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Results for “Visual Acuity”

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At least 163 records · Page 9Linked to original sources

PubMed1994

Visual outcome after laser photocoagulation for subfoveal choroidal neovascularization secondary to age-related macular degeneration. The influence of initial lesion size and initial visual acuity. Macular Photocoagulation Study Group.

OBJECTIVE: To provide detailed information specific to the initial visual acuity and initial lesion size on the outcome of patients with subfoveal choroidal neovascularization (CNV) secondary to age-related macular degeneration. DESIGN AND PATIENTS: The 189 eyes assigned to laser photocoagulation and the 184 eyes assigned to observation in the Subfoveal New CNV Study were divided into nine subgroups based on initial visual acuity and initial lesion size. MAIN OUTCOME MEASURES: The pattern of visual acuity loss for both treated and untreated eyes through 4 years of follow-up was compared among the subgroups. Reading speed and contrast thresholds also were examined. RESULTS: Four patterns (A, B, C, D) of visual acuity loss in treated eyes relative to untreated eyes were identified. Eyes in group A (small lesion and moderate or poor initial visual acuity or medium lesion and poor visual acuity) had the best visual outcome with treatment; treated eyes were better throughout follow-up. Eyes in group B (small lesion and good initial visual acuity or medium lesion and moderate or good visual acuity) had substantial treatment benefit by 12 months, but were worse immediately after treatment. Eyes in group C (large lesion and poor initial visual acuity) had a small treatment benefit throughout follow-up. Eyes in group D (large lesion and moderate or good visual acuity) had the worst visual outcome with treatment; treated eyes were substantially worse for the first 18 months and were not appreciably better through 4 years of follow-up. CONCLUSIONS: Recommendations for treatment of subfoveal CNV should take account of the initial visual acuity and lesion size. Eyes in group D are poor candidates for laser treatment.

Aged↗

PubMedDate not supplied

Treating myopia with acoustic biofeedback: a prospective study on the evolution of visual acuity and psychological distress.

OBJECTIVE: The effects of a visual training technique on changes in myopia, visual acuity, and psychological distress were studied in a controlled prospective study. METHOD: A group of 33 female students with myopia < or = 3.50 diopters (D) underwent visual training using an acoustic biofeedback technique. A group of 22 female students with myopia and a group of 27 students with emmetropia formed the two control groups, matched for school, age, sex, and refractive error. Manifest and cycloplegic refraction, visual acuity, personality profile (CPI), and psychological distress (SCL-90) were measured at the baseline (T0), at 10 weeks (T1), and after 12 months (T2). RESULTS: At T2, myopia significantly progressed both in the treated and in the untreated students with myopia. Visual acuity improved only in the treated myopia group (despite refraction objectively being worse). No differences were found among the personality profiles in the three groups. All items indicative of psychological suffering improved in the group treated for myopia whose visual acuity was ameliorated. CONCLUSIONS: The visual training technique led to no improvement in objective measures of visual acuity, but did lead to an improvement in one relatively subjective measure of visual acuity and a parallel improvement in psychological conditions. The students with myopia who were treated consequently had a greater sense of general well-being.

Accommodation, Ocular↗

PubMed1989

[Statistical evaluation of visual acuity].

The statistical evaluation of the visual acuity has to be based on the non-parametric test as the decimal scale of the visual acuity forms a serial scale and not the intervallic one. From the theoretic point of view, the most advantageous approach uses the paremetric statistical tests. Visual acuity is measured on optotypic tables with log gradiation of the optotype size. At present time optotypes of this kind are not available in Czechoslovakia.

Humans↗

PubMed1992

Set shot shooting performance and visual acuity in basketball.

Common sense suggests that decreasing visual acuity will have a negative effect on basketball shooting performance. To test the hypothesis that basketball shooting performance monotonically decreases with decreasing acuity, 19 subjects attempted 25 set shots from a fixed location at each of 5 different acuity levels: 6/6 or better and vision blurred (by optical defocus) to visual acuities of 6/12, 6/24, 6/48, and 6/75. Our results revealed a small but statistically nonsignificant decrease in shooting performance between the 6/6+ and 6/12 conditions. For visual acuities between 6/12 and 6/75, the number of baskets made remained constant. We conclude that decreases in visual acuity over the range of 6/6+ to 6/75 resulting from defocus do not significantly reduce set shot shooting performance.

