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PubMed1986

Objective techniques of visual acuity assessment in infancy.

Three primary techniques for objective assessment of visual acuity in the preverbal infant are variations of optokinetic nystagmus, forced preferential looking and visual evoked potentials. Although these tests are useful, the clinician must be aware of their shortcomings. Failure to evoke optokinetic nystagmus may reflect the infant's lack of interest in the stimulus, an inherently uninteresting stimulus, or a defect in the motor system generating the nystagmus, other than failure to see the stimulus. Forced choice preferential looking has provided useful information about visual development in preverbal infants. The need for more complex stimuli to yield more precise estimates of acuity than the standard grafting stimuli, especially in cases of amblyopia, is discussed. Visual evoked potentials, like forced preferential looking, may grossly overestimate the acuity of the amblyopic patient. Of the techniques discussed, it holds the most promise.

Evoked Potentials, Visual↗

PubMed1986

Performance of the dot visual acuity test with uncorrected ametropia resulting in target blur.

The dot visual acuity test is used to test the acuity of children between the ages of 2 and 4 years who do not respond to the tumbling E test. Because the test involves the detection of a black dot on a white background it is appropriate to ask if the detection threshold is lowered artificially in the presence of target blur. Twenty-one children (42 eyes) were used in the study. Refractive errors were fully corrected and each subject's lag of accommodation was measured. A monotonic decrease in acuity was found with increasing amounts of optical blur. The explanation for the decreased acuity is found in the reduced retinal image contrast of the blurred target.

Accommodation, Ocular↗

PubMedDate not supplied

Predictors of visual acuity and the relative afferent pupillary defect in optic neuropathy.

The relationships among visual acuity (log MAR), diagnostic category, age, the magnitude of a relative afferent pupillary defect (RAPD) in log units, photopic foveal thresholds to white and colored light (dB), and the mean deviation on the Humphrey visual field (dB) were studied in patients with various optic neuropathies. All acuity and dB values were expressed as interocular differences, the majority of cases having normal acuity in the fellow eye. In multiple regression analyses, acuity and RAPD were alternately chosen as the dependent or response variable with all remaining variables serving as the predictors or independent variables. The main finding was that the only significant predictor of a RAPD was the interocular mean deviation difference on the Humphrey field and the only significant predictor of acuity was the foveal threshold to white light. Redundant and insignificant variables were therefore identified with multiple regression analysis. Subsidiary findings include: (a) although diagnostic group was not a significant predictor in the above, simple linear regression line slopes relating RAPD magnitude to the Humphrey mean deviation were significantly different between optic neuritis and compression categories; (b) for a given level of acuity, foveal thresholds were substantially worse in these cases with neuronal damage than in strabismic amblyopia, refractive error, or corneal damage; and (c) sensitivity losses for red vs. blue light were similar.

Adaptation, Ocular↗

PubMed1999

Assessment of long-chain polyunsaturated fatty acid nutritional supplementation on infant neurobehavioral development and visual acuity.

The aims of this paper are (i) to consider how best to examine effects of long-chain polyunsaturated fatty acid nutritional supplementation or deficiency on infant neurobehavioral development, after controlling for other factors that might influence outcome, including maternal demographic, intellectual, and personality characteristics, and (ii) to present new findings on the relation between visual acuity and processing speed and the effects of prenatal alcohol exposure and visual acuity on infant information processing. The following topics are also addressed: (i) breastfeeding and intelligence, (ii) criteria for the selection and control of potential confounding variables, and (iii) new infant information processing measures.

Ethanol↗

PubMed2005

Age-related maculopathy and cataract surgery outcomes: visual acuity and health-related quality of life.

PURPOSE: To assess visual acuity (VA) and health-related quality of life (HRQoL) outcomes in patients with and without age-related maculopathy (ARM) after cataract surgery. METHODS: Patients aged 60+ years who had undergone cataract surgery at the Westmead Hospital during 2001-2003 were re-examined 1-3 years after surgery. Tests included VA and assessment of visual- and HRQoL using standardised questionnaires (VF-14, SF-12). Preoperative comorbidity data were collected from medical records. Poor surgical outcomes (VA<6/12; no VA improvement; lowest quintile of VF-14, SF-12 scores) were compared in patients with and without ARM, adjusting for age, sex, preoperative systemic comorbidities, ocular comorbidities and surgical or postoperative complications. RESULTS: Of 622 surviving patients, 454 (73%) were followed up for a mean period of 2.8 years. Similar proportions with VA>or=6/12 were observed in patients with (80.2%) and without (88.8%) pre-existing ARM. Preoperative early ARM was only associated with slightly lower mean VF-14 scores (87.64 with vs 92.58 without ARM, P=0.01). Increasing age and preoperative ocular comorbidities were associated with all poor outcomes measured. Low SF-12 scores were associated with preoperative systemic comorbidities. CONCLUSION: Our study documents favourable cataract surgical outcomes 1-3 years after cataract surgery in patients with preoperative ARM.

