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Results for “Visual Acuity”

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PubMed2004

Long-term changes in visual acuity and refractive error in amblyopes.

PURPOSE: To report long-term changes in visual acuity and refractive error for strabismic, anisometropic, and isoametropic amblyopes. METHODS: Records of patients with strabismic amblyopia, anisometropic amblyopia, and isoametropic amblyopia who were treated from 1983 to 1993 were reviewed. Excluded were patients having ocular or neurological diseases, developmental delay, and follow-up <4 years after treatment cessation. Data included best-correctable visual acuity and spherical equivalent refractive error of the amblyopic and the nonamblyopic eye at pretreatment, posttreatment, and long-term follow-up. RESULTS: Records for 61 patients met the inclusion criteria. For strabismic amblyopia (n = 22), mean visual acuity in amblyopic and nonamblyopic eyes improved 0.36 and 0.05 logarithm of the minimum angle of resolution (logMAR) units after a mean treatment time of 1 year. At long-term follow-up (mean = 9.3 years after treatment), visual acuity in the amblyopic eye regressed 0.09 logMAR and visual acuity in the nonamblyopic eye improved 0.10 logMAR units. For anisometropic amblyopia (n = 26), mean visual acuity in amblyopic and nonamblyopic eyes improved 0.30 and 0.02 logMAR units, respectively, after a mean treatment period of 1.1 year. At the long-term follow-up visit (mean = 7.1 years after treatment), visual acuity in the amblyopic eye regressed 0.09 logMAR unit and in the nonamblyopic eye improved 0.03 logMAR unit. Repeated-measures analysis of variance showed no significant effect of type of amblyopia on visual acuity of the amblyopic eye and a significant effect of visit due to treatment but not regression. The changes in visual acuity in the nonamblyopic eye from the pretreatment to the follow-up visit were significant and interacted with type, the changes being larger in strabismic amblyopia. For strabismic amblyopia, the mean refractive error in amblyopic and nonamblyopic eyes changed from +2.15 D and +1.85 D, respectively, initially to +0.45 D and +0.58 D, respectively, at the follow-up visit. For anisometropic amblyopia, the mean refractive error in amblyopic and nonamblyopic eyes changed from +1.04 D and +0.12 D, respectively, initially to +0.23 D and -0.94 D, respectively, at the follow-up visit. The effect of visit on amblyopic and nonamblyopic refractive errors was significant. For isoametropic amblyopia (n = 13), visual acuity in both right and left eyes initially was 0.39 logMAR unit and improved to 0.14 logMAR unit in each eye after a mean follow-up of 8.9 years. Refractive error in the right and the left eyes changed from -1.22 D and -1.14 D, respectively, to -2.68 D and -2.56 D, respectively, at follow-up. These differences were all significant. CONCLUSIONS: After treatment and with long-term follow up, visual acuity regresses but not significantly in the amblyopic eye in strabismic amblyopia and anisometropic amblyopia. At the same time, visual acuity in the nonamblyopic eye improves slightly. Visual acuity also improves significantly over time in isoametropic amblyopia. The refractive error of both amblyopic and nonamblyopic eyes tends to show a myopic shift regardless of the type of amblyopia.

Adolescent↗

PubMed2006

Relationship between optical coherence tomography-measured central retinal thickness and visual acuity in diabetic macular edema.

OBJECTIVE: To compare optical coherence tomography (OCT)-measured retinal thickness and visual acuity in eyes with diabetic macular edema (DME) both before and after macular laser photocoagulation. DESIGN: Cross-sectional and longitudinal study. PARTICIPANTS: Two hundred ten patients (251 eyes) with DME enrolled in a randomized clinical trial of laser techniques. METHODS: Retinal thickness was measured with OCT and visual acuity was measured with the electronic Early Treatment of Diabetic Retinopathy procedure. MAIN OUTCOME MEASURES: Optical coherence tomography-measured center point thickness and visual acuity. RESULTS: The correlation coefficients for visual acuity versus OCT center point thickness were 0.52 at baseline and 0.49, 0.36, and 0.38 at 3.5, 8, and 12 months after laser photocoagulation. The slope of the best fit line to the baseline data was approximately 4.4 letters (95% confidence interval, 3.5-5.3) of better of visual acuity for every 100-mum decrease in center point thickness at baseline with no important difference at follow-up visits. Approximately one third of the variation in visual acuity could be predicted by a linear regression model that incorporated OCT center point thickness, age, hemoglobin A1C, and severity of fluorescein leakage. The correlation between change in visual acuity and change in OCT center point thickening 3.5 months after laser treatment was 0.44, with no important difference at the other follow-up times. A subset of eyes showed paradoxical improvements in visual acuity with increased center point thickening (7%-17% at the 3 time points) or paradoxical worsening of visual acuity with a decrease in center point thickening (18%-26% at the 3 time points). CONCLUSIONS: There is modest correlation between OCT-measured center point thickness and visual acuity, and modest correlation of changes in retinal thickening and visual acuity after focal laser treatment for DME. However, a wide range of visual acuity may be observed for a given degree of retinal edema. Thus, although OCT measurements of retinal thickness represent an important tool in clinical evaluation, they cannot substitute reliably as a surrogate for visual acuity at a given point in time. This study does not address whether short-term changes on OCT are predictive of long-term effects on visual acuity.

