SEARCH · PubMed Health

Results for “Visual Acuity”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40Linked to original sources

PubMed1991

Improvement in visual acuity in chronic aphakic and pseudophakic cystoid macular edema after treatment with topical 0.5% ketorolac tromethamine.

Ketorolac tromethamine 0.5% ophthalmic solution treatment was compared to placebo treatment in 120 patients with chronic aphakic or pseudophakic cystoid macular edema (six-month or more duration of distance visual acuity of 20/40 or less and angiographic evidence of cystoid changes) during a four- to five-month double-masked, multicenter study in which patients were randomly assigned. A statistically significant improvement in distance visual acuity (two lines or more) was observed in the ketorolac-treated group as compared to the placebo-treated group after 30 days (P = .038), 60 days (P = .017), and 90 days (P = .008) of treatment. This improvement in visual acuity remained statistically significant one month after cessation of treatment (P = .001). Nine ketorolac-treated patients and two placebo-treated patients demonstrated a decrease in visual acuity one month after treatment was discontinued. Seven of the nine ketorolac-treated patients experienced an improvement in visual acuity after retreatment as compared to none of the placebo-treated patients. This study offers evidence for a more optimistic outlook in the medical treatment of chronic aphakic and pseudophakic cystoid macular edema.

Administration, Topical↗

PubMedDate not supplied

Effects of sighting and sensory dominance on monovision high and low contrast visual acuity.

We investigated the relationship between ocular dominance and monovision visual performance in 15 presbyopic subjects. Ocular dominance was determined using sighting (hole-in-the-card and mirror tests) and sensory (anisometropic blur suppression test) methods. Correcting the dominant sighting eye for a given viewing distance was found to be an unreliable method of optimizing blur suppression or binocular high/low contrast visual acuity at that distance. If there is any advantage to a particular strategy for selecting the distance monovision eye, it must be realized in vision performance areas other than visual acuity.

Adult↗

PubMed1979

Late diagnosis of choroidal malignant melanomas in eyes with clear media and low visual acuity.

Five patients seen in a one-year period with advanced malignant melanoma of the choroid in eyes with low visual acuity and clear media are reported. The low visual acuity appeared clinically to be antecedent to the malignant tumor; although in certain cases it may have been related to the occult melanoma, this was not appreciated clinically. Because of the low visual acuity, these patients did not have vision symptoms referable to the melanoma, and the malignancy was diagnosed late in its course. All five cases had extrascleral extension of the tumor at the time of surgical treatment; three are dead of metastatic disease, and two have undergone orbital exenteration with only brief follow-up periods. This experience suggests that eyes with clear media and low vision owing to presumably unrelated causes should undergo periodic examination to rule out the presence of a growing malignant melanoma and to prevent its late diagnosis.

Abdominal Neoplasms↗

PubMed1997

The impact of early lens opacity progression on visual acuity and refraction.

The purpose of the present study was to evaluate the change in visual acuity and refraction taking place in eyes with progressing early lens opacities. Four hundred and ten hypercholesterolemic men in Eastern Finland who participated in the Kuopio Atherosclerosis Prevention Study were followed up for 3 years. Lens opacities were graded using the lens opacity classification system II (LOCS II). The change of visual acuity and refractive error from baseline to a 36-month examination was compared for different types of lens opacities. During the 3-year period, progression in the LOCS II was observed in 9.2% of the eyes for nuclear, in 4.8% for cortical and in 0.5% of the eyes for posterior subcapsular opacities. Increasing nuclear sclerosis reduced visual acuity statistically significantly both with and without correction. Hypermetropization was seen to continue in eyes with no lens opacity progression. Myopization was more common in eyes with lens opacity progression, although this was not statistically significant.

Adult↗

PubMed1982

Comparing frontal and lateral viewing in the pigeon. I. Tachistoscopic visual acuity as a function of distance.

Pigeon's visual acuity has mainly been tested in free viewing conditions so that the direction of gaze could not be controlled. In order to be able to compare the resolving power of the two retinal areas of higher cellular density--the area dorsalis in the red field with frontal binocular projection and the fovea centralis with lateral monocular projection--a method of behavioural fixation was used. This method consists in a forced pecking schedule and a tachistocopic presentation of the stimulus. The pigeon has to discriminate the orientation (vertical, positive; horizontal, negative) of square gratings of increasing spatial frequency. Tests were done with the stimuli appearing 25 degrees below the beak for frontal and 80 degrees back from the beak for lateral viewing, at distances of 10, 20, 40 and 80 cm for each direction. Results show that while frontal acuity decreases with distance, lateral acuity increases with distance. These psychophysical data confirm previous dioptric measurements done on frozen eyes, showing that the pigeon is myopic in the frontal field and hyperopic in the lateral field. Pigeons seem to be well adapted for visually guided frontal tasks at near distances (feeding, landing) and for visually guided lateral tasks at far distances (warning).