Aged↗

PubMedDate not supplied

Visual acuity following cataract surgeries in relation to preoperative appropriateness ratings.

The authors initiated this study to consider if the formal preoperative assessment of appropriate or inappropriate utilization of cataract surgery by an expert panel could predict postoperative improvement or decline in visual acuity. They evaluated the association between ratings of appropriateness, as determined by the RAND-UCLA method, and measurements of postoperative visual acuity using Fisher's exact tests for tables greater than 2 x 2. For 768 patients, improvement of at least 2 Snellen chart lines occurred in 89% of surgeries rated as appropriate or appropriate and crucial, 68% rated as uncertain, and 36% rated as inappropriate (P < 0.0001, Fisher's exact test). These results provide evidence supporting the validity of the RAND-UCLA method to assess the appropriateness of surgery.

Aged↗

PubMed1984

Classification of human senile cataractous change by the American Cooperative Cataract Research Group (CCRG) method: III. The association of nuclear color (sclerosis) with extent of cataract formation, age, and visual acuity.

Nineteen hundred and seventy-six immature human cataracts extracted intracapsularly were classified according to the Cooperative Cataract Research Group (CCRG) method of cataract classification. Data on cataract location and extent, nuclear color, preoperative visual acuity, age, and sex were organized and stored in the PROPHET system. The data were examined for relationships between nuclear color (sclerosis) and the age of the cataractous lens, the extent of opacification in seven anatomical regions including the degree of nuclear opacification and the preoperative visual acuity. Nuclear color correlates with age in a curvilinear manner. Nuclear yellowing increases gradually with increasing nuclear opacification, but the color change is so slight as to be useless for the purposes of inferring the intensity of nuclear opacification from the color of the nucleus. There is no association between the extent of anterior cortical, equatorial cortical, posterior cortical, subcapsular or supranuclear opacification, and nuclear color. Nuclear color impairs vision only for the range dark yellow through black. These data justify the recommendation that nuclear color be abandoned as the single index of the severity of any type of senile cataractous change.

Age Factors↗

PubMed1972

Visual acuity in the blue cone monochromat.

1. To isolate the blue cones of the normal eye, blue sine-wave gratings were superimposed on a bright yellow background. Threshold contrasts for resolution of the gratings were then determined.2. Under these conditions visual acuity for high contrast gratings on four normal subjects was on the average 0.31 min(-1). This is about a factor of 6 lower than grating acuity under optimal conditions.3. The contrast sensitivity of two subjects who lack the normal red and green receptor mechanisms was measured using blue sinusoidally modulated gratings. Visual acuity was found to be greatly reduced from normal. The low acuity of these individuals is due to both a reduction in contrast sensitivity and a reduction in resolution.4. The spatial resolving characteristics of these subjects resembles the vision of the normal eye under conditions which isolate the blue sensitive mechanisms.5. The vision of the cone monochromat differs significantly from that of the more typical rod monochromat. The rod monochromat has even lower acuity than the blue cone monochromat for high contrast gratings but has much greater contrast sensitivity for gratings of low spatial frequency.

Color Vision Defects↗

PubMed2006

Comparison of visual acuity loss in patients with different stages of Stargardt's disease.

