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PubMed1996

The Freiburg Visual Acuity test--automatic measurement of visual acuity.

The Freiburg Visual Acuity test is an automated procedure for self-administered measurement of visual acuity. Landolt-Cs are presented on a monitor in one of eight orientations. The subject presses one of eight buttons, which are spatially arranged on a response box according to the eight possible positions of the Landolt-Cs' gap. To estimate the acuity threshold, a best PEST (best Parameter Estimation by Sequential Testing) procedure is used in which a psychometric function having a constant slope on a logarithmic acuity scale is assumed. Measurement terminates after a fixed number of trials. With computer monitors, pixel-discreteness artifacts limit the presentation of small stimuli. By using anti-aliasing, i.e., smoothing of contours by multiple gray levels, the spatial resolution was improved by a factor of four. Thus, even the shape of small Landolt-Cs with oblique gaps is adequate and visual acuities from 5/80 (0.06) up to 5/1.4 (3.6) can be tested at a distance of 5 m.

Diagnosis, Computer-Assisted↗
PubMed2003

Comparison of contrast sensitivity, visual acuity, and Humphrey visual field testing in patients with glaucoma.

BACKGROUND: Despite their normal or near-normal Snellen visual acuity, patients with glaucoma often complain of "poor" vision. OBJECTIVE: To investigate the relationship between large-letter contrast sensitivity, high-contrast visual acuity, and visual field defects in patients with glaucoma who have 20/40 or better visual acuity. DESIGN: Prospective, cross-sectional case series. PATIENTS AND METHODS: We evaluated 250 eyes of 144 subjects from the Glaucoma Service at the University of Illinois at Chicago College of Medicine. Subjects with a diagnosis of glaucoma, suspected glaucoma, or ocular hypertension who met the 20/40 or better vision requirement were recruited. Visual acuity was measured using the rear-illuminated Lighthouse Visual Acuity Chart at 4 m. Contrast sensitivity was measured using the Pelli-Robson Chart in a front-illuminated box with even luminance across the chart. Visual fields of the patients were measured using the 24-2 full-threshold program on the Humphrey Visual Field Analyzer. RESULTS: A significant correlation (r = 0.57, P < 0.001, n = 127) was found between the visual field mean deviations and the contrast sensitivity scores. The correlation (r = -0.322, P < 0.001, n = 127) was less between the visual field mean deviation and the log MAR visual acuity values, as was the correlation between the contrast sensitivity scores and log MAR visual acuity values (r = -0.370, P < 0.001, n = 127). In the subgroup of patients with chronic open-angle glaucoma, the correlation between the mean visual field deviation and the contrast sensitivity score was higher at 0.689 (P < or = 0.001, n = 62). CONCLUSIONS: Reduced contrast sensitivity is significantly correlated with visual field losses in patients with glaucoma and a visual acuity of 20/40 or better. The study data support the conclusion that, compared with visual acuity, the disease process preferentially affects contrast sensitivity. In our previous work, contrast sensitivity was shown to be more related than visual acuity to real-world function in patients with early glaucomatous changes.

Contrast Sensitivity↗
PubMed2003

The relationship between performance-based visual acuity screening, self-reported visual acuity, and neuropsychological performance.

Despite frequent cautions in the literature concerning the importance of visual acuity in neuropsychological testing, there are few published empirical investigations of what constitutes "sufficient" visual acuity, nor are there published guidelines for performance-based visual screening techniques. The current study attempted to validate the utility of a visual acuity screening technique by examining individuals with varying visual ability on neuropsychological measures. Results revealed declines on neuropsychological measures associated with reduced visual acuity, as well as discrepancies between self-reported and measured visual acuity, with neuropsychological performance being more closely related to a performance-based measure of visual acuity than to self-reported visual acuity. Clinical implications are discussed.

Adult↗
PubMed2002

[Visual acuity measured via the Freiburg visual acuity test (FVT), Bailey Lovie chart and Landolt Ring chart].

