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Results for “Visual Acuity”

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PubMed1977

Spatial frequency and light-spread descriptions of visual acuity and hyperacuity.

Resolution (visual acuity) and differential spatial localization (hyperacuity) targets were selected to allow rigorous psychophysical measurements as well as ready expression of both their spatial frequency spectrum and their retinal image light distribution. Thresholds were about 1 arc min for acuity and 4-6 arc sec for hyperacuity. As is consistent with the reciprocal relationship between the space and spatial frequency domains, the small locally restricted spatial differences between just distinguishable patterns are represented in the frequency domain by equally small differences, which are distributed over the entire spatial frequency spectrum. While they occur in many test situations, phase variations of spatial frequency components are not necessary for achieving optimum acuity and hyperacuity.

Female↗

PubMed1995

Factors affecting long term results of successfully treated amblyopia: initial visual acuity and type of amblyopia.

AIMS: The study aimed to assess the effect of initial visual acuity and type of amblyopia on the long term results of successfully treated amblyopia. METHODS: The visual acuity of 94 patients, who had been successfully treated for unilateral amblyopia by occlusion of the good eye and followed up to the age of 9 years, was examined 6.4 years, on average, after cessation of treatment. Patients were divided into two groups according to the depth of amblyopia before occlusion therapy was started: those with visual acuity between 20/60 and 20/100 and those with visual acuity of 20/100 or worse. RESULTS: Deterioration of visual acuity was observed in 42% of patients in the first group and in 63% of patients in the second group. Their average deterioration, as measured by the Snellen chart, was 0.58 and 1.54 lines, respectively. The results were also assessed by the division of patients into three groups according to the type of amblyopia: strabismic, strabismic anisometropic, and anisometropic. Deterioration of visual acuity occurred in 46%, 79%, and 36% of patients in these three groups, with an average deterioration on the Snellen chart of 0.70, 2.04, and 0.64 lines, respectively. CONCLUSION: It is concluded that low initial visual acuity and strabismic anisometropic amblyopia are risk factors for deterioration of visual acuity in the long term, following the successful earlier treatment of eyes with amblyopia.

Adolescent↗

PubMed1990

Testing visual acuity of children using vanishing optotypes.

To test visual acuity in children, we developed a chart constructed so that the mean Fourier transform of the luminance of the figures on the chart at zero spatial frequency is the same as the background luminance. When the eye reaches its limit of resolution, the figures vanish into the gray background of the chart rather than becoming "blurred" as in conventional visual acuity charts. We compared the number of errors in determining the visual acuity of children aged 3-4.5 years using this high-frequency chart and a standard black-and-white high-contrast chart. Significantly fewer errors were found with the high-frequency chart, suggesting that this type of testing may improve the accuracy of visual acuity measurements in children.

Child, Preschool↗

PubMed2003

Improved functional visual acuity after punctal occlusion in dry eye patients.

PURPOSE: To report an increased functional visual acuity, which was recently reported as a simulation of visual function of daily acts of gazing, in dry eye patients after punctal occlusion. DESIGN: Prospective comparative interventional study. METHODS: We measured ordinary best-corrected visual acuity and functional visual acuity in eight eyes of eight dry eye patients after punctal occlusion, and compared the results with those of 22 eyes of 22 dry eye patients without punctal occlusion. RESULTS: Functional visual acuity in dry eye patients after punctal occlusion was 0.962 in decimal notation, which was significantly higher than that of patients without punctal occlusion, 0.283 (P <.0001). CONCLUSIONS: This study shows that punctal occlusion can improve the impaired functional visual acuity of dry eye patients.

Dry Eye Syndromes↗

PubMed1991

The Beaver Dam Eye Study: visual acuity.