Animals↗

PubMed2001

A utility analysis correlation with visual acuity: methodologies and vision in the better and poorer eyes.

OBJECTIVE: To ascertain the correlation between visual acuity levels and ophthalmic utility values obtained using time tradeoff and standard gamble utility analysis methodologies. METHODS: Three hundred twenty-five consecutive patients with visual loss to 20/40 or less in at least one eye with predominantly vitreoretinal pathology were evaluated in a cross-sectional fashion using a standardized testing methodology to obtain ophthalmic time tradeoff and standard gamble utility values. Spearman correlation coefficients were employed to correlate the utility values with visual acuity in better seeing and poorer seeing eyes. RESULTS: The Spearman correlation coefficient for time tradeoff utility values and vision in the better seeing eye was 0.455 (p < 0.001), while that for time tradeoff utility values and visual acuity in the poorer seeing eye was 0.268 (p < 0.001). The coefficient for standard gamble utility values and the better seeing eye was 0.371 (p < 0.001), while that for standard gamble utility values and vision in the poorer seeing eye was 0.250 (p < 0.001). CONCLUSIONS: There is a greater correlation between ophthalmic utility values and vision in the better seeing eye, as versus vision in the poorer seeing eye. Time tradeoff ophthalmic utility values demonstrate a greater correlation with vision in the better seeing eye than do standard gamble utility values.

Aged↗

PubMedDate not supplied

Visual acuity losses in pigeons with lesions of the nucleus of Edinger-Westphal that disrupt the adaptive regulation of choroidal blood flow.

Choroidal blood flow (ChBF) in birds is regulated by a neural circuit whose components are the retina, the suprachiasmatic nucleus, the medial division of the Edinger-Westphal nucleus (EWM), the ciliary ganglion, and the choriod. We have previously shown that lesions of EWM appear to result in pathological alterations in the retina. To determine whether EWM lesions also lead to altered visual functions, we have examined the effects of EWM lesions on visual acuity in pigeons. Bilateral lesions of EWM were made electrolytically, and visual acuity for high-contrast, square-wave gratings was determined behaviorally about 1 year later and compared to that of a group of pigeons that had received sham lesions of EW about 1 year prior to acuity testing. Because lesions targeting EWM invariably resulted in damage to the adjoining lateral part of the Edinger-Westphal nucleus (EWL), which controls pupillary constriction and accommodation, two additional control groups were studied. In one such control group, bilateral lesions in the area pretectalis (AP), which innervates the pupillary control part of EWL and thereby controls pupillary constriction, were made and the effects on visual acuity determined about 1 year later. In the second such control group, the effects of acute accommodative and pupillary dysfunction on acuity were studied in pigeons made cycloplegic. The accuracy of all lesions was later confirmed histologically. The mean acuities of birds with AP lesions (9.1+/-1.4 cycles/deg) and sham lesions (7.1+/-1.5 cycles/deg) were not significantly different from normal, based on published normative data on pigeons. In contrast, pigeons with lesions that completely destroyed EW bilaterally showed visual acuity (2.7+/-0.1 cycles/deg) that was well below the acuity of the sham and AP-lesion control groups. The acuity of the cycloplegic pigeons (4.8+/-0.3 cycles/deg) and one pigeon with a nearly complete bilateral EWL but a unilateral EWM lesion (6.4 cycles/deg) indicated that only about half of the loss with a bilateral EW lesion could be attributed to accommodative dysfunction. Thus, bilateral destruction of EWM appears to have led to a loss in visual acuity. This conclusion suggests that disruption of adaptive neural regulation of ChBF may impair visual function. Destruction of EWM was, however, associated with damage to the somatic components of the oculomotor and trochlear nuclei. The possibility cannot be excluded that such damage also contributed to the acuity loss.

Adaptation, Physiological↗

PubMed1976

Visual acuity at hyperbaric air pressure.

