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Results for “Visual Acuity”

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At least 343 records · Page 19Linked to original sources

PubMed2003

Long-term anatomic and visual acuity outcomes after initial anatomic success with macular hole surgery.

PURPOSE: To investigate the anatomic and visual outcomes in patients with initial anatomic success after macular hole surgery and with at least 5 years of follow-up. DESIGN: Retrospective, noncomparative, consecutive case series. METHODS: Medical records of all patients who underwent surgery for idiopathic full-thickness macular holes by two surgeons (W.E.S., H.W.F.) at the Bascom Palmer Eye Institute between January 1, 1991, and December 31, 1996, were reviewed. All patients who had initial anatomic success with macular hole surgery and who had 5 years or more of follow-up postoperatively were included in the study. Main outcome measures included the rate of macular hole reopening and visual acuity outcomes. RESULTS: Seventy-four eyes of 66 patients with a median age of 68.0 years (range, 45.0-86.8 years) were identified. The median duration of macular hole was 6.0 months (range, 1.1-93.8 months), and the median duration of follow-up after macular hole surgery was 91.0 months (range, 60.0 to 114.8 months). The hole reopened in 9 eyes (12%) during the follow-up interval; 6 of these eyes underwent reoperation, and the hole closed in 4 of 6 (67%). Preoperative visual acuity ranged from 20/50 to 20/400 (mean, 20/129; median, 20/100). In the 62 eyes that underwent cataract extraction (CE) after macular hole surgery, CE was performed at a median of 13.9 months after macular hole surgery. Patients achieved their best postoperative visual acuity at a median of 28.5 months after macular hole surgery. Best postoperative visual acuity ranged from 20/20 to 20/400 (mean, 20/36; median, 20/30). Visual acuity at last follow-up ranged from 20/25 to counting fingers (mean, 20/56; median, 20/40). At last follow-up, 43 eyes (58%) had a visual acuity of 20/40 or better, and 57 (77%) had an improvement in visual acuity of 3 or more Snellen lines compared with their preoperative acuity. CONCLUSIONS: Macular hole closure and visual acuity improvement after initially successful macular hole surgery persist at follow-up of 5 years and longer in the majority of patients; delayed visual acuity improvement is not attributable to cataract surgery alone.

Aged↗

PubMed2001

Visual acuity in contact lens wearers.

PURPOSE: The difference between high- and low-contrast visual acuity provides a sensitive indicator of vision loss in ocular disease; however, the effect of refractive error correction on this difference is still debated. METHODS: High- and low-contrast visual acuity was measured in 116 rigid gas permeable contact lens wearers, 51 spectacle wearers, and 50 soft contact lens wearers with habitual and best correction. Twenty-nine of the soft contact lens wearers reported that they wore disposable contact lenses (discarded on a monthly or more frequent basis), whereas the other 21 soft contact lens wearers wore traditional soft contact lenses. RESULTS: Rigid gas permeable contact lens wearers had statistically worse high-contrast habitual visual acuity than spectacle wearers (Tukey-Kramer, p = 0.0075). Traditional soft contact lens wearers had significantly worse low-contrast visual acuity compared with all other groups (Tukey-Kramer, p < 0.02 for each comparison). Traditional soft contact lens wearers had a significantly larger difference between high- and low-contrast visual acuity with best correction compared with rigid gas permeable wearers (Tukey-Kramer, p = 0.0099). CONCLUSIONS: Rigid gas permeable contact lens wearers had statistically worse habitual high-contrast visual acuity compared with spectacle wearers, but no difference was present under best-corrected conditions. We hypothesize that rigid gas permeable contact lens wearers were not wearing their optimal correction habitually. Traditional soft contact lens wearers had significantly worse low-contrast visual acuity. They also had a larger difference between their best-corrected high- and low-contrast visual acuity scores compared with rigid gas permeable contact lens wearers.

Adolescent↗

PubMed1990

Correlation between histological and behavioral measures of visual acuity in a zooplanktivorous fish, the white crappie (Pomoxis annularis).