PURPOSE: To investigate a previously reported observation that the presence of diffuse, as compared with localized, fundus flecks is an indicator of a more severe course for visual acuity (VA) loss beyond 20/200 in patients with Stargardt's disease. DESIGN: Retrospective clinic-based cross-sectional study. PARTICIPANTS: Four hundred five patients with Stargardt's disease. METHODS: Visual acuity in 405 patients with Stargardt's disease was analyzed at their initial and most recent visits. The stage of Stargardt's disease and appearance of the macula were recorded. The diagnosis and stage of Stargardt's disease were based on the extent and appearance of fundus flecks. MAIN OUTCOME MEASURES: Best-corrected VA, stage of Stargardt's disease, and appearance of the macula at the initial and most recent visits were used in the cross-sectional analysis. RESULTS: At their initial visit, 199 patients were identified as having stage 1 Stargardt's disease, of whom 97.5% maintained 20/200 or better VA in at least one eye. One hundred eighty-five were identified as having stage 2 or stage 2-3 Stargardt's disease combined, of whom 83.2% maintained 20/200 VA or better. Patients with stage 1 were more likely to maintain 20/200 or better VA in at least one eye when compared with patients with stage 2/stage 2-3 Stargardt's disease (chi2(1) = 21.25, P<0.001). Ninety-nine percent of stage 1 patients and 94.1% of stage 2/stage 2-3 patients maintained 20/400 or better VA in at least one eye (chi2(1) = 5.72, P = 0.017). CONCLUSIONS: Patients with stage 1 Stargardt's disease exhibiting fundus flecks limited to the posterior pole are more likely to maintain a level of VA at 20/200 or better when compared with patients with stage 2/stage 2-3 disease who have diffuse fundus flecks. Nevertheless, over 80% of the patients with stage 2/stage 2-3 Stargardt's disease still maintained VA of 20/200 or better. Only 5.9% of patients with stage 2/stage 2-3 had VA levels worse than 20/400. In our cohort of patients with Stargardt's disease and diffuse fundus flecks, the majority of patients did not lose VA to a greater extent than those with localized flecks.

Adolescent↗

PubMed1994

Luminance effects on visual acuity and small letter contrast sensitivity.

The purpose of this study was to evaluate the effects of luminance on visual acuity (VA) and small letter contrast sensitivity (SLCS). Computer-generated letter charts were used to measure VA and SLCS [6/7.5 (20/25) Snellen equivalent] as a function of stimulus luminance. Letter size (VA) and contrast (SLCS) were varied in equal logarithmic steps, making the task and scoring procedure comparable for the two types of measurement. Both VA and SLCS decreased with decreasing luminance, but the effect was far greater in the contrast domain. Reducing luminance from 116 cd/m2 to 0.23 cd/m2 produced a 3 x reduction in VA, but a 17 x reduction in SLCS. The greater sensitivity of SLCS to luminance endured even after correction for greater measurement variability. SLCS is a sensitive approach for detecting resolution loss undisclosed by standard measures of VA. It may be useful for monitoring visual loss from light attenuation in early cataracts, and for detecting subtle resolution loss from neural or pathologic factors in ocular and neuro-ophthalmologic disease.

Adult↗

PubMed1988

Assessment of contrast sensitivity of patients with macular disease using reduced contrast near visual acuity charts.

A set of near Bailey-Lovie logMAR letter charts that varied in contrast from 0.40 dB (C = 0.95) to 58.0 dB (C = 0.001) were used to measure the middle and high spatial frequency range of the contrast sensitivity function (CSF) of 15 subjects with age-related maculopathy (ARM) and 15 age-matched normal subjects. The letter charts were shown to have good test-retest reliability. Compared with measures made using CRT generated square wave gratings of variable contrast and spatial frequency they were also shown to provide a valid measure of CSF in the mid to high spatial frequency range. The 20.0 dB letter chart alone was shown to be a good screening device for macular disease. The letter charts do not provide a measure of the peak of the CSF and a supplementary test of contrast sensitivity is needed to quantify contrast sensitivity at a low spatial frequency. Three measures are proposed as necessary to document foveal visual capability of patients with macular disease: distance logMAR visual acuity to measure high spatial frequency resolution, visual acuity with letter charts of 20 dB contrast to assess mid spatial frequency resolution; and contrast sensitivity for the detection of an edge to estimate contrast sensitivity for larger objects.

Aged↗

PubMedDate not supplied

Sinusitis associated with disorders of visual acuity.

We report a case of sinusitis associated with disorders of visual acuity. The patient's vision was dramatically improved by sinus surgery despite the fact that the changes in the ethmoidal cells were slight and had no direct observable relation to the optic nerve canal. Possible mechanisms involved in nasal optic neuritis are discussed.

Adult↗

PubMedDate not supplied

[Visual acuity study in the child 18 months to 2 years old].

Visual acuity for a child may be determined using objective instrumental methods (especially for children under 18 months) or using clinical examination at the optotype--subjective methods (for children after 18 months). The use of 2 or 3 different optotypes, which are attractive for children, is necessary because of their great capacity of memorizing the tests. The author presents a personal optotype model, with seven different images, which have to be recognized by the children from a distance of 2.5 m.

Humans↗

PubMed2006

The effect of decreased visual acuity on clinical color vision testing.

