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Results for “Visual Acuity”

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At least 901 records · Page 50Linked to original sources

PubMed2001

Visual evoked potentials in relation to visual acuity in macular disease.

PURPOSE: To investigate how central retinal function contributes to pattern visual evoked cortical potentials (PVECPs), we recorded transient and steady-state PVECPs in patients with macular disease and compared the results with those of patients with optic neuritis. The results were also evaluated for correlation with visual acuity and kinetic perimetric measurements. METHODS: PVECPs to 3 rev/s stimulation (transient) and 12 rev/s stimulation (steady-state) for check sizes 15' and 30' were obtained from all patients and age-matched healthy controls. The peak latency and amplitude of the P100 component of the transient VECP and the amplitudes of the steady-state VECP were measured and evaluated. RESULTS: Patients with macular disease produced significant delay of P100 latency and amplitude attenuation of the steady-state VECP, as compared with healthy subjects. P100 latency delay was less in patients with macular disease than in those with optic neuritis, while the attenuation rate of the steady-state VECP amplitude was similar between groups. Visual acuity was correlated with P100 latency and steady-state VECP amplitude reduction. CONCLUSIONS: Although the delay of latency was less in patients with macular disease than in those with optic neuritis, the electrophysiologic alterations that occur in macular disease demonstrate a potential for diagnostic value at the level of the retina.

Adolescent↗

PubMed1988

Usefulness of computerized visual acuity testing in a pediatric ophthalmology clinic.

We investigated the usefulness of a computerized illiterate-E-style acuity test in 111 children ranging in age from 3 to 13 (mean 6.56) years consecutively referred to a large pediatric ophthalmology clinic. Visual acuity was measured in both eyes of each subject by means of conventional testing with an optical projection device and computerized testing with a program run on a microcomputer. Of the 222 eyes 155 (70%) showed no difference in visual acuity between the two procedures. A difference of one acuity line was found for 63 eyes (28%), and a difference of two lines was found for 4 eyes (2%). The conventional test yielded a higher acuity score in 75% of the cases in which a one-line difference was found and 50% of those in which a two-line difference was found. Our results indicate that computerized testing is a valid and effective method of assessing visual acuity in children.

Adolescent↗

PubMed1995

Effect of retinal image motion on visual acuity and contour interaction in congenital nystagmus.

This study determined how contour interaction (the degradation of visual acuity by the presence of nearby contours) is affected by the incessant retinal image motion that occurs in observers with congenital nystagmus (CN). Visual acuity was measured for single, high-contrast, black Landolt Cs, presented without and with flanking bars (contour-to-C separation = 1, 2, 5, or 10 multiples of the gap width of the C). Stimuli were presented against either a white or a black surround. For comparison, acuity was also determined in normal observers, with and without motion of the stimulus to simulate the retinal image motion in jerk CN. The results show that the peak magnitude of contour interaction (the maximal degradation in acuity attributable to contour interaction) is significantly larger in the observers with CN than in normals. When acuity targets are presented against a black surround, contour interaction also occurs over a wider spatial extent in the observers with CN. Imposed image motion increases the extent of contour interaction in normal observers, but not sufficiently to account fully for the results of the observers with CN. We suggest that the additional contour interaction found in observers with CN may be attributable to the presence of amblyopia. For a small contour-to-C separation, contour interaction is significantly greater when stimuli are presented against a black rather than a white surround. Consequently, single-letter acuity may be appreciably underestimated clinically when an adjustable window is used to isolate letters on a projected acuity chart.

Form Perception↗

PubMed2003

Predicted corneal visual acuity in keratoconus as determined by ray tracing.