Estimates of visual acuity in a pelagic freshwater zooplanktivorous fish, the white crappie (Pomoxis annularis, Centrarchidae), were made using a behavioral measure, the maximum observed prey pursuit distance (MxPD), and a histological measure, the density of cone cells in the retina. The greatest number of pursuits occurs in the 0-30 degrees wedge of the visual field; 87% of all pursuits occur in the first 40 degrees. The longest pursuits (200 mm) also occur in this area and generally get shorter from 0 to 180 degrees (from forward-directed) in the visual field. Consistent with the behavioral results, the largest number of cone photoreceptors (13,000/mm2) is found in the far temporal retina along the eye's horizontal meridian. Cone cell densities in the corresponding region of the nasal retina are approximately half this value. The number of cones decreases dorsally and ventrally from the horizontal meridian. Although the absolute values of visual acuity calculated from cone cell topography (i.e. MxPDs of 500 mm) are 2-3 times greater than those observed behaviorally (i.e. MxPDs of 200 mm), the trends in visual acuity across the visual field obtained from both measures are consistent. We suggest that overestimates of visual acuity obtained from cone cell counts alone result from this measure's not accounting for, among other properties of the nervous system, cone cell convergence onto ganglion cells and higher brain centers. Behavioral measures of visual acuity are, therefore, likely to yield a more accurate estimate of an animal's visual abilities.

Animals↗

PubMed1980

New visual acuity test for pre-school children.

A new test chart was developed for the measurement of visual acuity of pre-school children. The symbols of the test are circle, square, apple and house. These were so designed that each symbol measures visual acuity similarly. This feature of the test was verified experimentally. The visual acuity values measured by the individual symbols correlated highly with the visual acuity values measured with the whole test (0.82-0.86). The correlation between the visual acuity values measured repeatedly, the reliability of the new test, was found to be 0.94 for adult subjects. The new visual acuity test thus fulfils the statistical criteria of a good visual acuity test. Because both children and nurses seem to like the new test, it may be useful in the assessment of visual acuity in pre-school children.

Child, Preschool↗

PubMed1966

Visual acuity in a stumptail macaque.

Visual acuity in a normal stumptail macaque is 1.4 minutes of arc-similar to man's. Destruction of the fovea by photocoagulation decreased acuity to 9 minutes of arc. These facts suggest that the fovea in the macaque has the same physiological role in visual acuity as in man.

Animals↗

PubMed1998

Development and validation of a visual acuity chart for Australian Aborigines and Torres Strait Islanders.

BACKGROUND: A new visual acuity chart was designed for use with Australia's indigenous population to overcome perceived inadequacies of conventional English letter charts for this group. This chart, which incorporates a black and white turtle icon, is described, and validation data are presented. METHODS: The chart is based on logarithm of the minimum angle of resolution (logMAR) principles and incorporates a turtle symbol modified from the design of an indigenous artist. The task is one of discrimination, with subjects being required to distinguish the split tail of the turtle from its head, which has the same overall shape and average luminance; the body of the turtle provides no directional cues which might assist in this judgment. The chart was validated in two ways: Experiment I. Performance was compared with the Bailey-Lovie and Konig bar charts in terms of unaided visual acuity data for 90 subjects (mean age: 38.3 +/- 20.3 years) and Experiment II. Data were obtained for 10 young subjects for these 3 charts and an Illiterate E chart, with refractive blur imposed with trial lenses over habitual distance corrections (spherical: +0.50, +1.00, +2.00, and +4.00 D; cylindrical: +1.00 and +2.00 D, axes 45, 90, and 180 degrees). To avoid cultural and literacy issues as possible sources of differences in performance between the charts in this validation study, subjects were selected from the wider Australian population rather than specifically from its indigenous segment. RESULTS: Experiment I: The Turtle chart performed most like the Konig Bar chart for this component of the validation exercise. Nonetheless, results for the Turtle chart correlated highly with those for the Bailey-Lovie chart as well as the Konig Bar chart, although there were subtle differences between charts in the rate of decline of visual acuity as visual performance decreased. Experiment II: The turtle chart behaved most like the Illiterate E chart with imposed spherical focusing errors, with the Bailey-Lovie chart showing a faster decline and the Konig Bar chart showing a slower decline in performance, with increasing defocus. All 4 charts showed similar directional biases with astigmatic defocus, being most affected by oblique (45 degrees) astigmatism. CONCLUSION: The Turtle chart met the criteria set for its validation as a visual acuity chart in that it gave comparable results to the other commonly used visual acuity charts, both in the case of unaided vision and when refractive blur was imposed.

Adolescent↗

PubMed1993

Dynamic visual acuity of normal subjects during vertical optotype and head motion.

