ETDRS-fast: implementing psychophysical adaptive methods to standardized visual acuity measurement with ETDRS charts.

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.

Retroillumination versus reflected-light images in the photographic assessment of posterior capsule opacification.

PURPOSE: To investigate the relative merit of retroillumination and of reflected light slit-lamp-derived photographs in the assessment of the opacification of the posterior lens capsule. METHODS: Retroillumination and slit-lamp-derived reflected-light photographs were taken on 23 consecutive eyes with posterior capsule opacification (PCO) in uncomplicated pseudophakia. Subjective grading was performed on both types of photographs to evaluate the extent and density of posterior capsular opacification. Best-corrected visual acuity (BCVA) before and after YAG laser capsulotomy was used to assess the impact of capsular opacification on visual function. RESULTS: After capsulotomy all patients attained a BCVA > or = 46 letters (> or =20/32) with a mean increase of 25 letters, indicating that PCO was the cause of visual impairment in these patients. The relative capacity of retroillumination and of reflected-light photographs to adequately capture the extent and the severity of posterior capsule opacification varied considerably. Reflected-light images, in addition to frequently producing higher severity scores for the opacity than retroillumination photographs, in 4 of 23 eyes (17.4%) proved to be the only technique able to document the presence of PCO. CONCLUSIONS: Our results indicate that, with respect to retroillumination images, reflected-light photography has an increased ability to adequately capture the presence and the severity of PCO and that the use of only retroillumination images may lead to its underestimation. This may be relevant to clinical studies aiming to evaluate incidence and progression of this condition.

An independent evaluation of the Age-Related Eye Disease Study (AREDS) cataract grading system.

PURPOSE: To assess intra- and interobserver reproducibility of the Age-Related Eye Disease Study (AREDS) system for grading lens opacities and to provide data on its capacity to reliably detect changes in lens status. METHODS: Independent and replicate grading of 40 sets of lens photographs (one slit-lamp and two retroillumination photographs) were performed by three experienced observers. Patients were participants in the Collaborative Italian-American Clinical Trial of Nutritional Supplements which is testing the effect of a mineral-multivitamin supplement on age-related cataract (CTNS). Scatterplots and intraclass correlation were used to assess measurement error. RESULTS: Analysis revealed good intra- and interobserver reproducibility of the system. Greatest intraobserver measurement error showed 100% of pairs within 10% areal difference for cortical cataract, 97.5% within 15% areal difference for posterior subcapsular cataract, and 100% within 1 density unit difference for nuclear opacity. Greatest interobserver measurement error showed 95% of pairs within 10% areal difference for cortical cataract, 97.5% within 15% areal difference for posterior subcapsular cataract, and 97.5% within 1.5 density unit difference for nuclear opacity. CONCLUSIONS: The AREDS lens opacities grading system appears to be sufficiently reliable to detect changes of at least 10% areal involvement for cortical, 15% areal involvement for posterior subcapsular, and 1.0 units for nuclear opacities. It therefore seems sufficiently sensitive to adequately monitor progression of lens opacities in a longitudinal study of patients with early cataract. Its applicability in a population with advanced or complex mixed opacities must await further testing.

Second Generation Binocular Polaroid Test.

BACKGROUND: The aim of the study was to introduce a new test to detect small areas of suppression in the binocular visual field and to lower the minimum age at which a suppression test could be identified correctly. Two tests were compared: the Binocular Polaroid Test (poltest), introduced in clinical practice a few years ago and used in screening programs for vision impairment; and the Second Generation Binocular Polaroid Test (polstar), more recently designed to have simpler answers than the poltest. METHODS: One hundred and eighty-two children were examined consecutively. To assess the validity of the two tests, sensitivity, specificity, predictive value, and phi coefficient were calculated. The applicability of the two tests and the speed of the responses was assessed by means of the test of probability of binomial distribution. RESULTS: The polstar has appeared to be simpler and easier in younger patients (age range 20 to 36 months, P = 0.078), and has shown 100% of specificity with a sensitivity of 84% for the polstar 1 and of 100% for the polstar 2. CONCLUSION: The results appear to demonstrate that the poltest has been improved, and that the polstar may be considered an interesting investigation device for early detection of monocular visual impairment.