Few current population-based data on visual impairment are available. Visual acuity and impairment were measured in 4926 people between the ages of 43 and 86 years in the defined population participating in the Beaver Dam Eye Study. Visual acuity was measured after refraction, using standardized protocols. Of a possible maximum score of 70 (20/10), the mean number of letters correctly identified (right eye) varied from 55.7 (20/20, n = 1515) in people between the ages of 43 and 54 years to 41.2 (20/40, n = 795) in people 75 years of age or older. Age-specific mean visual acuity scores were consistently and significantly lower in women, who identified three fewer letters on the average than men. Rates of any visual impairment (20/40 or worse in the better eye) or legal blindness (20/200 or worse in the better eye), increased from 0.8% and 0.1%, respectively, in people between the ages of 43 and 54 years to 21.1% and 2.0%, respectively, in people 75 years of age or older. Multivariate analyses showed both sex (women) and age (older) to be significant and independent predictors of poorer visual acuity.

Adult↗

PubMed2004

Culture-proven endogenous endophthalmitis: clinical features and visual acuity outcomes.

PURPOSE: To investigate clinical features and visual acuity outcomes associated with endogenous endophthalmitis. DESIGN: Retrospective, observational case series. METHODS: Twenty-one eyes of 21 patients treated at Bascom Palmer Eye Institute for culture-proven endogenous endophthalmitis between 1996 and 2002 were reviewed. RESULTS: Patients were followed a mean of 3 months (range, 1 to 12 months). Fungal isolates occurred in 13 eyes (62%), gram-positive isolates in 7 (33%), and gram-negative isolates in 1 (5%). Twelve patients (57%) were hospitalized at the time of diagnosis and 6 patients (29%) died within 2 months of diagnosis. Initial treatment included tap and injection of intravitreal medication in 10 eyes (48%) and pars plana vitrectomy with injection of intravitreal medication in 11 eyes (52%). Final visual outcomes were obtainable for 18 eyes (two patients died within 10 days of diagnosis, and one patient was lost to follow-up). Eight (44%) of these 18 eyes achieved a visual acuity of 20/400 or better and 10 (56%) of 18 eyes achieved a visual acuity worse than 20/400, including 3 that were either enucleated or eviscerated. Three eyes with Aspergillus endophthalmitis had worse visual outcomes than eyes with either Candida (P =.036) or bacterial endophthalmitis (P =.024). CONCLUSIONS: Compared with published series of postoperative or post-traumatic endophthalmitis, patients with endogenous endophthalmitis are more likely to have fungal isolates with a predominance of Candida albicans. Endogenous endophthalmitis is generally associated with high mortality and poor visual acuity outcomes, particularly when caused by more virulent species such as Aspergillus.

Adult↗

PubMed1988

The relationship between indoor and outdoor Snellen visual acuity in cataract patients.

One hundred six cataractous eyes of 78 patients were evaluated to examine the relationship between indoor and outdoor Snellen visual acuity. While 81 of all cataractous eyes (76.4%) had Snellen visual acuities of 20/40 or better when tested indoors, only 33 eyes (31.2%) had 20/40 or better Snellen visual acuities when tested outdoors facing the sun. When tested indoors, only three eyes (2.8%) had Snellen visual acuities worse than 20/80, while 31 eyes (29.2%) had outdoor Snellen visual acuities worse than 20/80. Ten eyes (9.4%) had outdoor Snellen visual acuities worse than 20/200. Seventy-four eyes (69.8%) had outdoor visual acuities that were at least two Snellen lines worse than those measured indoors and 23 eyes (21.7%) had outdoor visual acuities that were at least five Snellen lines worse. The median difference between indoor and outdoor visual acuity was three Snellen lines. The need for increased precision in the ability to assess outdoor "real world" vision while in the ophthalmologist's examination room is discussed. Clearly, indoor Snellen visual acuity alone is insufficient to evaluate functional visual impairment in cataract patients.

Cataract↗

PubMedDate not supplied

Fundus findings and longitudinal study of visual acuity loss in patients with X-linked retinoschisis.