PURPOSE: To evaluate the optical quality of the central anterior corneal surface in normal eyes and in eyes with keratoconus, and to investigate the accuracy of the predicted corneal visual acuity (PCVA) index as determined by ray tracing analysis. METHODS: Twenty keratoconus eyes with contact lens-corrected visual acuity (VA) of 20/20 or better (11 patients, group A) and 20 eyes of 15 normal subjects (group B) were evaluated. After a detailed eye examination including measurement of pupil diameter, keratometry, topography and pachymetry, each subject eye was evaluated using ray tracing analysis with the Technomed C-scan colour ellipsoid topometer, using basic software (Technomed GmbH, Baesweiler, Germany). The PCVA was determined for each patient, and the results were analysed comparatively using two-sample t-test, regression analysis and Pearson correlation analysis. RESULTS: The average best spectacle-corrected VA was measured as 0.2 +/- 0.2 logMAR (20/32) in group A and -0.1 +/- 0.1 logMAR (20/16) in group B. The average PCVA measurements derived from ray tracing analysis for 3.0 mm, 3.5 mm and 4.0 mm pupil diameters were 0.06 +/- 0.12 logMAR, 0.14 +/- 0.13 logMAR and 0.21 +/- 0.17 logMAR, respectively, in group A, and -0.14 +/- 0.08 logMAR,-0.11 +/- 0.09 logMAR and -0.09 +/- 0.11 logMAR, respectively, in group B. There was good correlation between best corrected VA and PCVA in both groups for all pupil diameters measured (p < 0.007). CONCLUSION: Predicted corneal visual acuity as determined by ray tracing analysis is useful for estimating best spectacle-corrected VA in normal corneas and the effect of irregular corneal astigmatism on VA in eyes with mild to moderate keratoconus. Further studies are required to evaluate the efficacy of ray tracing in evaluation of aberrations of the optical system of the eye.

Adolescent↗

PubMed1998

Screening for ophthalmic disease in older subjects using visual acuity and contrast sensitivity.

OBJECTIVE: Despite early interest in contrast sensitivity as a screening test for ophthalmic disease, most published opinion suggests that there is no benefit over conventional measurement of visual acuity. Taking a primary care perspective of screening, the authors evaluated the ability to discriminate those with any diagnosed ophthalmic disease in a large sample representative of the general population. DESIGN: Retrospective analysis of a clinical, cross-sectional survey. Snellen visual acuity, contrast sensitivity (Arden plates, American Optical contrast sensitivity test), and ophthalmic diagnosis were reported previously. PARTICIPANTS: A sample of 3283 subjects, all aged at least 50 years, were selected randomly from residents of a health district in Sydney, Australia. Ophthalmologic diagnosis (ophthalmic disease presence/absence) had been confirmed for 2522 of these subjects. MAIN OUTCOME MEASURES: Signal detection techniques (the receiver-operating characteristics function [ROC], quality ROC [QROC], and weighted kappa coefficient of association [kappa(r)]) were used to evaluate test discriminability. RESULTS: Because analyses of right and left eyes were almost identical, only right eye results are presented. Advantages of kappa(r) over ROC were shown. Discrimination of those with diagnosed ophthalmic disease from those without ophthalmic disease was best with Arden plate 7 (kappa0.5 = 0.93) and was better than distance Snellen visual acuity (kappa0.5 = 0.59). Arden plate 7 (6.4 cyc/deg) correctly assigned 96% of subjects at its optimal pass-fail criterion. CONCLUSIONS: In the primary care setting, a person older than 50 years of age with reduced contrast sensitivity, as determined by Arden plate 7, requires extra care in subsequent examinations because this person is likely to have an ophthalmic disease.

Aged↗

PubMed2002

Visual acuity outcomes following vitreous loss in glaucoma and diabetic patients.