Diabetic Retinopathy↗

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↗

PubMed2005

Visual acuity and X-linked color blindness.

PURPOSE: Optimal sampling for visual acuity requires a fine array of cones with identical sensitivity. Thus, dichromats, whose inner fovea is made up of cones having the same spectral sensitivity, may have better than normal visual acuity. We investigated this by comparing the visual acuities of trichromats and X-linked dichromats, while taking into account the different molecular genetics underlying the disorder. METHODS: Our subjects were age- and refraction-matched groups of normals (n=8) and X-linked dichromats (n=13). The dichromats (four protanopes and nine deuteranopes) were genotyped and classified according to whether they carried a single (n=6) or multiple (n=7) visual pigment genes on their X-chromosome. Visual acuity was measured in both eyes with the Freiburger Visual Acuity Test. RESULTS: Normal trichromats and ungenotyped dichromats do not significantly differ in visual acuity, nor do ungenotyped protanopes and deuteranopes. However, multi-gene dichromats, who possess more than one photopigment gene in the array, all of which encode for the same long- or middle-wavelength sensitive photopigment, have significantly higher visual acuity than either normal trichromats or dichromats who have only a single-gene. CONCLUSIONS: Multi-gene dichromats may benefit from a reduction in chromatic aberration and chromatic noise in the high acuity channel, normally a consequence of combining signals from different cone photoreceptor types and of cone-specific patterns of retinal image defocus and blur. Single-gene dichromats may not share in the advantage because of other molecular differences that influence the development of the retinal mosaic and/or its visual pathways.

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↗

PubMed2005

Visual fields correlate better than visual acuity to severity of diabetic retinopathy.

AIMS/HYPOTHESIS: We compared the outcomes of perimetric and visual acuity tests in patients with diabetic retinopathy. METHODS: We examined 59 diabetic patients with different degrees of retinopathy using stereo fundus photography in accordance with the Early Treatment of Diabetic Retinopathy Study (ETDRS) and fluorescein angiography. Conventional white-on-white perimetry (WWP) and short wavelength automated perimetry (SWAP) were performed and analysed with reference to normal values. Visual acuity was measured with ETDRS charts. RESULTS: Regression analysis revealed that visual acuity was significantly associated with increasing severity of retinopathy according to the ETDRS scale when visual acuity was estimated by counting logarithm of minimum angle of resolution (LogMar) scores, but not when visual acuity was measured by the conventional reading of the smallest line that could be seen. Visual acuity decreased by 0.02 LogMar per ETDRS step (p=0.03). The degree of visual field loss was significantly associated with increasing severity of retinopathy according to the ETDRS scale, perimetric sensitivity decreasing by 0.44 dB per ETDRS step (p=0.0001) using WWP, and by 0.40 dB per ETDRS step (p=0.04) with SWAP. The size of the area of the foveal avascular zone and adjacent perifoveal intercapillary areas (PIAs) also affected the central visual field as obtained both by WWP (-2.6 dB/mm2, p=0.03), and by SWAP (-7.9 dB/mm2, p=0.002), but did not affect visual acuity. The regression model fit for peripheral retinopathy according to the ETDRS scale was better using WWP than SWAP or visual acuity, while SWAP testing was superior to both WWP and visual acuity when measuring effects caused by enlarged foveal avascular zones and PIAs. CONCLUSIONS/INTERPRETATION: Perimetry can provide more useful information than visual acuity on functional loss in diabetic retinopathy, particularly when the perifoveal capillary network is damaged.

Adult↗

PubMed2005

Association between intensity of posterior capsule opacification and visual acuity.

