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PubMed1982

Space shuttle suit alert system visual acuity problem.

The National Aeronautics and Space Administration (NASA) requested solution of a visual acuity problem that presbyopic astronauts had when viewing an alert system visual display attached to their Space Shuttle suits. Solutions wee analyzed in the context of constraints which prohibited major modifications of the suits. The solution to the problem was to mount Fresnel lens strips on the helmet so that presbyopic astronauts could view the visual display clearly.

Adult↗

PubMed2002

Consistency between visual acuity scores obtained at different test distances: theory vs observations in multiple studies.

OBJECTIVE: To investigate the consistency of visual acuity (VA) scores measured at 2 different distances in patients with or at risk for choroidal neovascularization. METHODS: Best-corrected VA scores measured at 2 distances for the same eyes at the same examinations were collected from 4 sets of randomized clinical trials among patients with or at risk of choroidal neovascularization. Within each trial, the pairs of VA scores were compared and their relationship was explored. RESULTS: After adjustment for test distance, VA scores obtained at the closer distance were found to be systematically lower than those obtained at the farther distance in all data sets. In the Submacular Surgery Trials pilot study, the average discrepancy between 2- and 0.5-m VA scores was 7.5 letters. In an ancillary study of the Macular Photocoagulation Study, the discrepancy between 10-ft and 5-ft VA scores was 3.1 letters. In the Laser to Drusen Trial pilot study, the discrepancy between 3.2- and 1-m VA scores was 7.3 letters. In the Treatment of Age-Related Macular Degeneration With Photodynamic Therapy Study, in which the VA scores at the closer test distance were censored, the estimated discrepancy between 2- and 1-m VA scores was 8.2 letters. Reduction in visual angle at closer test distance did not explain the discrepancy completely. Features of the macular lesion, poor accommodation of the elderly population with age-related macular degeneration, or the test charts did not account for the discrepancies. CONCLUSION: The VA scores at distances less than 2 m were lower than expected in all 4 studies. The observed discrepancy was consistent with findings from a study among healthy young subjects, suggesting that the phenomenon is real and common.

Algorithms↗

PubMed2005

Cataract surgery in patients with age-related maculopathy: preoperative diagnosis and postoperative visual acuity.

PURPOSE: To report the reliability in detecting age-related maculopathy (ARM) lesions before cataract surgery and postoperative visual acuity (VA) in cataract surgery patients with ARM. METHODS: Medical records of surgical patients in a large public hospital, west of Sydney, were reviewed retrospectively. Detection of ARM lesions was compared before and after surgery to determine sensitivity and specificity of preoperative diagnoses. Postoperative VA was assessed 4 weeks after surgery. RESULTS: Data were available for 721/784 eyes (92.0%) of 656 patients aged 60 years or older. ARM lesions were detected in 98 eyes (13.6%) before and 92 eyes (12.8%) after surgery. Sensitivities for detecting late ARM lesions, soft drusen and retinal pigment epithelium abnormalities preoperatively were 100%, 94% and 69%, respectively. Corresponding specificities were 100%, 100% and 77%, respectively. Postoperative VA achieved or remained 6/12 or better in 81.6% of eyes. CONCLUSION: A high sensitivity and specificity in detecting late ARM lesions and soft drusen preoperatively, and a good postoperative VA outcome is achievable in patients with preoperative early ARM lesions.

Aged↗

PubMed1976

Testing of visual acuity in young children: an evaluation of some commonly used methods.

In a comparative study of screening tests for visual acuity in young children, two groups of children were presented with three different tests. In the younger group (three to five years) three single opto-type tests were compared: Sheridan's five and seven letter matching test, the Fooks test and the E card test. The Sheridan test gave the best results and the E card test was found to be unsuitable for this age-group. The Fooks is an attractive test but was less sensitive in the detection of defects than the Sheridan test. In the older group (five to seven years) a single opto-type test, the Sheridan-Gardiner test, was compared with the E chart and the Snellen chart. The Sheridan-Gardiner test was found to have limitations in the detection of defects, including amblyopia, therefore results obtained by this method should not be considered to be directly comparable with those of the Snellen chart. The E chart gave good results in the detection of defects and there was less lateral confusion than had been expected. It has disadvantages, but there is still a place for its use in the screening of normal school-age children. The Snellen chart was the most effective test in the detection of defects, but not all the children were able to co-operate in its use. It is concluded that where it is possible to use the Snellen chart it should always be the method of choice.