INTRODUCTION: If different ways for correcting refractive errors of the human eye have to be compared, accurate and reproducible measurement procedures are necessary. METHODS: Binocular visual acuity of 130 students without pathologies was measured with the Freiburg Visual Acuity Test, the Bailey-Lovie chart and a Landolt ring chart (4 orientations). The reproducibility of the FVT was determined by repeated measurements. RESULTS: The average visual acuity was 1.93 +/- 0.03 (= 20/10.4) with the FVT, 1.82 +/- 0.03 (= 20/11) with the Landolt ring chart, and 1.48 +/- 0.02 (= 20/13.5) with the Bailey-Lovie chart. 50 % of all repeated measurements with the FVT were within an interval of +/- 0.035 logMAR from the mean value. 95 % were within +/- 0.1 logMAR. Results of earlier studies are discussed. CONCLUSION: On average, visual acuity values found with the Freiburg Visual Acuity Test were slightly larger as compared to the Landolt ring chart (difference = 0.025 logMAR). Taking the maximal difference of 0.05 logMAR tolerated by the international standard DIN EN ISO 8597 into account, both tests are equivalent. The results found with the Bailey-Lovie chart were substantially lower as compared to the Landolt ring chart (difference = 0.09 logMAR). The Freiburg Visual Acuity Test has a high reproducibility and measures visual acuity on a continuous scale that is not limited to the traditional visual acuity steps. Thus, it can be recommended as a reference procedure for comparative visual acuity studies.

Adult↗
PubMed2003

Effect of lesion size, visual acuity, and lesion composition on visual acuity change with and without verteporfin therapy for choroidal neovascularization secondary to age-related macular degeneration: TAP and VIP report no. 1.

PURPOSE: To determine whether differences in baseline lesion size and visual acuity might explain differing results found in three different lesion compositions (predominantly classic, minimally classic, and occult with no classic) among three placebo-controlled, randomized clinical trials evaluating photodynamic therapy with verteporfin (Visudyne, Novartis AG), also termed verteporfin therapy, in patients with subfoveal choroidal neovascularization (CNV) due to age-related macular degeneration (AMD). METHODS: Exploratory analyses were conducted in patients with predominantly classic or minimally classic lesions at enrollment in the Treatment of AMD with Photodynamic Therapy (TAP) Investigation and in AMD patients with occult with no classic CNV in the Verteporfin In Photodynamic Therapy (VIP) Trial. Baseline characteristics of patients among these three lesion compositions were compared. In addition, multiple linear regression modeling was used to explore the effect of baseline lesion size, visual acuity, and lesion composition on mean change in visual acuity from baseline to 24 months. RESULTS: At baseline, the mean size of predominantly classic lesions (3.4 disk areas) was smaller than that of minimally classic (4.7 disk areas) and occult with no classic lesions (4.3 disk areas). In the multiple linear regression model of individual lesion compositions, there was a significant treatment-by-lesion-size interaction for minimally classic and occult with no classic lesions, but not for predominantly classic lesions. Interaction between treatment and baseline visual acuity was not significant for any lesion composition. Small verteporfin-treated lesions lost less vision than large verteporfin-treated lesions in each lesion composition. In the multiple linear regression model that included all lesion compositions, lesion size was a more significant predictive factor for the magnitude of treatment benefit than either lesion composition or visual acuity. Smaller (4.0 disk areas or less) minimally classic and occult with no classic lesions had similar visual acuity outcomes to those observed in predominantly classic lesions. CONCLUSIONS: Based on exploratory analyses, lesion size in the TAP Investigation and VIP Trial was an important predictor of the magnitude of treatment benefit with verteporfin therapy in occult with no classic and minimally classic lesion compositions. In patients with AMD, treating smaller rather than larger neovascular lesions, regardless of lesion composition, likely will result in a better level of visual acuity.

Aged↗
PubMed2000

[Changes to visual acuity and the visual field in a case of meningioma operated at the anterior level].

It's presented a midline meningioma of anterior level case which preoperative has an importance affectation of the visual acuity and visual field, and postoperative in dynamic is founded the important improvement of visual acuity and visual field. It's discussed visual field topography and atrophy optic pathophysiology. It's a neuro-ophthalmology case example, where the cooperation neurosurgery-ophthalmology permit medical solution and restored in social life of the patient.

Female↗
PubMed2004

Screening for myopia and refractive errors using LogMAR visual acuity by optometrists and a simplified visual acuity chart by nurses.