PURPOSE: To investigate the correlation between the change in visual acuity and the difference in objective posterior capsule opacification (PCO) scores before and after neodymium:YAG (Nd:YAG) laser capsulotomy. SETTING: Department of Ophthalmology, Medical University of Vienna, Vienna, Austria. METHODS: Forty pseudophakic eyes of 35 patients with PCO of varying intensity were examined before and after Nd:YAG laser capsulotomy. Visual acuity was determined using the Early Treatment Diabetic Retinopathy Study (ETDRS) chart at 4 m and the Holladay reading chart at 40 cm. The pupil diameter under reading conditions was measured each time. Digital retroillumination images of the posterior capsule were taken, and the corresponding area inside the pupil was evaluated using the Automated Quantification of After-Cataract (AQUA) automated PCO analysis program. The change in visual acuity and difference between PCO scores before and after Nd:YAG laser capsulotomy were calculated for all eyes. RESULTS: The mean AQUA score (scale 0 to 10) was 3.56 before and 0.13 after Nd:YAG laser capsulotomy. The mean ETDRS visual acuity score (logMAR scale) was 0.28 and -0.07, respectively. The correlation coefficient between the differences in PCO score and distance visual acuity was 0.61 and near visual acuity, 0.62. CONCLUSIONS: The objective PCO score obtained by an automated image-analysis program correlates well with the PCO-induced decrease in visual acuity when the central area (inside the pupillary aperture) of the posterior lens capsule was evaluated. Objective PCO assessment by automated image-analysis systems is, therefore, a valuable and clinically relevant method for clinical studies of the development and prevention of PCO.

Cataract↗

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↗

PubMed2000

The advanced glaucoma intervention study, 6: effect of cataract on visual field and visual acuity. The AGIS Investigators.

OBJECTIVE: To investigate the effect of cataract on visual function and the role of cataract in explaining a race-treatment interaction in outcomes of glaucoma surgery. METHODS: The Advanced Glaucoma Intervention Study (AGIS) enrolled 332 black patients (451 eyes) and 249 white patients (325 eyes) with advanced glaucoma. Eyes were randomly assigned to an argon laser trabeculoplasty (ALT)-trabeculectomy-trabeculectomy sequence or a trabeculectomy-ALT-trabeculectomy sequence. From the AGIS experience with cataract surgery during follow-up, we estimated the expected change in visual function scores from before cataract surgery to after cataract surgery. Then, for eyes with cataract not removed, we used these estimates of expected change to adjust visual function scores for the presumed effects of cataract. In turn, we used the adjusted scores to obtain cataract-adjusted main outcome measures. MAIN OUTCOME MEASURES: Average percent of eyes with decrease of visual field (APDVF) and average percent of eyes with decrease of visual acuity (APDVA). RESULTS: Within the 2 months before cataract surgery, visual acuity was better in eyes of white patients than of black patients by an average of approximately 2 lines on the visual acuity test chart. Cataract surgery improved visual acuity and visual field defect scores, with the amounts of improvement greater when preoperative visual acuity was lower. Adjustments for cataract brought about the following relative reductions: for APDVF, a relative reduction of 5% to 11% in black patients and 9% to 11% in white patients; for APDVA, a relative reduction of 45% to 49% in black patients and 31% to 38% in white patients; and for the APDVF and APDVA race-treatment interactions, relative reductions of 25% and 45%, respectively. CONCLUSIONS: On average, visual function scores improved after cataract surgery. The findings of reduced race-treatment interactions after adjustment for cataract do not alter our earlier conclusion that the AGIS 7-year results support use of the ALT-trabeculectomy-trabeculectomy sequence for black patients and of the trabeculectomy-ALT-trabeculectomy sequence for white patients without life-threatening health problems. The choice of treatment should take into account individual patient characteristics and needs.

Adult↗

PubMed2002

Binocular visual acuity summation and inhibition in an ocular epidemiological study: the Los Angeles Latino Eye Study.

PURPOSE: To characterize binocular visual acuity summation and inhibition in participants of a population-based ocular epidemiologic study. METHODS: A complete ophthalmic examination of Latinos, aged 40 or more years, measured binocular and monocular distance visual acuities by a standard early-treatment diabetic retinopathy study (ETDRS) protocol. The proportions of participants who demonstrated binocular summation (i.e., binocular visual acuity was better than the better eye visual acuity by five or more letters), binocular inhibition (i.e., binocular visual acuity was worse than the better eye visual acuity by five or more letters), and visual impairment (visual acuity worse than 20/40) were calculated. RESULTS: In 1831 individuals, on average, binocular visual acuity was better than better eye visual acuity. Prevalence rates of binocular summation and inhibition were 21% and 2%, respectively. Compared with participants less than 65 years old or those with equivalent interocular visual acuity, older participants (> or =65 years) and those with interocular differences in visual acuity were more likely to demonstrate binocular inhibition (P < 0.01). The rate of visual impairment was significantly lower, when using binocular visual acuity than when using better eye or the American Medical Association (AMA) algorithm (5.2% vs. 6.9% and 9.5%, respectively P < 0.01). Participants with binocular inhibition had greater self-reported problems with driving activities (P < 0.05). CONCLUSIONS: The large proportion of individuals demonstrating binocular summation and inhibition suggests that in clinical or research settings, binocular visual acuity should be considered a primary measure of visual impairment, because it better equates the state in which the person usually functions.

Adult↗

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↗