Child↗

PubMed2000

The effect of bilberry nutritional supplementation on night visual acuity and contrast sensitivity.

PURPOSE: The purpose of this study was to investigate the effect of bilberry on night visual acuity (VA) and night contrast sensitivity (CS). METHODS: This study utilized a double-blind, placebo-controlled, crossover design. The subjects were young males with good vision; eight received placebo and seven received active capsules for three weeks. Active capsules contained 160 mg of bilberry extract (25-percent anthocyanosides), and the placebo capsules contained only inactive ingredients. Subjects ingested one active or placebo capsule three times daily for 21 days. After the three-week treatment period, a one-month washout period was employed to allow any effect of bilberry on night vision to dissipate. In the second three-week treatment period, the eight subjects who first received placebo were given active capsules, and the seven who first received active capsules were given placebo. Night VA and night CS was tested throughout the three-month experiment. RESULTS: There was no difference in night VA during any of the measurement periods when examining the average night VA or the last night VA measurement during active and placebo treatments. In addition, there was no difference in night CS during any of the measurement periods when examining the average night CS or the last night CS measurement during active and placebo treatments. CONCLUSION: The current study failed to find an effect of bilberry on night VA or night CS for a high dose of bilberry taken for a significant duration. Hence, the current study casts doubt on the proposition that bilberry supplementation, in the forms currently available and in the doses recommended, is an effective treatment for the improvement of night vision in this population.

Adult↗

PubMed1988

The effects of target borders on dynamic visual acuity: practical and theoretical implications.

The effects of target borders on the ability of observers to resolve moving targets (Landolt Cs) under a range of conditions were examined. Contrary to reported findings with stationary targets, it was predicted that the presence of borders would improve acuity for slow-moving targets because (i) overall stimulus energy is kept relatively constant as target detail varies, and (ii) a low-spatial-frequency component is held constant as target detail varies. In an experiment in which a two-sided border (above and below the target) was used, the predicted beneficial effect of the border at slow speeds was obtained. The results are discussed in terms of practical implications for the assessment of dynamic visual acuity as well as the potential neural mechanisms underlying performance.

Humans↗

PubMed2005

Screening for correctable visual acuity deficits in school-age children and adolescents.

BACKGROUND: Although the benefits of vision screening seem intuitive, the value of such programmes in junior and senior schools has been questioned. In addition to this there exists a lack of clarity regarding the optimum age, and frequency at which to carry out screening. OBJECTIVES: The objective of this review is to evaluate the effectiveness of vision screening programmes carried out in schools in reducing the prevalence of undetected, correctable visual acuity deficits due to refractive error in school-age children. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials - CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) on The Cochrane Library (Issue 3 2004), MEDLINE (1966 to August 2004) and EMBASE (1980 to August 2004). No language or date restrictions were placed on these searches. To date it has not been possible to carry out any manual searches but it is hoped to include these in a future update. SELECTION CRITERIA: We planned to include randomised controlled trials including randomised cluster controlled trials. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed study abstracts identified by the electronic searches. No trials were identified that met the inclusion criteria. MAIN RESULTS: As no trials were identified, no formal analysis was performed. A narrative synthesis of other retrieved studies was undertaken in order to explain current practice. AUTHORS' CONCLUSIONS: At present there are no robust trials available that allow the benefits of school vision screening to be measured. The disadvantage of attending school with a visual acuity deficit also needs to be quantified. The impact of a screening programme will depend on the geographical, and socio-economic setting in which it is conducted. There is therefore clearly a need for well planned randomised controlled trials, in various settings, to be undertaken so that the potential benefits and harms of vision screening can be measured.

Adolescent↗

PubMed2002

A preliminary report about the relation between visual acuity increase and compliance in patching therapy for amblyopia.

PURPOSE: The aim of this study was to establish a relation between visual acuity increase and compliance in children who have been prescribed patching therapy for their amblyopic eye. METHODS AND MATERIALS: In 14 new amblyopic children (mean age 4.3 +/- 1.9 years) compliance was measured electronically during one week, six months after starting patching therapy, with an Occlusion Dose Monitor (ODM), distributed through house visits. The children were diagnosed with anisometropia (5), strabismus (4) and anisometropia and strabismus (5). The degree of amblyopia was expressed as the ratio between the acuity of the amblyopic eye and the acuity of the good eye. Satisfactory increase in acuity was assessed by means of the following three criteria: acuity amblyopic eye / acuity good eye >75%, acuity exceeding 0.5 E-chart, three lines LogMAR acuity increase. RESULTS: Fourteen reliable recordings were obtained, which showed that children who did not patch, or were patched inconsistently, did not reach satisfactory acuity increase. CONCLUSION: There is indeed a statistically significant relation between acuity increase and measured compliance.