Adolescent↗

PubMedDate not supplied

Laser interferometric prediction of postoperative visual acuity in patients with genetic ectopia lentis.

PURPOSE: To compare preoperative laser interference visual acuity (LIVA) with postoperative Snellen visual acuity (SVA), and to evaluate clinical significance using laser interferometer in patients with genetic ectopia lentis. METHODS: We treated a series of 18 patients (34 eyes) with genetic ectopia lentis whose visual acuity did not improve with optical phakic or aphakic correction, or with modern microsurgery and automated suction-cutting devices. Laser interferometry and electroretinogram (ERG) were used for the examination of retinal function before surgery. RESULTS: There was not significant difference between the interferometric acuity before operation and the corrected visual acuity after operation (p > 0.05), and the coincidence rate between them was 80% (27 eyes). ERG examination showed normal function in most of the patients. CONCLUSIONS: The results showed that the laser interferometric acuity is a valuable method in evaluation of postoperative visual acuity in patients with ectopia lentis. In six eyes, the LIVA was lower than the initial corrected vision postoperatively, but ERG examination showed that the retinal function was normal in these patients. Therefore, in patients with genetic ectopia lentis, LIVA combined with ERG predicts visual acuity more accurately.

Adolescent↗

PubMed1987

An analysis of the effect of intravitreal blood on visual acuity.

We investigated the effect of diffuse hemorrhage on Snellen visual acuity in a model of vitreous hemorrhage in phakic and aphakic eyes. Two cylindrical test chambers with optical paths of 17 mm and 23 mm were constructed to simulate the effect of vitreous hemorrhage in phakic and aphakic eyes. The visual acuity was measured in two subjects in a double-masked fashion for 17 dilutions of whole blood between 1/100 and 1/12,800. The visual acuity decreased approximately linearly between the 1/800 and 1/4,800 dilutions of blood. The visual acuity was 20/20 in all dilutions of blood higher than 1/4,800. The visual acuity was reduced to hand motions or worse with 12.5 microliter of blood in the 5-ml test chamber under all test conditions. The visual acuity was 20/20 in all tests with 1.04 microliter of blood in the test chamber. The visual acuity decreased from 20/20 to hand motions with only a twelve-fold change in concentration of blood in the test chamber.

Aphakia↗

PubMed1992

Assessment of visual acuity via a telephone interview.

We compared the visual acuity of 89 patients obtained via a telephone interview with visual acuity elicited from the same patients in an ophthalmologist's office. Agreement within one line of vision between the telephone interview, in which patients used a modified Rosenbaum near card with attached patch, and the clinic near vision test was observed in 91% of eyes, while agreement within one line of vision between the telephone interview and clinic distance vision test was found in 86% of eyes. We conclude that testing visual acuity via a telephone interview is a potentially useful approach to assessment of visual acuity and prevalence of visual impairment in the larger population.

Adult↗

PubMed1998

Analysis of preoperative factors predictive of visual acuity in axial myopia.

PURPOSE: To identify the factors predicting visual acuity after cataract surgery in patients with high myopia. SETTING: Departments of Ophthalmology, Showa University School of Medicine and Showa University Fujigaoka Hospital, Kanagawa, Japan. METHODS: Stepwise regression analysis was used to identify the factors determining the visual acuity in 940 eyes with an axial length of 27.0 mm or longer having cataract surgery. Using a formula derived from the stepwise regression analysis, the predicted postoperative visual acuity was compared with the actual value measured in another group of 104 eyes. RESULTS: Five factors were identified to significantly determine postoperative visual acuity: axial length, age, corneal opacity, refractive power of the cornea, and history of retinal detachment surgery. There was a significant relationship between predicted and actual postoperative visual acuities (r = .51, P < .001). Postoperative visual acuity was similar in 63% of cases. CONCLUSION: The results showed that at least five factors determine visual acuity after cataract surgery in patients with high myopia.

Adolescent↗

PubMed1991

[Temporal integration in diseased eyes. I. Exposure duration in visual acuity testing].

