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Results for “Visual Acuity”

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At least 847 records · Page 47Linked to original sources

PubMed1981

Visual acuity in cats following surgically induced cyclotropia.

Visual acuity was measured, using a jumping stand technique, in cats which had undergone surgical cyclotorsion of one or both eyes. In cats with unilateral rotations acuity was depressed in the rotated eye and the extent of loss increased with larger amounts of rotation. Cats which had undergone bilateral rotations tended to have lower acuities than normal cats and there was a slight tendency for the eye with the greater rotation to show the larger deficit. Evidence is presented that the lowered acuities were not the result of peripheral damage and it is suggested that the defect may be considered as a form of strabismic amblyopia.

Amblyopia↗

PubMed1981

Night driving (mesopic) visual acuity in sober male alcoholics with and without liver disease.

Night driving (mesopic) visual acuity and recovery after dazzle has been reported to be reduced in patients with liver disease. Mesopic visual acuity and dazzle recovery were evaluated in 32 patients with alcoholic cirrhosis, 29 alcoholics without liver disease, and 27 age-matched normal controls. All subjects were sober for at least 7 days prior to visual testing, a mean sobriety period of 22 and 39 weeks in alcoholics and cirrhotics, respectively. Serum vitamin A levels and/or dark adaptation were normal in all. Mean best decimal acuities were not significantly different among the groups: alcoholic cirrhotics, 0.32 +/- 0.02; alcoholics, 0.32 +/- 0.02; and normals 0.33 +/- 0.03 at 2 min. Although cirrhotics had significantly higher SGOT and lower albumin levels than alcoholics, mesopic acuity did not relate to liver blood tests. Decimal acuity following a dazzle stimulus was not significantly worse in cirrhotics and alcoholics compared to normals. Sober patients with alcoholic cirrhosis or a history of alcoholism have no evidence of a static mesopic visual defect and therefore may not have impaired night driving vision.

Alcoholism↗

PubMed1997

Anti-aliasing and dithering in the 'Freiburg Visual Acuity Test'.

Anti-aliasing is a technique for improving spatial resolution at the cost of luminance resolution. Dithering is a technique for improving luminance resolution at the cost of spatial resolution. These techniques are applied to the testing of visual function in the 'Freiburg Visual Acuity Test': by employing anti-aliasing, spatial resolution was improved. Thus, even the shape of small Landolt-Cs with oblique gaps is adequate, and visual acuities from 5/80 (0.06) up to 5/1.4 (3.6) can be tested at a distance of 5 m. By employing dithering, subthreshold contrast stimuli can be generated on a conventional display having standard 8-bit video resolution. Rapid acquisition of a semi-objective and reliable acuity estimate makes the 'Freiburg Visual Acuity Test' useful for subject screening in vision research, as well as for routine assessments in the ophthalmic practice.

Computer Terminals↗

PubMed2005

Outcomes of visual acuity in carbon ion radiotherapy: analysis of dose-volume histograms and prognostic factors.

PURPOSE: To analyze the tolerance dose for retention of visual acuity in patients with head-and-neck tumors treated with carbon ion radiotherapy. METHODS AND MATERIALS: From June 1994 to March 2000, 163 patients with tumors in the head and neck or skull base region were treated with carbon ion radiotherapy. Analysis was performed on 54 optic nerves (ONs) corresponding to 30 patients whose ONs had been included in the irradiated volume. These patients showed no evidence of visual impairment due to other factors and had a follow-up period of >4 years. All patients had been informed of the possibility of visual impairment before treatment. We evaluated the dose-complication probability and the prognostic factors for the retention of visual acuity in carbon ion radiotherapy, using dose-volume histograms and multivariate analysis. RESULTS: The median age of 30 patients (14 men, 16 women) was 57.2 years. Median prescribed total dose was 56.0 gray equivalents (GyE) at 3.0-4.0 GyE per fraction per day (range, 48-64 GyE; 16-18 fractions; 4-6 weeks). Of 54 ONs that were analyzed, 35 had been irradiated with <57 GyE (maximum dose [Dmax]) resulting in no visual loss. Conversely, 11 of the 19 ONs (58%) irradiated with >57 GyE (Dmax) suffered a decrease of visual acuity. In all of these cases, the ONs had been involved in the tumor before carbon ion radiotherapy. In the multivariate analysis, a dose of 20% of the volume of the ON (D20) was significantly associated with visual loss. CONCLUSIONS: The occurrence of visual loss seems to be correlated with a delivery of >60 GyE to 20% of the volume of the ON.