PURPOSE: To determine the presence of fundus findings and natural course of visual acuity change in patients with juvenile X-linked retinoschisis (XLRS). METHODS: A retrospective longitudinal study of 38 patients with juvenile XLRS (age range, 9-65 years) was conducted. Best-corrected visual acuity, Goldmann visual fields, and results of slit-lamp biomicroscopy of the anterior segment and dilated fundus examination were obtained for all patients. Visual acuity findings at the most recent and initial visits were compared. Follow-up ranged from 1 year to 28 years (mean, 10.2 years). Twenty-five patients were observed for > 5 years, and 11, for > or = 15 years. RESULTS: Foveal lesions varied from predominantly radial striations (3%), microcystic lesions (34%), honeycomblike cysts (8%), or their combinations (31%) to non-cystic-appearing foveal changes, such as pigment mottling (8%), loss of the foveal reflex (8%), or an atrophic-appearing lesion (8%). Twelve patients (32%) had situs inversus of their retinal vessels. We observed a superior nasal restriction in the peripheral visual field even in the absence of clinically apparent peripheral retinoschisis. Of the 38 patients who were seen more than once, using logarithm of the minimum angle of resolution (logMAR) comparison, 4 had a decrease in visual acuity of > 0.1 logMAR, equivalent to > 1 line on an ETDRS chart, in their better seeing eye, and 3 had a reduction in visual acuity of > 0.2 logMAR in their better eye. CONCLUSIONS: A limited change in visual acuity was observed in our cohort of 38 patients with XLRS even over an extended period. However, those patients with non-cystic-appearing changes within the fovea, including pigment mottling or an atrophic-appearing lesion, tended to have a more appreciable degree of visual acuity impairment compared with those patients with a cystic-appearing foveal change.

Adolescent↗

PubMed1994

[Visual acuity of military personnel with civilian or military driver's license on consulting an ophthalmologist].

Visual acuity was tested in 1861 members of the German armed forces who possessed military or civilian driving licences, first by means of a screening test (Roden-stock R12) and second by an ophthalmologist observing German Industrial Standard 58220, part 3. The tests were done with the patients wearing any corrective spectacles in use before the appointment. In 27.6% of all subjects the monocular or binocular visual acuity was less than 1.0. Binocular visual acuity less than 1.0 was found in 17.0%, less than 0.8 in 7.3% and less than 0.5 in 0.9%. After adjustment of the corrective lenses by the ophthalmologist these figures were reduced to visual acuity less than 1.0 in 1.6%, less than 0.8 in 0.4% and less than 0.5 in 0.1%. The frequency of suboptimal visual acuity showed no difference in driving licence classes. We found fewer cases of suboptimal visual acuity in our patients than Kratz and Häseker found in the civilian community in the study published in 1986. The age distribution was also different. In contrast to former publications, which showed an age-related progression, our population had the lowest number of subjects with subnormal visual acuity in the age group 35-45 years. The screening test for visual acuity and the test by the ophthalmologist showed the same results in 76.8% of cases.

Adult↗

PubMed1999

Visual acuity impairment in patients with retinitis pigmentosa at age 45 years or older.

OBJECTIVE: To determine the severity of visual acuity impairment in patients, age 45 years or older, with either isolated or identifiable genetic subtypes of retinitis pigmentosa (RP) and Usher syndrome. DESIGN: Multicenter, retrospective, cross-sectional analysis. PARTICIPANTS: Visual acuity data were obtained on 999 patients with different genetic subtypes of RP and Usher syndrome, age 45 years or older, from 4 major eye care centers in the United States. INTERVENTION: The best-corrected visual acuity obtained on these patients from the eye with better vision on their most recent visit was used for the analysis. MAIN OUTCOME MEASURE: Best-corrected visual acuity was the main parameter analyzed for the study, and it was obtained with Snellen or Feinbloom low vision charts or with a B-VAT II monitor (Mentor). RESULTS: The final analyses were done on 982 patients (17 patients with a sector form of RP were analyzed separately). Of the 982 patients, 506 (52%) had a visual acuity of 20/40 or better, and 678 (69%) had a visual acuity of 20/70 or better in at least one eye. There were 243 (25%) patients who had a visual acuity of 20/200 or worse in both eyes. Five (0.5%) patients had no light perception in both eyes. The odds ratio for any patient having a visual acuity of 20/200 or worse in this population was 1.4 for each difference of 10 years of age. Similarly, the odds ratio of a patient having a visual acuity of 20/40 or better in at least one eye was 0.95 for a 10-year age difference. CONCLUSIONS: In this large population of patients with RP and Usher syndrome from four centers, it was rare for such patients to lose all vision in both eyes. One fourth of the patients had a visual acuity of 20/200 or worse in both eyes, and more than half of the population had a visual acuity of 20/40 or better in at least one eye. These data can be used to counsel such patients on the extent of potential visual acuity impairment from their disease.