PURPOSE: To analyze the visual acuity (VA) of patients with and without vitreous loss, while concurrently analyzing the effects of the pre-existing pathologies of glaucoma and diabetes on VA. METHODS: A retrospective study on 1013 cataract extractions from 1995 to 1999 was performed. Patients included in this study had intraocular lens implantation during phacoemulsification surgery, no intraoperative complications besides vitreous loss, had no other prior ophthalmic condition other than glaucoma or diabetes, and had a postoperative follow-up interval between one and 4 months. When indicated, vitrectomy was performed concurrently with phacoemulsification following vitreous loss. Patients diagnosed with both glaucoma and diabetes were excluded. The identified subjects were then placed into six groups: (1) patients with uncomplicated surgery; (2) patients with surgery complicated by vitreous loss; (3) glaucoma patients with uncomplicated surgery; (4) glaucoma patients with surgery complicated by vitreous loss; (5) diabetic patients with uncomplicated surgery; and (6) diabetic patients with surgery complicated by vitreous loss. A two-tailed, heteroscedastic t-test and power calculation were performed on the preoperative and postoperative visual acuities of the groups. RESULTS: There were statistically significant differences (P < 0.05) in the postoperative VA between patients with and without vitreous loss at the time of surgery. Patients with the pre-surgical conditions of diabetes or glaucoma did not display a statistically significant difference in postoperative VA when compared to controls. However, the pre-surgical condition of glaucoma displayed a trend, which showed it may contribute to a poorer postoperative VA (P = 0.072, power = 0.430). CONCLUSIONS: Vitreous loss is a risk factor for a decreased postoperative VA. Also while the pre-surgical condition of glaucoma may play a role in decreasing postoperative VA, diabetes does not.

Adult↗

PubMed2005

Visual acuity after Ruthenium(106) brachytherapy of choroidal melanomas.

PURPOSE: To report on conservation of visual acuity after Ruthenium(106) (Ru-106) brachytherapy of choroidal melanoma. METHODS AND MATERIALS: This study was a noncomparative interventional case series of 458 patients with choroidal melanoma treated at a single center between January 1993 and December 2001. The intervention consisted of Ru-106 brachytherapy delivering minimum scleral and apex doses of 300 Gy and 80 Gy, respectively, using a 15-mm or 20-mm plaque. For discrete, posterior tumors, the plaque was positioned eccentrically with its posterior edge aligned with the posterior tumor margin. To ensure correct plaque positioning, any overlying extraocular muscles were dis-inserted, and the locations of both tumor and plaque edges were confirmed by transillumination and indentation. The main outcome measures were conservation of vision of 20/40 or better, 20/200 or better, and Counting Fingers or better, according to baseline variables. RESULTS: The actuarial rate of conservation of 20/40 or better was 55% at 9 years, loss of such vision correlating with posterior tumor extension (p < 0.001), temporal tumor location (p = 0.001), increased tumor height (p = 0.01), and older age (p < 0.01) (Cox multivariate analysis). Similar analyses showed conservation of 20/200 or better in 57% of eyes at 9 years, loss correlating with reduced initial visual acuity (p < 0.001), posterior tumor extension (p < 0.001), and temporal tumor location (p = 0.006). Counting Fingers or better vision was conserved in 83% of patients at 9 years, loss correlating with increased tumor height (p < 0.0001). Local tumor recurrence occurred in 9 patients (actuarial rate, 3% at 9 years). CONCLUSION: Ruthenium(106) brachytherapy of posterior choroidal melanoma achieves good conservation of vision if the tumor does not extend close to the optic nerve or fovea.

Adult↗

PubMed1996

Plaque radiotherapy for juxtapapillary choroidal melanoma. Visual acuity and survival outcome.

OBJECTIVES: To assess the effect of plaque radiotherapy on the visual acuity of patients with juxtapapillary choroidal melanoma and to determine the clinical predictive factors for radiation retinopathy, radiation papillopathy, local tumor recurrence, and distant metastasis. DESIGN: A retrospective review of the medical records of 93 patients with juxtapapillary choroidal melanoma who were treated initially with plaque radiotherapy. RESULTS: During a mean follow-up of 78 months, radiation retinopathy developed in 81 patients (87%) and radiation papillopathy developed in 48 patients (52%) after a mean interval of 21 and 27 months, respectively. The univariate variables that were significant predictors of radiation retinopathy were history of diabetes mellitus (P = .05) and use of a notched radioactive plaque (P = .04). The factors predictive of radiation papillopathy were age (> 45 years; P = .01), history of diabetes mellitus (P = .05), mushroom-shaped tumor configuration (P = .006), and nasal location of the tumor (P = .04). By using Kaplan-Meier survival curves, we found that the proportion of the 93 patients with radiation retinopathy was 87 (94%) at 5 years and with radiation papillopathy was 53 (57%) at 5 years. By using life-table analysis, we found that the proportion of the 93 patients who experienced a decrement of at least 3 lines of visual acuity was 67 (72%) by 50 to 60 months. Local tumor recurrence was documented in 14 patients (15%) after a mean interval of 41 months. The age of the patient (< 35 years; P = .02) and the superior (P = .004) and inferior (P = .05) locations of the tumor were predictive of local tumor recurrence. Distant metastasis developed in 11 patients (12%) after a mean interval of 44 months. The factors predictive of distant metastasis were a tumor with a basal diameter larger than 6.0 mm (P = .05), the superior location of the tumor (P = .01), and local tumor recurrence (P < .001). CONCLUSION: Based on these observations, plaque radiotherapy remains a potential option vs enucleation for the management of juxtapapillary choroidal melanoma.

