinogram (ERG) function. The questionnaire and functional tasks were clustered into three categories: “reading,” “mobility,” and “peripheral detection.” Results Self-report was correlated significantly with actual task performance. Task performance was correlated significantly with clinical test performance. Moderate or worse difficulty in performance was observed only for visual acuity worse than 20/40; log contrast sensitivity less than 1.4; a visual field area smaller than 2000 deg 2 (area equivalent to a 50-degree diameter of visual field to the Goldmann II-4-e target); and ERG amplitudes less than 10 microvolts for 32-Hz light-adapted white flicker. Conclusions Despite the significant correlations, there remains variability in task performance that is unaccounted for in some individuals with low levels of clinical test performance. The assessment of actual task performance validated the use of self-reports in individuals with RP.