Adult↗

PubMed1986

[Effect of contact lenses and visual acuity on the registration of saccadic eye movements using an infrared reflection method].

In order to examine the influence of contact lenses and visual acuity on recordings of saccadic eye movements with the infrared reflection method, horizontal 20 and 30 degrees saccades were recorded with and without contact lenses in 16 subjects (32 eyes) usually wearing contact lenses. As far as the main parameters of the saccades (accuracy, peak velocity and duration) were concerned, the reliability of the measurements (recognizable through the mean values) was not essentially influenced by the contact lenses. The precision of the measurements (recognizable through the standard deviation) was with the contact lenses significantly but, for clinical use, not essentially worse. The velocity waveforms of the saccades, however, were considerably changed by contact lenses in some cases. This is why examinations, in which saccadic velocity waveforms are used for diagnosis, should be performed without contact lenses. Visual acuity had no measurable influence on the main parameters of the saccades. However, considerably more corrective saccades were observed with contact lenses than without. There were reasons to believe that not the contact lenses themselves, but better visual acuity was responsible for the larger number of corrective saccades.

Adult↗

PubMed1988

Reliability and validity of the dot visual acuity test.

The reliability of the dot visual acuity test (DVAT) was demonstrated using the test-retest method. The test, however, was not found to be valid when comparing it with the Sjögren test. Since the DVAT has previously been shown to be valid when compared to the Tumble E test, these results bring into question the validity of the Sjögren test when compared to the Tumble E test.

Child↗

PubMed1992

Practically corrected visual acuity after extracapsular cataract extraction with or without intraocular lens implantation.

We examined retrospectively a total of 171 patients (236 eyes) who had undergone extracapsular cataract extraction (ECCE) with or without intraocular lens implantation (IOL). The best and practically corrected visual acuities were determined 6 months after surgery. Practically corrected visual acuity of the ECCE group was significantly worse than that of ECCE plus IOL group of patients who had undergone unilateral cataract surgery. In patients who had undergone bilateral surgery, visual improvement was almost optimal in both groups. With regard to practically corrected visual acuity, ECCE plus IOL was the preferable procedure for elderly patients who had had unilateral cataract.

Aged↗

PubMed1992

The relationship of visual acuity, tactile sensitivity, and mobility of the upper extremities to proficient breast self-examination in women 65 and older.

The purpose of this study was to describe the relationship of visual acuity, tactile sensitivity, and mobility of the upper extremities to the performance of proficient breast self-examination (BSE) in women 65 and older. A convenience sample of 32 women, ages 66-89, met with the investigator to have their visual acuity, tactile sensitivity, and upper extremity mobility tested. Their ability to perform the visual, tactile, and upper extremity components of proficient BSE also was tested by using simulated breast models (SBMs). Thirty of the women had adequate visual acuity (< or = 20/40 Snellen equivalent) but were unable to visually detect the abnormalities on the SBM. Thirty of the women had tactile sensitivity of 10 mm (1 cm) or better on the static two-point discrimination test of the second, third, and fourth digits of each hand. Yet, only 13 of these women were able to locate the 1 cm lump; only 12 were able to locate the 5 mm lumps; and none were able to locate the 3 mm lump. The subjects' ability to pass the upper extremity mobility component of proficient BSE was significantly related to their ability to pass the upper extremity range of motion criteria. Limitations and deficits, mostly of the hands and shoulders, were revealed. When teaching BSE to older women, nurses are responsible for assessing limitations and deficits in their ability to perform proficient BSE and, if necessary, for intervening with alternatives. The need for further research in this area is indicated to improve assessment and education of older women regarding the use of proficient BSE for early detection of breast cancer.

Age Factors↗

PubMed1991

Etiology of reduced visual acuity in congenital nystagmus.

A study was undertaken to identify the etiologic factor of reduced visual acuity in congenital nystagmus. Fourteen children with congenital nystagmus and reduced visual acuity were examined, using a modified "E" game test. Their success rate in identifying vertical lines was compared with their success rate in identifying horizontal lines. The children identified both vertical and horizontal lines with a similar rate of success. These results may indicate that poor vision in congenital nystagmus patients is partly the result of amblyopia.