The visual acuity of five divers in a dry pressure chamber was measured with a Landolt C test. Only one of them showed a significant reduction at 7.0 atm. These results contrast sharply with open sea experiments, which show a considerable reduction at much lower pressures (Baddeley, 1968). It is suggested that besides stresses, luminance differences, also turbidity, as a function of depth may account for the discrepancy.

Air Pressure↗

PubMed2005

Normal visual acuity in 17--18 year olds.

PURPOSE: The aim of this work was to establish visual acuity norms in 17-18-year-olds. METHODS: In a previous, population-based study carried out in 1998, a total of 1046 12-13-year-old children were examined with a full eye examination. In 2003, 25% (n=262) of these children were randomly selected and invited to a re-examination; 147 subjects agreed to participate and 116 attended. The examined group did not significantly differ from the original sample in terms of the prevalence of ocular and visual disorders. Best corrected monocular visual acuity (VA) was assessed with the revised 2000 ETDRS logMAR chart. RESULTS: Mean best corrected VA was -0.10 logMAR across the examined group. There was no significant difference between right and left eyes. By excluding nine subjects who had significant ametropia and/or ocular or visual pathology, mean VA increased to -0.12 logMAR (SD 0.07). The mean interocular difference in VA among normal subjects was 0.04 logMAR. CONCLUSIONS: Visual acuity in teenagers is significantly better than 0.0 logMAR and the interocular difference is low in healthy eyes.

Adolescent↗

PubMed2001

A 5-year follow-up study for distance visual acuity after low dose radiation on subfoveal choroidal neovascularization in age-related macular degeneration.

In a prospective study with a 5-year follow-up, we assessed the effect of a single series of low-dose radiation on the distance visual acuity in eyes with angiographically confirmed subfoveal choroidal neovascularization (CNV) in age-related macular degeneration (ARMD). The posterior pole of 12 eyes was treated with 5 Gy (4 x 1.25 Gy), and 34 eyes treated with 8 Gy (4 x 2 Gy). The best corrected distance visual acuity was measured at the time of treatment, and annually thereafter for 5 years. The study obtained complete follow-up for 11 patients in the 5-Gy group (nine classic, two occult CNVs), and 29 patients in the 8-Gy group (12 classic, 17 occult CNVs). At baseline, the mean distance visual acuity of the treated eyes was 0.16 (20/125) in the 5-Gy group, and 0.2 (20/100) in the 8-Gy group. Five years later, an average loss of 3.2 lines was present in the 5-Gy group, and 4 lines in the 8-Gy group. After 5 years, an average loss of 2 lines was found in a control group consisting of 18 second eyes with low stage dry ARMD, with a mean distance visual acuity of 0.5 (20/40) at baseline. Statistical analyses with Wilcoxon and Mann-Whitney U-tests showed that a single series of low dose radiation with either 5 Gy or 8 Gy was not able to stabilize the distance visual acuity of eyes with subfoveal CNV in ARMD during a 5-year follow-up.

Aged↗

PubMed1991

Effectiveness of vision-screening in pre-school populations with preferential-looking cards used for assessment of visual acuity.

Screening the vision of pre-school populations has been suggested as a way to assure early identification of vision problems as well as early intervention, thereby enabling normal development of the visual system and learning process. In a masked investigation, 119 pre-school children enrolled in Project Headstart with a mean age of 3.51 years (range 3 to 5 years) had their vision screened using the Modified Clinical Technique (MCT). Monocular visual acuities in this population were determined using preferential-looking (PL) cards. Visual acuity assessment of young children in screening settings is at best a challenge; yet, all 119 children were able to complete monocular acuity assessments on each eye. Acuities for nonreferrals (individuals who passed the screening) were significantly better than for referrals (individuals who failed the screening) at the 0.0167 level using a two-tailed Fisher's Exact Test with the Bonferroni Method for multiple comparisons. The effectivity of the screening technique as determined by phi-coefficient remained highest (phi = +0.94) with the visual acuity referral criterion set at 6/12 (20/40) or less either eye and/or greater than or equal to a 2-octave difference between the eyes. The resultant referral rate (17.6%) was higher than that predicted by extrapolation from the Orinda Study for this age group (12.3%) but expected because of the different socioeconomic group. PL cards enabled monocular visual acuity measurement on 100% of the children tested and measurably increased the effectiveness of the screening procedure.

Child, Preschool↗

PubMed2001

[Impact of pterygium size on corneal topography and visual acuity - a prospective clinical cross-sectional study].