PURPOSE: To characterize the effect of passive vertical head motion on dynamic visual acuity of young, normally sighted subjects wearing telescopic spectacles, and to relate this to the velocity of images on the retina. METHODS: Static visual acuity was measured without motion. Dynamic visual acuity was measured during vertical, sinusoidal motion of either optotypes or of a servo-driven rotating chair in which subjects were seated. Dynamic visual acuity for head motion was measured unaided, as well as with 1.9X, 4X, and 6X telescopic spectacles. Vertical eye movements were recorded using magnetic search coils. RESULTS: During optotype motion, acuity declined with increasing velocity to a minimum of approximately 20/200 at 100 degrees/sec. Pursuit gain (eye velocity/optotype velocity) for moving optotypes was low except for optotype velocities of 20 degrees/sec of less. Dynamic visual acuity without telescopic spectacles was not sensitive to head motion. Static visual acuity improved with increasing telescopic spectacle power, but dynamic visual acuity became progressively impaired by head motion as telescopic spectacle power was increased. Compared with static visual acuity, head motion with peak velocity of 40 degrees/sec reduced acuity two-fold for 1.9X telescopic spectacles, fourfold for 4X telescopic spectacles, and eightfold for 6X telescopic spectacles. Visual vestibulo-ocular reflex gain with telescopic spectacles increased to values markedly above 1.0, but was always less than telescopic spectacle magnification. There was visual tolerance of slip velocities of 2 degrees/sec or less, above which acuity declined in proportion to the 0.6 power of retinal slip velocity. Above 2 degrees/sec, retinal slip velocity accounted for 95% of the variance in dynamic visual acuity. CONCLUSIONS: These results confirm that acuity is sensitive to retinal image motion in the vertical direction, and extend this finding to indicate that sensitivity of acuity to vertical head motion during wearing of telescopic spectacles is attributable to retinal image slip velocity.

Adult↗

PubMed1989

Comparison of four methods of assessing visual acuity in young children.

The purpose of this study was to determine which of four tests, the Acuity Cards, the Dot Visual Acuity test, the Broken Wheel test, or the American Optical (AO) pictures, might be most useful for clinical assessment of visual acuity in 2- and 3-year-olds. Data related to clinical utility including success rates, required test times, reliability, and acuity norms were collected. High success rates and short test times support use of the Acuity Cards for 2-year-olds. For testing 3-year-olds a measure of recognition acuity, the Broken Wheel test, may be most useful.

Adult↗

PubMed2004

Comparison of the amblyopia treatment study HOTV and electronic-early treatment of diabetic retinopathy study visual acuity protocols in children aged 5 to 12 years.

PURPOSE: To compare two established visual acuity protocols: the Amblyopia Treatment Study HOTV (ATS HOTV) visual acuity protocol and the Electronic-Early Treatment of Diabetic Retinopathy Study (E-ETDRS) protocol, in children aged 5 to 12 years. DESIGN: Prospective cohort study. METHODS: Crowded HOTV optotypes and crowded ETDRS optotypes were presented to 236 consecutive children aged 5 to 12 years using an electronic visual acuity tester (Palm handheld, personal computer, and monitor). Twenty-three percent of the children were classified as amblyopic, 35% as having uncorrected refractive error, 36% as normal, and 6% as other. Visual acuity test results were converted to logarithm of minimal angle of resolution (logMAR) units for analysis. RESULTS: In developmentally normal children (n = 230), testability was 100% for HOTV in 5- to 12-year-olds and 100% for E-ETDRS in 7- to 12-year-olds. The E-ETDRS testing could be completed in 52% of 5-year-olds and in 87% of 6-year-olds. Visual acuity performance was better when measured by HOTV compared with E-ETDRS (median difference 0.06 logMAR [three letters on a chart with five letters/line], P =.0001), and the difference was found in normal eyes, eyes with refractive error, and amblyopic eyes. CONCLUSIONS: The ATS HOTV protocol yields slightly better visual acuity performance compared with E-ETDRS in 5- to 12-year-olds, but on average by less than a logMAR level. This systematic difference is important when a physician changes testing modality as a child matures and should be considered when interpreting the results of recent and ongoing clinical trials in amblyopia.

Amblyopia↗

PubMed2004

The effect of LASIK on best-corrected high-and low-contrast visual acuity.