Brachytherapy↗

PubMedDate not supplied

Correlation between contrast sensitivity and visual acuity in retinitis pigmentosa patients.

PURPOSE: High-contrast figures such as Landolt rings are insufficient to evaluate the function of the foveal cones of retinitis pigmentosa (RP) patients. We investigated the correlation between visual function as determined with Landolt rings and with the Vistech Contrast Sensitivity Function Test (VCTS) at various spatial frequencies, in addition to the Cambridge Low Contrast Grating (CLCG). METHODS: The study included 30 retinitis pigmentosa patients (53 eyes). All patients were assessed with Landolt rings, the Vistech method, and the CLCG. We estimated the relative contribution of contrast sensitivity to visual acuity by VCTS at each spatial frequency and by CLCG by simple linear regression analysis. RESULTS: The results of the regression analysis of VCTS at 1.5, 3.0, and 6.0 cycles/degree showed a significant correlation between Landolt rings and VCTS and between CLCG and VCTS that was strongest at 6.0 cycles/degree. There was no significant correlation between Landolt rings and VCTS or between CLCG and VCTS at 12.0 and 18.0 cycles/degree. Patients with a visual acuity of 20/25 and CLCG greater than 100 were divided into two groups according to their contrast sensitivity at 18.0 cycles/degree on VCTS. CONCLUSIONS: The VCTS at the highest frequency was useful for evaluating the foveal visual function in RP patients having good visual acuity with the Landolt rings. Thus, contrast sensitivity should be useful in detecting minute impairment or improvement of visual function in RP.

Adolescent↗

PubMed1990

Visual acuity assessment from birth to three years using the acuity card procedure: cross-sectional and longitudinal samples.

We used the Teller Acuity Cards (TAC) to test 7 groups of 20 healthy infants and children ranging in age from 1 week to 36 months. We also tested 27 of these children at least twice within their first year. We had two primary goals: (1) to provide normative data on the development of visual acuity as assessed with the new version of the TAC (Vistech, Inc.) and (2) to investigate the predictive value of the TAC. The results from the cross-sectional samples show that our estimates of visual acuity are consistent with those reported by other researchers who used earlier versions of the TAC. The longitudinal data indicate that, on the average, an early estimate of visual acuity was not predictive of a later estimate, at least within the first year. The results are discussed in terms of the usefulness of the TAC for testing normal and clinical populations.

Child, Preschool↗

PubMed1991

Acute optic neuritis with normal visual acuity. Comparison of symptoms and signs with psychophysiological, electrophysiological and magnetic resonance imaging data.

In a prospective study of hitherto 70 patients with acute optic neuritis (ON), 18 patients aged 15-49 years (12 women, 6 men) were diagnosed as having very subtle form of ON (bilateral in 4 patients), characterized by normal visual acuity. However, their symptoms were sudden functional visual disturbances, most frequently blurred vision accompanied by pain in or around the affected eye(s). In 5 patients, the ON was a manifestation of clinically definite multiple sclerosis (MS); the remaining 13 patients had monosymptomatic ON. The duration of visual symptoms ranged from 2 to 28 days (median 7 days) at the time of examination. Although 18 patients had a normal visual acuity, i.e. 6/6 c.c. (Snellen's notation) or better, extensive studies of the visual functions (using sensitive supplementary tests) revealed various abnormalities, primarily various visual field defects, abnormal contrast sensitivity, abnormal VEP and colour vision deficiencies (often of blue-yellow type). Magnetic resonance imaging (MRI) of the brain revealed demyelinating lesions in 10 of the 13 patients with monosymptomatic ON, and in all 5 patients with definite MS. The extended disease spectrum gives reason to hypothesixe that ON may occur more frequently than previously reported, and that the described subtle form of ON could be an unnotified precocious manifestation of the demyelinating disease.