PURPOSE: To compare the sensitivity and specificity of a widespread method of screening for refractive errors in Singapore schoolchildren using a simplified acuity screening chart with a more rigorous method using the Early Treatment Diabetic Retinopathy Study (ETDRS) chart. A secondary aim is to estimate the best cutoff values for the detection of refractive errors using these two methods. METHODS: This is a population-based study, involving 1779 schoolchildren from three schools in Singapore. Logarithm of the minimum angle of resolution (logMAR) visual acuity was recorded using a modified Bailey-Lovie chart by trained optometrists, and visual acuity measurement was also undertaken using a simplified 7-line visual acuity screening chart by school health nurses. The main outcome measures were the receiver-operating characteristics (ROC's) of logMAR and the simplified screening visual acuity to detect myopia or any refractive errors. The difference between measurements, simplified screening visual acuity--logMAR visual acuity, was calculated. RESULTS: The optimal threshold using the simplified screening visual acuity chart for the detection of myopia or any refractive error was 6/12 or worse. Using logMAR visual acuity, the most efficient threshold for the detection of myopia was 0.26, but this was 0.18 for the detection of any refractive error. The area under the ROC curves was significantly greater in the case of the logMAR visual acuity measurement compared with the simplified screening visual acuity measurement for the detection of myopia or any refractive errors. The 95% limits of agreement for the two methods (simplified screening--logMAR acuity) was -0.219 to +0.339. CONCLUSIONS: Bearing in mind that the visual acuity measurements were performed by two different groups of professionals, visual acuity screening using the ETDRS method appears to be more accurate than the simplified charts for the detection of myopia or any refractive errors in children.

Child↗
PubMed1993

Outcomes of cataract surgery. Improvement in visual acuity and subjective visual function after surgery in the first, second, and both eyes.

OBJECTIVE: No previous study documents improvement in visual acuity and subjective visual function associated with cataract surgery in the first eye, second eye, and both eyes. Measurement of subjective aspects of visual function and quality of life provides information that cannot be obtained with simple measurement of Snellen visual acuity. METHODS: From 76 ophthalmology practices in three cities, patients undergoing cataract extraction with intraocular lens implantation (n = 613) and comparison patients (n = 408) were enrolled in a prospective study. Questionnaires elicited visual function information before and after surgery, and visual acuity was obtained from the ophthalmologic record. RESULTS: Among patients with cataract and no other eye disease, baseline subjective visual function before surgery in the second eye was better than that before surgery in the first eye. Improvement in subjective visual function was approximately equal postoperatively in first and second eyes. Improvement in subjective function in both eyes postoperatively was significantly greater than that after surgery in the first eye or second eye alone. No statistically significant difference across surgical groups in the proportion of patients demonstrating improvement in visual acuity was observed. CONCLUSION: Patients who underwent surgery in both eyes reported greater improvement in subjective visual function than did those who underwent surgery in one eye. Thus, there seems to be a benefit associated with restoring binocular vision in this population. These findings support the policy recommendation that cataract surgery in both eyes remains the appropriate treatment for patients with bilateral, cataract-induced visual impairment.

Aged↗
PubMed2005

The effect of relative distance enlargement on visual acuity in the visually impaired.

BACKGROUND: Prescribing magnification is typically based on distance or near visual acuity. This presumes a constant minimum angle of visual resolution with working distance and therefore enlargement of an object moved to a shorter working distance (relative distance enlargement). This study examines this premise in a visually impaired population. METHODS: Distance letter visual acuity was measured prospectively for 380 low vision patients (distance visual acuity between 0.3 and 2.1 logMAR) over the age of 57 years, along with near word visual acuity at an appropriate distance for near lens additions from +4 D to +20 D. Demographic information, the disease causing low vision, contrast sensitivity, visual field and psychological status were also recorded. RESULTS: Distance letter acuity was significantly related to (r = 0.84) but on average 0.1 +/- 0.2 logMAR better (1 +/- 2 lines on a logMAR chart) than near word acuity at 25 cm with a +4 D lens addition. In 39.8 per cent of patients, near word acuity was more than 0.1 logMAR worse than distance letter acuity. In 11.0 per cent of subjects, near visual acuity was more than 0.1 logMAR better than distance letter acuity. The group with near word acuity worse than distance letter acuity also had lower contrast sensitivity. The group with near word acuity better than distance letter acuity was less likely to have age-related macular degeneration. Smaller print size could be read by reducing working distance (achieved by using higher near lens additions) in 86.1 per cent, although not by as much as predicted by geometric progression in 14.5 per cent. DISCUSSION: Although distance letter and near word acuity are highly related, they are on average 1 logMAR line different and this varies significantly between individuals. Near word acuity did not increase linearly with relative distance enlargement in approximately one in seven visually impaired, suggesting that the measurement of visual resolution over a range of working distances will assist appropriate prescribing of magnification aids.

