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Results for “Visual Acuity”

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At least 1,063 records · Page 59Linked to original sources

PubMed1983

Laser interferometric visual acuity in senile macular degeneration.

Twenty-nine eyes from 15 patients were affected by senile macular degeneration and had clear ocular media. Tests with retinal interference fringe patterns produced by a low-energy helium-neon laser and Snellen's charts showed that in 13 eyes, interferometric and Snellen's acuities were within one line. In the remaining 16 eyes, laser interferometric acuities were notably better than Snellen's acuities. Our results suggest that laser interferometric visual acuities, prior to lens extraction, will prove inconsistent in accurately predicting postoperative Snellen's acuities in patients with senile macular degeneration.

Aging↗

PubMed2003

Pattern ERG correlates of abnormal fundus autofluorescence in patients with retinitis pigmentosa and normal visual acuity.

PURPOSE: To examine the functional significance of central abnormalities present in fundus autofluorescence (AF) images in patients with rod-cone dystrophy and good visual acuity. METHODS: Thirty patients were selected according to three criteria: a clinical diagnosis of retinitis pigmentosa (RP) confirmed with International Society for Clinical Electrophysiology of Vision (ISCEV) standard ERGs, a parafoveal ring of increased high density on fundus AF imaging, and a visual acuity of 20/30 or better. Macular function was assessed with pattern electroretinography (PERG) to checkerboard stimuli of different field sizes. Fundus AF imaging was performed with a confocal scanning laser ophthalmoscope. RESULTS: The radius of the parafoveal ring of high density varied between 1.5 degrees and 9 degrees. The PERG P50 amplitude correlated highly with the radius of the ring of increased autofluorescence (r = 0.80, P < 0.0005, n = 30). PERGs to smaller circular field sizes were present, but increasing field size to beyond that of the high-density autofluorescence ring did not produce further increases in P50 amplitude. There was a high correlation between the minimum stimulus size required to elicit a maximum-amplitude PERG and the radius of the ring (r = 0.87). CONCLUSIONS: The high correlation between AF imaging and PERG, an established technique in the assessment of central retinal function, demonstrates the likelihood that autofluorescence abnormalities have functional significance and may therefore be a valuable additional parameter in the monitoring of these patients.

Adolescent↗

PubMed1979

[Improvement of visual acuity of intensely myopic patients during their eye-cure stay at Bad Hall (author's transl)].

Intensely myopic patients in the Eye Department of the Paracelsus-Institute in Bad Hall (Upper Austria) were subjected to visual acuity tests whereby the conditions of examination were held constant (optotype-projector, panoramic visual range, exactly defined break-off criteria). Results showed that 33% of the patients, who had completed combined iodine treatments and ophthalmo-iontophoresis, showed an improvement in visual acuity of 3 or more optotypes, corresponding to an average increase thereof of 0,13 from the initial visual power. Side effects of intense myopia (dilatation tension and degenerative changes at the posterior eye pole) should thus be regarded as an indication of the successful application of the combined balneotherapy, mineral water treatment and eye-cure in Bad Hall.

Aged↗

PubMed1995

Two types of foveation strategy in 'latent' nystagmus: fixation, visual acuity and stability.

The authors studied the foveation dynamics of two individuals with latent/manifest latent nystagmus (LMLN) to test the hypothesis that oscillopsia suppression and good visual acuity require periods of accurate target foveation at low slip velocities. Congenital nystagmus (CN) waveforms contain post-saccadic foveation periods; the LMLN waveform does not and yet allows for both oscillopsia suppression and good acuity. During fixation with both eyes open, there were intervals when the eyes were still and correctly aligned; at other times, there was esotropia and nystagmus with slow-phase velocities less than +/- 4 deg/sec and each fast phase pointed the fovea of the fixating eye at the target. However, cover of either eye produced LN and a different strategy was employed: the fast phases carried the fixating eye past the target and the fovea subsequently reacquired it during the slowest parts of the slow phases. The authors confirmed this in both subjects, whose high acuities were made possible by foveation occuring during the low-velocity portions of their slow phases. A nystagmus foveation function (NFF), originally developed for CN, was calculated for both LN and MLN intervals of fixation and it was found to track visual acuity less accurately for individuals with high acuity. Individuals with LMLN exhibit two different foveation strategies: during low-amplitude LMLN, the target is foveated immediately after the fast phases; and during high-amplitude LMLN, target foveation occurs towards the end of the slow phases. Therefore, the saccadic system can be used to create retinal error rather than eliminate it if this strategy is beneficial. Individuals with LMLN foveated targets with the same eye-position and -velocity accuracy as those with CN and the NFF provides a rough estimate of acuity in both. Current calibration methods for both infrared and search-coil techniques need to be altered for subjects with LMLN.