PURPOSE: Pterygia may cause topographic changes featuring increase of astigmatism. The purpose of this study was to quantify the impact of the head-limbus-distance (=height) and limbal base length of the pterygium on the anterior corneal curvature and visual acuity before excision. PATIENTS AND METHODS: In 52 eyes (19 female, 33 male) with a mean age of 53 +/- 14 years the pterygium size (height, base length, area) was quantified using projected preoperative clinical slides and was correlated with visual acuity, refractive, keratometric, topographic astigmatism and Surface Regularity Index (SRI), Surface Asymmetry Index (SAI) of the TMS-1 videokeratoscope. RESULTS: The mean height of the pterygium was 3.1 +/- 1.4 (0.8 to 6.7) mm, the mean base length was 5.1 +/- 1.4 (2.9 to 7.8) mm, the estimated mean area was 11.4 +/- 6.9 (2.1 to 29.4) mm(2). The increasing pterygium height and area resulted in a highly significant elevation of the preoperative SRI and SAI values (p </= 0.01). The amount of keratometric (p=0.02) and topographic astigmatism (p=0.001) correlated significantly with height and area of the pterygium. In addition, pterygium size correlated significantly with the differences of zonal corneal power between steepest and flattest hemimeridian in the 3-mm zone or 5-mm zone, respectively (p </= 0.01). Best-corrected visual acuity and height/area of the pterygium correlated significantly inversely (p=0.001). Visual acuity seemed to be mostly unaffected up to a height of 2.5 mm. Overall, the impact of the base length was much less striking. Topographic astigmatism (3.3 +/- 2.8 D) was significantly larger than keratometric astigmatism (2.1 +/- 2.1 D) (p=0.001). The larger the pterygium, the larger was the difference between keratometric astigmatism and subjectively tolerated spectacle cylinder (p </= 0.01). CONCLUSIONS: Increasing distance of the pterygium head from the limbus results in increased amount and irregularity of preoperatively induced corneal astigmatism. This may explain the patient's decrease in visual acuity before the pterygium reaches the optical axis. Our data may help to determine the adequate time point for primary pterygium excision.

Adult↗

PubMed1977

Effects of luminance and contrast on visual acuity, ages 16 to 90 years.

Visual acuity of persons aged 16 to 90 years was measured with Snellen letters of varied contrast at 10, 1, 0.1, and 0.01 fl chart luminances. Percentage losses of seeing with age were computed. At 10 fl luminance, perception of high- and medium-contrast letters has changed little at age 40, but about twice as much light is needed to see low-contrast letters as at age 20. By age 70, no 2-min-subtense (20/40) letters were seen at 0.01 fl luminance. The need of older people for increased lighting during indoor tasks and night driving is discussed.

Adolescent↗

PubMed2006

Visual acuity at 10 years in Cryotherapy for Retinopathy of Prematurity (CRYO-ROP) study eyes: effect of retinal residua of retinopathy of prematurity.

OBJECTIVE: To describe recognition (letter) acuity at age 10 years in eyes with and without retinal residua of retinopathy of prematurity (ROP). DESIGN: Presence and severity of ROP residua were documented by a study ophthalmologist. Masked testers measured monocular recognition visual acuity (Early Treatment of Diabetic Retinopathy Study) when the children were 10 years old. Two hundred forty-seven of 255 surviving Cryotherapy for Retinopathy of Prematurity (CRYO-ROP) randomized trial patients participated. A reference group of 102 of 104 Philadelphia-based CRYO-ROP study participants who did not develop ROP was also tested. RESULTS: More severe retinal residua were associated with worse visual acuity, regardless of whether retinal ablation was performed to treat the severe acute-phase ROP. However, within each ROP residua category, there was a wide range of visual acuity results. CONCLUSIONS: This is the first report of the relation between visual acuity (Early Treatment of Diabetic Retinopathy Study charts) and structural abnormalities related to ROP in a large group of eyes that developed threshold ROP in the perinatal period. Visual deficits are greater in eyes with more severe retinal residua than in eyes with mild or no residua. However, severity of ROP residua does not predict the visual acuity of an individual eye because within a single residua category, acuity may range from near normal to blind.

Child↗

PubMed1995

Visual acuity following extracapsular cataract extraction in diabetes: a meta-analysis.