Aged↗
PubMed1981

[Determination of visual acuity by the visually evoked cortical potential (author's transl)].

Monocularly evoked cortical potentials were recorded monopolarly (3 cm above Prot. occ. ext. sup.) to steady-state checkerboard stimuli (check sizes 1.4 to 26 min, rev. freq. 7/s, mean luminance 10.8 cd/m2, field diameter 4.5 deg., centr. fix.). For a number of visual acuities (obtained by inserting plus lenses up to 3.0 dpt) the smallest check size evoking reliable VECPs was related to the visual acuities obtained at a visual test chart. The use of 20 instead of 100 per cent contrast stimuli provided a significant decrease of slope of threshold check size versus visual acuity, resulting in a three-fold increase in the resolution of data. The method permits the evaluation of visual acuities between 0.1 and 1.0 in normals and patients within limits of +/- log 0.1 (1 sigma) and +/- log 0.2 visual acuity (2 sigma).

Adult↗
PubMed2000

A comparison of visual acuity, predictability, and visual function outcomes after intracorneal ring segments and laser in situ keratomileusis.

PURPOSE: To compare correction of low myopia by intrastromal corneal ring segments (ICRS) and by laser in situ keratomileusis (LASIK) with respect to early visual recovery and refractive outcomes. METHODS: Eighty-two eyes implanted with ICRS in a phase III study for US Food and Drug Administration review were matched with 133 eyes treated with LASIK by criteria of age (> 18 years, < 65 years), preoperative myopia (-1.00 to -3.50 diopters [D]), astigmatism (< or = 1.00 D), single treatment, and attempted full correction. Examinations were performed preoperatively and postoperatively at days 1 and 7 and months 1 and 3. Visual acuity and manifest refraction data were collected retrospectively. Visual function scores were assigned, and summarized results were compared. RESULTS: Uncorrected visual acuity was 20/20 or better at day 1 in 24% of eyes (20/82) after ICRS and in 55% of eyes (73/133) after LASIK, and at month 3 in 75% of eyes (58/77) after ICRS and in 67% of eyes (84/126) after LASIK. Spherical equivalent refraction at month 3 was within +/- 1.00 D of intended correction in 99% of eyes (76/77) after ICRS and in 96% of eyes (121/126) after LASIK. Excellent visual function scores were noted at month 3 in 90% of eyes (69/77) after ICRS and in 78% of eyes (98/126) after LASIK. CONCLUSION: Patients treated with LASIK showed better uncorrected visual acuity immediately following surgery; however, beyond 1 month, patients treated with ICRS achieved better uncorrected visual acuity that continued to improve with time. Visual function scores indicate that ICRS eyes see at higher levels of uncorrected visual acuity than LASIK eyes do with the same refractive error. The ICRS and LASIK were comparable in the correction of mild myopia.

Cornea↗
PubMed2005

Estimating visual acuity by character counting using the Snellen visual acuity chart.

PURPOSE: This study examines visual acuity estimation with character counting, which can be used in subjects with nonorganic visual loss. METHODS: The right eyes of 35 healthy subjects were fogged with plus lenses and tested with the Snellen visual acuity chart (Reichert 11180). Visual acuity and counting level were assessed under various degrees of fogging, up to a maximal fogged acuity of 20/200. Counting level was defined as the smallest line that subjects could count the number of characters correctly. For each counting level, the visual acuity that 95% of subjects could see equal to or better than was determined. RESULTS: A counting level of 20/10 estimates (ie 95% chance) a visual acuity equal to or better than 20/30. Counting levels 20/15, 20/20, and 20/25 estimate visual acuities of at least 20/50, 20/80, and 20/80, respectively. Counting levels 20/30-20/60 estimate a visual acuity of at least 20/200. CONCLUSIONS: Character counting appears to be a useful technique of obtaining a rough estimate of visual acuity in subjects unable to be tested by standard methods, such as those with non-organic visual loss.

Adult↗