Amblyopia↗

PubMed1978

Visual acuity for single lines as a function of hue and age.

176 students in grades 2-12 were tested for visual acuity as a function of minimally resolvable red, yellow, green, and blue lines. A 3-way mixed analysis of variance revealed significant differences among the colors, with better acuity for longer wavelengths. Significant age effects as well as a sex X condition interaction were also found. Post hoc analysis revealed a significant quartic trend for age. It is argued that the differential acuity thresholds for hue and the curvilinear age trend may depend upon the coordination of the accommodation and refractive power of the eye, which are affected by differential growth rates of the lens and the axial length of the eye.

Accommodation, Ocular↗

PubMed1987

Visual acuity prediction using the VER--temporal aspects.

A pattern reversal stimulus (check size 5.5 min arc) was used to elicit visually evoked responses (VER's). The peak to trough amplitude of the VER wave was measured and compared to the subjective visual acuity (Landolt C) in 30 subjects. The recordings were made at 3, 6, and 12 pattern reversals per s. The correlation coefficients are reasonably high (r = 0.81) for both the 3 and 6 reversal rates with a considerably lower correlation coefficient (r = 0.54) for the 12 reversals per s stimulus. Repeatability measurements on a further 6 subjects taken over a 5-week period produced an amplitude coefficient of variation of 13% for the 6 subjects with the 3 reversals per s stimulus.

Adolescent↗

PubMed1996

Assessment of visual acuity in the supine position.

OBJECTIVE: To determine whether a modified Snellen eye chart could be used to accurately assess visual acuity (VA) in the supine position. METHOD: This was a prospective study involving ED staff volunteers comparing VA on a standard Snellen eye chart with VA on a size-reduced ceiling-mounted modified Snellen eye chart. RESULTS: Fifty-six volunteers participated. VA ranged from 20/10 to 20/200 on both of the charts, but 87% of the volunteers had VA of 20/50 or better. The VA results for the 2 charts were highly correlated; right eye r = 0.931 and left eye r = 0.953. Weighted ks showed substantial agreement for both eyes; kappa = 0.63 and 0.79 for the right and left eyes, respectively. In only 4 of 112 paired measurements did the VA recorded with the ceiling chart differ by > 1 line from that recorded on the Snellen chart. CONCLUSION: There is an excellent correlation between VAs determined in the erect and the supine positions using the standard Snellen eye chart and the modified ceiling-mounted version. Substantial agreement exists between readings using the 2 charts. Although additional testing is warranted in an ophthalmologically diverse patient population, use of this chart for the assessment of VA in the supine ED patient may allow for earlier VA evaluation.

Adolescent↗

PubMed1995

Large sample population age norms for visual acuities obtained with Vistech-Teller Acuity Cards.

PURPOSE: To determine population age norms in the first three years of life for binocular and monocular grating visual acuity (VA) obtained with Vistech-Teller Acuity Cards (TAC). METHODS: TAC was used to estimate grating acuity in 646 healthy infants and children born at due date +/- 2 weeks, all of whom underwent ophthalmologic and orthoptic evaluation. The sample consisted of 20 age groups from 0 to 36 months. Sixty-nine percent of the children attended day care centers in the city of São Paulo. The sample was composed of white (63.0%), mulatto (25.2%), African-Brazilian (11.0%), and Asian (0.8%) infants and children, most of whom (97%) were from low-income families. Tests were conducted by eight highly trained testers, six of whom were orthoptists. RESULTS: Binocular and monocular norms for grating VA are presented in terms of tolerance limits for 90% of the population with 95% probability. The range of tolerance limits is approximately 2.5 octaves at most ages. There were no statistical differences among scores obtained by the different testers. There were no differences in VA due to race, sex, and first or second eye tested. The results on binocular (99.3%) and monocular (96.2%) testability and on mean test duration (13 minutes for one binocular and two monocular measurements) confirm the clinical applicability of TAC. CONCLUSIONS: The binocular and monocular grating VA norms obtained in this large-sample study are different from the preliminary norms published with the TAC. Results from this and other studies (see Mayer et al, page 671, this issue) strongly point to a need for redefinition of the preliminary VA norms.