Acute Disease↗

PubMed2004

[Evaluation of subjective complaints of patients with a visual acuity of 20/30 to 20/20 before and after cataract surgery].

PURPOSE: To quantify patient's functional visual complaints in early cataract and after cataract surgery. PATIENTS AND METHODS: Forty-nine patients scheduled for cataract surgery with a visual acuity of 20/30 or better on Snellen optotypes at the time of patient selection and no other ocular pathology were evaluated subjectively for visual functions preoperatively and 12 months postoperatively. Subjective visual functions were evaluated using a questionnaire that evaluated patient's visual functions by assessing the degree of difficulty they experience in performing tasks involving distance vision, near vision, mesopic vision and glare conditions. RESULTS: The questionnaire scores were correlated with visual performance both before cataract surgery and thereafter. Significant improvement of subjective visual performance was described postoperatively. CONCLUSION: Questionnaire should be considered as adjuncts to visual acuity and constrast sensitivity testing in evaluation of early cataract.

Adult↗

PubMed1998

A new approach to visual acuity screening for pre-school children.

The Melbourne Initial Screening Test (MIST) is a vision screening technique which combines the features of an established procedure, the five-letter Sheridan Gardiner Single (SGS) test, with a pass/fail method of assessment. It is a simple screening test for children aged 3.5-4.5 years, which is designed to be easy to use. This paper reports on the preliminary results of a comparison of threshold acuity using the 5-letter single-optotype Sheridan Gardiner (SG) test and the MIST results obtained by orthoptists, and a comparison of MIST results obtained by orthoptists and child health nurses. The orthoptists tested 225 children and the nurses tested 868 children. The MIST results obtained by the orthoptists were similar to the SGS in that there was agreement between the test results in 202 (94%) cases. The MIST has a similar rate of subject compliance (95%) as the SGS test (96%). The rate of compliance for orthoptists' and nurses' use of the MIST was similar, with 97% of children being compliant for the nurses and 96% for the orthoptists. The results suggest that the MIST, using a pass/fail method of assessing visual acuity compared to an assessment of threshold visual acuity, may be useful as part of pre-school vision screening since it is easier than the traditional testing of threshold visual acuity and gives similar results to the SG single-optotype test.

Child, Preschool↗

PubMed2003

Effect of visual acuity on biometry prediction error after cataract surgery.

PURPOSE: To determine the effect of visual acuity on biometry prediction error. SETTING: Postgraduate teaching hospital. METHODS: The study was an observational case series of the first operated eye of 2149 consecutive patients who had cataract surgery. Biometry prediction error was defined as the difference between the planned refraction determined by biometry and the spherical equivalent of the final refraction. The principal outcome measure was the percentage of eyes within +/-1.00 diopter (D) of the intended refraction. This outcome was calculated for patients with visual loss caused by cataract alone, defined as eyes with a postoperative acuity of 6/6 or better, and eyes with different levels of postoperative visual acuity. RESULTS: Complete data were available for 1978 eyes (92%). Of these, 1438 (73%) were within +/-1.00 D of the intended refraction. When the final corrected visual acuity was 6/6 or better, the percentage of eyes within +/-1.00 D of the predicted refraction was at least 78%. When the preoperative acuity was worse than 6/60, 74% in the counting fingers group and 69% in the hand movements group with a final corrected acuity of 6/6 or better were within +/-1.00 D. This trend bordered on statistical significance (P =.05). There was a rapid reduction in the percentage of eyes within +/-1.00 D of the intended refraction as the postoperative acuity decreased because of ocular comorbidity, with a statistically significant difference between eyes with a postoperative acuity of 6/6 or better and each group with an acuity of 6/9 or worse (P<.01). CONCLUSIONS: In eyes without visually significant ocular comorbidity, cataract must reduce vision to 6/60 or worse before there is an increase in biometry prediction error. In contrast, ocular comorbidity that reduces the postoperative acuity causes an early and marked increase in biometry prediction error.