Critical duration in visual acuity testing can be viewed as an expression of temporal integration in the human visual system. We examined this phenomenon in 13 eyes with central serous retinopathy (CSR) and 6 eyes with macular edema, by measuring visual acuity at several limited exposure times. The results were then compared with those for 17 normal eyes. The acuity target was a single Landolt ring projected upon a small square screen. The size, direction, and exposure time of the target were computer controlled. The mean critical durations of the CSR and macular edema groups were 1.78 sec. and 2.69 sec. respectively. These values were significantly (p less than 0.01) longer than the mean critical duration of the normal control group (0.62 sec.). Although the mechanism behind the longer critical duration in diseased eyes remains poorly understood, we believe this method provides a possible approach to the study of diseased visual conditions.

Humans↗

PubMed1994

Visual acuity in infants and children with Down syndrome.

The authors used the Teller acuity cards to assess the visual acuity of 51 infants and children with Down syndrome aged between two months and 18 years. The success rate and test times were comparable to those reported for normally developing children. Even those subjects in the study who were free of ocular disorders and/or who were wearing optical correction during testing showed significantly poorer visual acuity than individuals without Down syndrome. The development of visual acuity in infants and children with Down syndrome lags behind that of age-matched peers without Down syndrome, especially after the age of six months. These findings are discussed in terms of the neurological and optical factors that might account for the deficits in visual acuity that were observed.

Adolescent↗

PubMed1988

Effect of luminance on photopic visual acuity in the presence of laser speckle.

Visual acuity in coherent and incoherent light has been determined by using square-wave gratings of 100% contrast. Luminance was varied from 3 to 400 cd/m2. Coherent illumination resulted in a 40% loss of visual acuity. This is probably due to the masking effect of coherent spatial noise (speckle). However, the most interesting finding is the change in shape of the photopic visual-acuity-luminance function. With coherent illumination, the function is vertically displaced and of a different gradient. An increase in luminance produces a decrease in visual acuity. This indicates that the masking effect of the speckle is dependent on luminance. Two observers were used, and similar results were obtained by both.

Adult↗

PubMed1995

Contrast visual acuities in cataract patients. III. Changes of contrast acuity profiles in normal and pathological eyes.

We compared pre- and postoperative visual acuities in 45 cataract patients without ocular pathology except lens opacity (group 1) and 20 patients with ocular pathologies and lens opacity (group 2) using Variable Contrast Visual Acuity Charts. Charts 1 and 4 have 90% contrast; chart 4 has white optotypes on a black background (reverse polarity), charts 2 and 3 have 15% and 2.5% contrast, respectively. The mean preoperative visual acuities of groups 1 and 2 measured with the high-contrast Landolt optotypes ranged from 0.02-0.80 and 0.22-0.40, respectively. Visual acuity improvements between the pre- and postoperative periods ranged from 1.37-1.61 and 0.52-1.24 octaves in groups 1 and 2, respectively, with the different charts. Visual acuity improvement was poorest with chart 3. The group 1 mean preoperative visual acuity measured with chart 2 was 1.11 octaves lower than with chart 1. In group 2, the visual acuity reduction was 1.81 octaves. The relation between the visual acuities measured with the high-contrast intermediate-contrast optotypes are important for predicting postoperative visual acuity improvement. An abnormal contrast acuity profile may indicate the presence of additional ocular pathologies.

Adult↗

PubMed1982

Visual acuity as a function of age.

The literature relating visual acuity and the aging process is reviewed. The Snellen fraction, parameters affecting visual acuity and difficulties in comparing different studies in visual acuity are discussed. Visual acuity was found to be a poor 20/1,000 to 20/800 at birth but improved to an almost normal acuity of 20/20 during the first year of life and remained relatively constant from 40 to 50 years of age. There was a moderate but steady decline in acuity as a person ages above 60 and on to the age of 80. The disease and physiological etiologies for this loss in acuity are provided. Methods which may be used to maintain or improve visual performance with age are suggested.

Adolescent↗

PubMed1990

[Clinical study for prediction of postoperative visual acuity in cataract patients].