Aged↗

PubMed2004

[Comparison of preoperative retinometer values with postoperative visual acuity after surgery of epiretinal membranes].

BACKGROUND: We report about our clinical experience when comparing the preoperative retinometer values with the postoperative visual acuity after microsurgical excision of epiretinal membranes (ERM). PATIENTS AND METHODS: Pars plana vitrectomy with membrane peeling was performed in 56 eyes of 53 patients. Preoperatively, we obtained the distant and near visual acuity and the retinometer value. Postoperatively, we compared the preoperative retinometer value to the best postoperative visual acuity. RESULTS: The preoperative retinometer value was in 39 eyes (70 %) equal to the best postoperative distant visual acuity (+/- 1 line) and in 34 eyes (61 %) equal to the best near visual acuity (+/- 1 line). A difference of + 2 or - 2 lines or more from the retinometer value was found in 17 eyes (30 %) for the best postoperative distant visual acuity and in 22 eyes (39 %) for the best near visual acuity. 49 eyes (87.5 %) had a better visual acuity after pars plana vitrectomy, 6 eyes (10.7 %) had equal visual acuities and one eye (1,8 %) was worse than the preoperative visual acuity. The average improvement of vision after the operation was + 2.5 lines for the distant and + 2.4 lines for the near visual acuity. CONCLUSIONS: The preoperative retinometer examination is a precise method for obtaining the visual acuity of patients selected for pars plana vitrectomy with membrane peeling. Uncertain results can be achieved in eyes with very opaque ERM and ERM with macular edema.

Aged↗

PubMed2003

Visual acuity loss and clinical observations in a large series of patients with Stargardt disease.

PURPOSE: To assess visual acuity impairment in Stargardt disease. DESIGN: Retrospective clinic-based cross-sectional study. PARTICIPANTS: Three-hundred sixty-one patients with Stargardt disease. METHODS: Clinical findings in 361 patients were analyzed as part of a cross-sectional evaluation. Visual acuity at their most recent visit, fundus photographs, and electroretinographic findings were reviewed, and patients were categorized into four clinical phenotypes. Seventy-three patients with 20/40 or better vision and 38 patients with 20/50 to 20/100 vision in the better seeing eye at their initial visit who were followed for at least 1 year were included in a survival analysis. For analysis purposes, these latter patients were categorized into four 20-year age groups according to their age at initial visit. MAIN OUTCOME MEASURES: Best-corrected visual acuity from the eye with better vision on the most recent visit was used in the cross-sectional analysis. For the survival analysis, best-corrected visual acuity was used from the eye with better vision on the initial visit. RESULTS: Eighty-two of the 361 patients (23%) had 20/40 or better acuity in at least one eye, 64 (18%) 20/50 to 20/100, and 199 (55%) 20/200 to 20/400, whereas 16 (4%) had worse than 20/400 in each eye at their most recent visit. In the patients with visual acuity of 20/40 or better, 59 (72%) had foveal sparing visible on ophthalmoscopic examination. The median time to develop visual acuity of 20/200 or worse was 22 years for the patients with 20/40 or better visual acuity at their initial visit. Those seen initially in the first two decades of life with this level of acuity showed a median time of 7 years to reach a visual acuity of 20/200 or worse compared with 22 years and 29 years for those who were initially seen at ages 21 to 40 or 41 to 60, respectively. Analyzing by the four 20-year age groups, the log rank statistic indicated significant differences in the survival experience among the four groups (P = 0.004). The median time to develop 20/200 vision or worse was 6 years for the patients with 20/50 to 20/100 visual acuity at their initial visit, and this result, based on the log rank statistic, was independent of age group at initial visit (P = 0.852). CONCLUSIONS: In a large cohort of Stargardt patients, a cross-sectional analysis showed that almost a quarter had vision of 20/40 or better, whereas 4% had acuity of worse than 20/400. The presence of foveal sparing ophthalmoscopically was associated with a higher prevalence of 20/40 or better visual acuity. Survival analysis showed that the prognosis of patients who initially were seen with visual acuity of 20/40 or better is related to age at initial visit.