Adult↗

PubMed1995

Bilateral microphthalmos with poor visual acuity, high hyperopia, and papillomacular retinal folds in siblings.

Ophthalmological examinations were carried out on a 4-year old girl and her 2-year-old brother who have had poor visual acuity since birth. A consanguineous relationship was found between the parents. Both children had bilateral microphthalmos, poor visual acuity, high hyperopia, and papillomacular retinal folds. No ocular coloboma or systemic abnormality was found. We believe that the ophthalmic findings in these patients are rare.

Child, Preschool↗

PubMed1991

Variability of monocular visual acuity during binocular viewing.

Two patients observed changes in the visual acuity of one eye when both eyes were viewing simultaneously in certain directions of gaze. While viewing targets presented during the Turville Infinity Balance (TIB) test, the acuity of the affected or amblyopic eye improved when the nonamblyopic eye was covered and binocular vision suspended. The vision of the amblyopic eye was also improved when an appropriate prism was held in front of either eye. The direction of the prism base was based upon the interrelations of horizontal, vertical, and cyclotorsional anisophoria and the amount of prism was the minimum necessary to improve the vision in the amblyopic eye and neutralize vertical fixation disparity. The correlation of variable monocular acuity, stereopsis, and fixation disparity with oculomotor balance is recorded and discussed.

Adult↗

PubMed1984

The development of visual acuity in the Mongolian gerbil (Meriones unguiculatus).

The development of visual acuity for vertically oriented gratings was followed in gerbil pups from 34 days of age until adulthood using a jumping stand procedure. Acuity was found to improve gradually from an initial level of about 0.7 cycles/degree to asymptotic values of 1.2-1.6 cycles/degree by 70 days of age. Acuity did not vary as a function of viewing distance over the range tested (17.5-46 cm). Practice was found to play some role in the acuity changes seen but cannot alone explain the results. The contributions of other performance variables and of neural development are considered.

Animals↗

PubMedDate not supplied

Symmetry of refractive and visual acuity outcome in the Prospective Evaluation of Radial Keratotomy (PERK) study.

In the Prospective Evaluation of Radial Keratotomy (PERK) study, the symmetry of refractive and visual acuity outcome was analyzed in 269 patients with bilateral radial keratotomy with a single operation in each eye. Patients were required to wait 1 year after surgery on the first eye before having surgery on the second eye. At 1 year after surgery on the second eye, 98% of patients had 3.00 diopters or less difference between their two eyes in the spherical equivalent of the cycloplegic refraction (100% before surgery), and 96% of patients had 3.00 D or less difference between their two eyes in the amount of refractive power in the vertical meridian (100% before surgery). Thus, surgically induced refractive anisometropia was not a major complication in the PERK study. However, 14% of patients had four to eight Snellen lines difference in the uncorrected visual acuity between their two eyes (1% before surgery), emphasizing that induced asymmetry of refraction is a potential clinical problem for some patients.

Adult↗

PubMed1993

Relative letter and position difficulty on visual acuity charts from the Early Treatment Diabetic Retinopathy Study.

Ten Sloan letters were used in the visual acuity charts developed for use in the Early Treatment Diabetic Retinopathy Study. We used the data from the 3,710 Early Treatment Diabetic Retinopathy Study subjects to investigate the relative difficulty of the ten Sloan letters and to evaluate whether the position of a letter on a line affected its relative difficulty. In general, our findings were consistent with those of the previous study. The four letters with curved contours (C, O, S, and D) were more difficult to discern at threshold than the six letters (Z, N, H, V, R, and K) composed of straight lines. Our data demonstrate that under these test conditions, letters at the end of a line are more likely to be read incorrectly than letters at the beginning of the line. This finding indicates that these data are probably not useful for evaluating possible crowding phenomena.