Biometry↗

PubMedDate not supplied

Visual acuity and scar size in eyes with age-related subfoveal choroidal neovascular lesions, 30 months after radiation therapy.

PURPOSE: In a study to determine the effectiveness of ionizing radiation on the deterioration of visual acuity (VA) due to choroidal neovascularisation (CNV) the affected eyes of 10 patients were treated with a total dose of 24 Gy (6 Gy fractions). A special lens-sparing technique was used to avoid cataract development. During 30 months of follow-up the visual acuity (VA) and scar size (SS) of the treated eyes and fellow eyes of all 10 patients were evaluated. RESULTS: After 30 months of follow-up 5 eyes showed a stable VA and fluorescein angiogram (FA) appearance. Concerning 4 out of 5 eyes with progressive disease, the 4 eyes treated with radiation therapy had better VA and smaller SS as compared with the untreated fellow eyes with exudative AMD. CONCLUSIONS: The results suggest that 24 Gy either stabilizes or delays the deleterious effects of CNV on the visual acuity. Until now no late side effects have been observed.

Aged↗

PubMed1998

Visual acuity, contrast sensitivity and retinal magnification in a marsupial, the tammar wallaby (Macropus eugenii).

The visual acuity of the tammar wallaby was estimated using a behavioural discrimination task. The wallabies were trained to discriminate a high-contrast (86%) square-wave grating from a grey field of equal luminance (1000-6000 cd m-2). Visual-evoked cortical potentials were used to measure the complete contrast sensitivity function. The stimulus was a sinusoidal phase reversal of a sinusoidally modulated grating of various spatial frequencies and contrasts with a mean luminance of 40 cd m-2). The behavioural acuity was estimated to be about 4.8 cycles/deg. The contrast sensitivity peaked at about 0.15 cycles/deg and declined towards both lower and higher spatial frequencies. The cut-off frequency of the contrast sensitivity function is slightly lower than the behaviourally measured acuity at about 2.7 cycles/deg. The retinal magnification factor was estimated anatomically from laser lesions to be about 0.16 mm/deg. Based on the known ganglion cell density and the retinal magnification factor, an anatomical upper limit to visual acuity of about 6 cycles/deg can be calculated. The differences in estimates of visual acuity between the behavioural and anatomical methods on the one side and physiology on the other side are discussed.

Animals↗

PubMed1989

Potential visual acuity measured with and without pupil dilation.

Potential visual acuities were measured with the Randwal IRAS portable interferometer, with and without pupil dilation, on a sample of predominately elderly patients with mild to moderate cataract. No clinically significant difference was found between interferometer potential acuities before and after pupil dilation.

Aged↗

PubMed2006

Visual acuity thresholds for cataract surgery and the changing Australian population.

OBJECTIVE: To examine the relation between visual acuity thresholds for cataract surgery for the changing Australian population. METHODS: Population-based 5-year incidence data for 2594 people were used to calculate age-specific prevalence of incident cataract and existing cataract backlog. The cataract surgery rates (CSRs) per million people were estimated for different acuity thresholds for the Australian population at different times. RESULTS: In 2005, after adjusting by age, the estimated CSRs for Australia were 1470, 3110, 5080, and 6440 for visual acuities of less than 6/60, less than 6/18, less than 6/12, and less than 6/9, respectively, whereas the actual CSR was 9000. Although the acuity threshold had the greatest impact, the CSR for less than 6/12 increased 3-fold from 2300 in 1950 to 7210 in 2020 because of demographic changes. CONCLUSIONS: Demographic changes, with an increasing proportion of older people, will continue to increase the need for cataract surgery, as will a reduction in the visual impairment threshold. Plans for the future for eye care services should take these factors into account.

Adult↗