Amblyopia↗

PubMed1991

Visual acuity degradation resulting from dispersion in polycarbonate.

Visual acuities (VA) were measured through a series of prisms in order to quantify the blur that results from dispersion in polycarbonate. The mean VA of 40 eyes was reduced from a starting level of 20/13 unaided to 20/31 through 16 prism diopters of polycarbonate. The decline was a linear function of prismatic power. The blurring effect of polycarbonate was significantly greater than that of CR39. The blur from polycarbonate was found to be great enough that it should be taken into account whenever polycarbonate is considered for spectacle lenses. A graphical display is provided which can be used by the clinician to predict the degree of blur from a known polycarbonate lens.

Adult↗

PubMed2004

Comparison of fundus autofluorescence with photopic and scotopic fine-matrix mapping in patients with retinitis pigmentosa and normal visual acuity.

PURPOSE: To compare psychophysically determined spatial variations in photopic and scotopic sensitivity across the macula in patients with retinitis pigmentosa (RP) and normal visual acuity who manifest an abnormal high-density ring of fundus autofluorescence (AF). METHODS: Eleven patients with a clinical diagnosis of RP were examined. All had rod-cone dystrophy (International Society for Clinical Electrophysiology of Vision [ISCEV]-standard ERGs), visual acuity of 6/9 or better, and an abnormal parafoveal annulus of high density AF. Fine-matrix mapping (FMM) was performed over macular areas of abnormal high-density AF under photopic and dark-adapted conditions. Pattern ERGs (PERGs) were performed in 9 of 11 patients, by using different sizes of circular checkerboards. RESULTS: Rings of high-density AF varied between patients (approximately 3 degrees -18 degrees in diameter). Photopic sensitivity was preserved over central macular areas, but there was a gradient of sensitivity loss over high-density segments of the ring and severe threshold elevation outside the arc of the ring. Scotopic sensitivity losses were more severe, and they encroached on areas within the ring. The radius of the high-density ring correlated with the lateral extent of preserved photopic sensitivity (r=0.86) and PERG data. CONCLUSIONS: High-density rings of AF, which are present in some patients with RP with normal visual acuity, demarcate areas of preserved central photopic sensitivity. Scotopic sensitivity losses encroach on areas within the ring of high density and may reflect dysfunction before accumulation of lipofuscin.

Adult↗

PubMed2000

Improving the reliability of visual acuity measures in young children.

Whilst the methodology of adult letter acuity measurement has been substantially refined over the last two decades, relatively little development has occurred in methods for quantifying letter acuity in young children. This study compares a recently developed visual acuity test (Glasgow Acuity Cards), which incorporates several key design features used in adult test charts to improve the sensitivity and reliability of visual acuity measurements. The equivalence of acuity measurements made with Glasgow Acuity Cards were compared with the Bailey-Lovie logMAR chart and Snellen chart in adults, and with traditional Single Letter Acuity and a modified Single Letter Acuity test in children. The test-retest reliability of acuity measurements made with Glasgow Acuity Cards and the Single Letter Acuity tests were also assessed in a large group of visually normal children. In addition, the ability of the pre-school letter acuity tests to detect differences in acuity between the two eyes, and to detect amblyopia were examined. Ninety-five percent of vision measurements made with the Bailey-Lovie chart and Glasgow Acuity Cards differ by less than 0.07 log unit. Furthermore, the sensitivity of Glasgow Acuity Cards to detecting changes in acuity longitudinally and inter-ocular differences in acuity is considerably greater as compared with traditional Single Letter Acuity tests. Improvements in paediatric acuity chart design are important for the effective detection and management of children with amblyopia.

Adolescent↗

PubMed1975

Retinal pigmentation, visual acuity and brightness levels.

This study investigates the hypothesis that the degree of retinal pigmentation in the human eye is adaptive as it relates to the maintenance of visual acuity in optically stressful environments, deserts and snowfields. Eighty-four subjects were examined, an estimation of their degree of retinal pigmentation made by ophthalmoscopic examination and their binocular visual acuity tested over ten levels of brightness. The general level of retinal pigmentation did not influence mean visual acuity within the levels of brightness used in this study. The hypothesis was, therefore, rejected, but with the proviso that this study should be extended to even higher levels of brightness than were obtained here. There was no difference in mean pupil size at various levels of illumination between individuals grouped by degree of retinal pigmentation.