Diabetic Retinopathy↗

PubMed1993

[Visual acuity and automobile driving fitness in the elderly].

BASIC REMARKS: Both physiological age-related degeneration of the organ of sight and its adnexa, and pathological age-related diseases, such as cataract, glaucoma or senile macula degeneration, impair a person's eyesight. MAJOR POINTS DISCUSSED: The consequences include a decrease in visual acuity, impairment of the visual field, diminishment of dark adaptation, twilight vision, contrast perception, and stereoscopic vision, together with a dramatic increase in sensitivity to light. All these phenomena may greatly reduce the elderly person's ability to cope with the demands made by modern traffic. Our investigations do, however, indicate that in parallel with increasing life expectancy, the physiological and pathological age-related changes in the organ of sight may be occurring later than formerly. Moreover, modern surgical techniques, for example senile cataract with implantation of an intraocular lens, may achieve optical rehabilitation. CONCLUSION: Active participation of the elderly in road traffic, for example driving a car, is certainly possible from the point of view of the ophthalmologist. Nevertheless, the introduction of regular testing of vision from the age of 65 onwards is to be recommended.

Accidents, Traffic↗

PubMed2000

Reduced visual acuity impairs place but not cued learning in the Morris water task.

The Morris water task is a standard method for testing spatial learning in rodents. In a place version of the task, animals utilize multiple visual cues to learn the location of a hidden platform. The ability of animals to locate a cued platform is often used to qualitatively test for possible non-cognitive contributions to deficient place learning, including reduced visual function. We investigated the role of visual acuity in water maze performance quantitatively by depriving rats of pattern vision during a critical period for visual plasticity, which reduced their acuity by approximately 27% and then tested them in typical place and cued platform configurations of the Morris water task. Animals with reduced visual acuity had a significant deficit in place learning, but eventually reached the same escape latency as non-deprived animals. Deprived and non-deprived animals, however, did not differ in their ability to locate a cued platform following place learning. These data indicate that reduced visual acuity in rats can influence measurement of their place learning and that a typical cued platform version of the task cannot detect a modest, but significant, visual deficit.

Animals↗

PubMed1979

Vitamin B-complex deficiency and visual acuity.

1. A study was carried out on 973 school children to find out any relationship between vitamin B-complex deficiency signs and defective vision, and the effect of supplementation of B-complex vitamins on visual acuity. 2. The results of the study showed a significant association between presence of clinical signs of vitamin B-complex deficiency and defective vision. 3. Supplementation with vitamin B-complex was found to have a beneficial effect in improving the visual-acuity status of defective children and in preventing visual defects from developing. 4. It is concluded, therefore, that from the present study it appears that the relationship between vitamin B-complex deficiency and visual defects could be one of 'cause and effect'.

Adolescent↗

PubMed1994

Development of visual acuity in relation to plasma and erythrocyte omega-6 and omega-3 fatty acids in healthy term gestation infants.

The development of preferential looking acuity was studied prospectively to 3 mo of age in exclusively breast-fed and formula-fed term gestation infants. The formula contained (% of total fatty acids) 17.9% linoleic acid (18:2 omega-6) and 2.1% alpha-linolenic acid (18:3 omega-3) but no docosahexaenoic acid (22:6 omega-3) or arachidonic acid (20:4 omega-6). The breast milk contained (mean +/- SEM) 13.4 +/- 0.8% 18:2 omega-6, 1.5 +/- 0.1% 18:3 omega-3, 0.51 +/- 0.03% 20:4 omega-6, and 0.22 +/- 0.02% 22:6 omega-3. Preferential looking acuity, assessed by the acuity-card procedure, and plasma phospholipid and erythrocyte phosphatidylcholine and phosphatidylethanolamine fatty acids were determined at 14 d and 3 mo of age. There were no significant differences in acuity at 14 d or 3 mo, despite substantial differences in erythrocyte and plasma lipid 22:6 omega-3. Visual acuity was [mean (cycles/degree) +/- SD (octaves)] 3.93 +/- 0.54 and 4.77 +/- 0.48 and erythrocyte phosphatidylethanolamine %22:6 omega-3 was (mean +/- SE) 7.6 +/- 0.5 and 4.0 +/- 0.2 in the 3-mo-old breast-fed and formula-fed infants, respectively. These studies show that feeding formula containing 2.1% 18:3 omega-3 (approximately 1.0% energy) results in development of visual acuity similar to breast-feeding in term infants to > or = 3 mo of age.

