Eduard Jaeger's Test-Types (Schrift-Scalen) and the historical development of vision tests.
(33/745)
PURPOSE: Eduard Jaeger's original Test-Types were carefully evaluated: (1) to determine whether Jaeger had maintained a consistent standard, (2) to establish the correct Snellen equivalent for Jaeger's Test-Types, (3) to answer the question of why and how the standard was lost, and (4) to compare the visual angle of optotypes to lines of continuous text. METHODS: All original Viennese editions of Jaeger's Test-Types, as well as first generation United Kingdom (UK) and United States (US) versions, were evaluated. Data were collected objectively using a microruler with a 20X loupe and subjectively using a laser distance-measuring device. The data were analyzed using Microsoft Excel. All previous measurements of Jaeger's Test-Types, objective and subjective, collected over the past 133 years were compared to the current data and to each other. RESULTS: The correct Snellen equivalent of Jaeger's Test-Types was determined. The visual angle created from the measurement of the height of lowercase letters, without ascenders or descenders, provides an accurate method of assigning a visual angle of a line of continuous text. Comparing the typefaces used in printing first generation UK and US versions of Jaeger's Test-Types to the Viennese editions provided an explanation for the absence of a consistent standard for Jaeger's Test-Types today. CONCLUSIONS: All 10 versions of Jaeger's original Test-Types are virtually identical and established a gold standard for reading vision tests. Jaeger's standard was lost when his Test-Types were first printed in the UK and the US using local typefaces. The Jaeger standard has been re-established. Visual angles determined using continuous text are comparable to those obtained by using optotypes. (+info)
Psychometric properties of the 25-item NEI-VFQ in a Hispanic population: Proyecto VER.
(34/745)
PURPOSE: To assess the psychometric properties of the NEI-VFQ-25 in a population-based study of older Hispanic persons living in the United States, explore other demographic factors that affect participant response, and observe the comparability of the Spanish and English versions of the instrument. METHODS: A sample of randomly selected block groups in Tucson and Nogales, Arizona, were selected for study. Participants were interviewed at home; a majority of the interviews were conducted in Spanish. The home interview included questions from the NEI-VFQ-25 and HHANES: Presenting acuity was done using ETDRS methodology, followed by a standardized eye examination by an ophthalmologist. The authors analyzed the internal consistency of the NEI-VFQ-25 responses using Cronbach's alpha coefficient and the construct validity by assessing the relationship between presenting acuity and scale scores, adjusting for age and gender. A second model was also explored to determine whether other demographic variables affected scale scores; differences in reporting between the Spanish and English versions was observed in this model, used in a subset of the population that minimized interviewer effect. RESULTS: Of the 4774 participants in the study, 99.7% had completed questionnaires, not completed by proxy. The highest nonresponse rate occurred in the Driving scale, with 25% of participants not driving for reasons other than problems with vision. Internal consistency was high, with Cronbach alpha ranging between 0.65 and 0.86 for scales with multiple items. Adjusting for age and gender, those with presenting acuity worse than 20/40 scored significantly lower than those with presenting acuity 20/40 or better, for all scales. The demographic variables with the most consistent association across the NEI-VFQ-25 scales were presenting acuity, income, and gender. No significant differences in reporting were found between the Spanish and English versions of the questionnaire in the subset of the population. CONCLUSIONS: In this study of Hispanic people age 40 years or older, the NEI-VFQ-25 was sensitive to presenting acuity and other demographic variables, such as age, gender, and income. The findings from this psychometric analysis provide evidence of the reliability and validity of some of the scales in the 25-item NEI-VFQ when used among people with a range of visual acuity level, providing other explanatory variables are also considered. (+info)
Visual dysfunction between migraine events.
(35/745)
PURPOSE: To evaluate interictal visual dysfunction in persons with migraine in terms of spatiotemporal selectivity and location within the visual pathways. METHODS: The vision of a group of 15 persons who had experienced migraine with aura was compared with that of 15 normal age-matched control subjects. A range of thresholds was measured to evaluate precortical (background modulation, contrast thresholds for static, and moving stimuli), area V1 (orientation discrimination and motion discrimination thresholds), and higher order (global dot motion thresholds) visual processes. Testing was performed centrally and at 10 degrees in the superior visual field. For each of the tests, the spatial and temporal parameters of the stimuli were selected to bias detection toward either parvocellular or magnocellular visual mechanisms. RESULTS: No defects were found for parvocellular processes. Significant (P: < 0.05) losses were apparent with the temporal background modulation method (16 Hz), orientation discrimination (0.5 cyc/deg), and global dot motion tasks. CONCLUSIONS: Both cortical and precortical visual dysfunction were identified in migraine group 7 days after the headache. This loss was selective for targets with temporal modulation of approximately 16 Hz. (+info)
Contour integration deficits in anisometropic amblyopia.
(36/745)
PURPOSE: Previous retrospective studies have found that integration of orientation information along contours defined by Gabor patches is abnormal in strabismic, but not in anisometropic, amblyopia. This study was conducted to reexamine the question of whether anisometropic amblyopes have contour integration deficits prospectively in an untreated sample, to isolate the effects of the disease from the effects of prior treatment-factors that may have confounded the results in previous retrospective studies. METHODS: Contour detection thresholds, optotype acuity, and stereoacuity were measured in a group of 19 newly diagnosed anisometropic amblyopes before initiation of occlusion therapy. Contour detection thresholds were measured using a card-based procedure. RESULTS: Significant interocular differences in contour detection thresholds were present in 14 of the 19 patients with anisometropic amblyopia. CONCLUSIONS: Contour integration deficits are a common, but not universal, finding in untreated anisometropic amblyopia. Differences in the prevalence of contour integration deficits between the present study and that of another study may lie in differences in treatment history and/or in the sensitivity of the two different contour integration tasks. (+info)
The development of a "reduced logMAR" visual acuity chart for use in routine clinical practice.