PURPOSE: Evaluate the effect of visual acuity on color vision testing. DESIGN: University based clinical experimental study. METHODS: Right eyes of 12 healthy subjects were fogged with plus lenses to logMAR 1.88 and assessed with D-15 panel, Ishihara, and Hardy-Rand-Rittler (HRR) plates. Subjects were tested at lesser degrees of fogging, 0.1 logMAR intervals. The acuity at which 5% of the population tests abnormally was estimated as follows. The average acuity at which a 10% reduction in correct responses occurred was determined. From this, two standard deviations were subtracted. Examination devices were compared using repeated measures analysis of variance. RESULTS: Color vision testing did not significantly differ from baseline up to logMAR 1.40 (D-15 panel), 1.10 (HRR plates), and 0.72 (Ishihara plates). Testing devices were significantly different (P < .005). CONCLUSIONS: Color vision testing is accurate up to logMAR 1.40 (20/501) with D-15 panel, 1.10 (20/252) with HRR plates, and 0.72 (20/106) with Ishihara plates.

Adult↗

PubMed1990

The nature and basis of age-related changes in dynamic visual acuity.

The ability of observers to resolve moving targets, or dynamic visual acuity (DVA), was determined for a group of young adults (M age = 19.6 years) and a group of older adults (M age = 67.6 years). Targets were presented at two luminance levels over a range of velocities (30, 60, 90, and 120 deg/s) and at 2 durations (200 and 600 ms). The younger subjects exhibited superior DVA under nearly all conditions, but this effect was essentially eliminated by the luminance adjustment. These results are interpreted in terms of decreased retinal illumination in the older subjects rather than in terms of age-related changes in the underlying eye movement systems. Practical and theoretical implications are discussed.

Adult↗

PubMed1994

Visual acuity and hemispheric asymmetries in pigeons.

Pigeons and domestic chicks tested under monocular conditions in pattern distinction tasks generally show higher discrimination performances with the right eye seeing. At least two different mechanisms could mediate this asymmetry: the dominance of the right eye could either be due to hemispheric differences in the cognitive operations performed during these tasks, or may reflect a lateralization in the spatial frequency discrimination capacity of the left and the right eye system. The aim of the present study was to decide between these two hypotheses. Therefore nine adult homing pigeons (Columba livia) were tested with the left or the right eye seeing in a visual acuity task using high-contrast square wave gratings. Visual acuity, defined as the spatial frequency at which the psychometric function crossed the 75% correct line was virtually identical for the two eyes with 6.6 for the left and 6.4 c/deg for the right eye. Thus, visual lateralization as demonstrated in various pattern discrimination tasks seems not to depend on asymmetries in acuity but probably reflects hemispheric differences in the visual processing mode.

Animals↗

PubMed2003

[Vitreous body floaters and vitrectomy with full visual acuity].

PURPOSE: To evaluate the role of vitrectomy in patients with visually disturbing vitreous body floaters and full visual acuity (VA). METHODS: A total of 9 eyes from 8 patients (2 female, 7 male, median age 57 years) with a preoperative VA of 1.0 were analysed retrospectively. The median duration of symptoms was 12 months. In all eyes a pars plana vitrectomy was performed. The median follow-up period was 13 months. RESULTS: No intraoperative or postoperative complications were observed. In all patients vision improved subjectively and objective VA remained unchanged. In 2 out of 5 phacic patients a cataract extraction was performed during the follow-up period. CONCLUSIONS: In a selected group of patients vitrectomy can improve subjective vision even in eyes with full objective VA. A critical patient selection with respect to psychological criteria and the individual risk of vitrectomy is extremely important.

Adult↗

PubMed2006

Refraction and visual acuity measurements: what are their measurement uncertainties?

The details of refractive and visual acuity measurement have been examined using the International Standards Organization (ISO) guidelines for the estimates of uncertainty. It is clear that there is a number of sources of uncertainty in quoted values. Some of these can be analysed statistically, using the ISO guidelines and can be used to estimate an uncertainty in the final recorded values. These should be regarded as minimum uncertainties because there are other factors involved such as unwanted accommodation, which will affect the final outcome. The analysis shows that the standard uncertainty (+/- one standard deviation) is about 0.3 D in refractive error measurement and about 0.04 in LogMAR acuity. The normally quoted expanded uncertainty, which provides a 95 per cent confidence level, would then be 0.6 D in refractive measurement and 0.08 in LogMAR acuity.

Humans↗