Jack Richman

Three clinical tests of the spatial contrast sensitivity function: a comparison.

ABSTRACT The purpose of this study was to establish a practical basis of comparison among three clinical tests designed to measure an observers spatial contrast sensitivity function (CSF): the AO contrast sensitivity test plates (Arden grating test), the Vistech VCTS 6500 chart, and the Nicolet CS‐2000 contrast sensitivity testing system (Optronics system). Each test was administered under standard conditions to a randomly selected subset of 71 normal observers. Scores were converted to absolute contrast and spatial frequency units for comparison. Results were similar for all three tests at intermediate and high spatial frequencies, but at low spatial frequencies the Vistech and Optronics tests yielded significantly lower sensitivity scores than the AO plates. This discrepancy is probably due to area truncation.

Validity and reliability of the MTI Photoscreener

Objectives. The prevalence and necessity for early detection sion problems illustrate the need for improved methods of vision screening in preschool children. This study assessed the validity and reliability of a new device, the MTI Photoscreener in a cross-sectional field study. Methods. An appropriate sample size (>140) was calculated and recruited for the study. All children (N = 161) in a migrant workers summer education program were screened with the MTI Photoscreener. Simultaneously and in a masked design, disease status was determined by the odified Clinic Technique, a well established method for diagnosing the conditions which the MTI screener was designed to detect. Results. Validity measures revealed a sensitivity of 54%, specificity of 87%, Ø coefficient of 0.40, and positive predictive value of 52%. Repeatability was assessed by the k coefficient, by a test for effect modification by examiner, and by comparison of sensitivity and specificity across 12 masked examiners. The k coefficient was 0.38. A test for effect modification suggested that differences existed among the examiners. Variability of sensitivity was high, but variability of specificity was low. Conclusions. Methods for vision screening in preschool children are limited. The MTI Photoscreener is an easy and efficient method, but the validity and reliability is a concern. Comparison of our results with other studies suggests future potential for this instrument provided protocols are refined and further field studies reveal efficacy.

The bead test: a critical appraisal.

An evaluation of the visual acuity levels obtained with the candy bead test (Bock) was performed. White beads (1 mm) were placed on a white felt background under controlled illumination. Ten subjects were required to localize randomly placed beads through increased degrees of induced optical blur. The visual acuity was then measured at the blur level yielding 60% accuracy in localization. The results indicate a range of visual acuity from 6/45 to 6/60 (20/150 to 20/200). These findings are significantly worse than the levels of acuity [6/18 to 6/24 (20/60 to 20/80)] found by other authors. Therefore, our findings raise concerns and indicate caution in the clinical interpretation of the bead test.