Although pre-operative retinopathy severity appears to be a major factor in determining the visual outcome of diabetic extracapsular cataract extraction, its precise relationship to post-operative visual acuity is ill defined. A meta-analysis was therefore carried out, and studies were included if pre-operative maculopathy and retinopathy status was sufficiently defined to permit discrimination of visual outcome between subgroups. Weighted mean proportions of eyes achieving a post-operative visual acuity > or = 6/12 were as follows: no retinopathy, 87%; non-proliferative retinopathy with no maculopathy, 80%; quiescent proliferative retinopathy with no maculopathy, 57%; non-proliferative retinopathy with maculopathy, 41%; quiescent proliferative retinopathy with maculopathy, 11%; active proliferative retinopathy, 0. Differences in visual outcome between groups were significant (chi 2 = 119.9, p < 0.0005), attributable mostly to the trend across groups (chi 2 for trend = 115.4, p < 0.0005). Logistic regression indicated that maculopathy was a more potent predictor of post-operative visual acuity < or = 6/12 (odds ratio 6.4, 95% CI 4.13-9.94, p < 0.0005) than quiescent proliferative retinopathy (odds ratio 3.33, 95% CI 2.04-5.42, p < 0.0005). The severity of retinopathy and maculopathy prior to cataract surgery in diabetics are the major determinants of post-operative visual acuity. Further study of the relationship between pre-operative retinopathy severity and the incidence of post-operative complications, progression of retinopathy and maculopathy is required to optimise the management of cataract in diabetes.

Cataract Extraction↗

PubMed1997

Design of an Arabic near visual acuity chart.

This paper describes the design of an Arabic test chart for measurement of visual acuity at near. The chart was designed employing specially selected Arabic letters and was based on the logMAR principle devised by Bailey and Lovie. Ten Arabic letters of nearly equal legibility values (0.92-1.05) (mean = 1.00), (SD = 0.05) were used in the design of the chart. Each row of the chart has 5 letters and row legibility values range from 4.82 to 5.03 with a mean of 4.92 (SD = 0.06). The logMAR method of visual acuity scaling was used, hence the sizes of letters in the rows progress in a uniform step of 0.1 log unit. The inter-letter spacing is equal to the width of each letter in the row, while inter-row spacing is equal to the height of letter in the subjacent row. The height of letters ranged from 3.67 to 0.46 mm corresponding to visual acuity of 2.4 M to 0.3 M which is equivalent to reduced Snellen 6/36 to 6/4.5 at 0.4 m. The chart is designed for use at 40 cm with a recommended luminance level of 160 cd/m2.

Arab World↗

PubMedDate not supplied

Bilateral optic disc edema in patients with severe systemic arterial hypertension: clinical features and visual acuity outcomes.

BACKGROUND AND OBJECTIVE: To report clinical features and visual outcomes in patients with bilateral optic disc edema and severe systemic arterial hypertension. PATIENTS AND METHODS: Records were reviewed of patients with bilateral optic disc edema, severe arterial hypertension, and 3 or more months of follow-up evaluated at Bascom Palmer Eye Institute between 1982 and 2003. RESULTS: Sixteen patients (median age = 41 years; median follow-up = 31 months) were identified. Median blood pressure on initial eye examination was 220 mm Hg systolic and 126 mm Hg diastolic. Among all study eyes, median visual acuity was 20/55 on presentation. At the last follow-up examination, an acuity of 20/50 or better was achieved in 20 (63%) eyes; 12 (75%) patients achieved a final acuity of 20/50 or better in at least one eye. Posterior segment abnormalities at last follow-up included disc pallor (n = 16), macular star (n = 7), retinal pigment epithelial atrophy (n = 7), epiretinal membrane (n = 5), branch retinal vein occlusion (n = 4), and persistent disc edema (n = 2). Causes of final acuity of less than 20/50 included optic atrophy, epiretinal membrane, serous retinal detachment, macular hole, and branch retinal vein occlusion. CONCLUSION: Most patients with bilateral optic disc edema and severe arterial hypertension maintained visual acuity of 20/50 or better in at least one eye.

Adolescent↗

PubMed1996

[How should visual acuity be measured?].

1) The ordinary Snellen chart with letter optotypes is not suited for research purposes. Unequal legibility of letters, unequal number of optotypes on rows of the chart and unequal progression of letter sizes limit the usage of such charts for screening purposes only. 2) The results of our computerised method for determining of visual acuity correlate very well with the results gained using the standardised Landolt optotype chart (r = 0.931). Our method brings whole line acuity, threshold visual acuity with its variability and a new parameter of line slope (decrease of correct readings from 95% to 5%), expressed in standardised rows (log MAR = 0.1). The results are printed on a simple printer and stored in a database.

Adolescent↗