Breast Feeding↗

PubMed1977

Effect of the Harvard Step Test on visual acuity.

A replication with 5 females in a laboratory setting of findings by Kashuk that physical activity improves visual acuity used the Harvard Step Test for the exercise load and grating acuity (resolution acuity) to determine possible changes. The results support Kashuk's work.

Female↗

PubMed1994

Task performance with visual acuity while wearing a respiratory mask.

Forty-six subjects were required to perform a console-monitoring and two hand-eye coordination tasks while wearing masks with lenses clouded to give seven levels of visual acuity. The console-monitoring task performance was found to be the most sensitive to visual acuity, followed by the random hand-eye coordination task. These results can be used to help predict performance degradation when lenses become clouded due to condensation or particulate deposition.

Adolescent↗

PubMed1991

Training effects on dynamic visual acuity with free-head viewing.

Training effects on dynamic visual acuity (DVA) were determined over a range of target durations and target velocities under the viewing condition of free-head movement. Dynamic acuity levels were lower than static acuity levels, and training was found to be very effective in improving performance, particularly under the most difficult conditions in which performance was poorest. Improvement was also most evident among those observers who initially exhibited the poorest DVA scores. Preliminary comparisons between DVA scores of a nonselect sample of college students and those of a small group of college athletes indicated that the athletes were not very different from the nonselect group and would also benefit from training on the task.

Attention↗

PubMed1999

Assessment of visual acuity in children aged 1 1/2-6 years, with normal and subnormal vision.

The aim of the study was to assess different visual acuity tests in the age group 1 1/2-6 years in 105 children with assumed normal vision, visual impairment due to ocular disease or strabismus. Acuity tasks for young children can be divided into three subtypes according to the kind of stimulus used. For "detection acuity", the stimulus should be detected or distinguished from the background, as assessed with the Stycar Rolling Balls. For "resolution acuity", the stimulus pattern should be resolved, as assessed with the Preferential Looking procedure (Teller Acuity Cards). For "recognition acuity", the stimulus must be recognized by the subject as assessed with the BUST-D symbol test, Sheridan Gardiner (S-G) single letters, LH single symbols and line tests, and also the HVOT test. Different acuity values were obtained with regard to detection, resolution and recognition acuities. Assessment with the Stycar Rolling Balls only gave a rough estimate of the visual function. There was an overestimation of the acuity values in all groups of children when using the Preferential Looking technique. Good agreement was found between the LH line and HVOT tests. The BUST-D test, S-G single letters, and LH single symbols gave slightly better acuity values than linear recognition tests. A "crowding ratio" was calculated by dividing the single optotype acuity by the linear acuity, and also by dividing the grating acuity by the optotype linear and single acuity. The crowding ratio varied in the individual children and in the different groups, being highest for strabismic amblyopia. The general conclusion is that reliable visual acuity measurements were not obtained until the visual acuity could be assessed with a recognition test using linear letters or symbols.

Adult↗

PubMed1988

A comparison study of dynamic visual acuity between athletes and nonathletes.

A comparison study of dynamic visual acuity (DVA) was conducted using samples of nonathletic college students and college baseball players. The experimental population consisted of 17 male baseball players ranging in age from 19-24 years. The control population was made up of 25 male graduate students ranging in age from 23-29 years. Subjects reported the direction of a 20/25 "Landolt C" target exhibiting uniform angular motion produced by a projection system. Angular target velocities between 10 deg/sec and 110 deg/sec with an exposure time of 400 ms were used. The results showed a statistically significant difference between the two groups' DVA. The mean DVA for the baseball players was 82.35 deg/sec and 69.90 deg/sec for the control group.

Adult↗