Adolescent↗

PubMed1999

The effect of abnormal fixational eye movements upon visual acuity in congenital nystagmus.

PURPOSE: The purpose of this study was to investigate the role that abnormal eye movements play in the degradation of visual acuity. METHODS: Visual acuity was measured monocularly in 10 normal subjects (26.7+/-4.3 years) and 5 subjects with congenital nystagmus (34.9+/-8.8 years), using Regan Repeat Letter charts (RRL) and a logMAR based test (LogMAR Crowded Acuity Test (CAT)) while eye movements were continuously recorded using a commercially available infrared limbal eye tracker (Type 54, Optoelectronic Developments, UK). The eye tracker was controlled via a virtual oscilloscope (Viewdac, Keighly Instruments, UK) on an IBM PC clone (Opus Technology 486). RESULTS: The mean visual acuity obtained with RRL was significantly higher than that obtained by CAT in the subjects with congenital nystagmus. A significant correlation was found between the root mean square value of the nystagmus waveform and the angular extent of CAT. Linear regression analysis revealed a correlation between the duration of the foveation periods and the linear acuity of the subjects with congential nystagmus. The nystagmus waveforms also demonstrated increased amounts of high frequency components (HFC: >3.0 Hz) when compared to the normal eyes. CONCLUSIONS: The results of this study reveal 1) RRL charts provide a measure of a subjects resolution limit which is less dependent on eye movements; 2) the duration of foveation periods has a significant effect on visual acuity measurements obtained using a linear test chart format; 3) the predominance of high frequency components in the congenital nystagmus waveforms lead to short foveation periods adding to the degree of fixation instability.

Adult↗

PubMed2004

Coincidence anticipation and dynamic visual acuity in young adolescents.

Research involving college-age students and women fast pitch softball players indicated that coincidence anticipation and dynamic visual acuity are different visual abilities. This study used an alternative procedure to measure dynamic visual acuity to re-examine their relationship. Coincidence anticipation and dynamic visual acuity were measured in 24 young adolescents (12 boys, 12 girls) 11 to 14 years of age. During the dynamic visual acuity procedure, the subject tracked an object of a constant size while the researcher manipulated the object's velocity. Analysis indicated that they are different visual abilities. Findings indicated that the dynamic visual acuity of boys was significantly better than that of girls, and coincidence anticipation between boys and girls did not differ.

Adolescent↗

PubMed2003

Measured visual acuity of fellow eyes as a prognostic factor in macular hole surgery.

PURPOSE: To investigate the effect of the vision of the fellow eye on the visual acuity of eyes after successful macular hole surgery. DESIGN: Prospective consecutive series. METHODS: A consecutive series of eyes with successful macular hole closure were studied and assigned to one of two groups according to the visual acuity of the fellow eye; a group with visual acuity less than 20/200 and a group with visual acuity of 20/200 or better. Preoperative and postoperative visual acuity in the two groups was measured based on the logarithm of the minimal angle of resolution (LogMAR), and postoperative visual acuity was also determined by using the multiple-letter visual acuity chart, which permitted measurement of visual acuity at an extrafoveal point. RESULTS: Group 1 (<20/200) consisted of 19 eyes and group 2 (>20/200) consisted of 51 eyes. LogMAR visual acuity at 6 months postoperatively was significantly better in group 1 than in group 2 (0.21 vs 0.41, P <.01). The logMAR change 6 months after surgery was significantly greater in group 1 than in group 2 (0.49 vs 0.23, P <.01). There was no significant difference between two groups in logMAR visual acuity at 6 months postoperatively determined with the multiple-letter visual acuity chart (0.20 vs 0.29, P >.05). CONCLUSIONS: Visual recovery after successful macular hole surgery is inversely correlated with vision in the fellow eye. Learning to use eccentric fixation may contribute to visual improvement after macular hole surgery.