In order to predict more quantitatively postoperative visual acuity in cataract patients, we employed the potential acuity meter (PAM). The PAM projects a Snellen visual acuity chart into the eye by a minute aerial aperture approximately 0.1 mm in diameter. The value of determining potential visual acuity is evident because of the frequent co-existence of macular abnormalities in cataract patients. The 20 cataract patients had an average of 64.8 years (range, 48 to 84 years), and 8 were men and 12 were women. In 23 of the 25 eyes examined, postoperative visual acuity was within two lines or better than the predicted visual acuity with the PAM. Provided the operator is skillful, and if one recognizes its limitations and indications, the PAM is a useful means of predicting postoperative visual acuity in patients with mild or moderate cataracts.

Aged↗

PubMedDate not supplied

Measurement of temporal summation of visual acuity with use of modified tachistoscope.

Visual acuity was measured in 18 normal eyes of 10 subjects ranging in age from 20 to 30 years, using a modified tachistoscope. We changed the exposure duration of the target (1-1000 msec) or background luminance (0.1-200 cd/m2). Visual acuity improved with increasing duration of exposure. At background luminance over 10 cd/m2, critical duration time was approximately 500 msec. At low luminances below 10 cd/m2, however, critical duration was prolonged. This tendency was also seen when pupil diameter was fixed at 3 mm using an artificial pupil. Visual acuity also could be determined as the product of background luminance and exposure duration. We concluded that these findings follow the Bloch-Bunsen-Roscoe law.

Adult↗

PubMed1995

Differences in visual acuity between the eyes: determination of normal limits in a clinical population.

We determined the difference in visual acuity between the right and left eyes of patients and also determined the maximal level of acuity expected in a group of visually normal individuals. Visual acuity was measured in the right and left eyes of 72 subjects aged from 16 to 67 years using Bailey-Lovie type charts. The chart was read until fewer than three letters were read on a line and acuities were based on each letter correct contributing -0.02 to the overall score. For 12 of these subjects, visual acuity was measured a further four times. Average visual acuities for right and left eyes were -0.137 and -0.126log MAR, respectively. The signed visual acuity difference was normally distributed and had a standard deviation of 0.050log MAR. The mean visual acuity difference for the 12 subjects for whom the measures were repeated was 0.033log MAR (SD of the signed visual acuity difference: 0.049log MAR). We conclude that if a patient has a difference in visual acuity between the two eyes of more than 5 letters on a Bailey-Lovie style chart, further investigation is indicated.

Adolescent↗

PubMed1993

Correlating visual acuity and electrooculogram recordings in Best's disease.

The visual function in 54 eyes of 27 patients with Best's disease was analyzed by retrospectively examining the Snellen visual acuities and the electrooculogram (EOG). Visual acuities, generally well maintained in most patients, were 20/40 (0.5) or better in 41 of 54 (75.9%) eyes, and showed no correlation with age. Those in the cicatricial stage had worse visual acuities than those in the previtelliform stage. The EOG was abnormal in 47 eyes (87.0%) with a subnormal light peak/dark trough (Lp/Dt) ratio less than 1.85. Seven eyes (13.0%) with an Lp/Dt ratio 1.85 or higher had significantly smaller Dt values compared with those with a low Lp/Dt ratio. The Lp/Dt ratio did not correlate with patient age or disease stage. No correlation existed between visual acuities and Lp/Dt ratios. The Lp/Dt ratio did not reflect the severity of the macular lesions. The results indicate that not only a low Lp/Dt ratio but also a low dark trough value in cases with a normal Lp/Dt ratio are helpful in diagnosing Best's disease.

Adolescent↗

PubMed1993

Repeated visual acuity measurement: establishing the patient's own criterion for change.

We measured visual acuity in 10 young subjects, 10 times each over a period of approximately 3 weeks, using Bailey-Lovie charts. We used a consistent end-point criterion and scored each letter read on the chart. We derived the mean and standard deviation of visual acuity measures for each subject, and for the group. The standard deviation for the group was about 3 times that of the individuals in the group. We calculated the criterion for reduction of visual acuity for the group, as group mean plus 1.96 group standard deviations; use of this criterion would consistently fail to detect patients with clinically significant reductions in visual acuity. We recommend that visual acuity be measured to threshold for every patient. Measuring visual acuity between three and five times provides an estimate of the patient's variability and allows a criterion for reduction of visual acuity to be established for the individual patient. Use of this criterion will enhance the sensitivity of visual acuity measurement as a diagnostic tool.

Adolescent↗