Aging↗

PubMedDate not supplied

Changes in visual acuity and refraction in the exfoliation syndrome. A five-year follow-up study.

PURPOSE: To examine changes in visual acuity (VA) and refraction in non-glaucomatous patients with unilateral exfoliation syndrome (EXS). METHODS: The best corrected values for VA (Snellen acuity cards) subjectively adjusted for refraction, and IOP were measured, and the development of lens opacities was examined in 46 non-glaucomatous patients with unilateral EXS. RESULTS: After five years the rate of conversion to bilateral exfoliation was 22% and to exfoliative glaucoma 30%. There was a significant decrease in VA in the exfoliative (E) eyes (median; QI, QIII, range: 1; 0.8, 1, 0.4-1.3 vs. 0.55; 0.4, 1, 0.05-1.4, p<0.0001) and the fellow, initially non-exfoliative (NE), eyes (1; 0.9, 1, 0.3-1.3 vs. 0.7; 0.5, 0.9, 0.1-1.4, p<0.0001) and a significant myopic change in refraction in the E eyes (+1.02 +/- 2.48 vs. +0.11 +/- 3.06, p=0.0001) and the NE eyes (+0.99 +/- 2.25 vs. +0.43 +/- 2.55 D, p<0.01). At study entry the difference in refraction between the fellow eyes (refraction in the NE eye--refraction in the E eye) was -0.27 +/- 1.00D. After five years it was +0.32 +/- 1.44 (p 0.016), reflecting greater myopic changes in the E eyes. The main type of lens opacification was nuclear sclerosis. CONCLUSIONS: In five years, significant decreases in VA and myopic shifts in refraction occurred in the E and fellow eyes. The E eyes showed significantly greater myopic changes than the fellow eyes; the cause was clearly nuclear sclerosis, which must be taken into account in the long-term management of patients with EXS.

Age Distribution↗

PubMed2001

Dynamic visual acuity during passive and self-generated transient head rotation in normal and unilaterally vestibulopathic humans.

To determine whether dynamic visual acuity (DVA) during head rotations on the stationary body can lateralize unilateral vestibular deafferentation and detect non-labyrinthine compensation mechanisms, 15 normal and 11 subjects with unilateral vestibular deafferentation underwent manually imposed and self-generated transient yaw head rotations during measurement of binocular DVA. DVA was measured by a four-alternative, forced choice, staircase procedure with optotype presentation only when head velocity exceeded thresholds of 50 degree or 75 degree/s. Eye and head movements were recorded using search coils to characterize ocular motor strategies. During directionally unpredictable, manually imposed contralesional rotation, unilaterally deafferented subjects had decreases in DVA from the static condition of 0.36 +/- 0.22 and 0.47 +/- 0.53 log of the minimum angle resolvable (logMAR, mean +/- SD), respectively, for 50 degree and 75 degree/s thresholds, not significantly greater than those of normal subjects (0.26 +/- 0.13 and 0.36 +/- 0.14, P>0.05). However, during manually imposed ipsilesional rotation, vestibulopathic subjects had decreases in DVA of 0.66 +/- 0.36 and 1.08 +/- 0.47 logMAR, significantly greater than during contralesional rotation ( P<0.01). The DVA reduction difference for the ipsi- and contralesional directions was less during self-generated than during manually imposed head rotations. The directional difference for manually administered head rotations yielded a robust diagnostic measure with essentially no overlap in performance with normal subjects. Diagnostic performance for DVA during self-generated head rotation was poorer. Recordings of eye and head movements made using search coils during DVA testing confirmed a deficient vestibulo-ocular reflex (VOR) during ipsilesional rotation, with most unilaterally vestibulopathic subjects employing predictive smooth eye movements and vestibular catch-up saccades. Measurement of DVA during transient head rotation on the body thus reliably can detect and lateralize vestibular pathology and compensatory mechanisms. Extravestibular mechanisms for compensation appear more effective during self-generated than manually imposed head rotations.

Adolescent↗

PubMed2005

Limits of visual acuity in the frontal field of the rock pigeon (Columba livia).