Adaptation, Biological↗

PubMed1991

[Visual acuity and color sensitivity in retinal detachment].

In patients with unilateral detachment of the retina after successful operation (buckling 3x, cerclage 3x, combined operation 4x), the visual acuity was assessed on Snellen optotypes or Landolt's ring chart. Optotype charts with rings were made according to recommendations of the commission for vision of the American Academy of Sciences. Snellen's visual acuity of healthy and affected eyes was 6/9-6/6. In all patients moreover sensitivity to contrast was examined assessed by means of a VISTESCH testing table. It was revealed that sensitivity for contrast in all operated eyes is significantly lower than in healthy eyes and that the threshold visual acuity and steepness of lines is significantly lower.

Color Perception↗

PubMed2005

Visual acuity and structural findings in old age-related macular degeneration.

BACKGROUND: Although exudative age-related macular degeneration (AMD) leads to a substantial visual loss in most patients there is still significant variation in the end- stage visual acuity level. We analysed lesions in eyes with long-standing AMD in order to find contributing factors for this variation. METHODS: Sixty-one out of 121 patients examined for exudative AMD and still alive 4.8-9.2 (mean 6.8) years after the acute phase were re-examined. The lesion size, area of subretinal fibrosis, geographic atrophy, presence of a persistent exudative process, and shortest distance to normal looking retina were measured from digital fundus photographs taken at the re-examination and correlated with visual acuity. RESULTS: Lesion size, the presence of a continuing exudative process, or subretinal fibrosis were independent predictors for poor vision. Better vision in the other eye was connected with poor vision in the affected study eye. CONCLUSIONS: In addition to lesion size, the presence of a continuing exudative process and subretinal fibrosis also have deleterious effects on long-term visual acuity after exudative AMD.

Aged↗

PubMed1989

Visual acuity after retrobulbar anesthesia.

Patients often say that they can see the surgical instruments with the operated eye during intraocular surgery. We examined 26 consecutive patients for visual acuity, ocular motility, and pupillary response before, during, and after retrobulbar anesthesia for cataract extraction. Twenty minutes after the anesthetic was injected, 19% of these patients had visual acuities better than 6/200, and 73% of patients described the movements of the instruments during surgery. Two patients (8%) recognized details on the ceiling after insertion of the intraocular lens. An afferent pupillary defect was found in 31% of patients. Although retrobulbar anesthesia results in a marked decrease in ocular motility and visual acuity, total akinesia and blindness do not occur. An incidental result of retrobulbar anesthesia may be a transient afferent pupillary defect.

Anesthetics, Local↗

PubMed1984

Effect of luminance, contrast, and eccentricity on visual acuity in senile macular degeneration.

We examined the effect of luminance on low contrast visual acuity in six patients with mild reductions in vision due to senile macular degeneration (SMD) and in six normals of approximately the same age. At the highest luminance tested the SMD patients showed a reduction in acuity compared to the controls, with eccentricity and contrast effects clearly shown. The SMD patients had difficulty performing the acuity task at the lower luminances (0.26 and 0.75 cd/m2); they showed little or no increase in visual acuity with increasing contrast levels at the lower luminances. Acuity was slightly influenced by target eccentricity at these luminances. These data suggest that the adaptation mechanisms allowing the normal visual system to operate efficiently over a wide range of luminances are affected in SMD, even when clinically measured acuity is only moderately depressed.

Aged↗

PubMed1990

Visual acuity and contrast sensitivity of the S cone pathway: preliminary measures with letter charts.

Letter charts were used to measure visual acuity and peak contrast sensitivity of the short wavelength sensitive (S cone)-pathway. The accommodative response was monitored retinoscopically. The mean visual acuity (0.92 logMAR) and spatial contrast threshold (8.7%) were comparable to values reported elsewhere, and variability was relatively low. Both S-pathway acuity and contrast sensitivity were selectively reduced in one patient with central serous retinopathy and in another with retinitis pigmentosa. These simple spatial tests offer an additional index of S-pathway integrity which will be useful for detection and evaluation of ocular disease.

Accommodation, Ocular↗