PURPOSE: To evaluate the effects of laser in situ keratomileusis (LASIK) and LASIK with concurrent astigmatic keratectomy (LASIK/AK) on high- and low-contrast visual acuity. METHODS: The setting was a university refractive surgery practice. Patients were recruited from those undergoing LASIK or LASIK/AK for myopia (>1.00 D spherical equivalent) between May 1996 and August 1997. All subjects were at least 21 years of age. Testing occurred preoperatively and 3 and 6 months after LASIK. Main outcome measures were best spectacle-corrected, high- and low-contrast visual acuity. RESULTS: For all subjects, there was a significant effect of surgery on nondilated low-contrast visual acuity (repeated measures two-way analysis of variance, p < 0.0001). Tukey's posthoc analysis showed that preoperative low-contrast visual acuity scores were significantly different from 3-month [0.08 logarithm of the minimum angle of resolution (logMAR)] and 6-month (0.11 logMAR) scores for patients undergoing LASIK and LASIK/AK. Under dilated conditions, there was a significant effect of surgery for high- and low-contrast visual acuity (analysis of variance, p < 0.0001 for both). Only changes in low-contrast visual acuity were clinically meaningful [LASIK, visual acuity reduction of 0.1 logMAR (1 line); LASIK/AK, visual acuity reduction of 0.15 logMAR (1.5 lines)]. When considering high and low myopes separately (LASIK only), the level of myopia had a significant effect on the visual acuity after surgery (analysis of variance, p = 0.01). Preoperative, dilated, low-contrast visual acuity scores for high myopes were significantly different from 3-month (0.14 logMAR) and 6-month (0.13 logMAR) scores. No differences were noted for low myopes. CONCLUSIONS: Clinically meaningful postoperative changes in low-contrast visual acuity were noted in patients undergoing LASIK and LASIK/AK under natural and dilated conditions. Postoperative, dilated, low-contrast visual acuity scores were significantly worse than preoperative scores for high myopes, but remained unchanged for low myopes.

Adult↗

PubMed1981

Visual acuity of the hospitalized veteran.

The visual status of 88,341 hospitalized veterans receiving care at Veterans Administration (VA) Medical Centers on October 4, 1978, was determined, based on clinical records and on personal observations by registered nurses. For 72% of this group of veterans, there were no notations of either eye or vision care rendered within the preceding 2 years. Within the group which had received eye or vision care within the prior 2 years, the combined incidence of legal blindness [visual acuity less than 6/60 (20/120)] and low vision [defined here as visual acuity between 6/15 (20/50) and 6/30 (20/100)] was 40%. These data are analyzed further, and implications concerning optometric care are discussed.

Blindness↗

PubMed2002

Quality of life with visual acuity loss from diabetic retinopathy and age-related macular degeneration.

OBJECTIVE: To compare the quality of life in patients with visual acuity loss occurring secondary to diabetic retinopathy with visual acuity loss occurring secondary to age-related macular degeneration (ARMD). METHODS: Consecutive patients with diabetic retinopathy and ARMD were evaluated using the time trade-off method of utility value analysis. Both groups were stratified according to the degree of visual acuity loss in the better-seeing eye (group 1: 20/20-20/25, group 2: 20/30-20/40, group 3: 20/50-20/100, group 4: < or =20/200). Utility values obtained from the patients, once stratified for visual acuity group, were compared with use of the t test and the Mann-Whitney U test. In addition, a 2-way analysis of variance was performed to control for potential confounding variables. RESULTS: No difference was found between the utility value means of the diabetic retinopathy (n = 333) and ARMD (n = 246) subgroups stratified according to visual acuity levels: group 1, P =.54; group 2, P =.96; group 3, P =.09; and group 4, P =.32. A 2-way analysis of variance demonstrated that, among the variables of ocular disease, sex, age, and visual acuity in the better-seeing eye, only visual acuity was significantly associated with utility values (P =.003). CONCLUSIONS: At similar levels of visual acuity loss, that associated with diabetic retinopathy causes a similar reduction in quality of life to that associated with ARMD. This information has important implications for use in cost-utility analyses of ophthalmic interventions.

Aged↗

PubMed2000

[The contrast study of preoperative flash visual evoked potential test and the postoperative resumed visual acuity in senile cataract patients].