(37/745)
BACKGROUND/AIMS: The advantages of logMAR acuity data over the Snellen fraction are well known, and yet existing logMAR charts have not been adopted into routine ophthalmic clinical use. As this may be due in part to the time required for a logMAR measurement, this study was performed to determine whether an abbreviated logMAR chart design could combine the advantages of existing charts with a clinically acceptable measurement time. METHODS: The test-retest variability, agreement (with the gold standard), and time taken for "single letter" (interpolated) acuity measurements taken using three prototype "reduced logMAR" (RLM) charts and the Snellen chart were compared with those of the ETDRS chart which acted as the gold standard. The Snellen chart was also scored with the more familiar "line assignment" method. The subjects undergoing these measurements were drawn from a typical clinical outpatient population exhibiting a range of acuities. RESULTS: The RLM A prototype chart achieved a test-retest variability of +/-0.24 logMAR compared with +/-0.18 for the ETDRS chart. Test-retest variability for the Snellen chart was +/-0.24 logMAR using clinically prohibitive "single letter" scoring increasing to +/-0.33 with the more usual "line assignment" method. All charts produced acuity data which agreed well with those of the ETDRS chart. "Single letter" acuity measurements using the prototype RLM charts were completed in approximately half the time of those taken using the ETDRS and Snellen charts. The duration of a Snellen "line assignment" measurement was not evaluated. CONCLUSION: The RLM A chart offers an acceptable level of test-retest variability when compared with the gold standard ETDRS chart, while reducing the measurement time by half. Also, by allowing a faster, less variable acuity measurement than the Snellen chart, the RLM A chart can bring the benefits of logMAR acuity to routine clinical practice. (+info)
Anomaly in visual acuity testing in children.
(38/745)
A popular and widely used method of visual acuity testing of young children is criticized on the grounds that it often fails to elicit amblyopia. The results obtained when the visual acuity of thirty amblyopic children was tested by different methods show that monotype testing gives an apparent acuity averaging three grades better than those derived from the standard Snellen's test. (+info)
The development of the Melbourne low-vision ADL index: a measure of vision disability.
(39/745)
PURPOSE: To develop a new test of activities of daily living (ADLs) appropriate for the low-vision population: the Melbourne Low-Vision ADL Index (MLVAI). METHODS: The MLVAI was designed as a desk-based clinical assessment, comprising 18 observed items on complex ADLs in part (a) and 9 questions on broad self-care ADLs in part (b). Each item was rated on a five-level descriptive scale from 0 to 4, based on independence, speed, and accuracy of performance. It was designed to be administered under standardized conditions with regard to the instructions, illumination, and working distances. The validity and reliability of the new MLVAI was determined for 122 subjects who were representative of the general low-vision population, in a cross-sectional study. RESULTS: Two items were found to be redundant and were eliminated from the test. Thus, the final test comprised 25 items, with 100 being the highest possible score. Cronbach's alpha indicated an internal reliability of 0.96, and an intraclass correlation coefficient indicated an overall reliability of 0.95. The SE of measurement was 4.5. According to Spearman's correlation coefficient, the test-retest reliability was 0.94 (P < 0.001), and the interpractitioner reliability for five different pairs of practitioners was 0.90 or higher (P < 0.001). With regard to validity, there was a moderately high correlation with vision impairment (r = -0.68, P < 0.001). Using Rasch analysis, content validity was also demonstrated by good separation indexes (4.70 and 9.88) and high reliability scores (0.96 and 0.99) for the person and items parameters, respectively. Separate calculation of indexes and reliability scores for parts (a) and (b) indicated high content validity and reliability of each part. However, the separation indexes and reliability scores were higher for part (a) than for part (b). The correlation coefficient for part (a) and part (b) was 0.68. CONCLUSIONS: The MLVAI is a highly valid and reliable standardized test of ADL performance for the general low-vision population. It may be used to assess patients with low vision and has the potential to be used as a measure of low-vision rehabilitation outcomes. (+info)
ETDRS-fast: implementing psychophysical adaptive methods to standardized visual acuity measurement with ETDRS charts.
(40/745)
PURPOSE: To measure visual acuity (VA) on Early Treatment Diabetic Retinopathy Study (ETDRS) charts with a modified faster procedure (ETDRS-Fast), based on adaptive psychophysics methods and to assess the method's validity and reproducibility. METHODS: Whereas the standard method for measuring VA with the ETDRS charts requires that the subject read all the letters beginning with the top row, in the ETDRS-Fast procedure, the subject is asked to read only one letter per row until a mistake is made. Then, following simple rules, the examiner finds a row from which the subject can begin reading all the letters downward, thus making the method identical with the standard method near threshold. VA determination was performed twice with both methods in 57 subjects in two separate sessions to assess validity and reproducibility. RESULTS: In both sessions the correlation between the two procedures was high (intraclass correlation coefficient 0.95), confirming the validity of the ETDRS-Fast procedure. Reproducibility was good for both procedures, with intraclass correlation coefficients of 0.94 for the standard and 0.96 for the ETDRS-Fast method. The ETDRS-Fast procedure allowed a significantly shorter test duration (-30%; P < 0.0001). CONCLUSIONS: Adaptive procedures allow accurate and fast determination of psychophysical thresholds by reducing the number of stimulus presentations when the subject is far from threshold. In the ETDRS-Fast method a few simple rules applied to optotype chart reading allow adaptation to each patient's level of VA. The ETDRS-Fast procedure significantly reduces test time and still yields results that are as accurate as those obtained with the standard method. (+info)