The eye of the rock pigeon is typical of a granivorous lateral-eyed bird, in that it has both a laterally projecting central fovea and a second high-density cellular area in peripheral retina (area dorsalis) which projects to the binocular frontal field below the beak. Such a dual system is faced with potentially different optical restraints arising from central and peripheral vision. We asked whether the frontal axis can support high resolution vision from a refractive resting position (predicted to be 25-33 cm; Fitzke et al, 1985 Journal of Physiology 369 33-44) to some near point of accommodation. We measured the visual acuity on the frontal axis in five pigeons using an operant discrimination of high-contrast square-wave gratings at a series of distances from 7 to 80 cm from the eye. The peak average acuity was 11.04 cycles deg(-1), which occurred 10 cm from the eye. The average of the maximum acuity of each bird at 10 cm was 12.8 +/- 1.1 cycles deg(-1), a value equal to the Nyquist frequency calculated from the peak ganglion cell density of the area dorsalis. However, this maximum acuity was restricted to a narrow depth in space, located around 10 cm from the eye, and at greater distances fell exponentially such that acuity was 50% of its maximum at 35 cm and less than 1 cycle deg(-1) at 100 cm. We propose that the range of high-acuity vision is limited in the frontal field by either increased refractive power and/or inaccuracy in frontal accommodation, and is optimized for a preferred far point located 10 cm from the eye.

Accommodation, Ocular↗

PubMed1981

[Visual acuity and binocular function in cases of bilateral pseudophakia (author's transl)].

Of 37 patients with bilateral pseudopakia, 33 had a visual acuity of at least 0.3 in the better eye and 26 at least 0.3 in the eye with poorer vision. Ten out of 17 patients achieved stereopsis of 100 angle-seconds and better. Normal perception of space-body relationships is rapidly regained after operation and patients are spared the trouble of getting accustomed to cataract lenses. Useful binocular function can be achieved.

Aged↗

PubMed2005

Reliability and consistency of visual acuity and contrast sensitivity measures in advanced eye disease.

PURPOSE: The purpose of this article is to establish reliability of standard visual function measures in patients with severe vision loss. METHODS: Legally blind subjects were enrolled in a repeated-measures study to determine the reproducibility of a battery of psychophysical vision measures. Tests reported here include ETDRS visual acuity (VA) under regular and dim illumination and Pelli-Robson letter contrast sensitivity (CS) under regular, dim, and glare conditions. Two to five test repetitions were performed at monthly intervals. Subject groups included retinitis pigmentosa (RP) (n = 29), macular disease (MD) (n = 17), optic nerve disease (ON) (n = 4), diabetic retinopathy (DR) (n = 5), and other retinal diseases (OR) (n = 10). RESULTS: For most subject groups, VA measures had mean 95% coefficient of repeatability (CR.95) of 0.20 (group means between 0.13 and 0.36) log units, and CS measures had mean CR.95 of 0.35 (group means between 0.19 and 0.48) log units. CONCLUSIONS: The established reliability of VA and CS tests in subjects with severe visual impairments will allow investigators to determine whether a significant change in vision has occurred during future clinical trials to reverse, halt, or slow vision loss. The criterion for change needs to be larger than for normally sighted controls, i.e., approximately two to three lines for VA and between eight to 11 letters for CS.

Adult↗

PubMed1999

An Arabic letter distance visual acuity test chart for young children and illiterate adults.

This paper describes the design of a kinetic response Arabic letter distance visual acuity test chart for young children and illiterate adults. An Arabic letter ein which has previously been used in the design of Arabic alphabet VA charts was employed. Four different orientations of the letter were constructed on a 5 x 5 unit format and graded according to log MAR principle of acuity scaling using an Apple computer. Inter-letter space in each row was made equal to the width of each letter in the row, and inter-row space was made equal to the height of letters in the next lower row. The chart has 14 acuity rows ranging from 4/40 to 4/2 (6/60 to 6/3) (20/200 to 20/10) (log MAR 1.0 to -0.3) at 4 metres. To establish the validity of the chart, acuity values obtained using the chart were compared with those from an existing Arabic log MAR distance VA chart and the Bailey and Lovie distance VA chart. Test retest reliability of the chart was also examined statistically. Results show that VA values from the new chart were significantly similar with those from which it was compared, and that values from the chart are reliable. The chart will be useful for evaluating vision, especially for young children and illiterate adults.

Adolescent↗