Comparing the CamBlobs2 contrast sensitivity test to the near Pelli-Robson contrast sensitivity test in normally-sighted young adults.

Abstract

Contrast sensitivity (CS) has been proposed as a potential method for patients to assess their vision at home. The CamBlobs2 contrast sensitivity test is meant to be performed easily in the clinic or at home. The purpose of this study was to determine the intra-visit coefficient of repeatability of the CamBlobs2 compared with the near Pelli-Robson test, and the limits of agreement between these two tests on normally-sighted subjects. Twenty-two normally-sighted subjects (mean age 28±4years) completed two trials of the near Pelli-Robson and CamBlobs2 contrast sensitivity tests within a single visit. Tests were performed monocularly on each eye in random order. Pelli-Robson tests were scored as 0.05logCS for each letter read correctly after deducting the first triplet. CamBlob2 tests were scored as the highest line where two or fewer blobs were marked correctly. The coefficient of repeatability was determined as 1.96 times the standard deviation of the difference between the two measurements using the same type of chart on the same eye. The limits of agreement between the two tests were evaluated using Bland-Altman analysis. The mean difference between intra-visit measurements for both the near Pelli-Robson and CamBlobs2 was less than 0.05logCS and the coefficient of repeatability was within ±0.20log CS for both left and right eyes. The mean±standard deviation differences between near Pelli-Robson and CamBlobs2scores was -0.08±0.08 (limits of agreement: -0.24 to 0.09) for right eyes and -0.05±0.10 (limits of agreement: -0.23 to 0.14) logCS for left eyes based on average measurements. The intra-visit repeatability of CamBlobs2 was consistent with the near Pelli-Robson contrast sensitivity test (±0.20logCS). With a 0.05 correction, the CamBlobs2scores showed excellent agreement with the near Pelli-Robson contrast sensitivity test.