Aged↗

PubMed1995

Visual acuity and contrast sensitivity in the elderly.

The visual acuity of the better eye in the elderly inhabitants of three communities (476 persons, aged 70 years or more) ranged from 0 to 1.4 (mean 0.7), and 12% saw less than 0.3. The logarithm of binocular contrast sensitivity ranged from 1.0 to 2.75 (n = 412, mean 2.19) in the Cambridge test and from 0.15 to 1.95 (n = 468, mean 1.48) in the Pelli-Robson test. The 72 subjects with healthy eyes had a mean visual acuity of 1.03 (range 0.5-1.4) in the better eye, and the two contrast sensitivity tests gave mean values of 2.45 and 1.69, respectively. Cortical, nuclear and mixed cataracts and macular pathology impaired both contrast sensitivity and visual acuity. The correlation between the three tests was good in the whole sample and in the different subgroups of cataract and macular changes. Individually, however, a few contradictory results were obtained. According to these results measurement of contrast sensitivity does not add much to the general information obtained in the elderly by visual acuity measurement alone, but in selected cases it may give valuable information.

Aged↗

PubMed1977

Maturation of evoked potentials and visual preference in 6-45-day-old infants: effects of check size, visual acuity, and refractive error.

Visual evoked potentials (VEPs) and the percentage time fixated (PTF) were investigated in response to checkerboard light flashes in 10 human infaed as a function of the size of check in the evoking stimulus (diffuse light, 11, 22, 45, 90 and 180 min of arc), the refractive lens strength the checkerboards were viewed through (-6 to +6 diopters), and the age of the infants (6-26 or 27-45 days). Check size significantly influenced VEP amplitude in infants as young as 6 days. The 11' checks evoked greater responses that diffuse light suggesting a visual acuity of better than 20/220. Only the 27--45-day-olds behaviorally discriminated the checks, PTF indicating an acuity of 20/120. Evoked potential refraction with spherical lention between VEP amplitude and check size measured from different VEP components at different ages indicated the function contained two modes or components. The first mode was inverted "U-shaped" and was obtained in response to check sizes less than 45'. It was primarily due to changes in amplitude of the early VEP components (less than 210 msec after the evoking stimulus) and was poorly correlated with the behavioral PTF measure. It was proposed that this mode reflected subcortical activity. The second mode was a linear increase in amplitude as check size was increased from 45' to 180'. It was primarily due to changes in the amplitude of late VEP components (240--400 msec after the evoking stimulus) and was highly correlated with the percentage time the infants fixated the various check sizes. It was proposed that this mode reflected cortical activity. Age selectively influenced the late VEP components and the PTF behavioral measure, these measures being influenced by check size only in the 27--45-day-old infants. This change in responsivity of late VEP components and the transition from passive to more active and discriminating visual preference, suggest the onset of increased cortical function between 28 and 45 days of age.

Age Factors↗

PubMed1991

Effect of induced blur on visual acuity and stereoacuity.

The acuities of three subjects with good visual acuity and stereoacuity were reduced by the addition of diffusing filters placed before one or both eyes; these subjects then underwent automated stereoacuity and visual acuity tests. Results were idiosyncratic and differed from subject to subject to such an extent that no general rule sufficed to describe the effect of different degrees of blur on visual acuity and stereoacuity. It had been thought that blur degraded stereoacuity more than visual acuity but most of the results from one subject indicated the opposite effect. The effects of monocular vs. binocular blur are discussed.

Form Perception↗