PURPOSE: To study the using value of flash visual evoked potentials (FVEP) in predicting the resumed visual acuities in senile cataract patients. METHODS: Forty-three eyes with senile cataract had been conducted extracapsular cataract extraction combined with posterior chamber intraocular lens implantation. The contrast study had been carried out in this research between preoperative FVEP, light projection and color discrimination tests with the postoperative regained visual acuities. RESULTS: There were significant correlations between the regained visual acuities and the amplitudes of FVEP (X1), the latencies of P1 wave (X2) as well as color discriminations (P < 0.01). The coefficients were 0.7277, -0.5678 and 0.4302 in sequence. There was no correlation between the resumed visual acuities and the light projection test before operation. The formula of linear regression between the visual acuities (Y) and the indexes of FVEP was Y = 0.2255 +0.047X1 -0.0026X2. CONCLUSION: FVEP is an effective method to evaluate the visual function before the cataract operation. It may predict the resumed visual acuity.

Aged↗

PubMed1983

Visual acuity and motor characteristics in congenital nystagmus.

Improvement in visual acuity at near fixation in patients with congenital nystagmus has been explained on the basis of nystagmus damping, caused by superimposed convergence innervation. However, an electronystagmographic study of 13 patients with congenital nystagmus and improvement in visual acuity at near fixation failed to show a consistent decrease of nystagmus intensity at near fixation. Visual acuity at near fixation improved regardless of whether the nystagmus intensity decreased or increased. Factors other than nystagmus amplitude or frequency may be modified by convergence innervation and cause an increase in visual acuity at near in patients with congenital nystagmus.

Adolescent↗

PubMed1989

Reproducibility of refraction and visual acuity measurement under a standard protocol. The Macular Photocoagulation Study Group.

The authors present results of a study in which certified visual acuity examiners in the Macular Photocoagulation Study Group, performed independent replicate refractions and visual acuity measurements on both eyes of patients whose visual acuities ranged from 20/20 to less than 20/800. Patients with neovascular age-related macular degeneration (AMD), ocular histoplasmosis, or idiopathic neovascularization were represented. A total of 328 observations for 164 eyes from 82 patients were available for analysis. Overall reliabilities of the refraction data and the visual acuity data were 98.9% and 98.7%, respectively. Differences between replicate measurements were small; 87% were less than one line. However, differences were greater in patients with visual acuity less than 20/100 and in patients with AMD. These results indicate that the reliability of refraction and visual acuity measurements under a standard protocol is high and may depend on both visual acuity level and disease process. If a standard, systemic procedure is used for refraction and visual acuity testing, the clinician may be able to differentiate between true changes and measurement error, even among low vision patients with AMD.

Aging↗

PubMed1999

[Effect of levodopa therapy on visual evoked potentials and visual acuity in amblyopia].

Amblyopia represents the most common form of visual impairment in children, affecting approximately 2% of the population. To determine the efficacy of the dopamine agonist levodopa for childhood amblyopia, a double-masked, placebo-controlled randomised study was performed on 32 amblyopic children with central fixation between 4 and 17 years. Subjects received 2 mg/kg levodopa benzeraside or placebo 3 times per day over a 1 week period. Estimates of visual acuity for each eye (Snellen visual acuity) were obtained, and pattern-shift visually evoked potentials (VEP) were examined by an opthalmologist and a neurologist. At the end of dosing regimens, the levodopa group was significantly improved in visual acuity by 1.4 lines and pattern VEP amplitudes. No changes could be detected after placebo administration. One week after the termination of the treatment, Snellen line acuity and pattern VEP amplitude were decreased to pretreatment levels. The transient effect of levodopa points to a long-term treatment with the substance. Our results should therefore encourage further long-term clinical trials investigating the therapeutic potential of levodopa in amblyopia.

Adolescent↗

PubMed1991

The deterioration of visual acuity by exercise under a mesopic vision environment.

Visual acuity deteriorated following 15-minute bicycle ergometer pedaling under the condition of a mesopic vision environment. Visual acuity decreased sharply as the load increased. The visual functions which changed significantly after the exercise in the mesopic vision environment were visual acuity (deterioration) and accommodative near point distance (extension).

Accommodation, Ocular↗

PubMed1977

Objective determination of human visual acuity: pattern evoked potentials.

The natural visual acuities of 15 adult persons were predicted on the basis of changes in visual evoked potentials (VEP's) to flashed patterns of various sized dots. An objective method was used to quantify the VEP's, based on the minimum-sized stimulus that would elicit a pattern VEP- the VEP pattern threshold. This measure was highly correlated with recognition and resolution measures of perceptual visual acuity (r's as high as 0.89). The regression equation between the VEP measures and predicted perceptual measures of acuity enabled the objective estimation of perceptual acuity to within +/- 0.29 decimal units.

Adult↗