Do the Pelli-Robson and Test Chart 2000 Xpert demonstrate comparable contrast sensitivity results?

Aim: To establish whether the contrast sensitivity threshold obtained with the computerised Test Chart 2000 Xpert is comparable with the printed Pelli-Robson chart. Methods: Healthy volunteers from a student population were recruited. The inclusion criteria included: monocular visual acuity of at least 0.2 logMAR, no history of any ocular abnormalities and amblyopia, no sign of any manifest strabismus and a Frisby stereo-acuity threshold of at least 85 seconds of arc. Visual acuity was assessed at 1 m to allow the contrast sensitivity to be directly comparable. The results were statistically analysed using a two-factor ANOVA and a paired t-test. Results: Twenty participants (7 male, 13 female) were recruited with a mean age of 20.9 ±6.0 years. The average visual acuity tested at 1 m was -0.05 ±0.12 logMAR for the right eye, -0.07 ±0.11 logMAR for the left eye and ±0.11 ± 0.12 logMAR tested binocularly. The average contrast sensitivity using the Pelli-Robson chart was 1.63 ± 0.02 log unit for the right eye, 1.62 ±0.04 log unit for the left eye and 1.70 ±0.05 log unit when tested with both eyes open. The average contrast sensitivity using the computerised Test Chart 2000 Xpert was 1.84 ±0.13 log unit for the right eye, 1.85 ±0.15 log unit for the left eye and 2.02 ±0.20 log unit when tested with both eyes open. A significant difference was found in contrast sensitivity scores between the two tests ( p < 0.001, paired t-tests). The Test Chart 2000 Xpert also consistently gave higher contrast sensitivity scores when compared with the Pelli-Robson. Weak correlations were noted between visual acuity and both contrast sensitivity tests testing right eye, left eye and with both eyes open, with Pearson’s correlation coefficient values ranging between r = 0.40 and r = 0.11. Conclusion: The study was carried out to determine whether the contrast sensitivity threshold values obtained with the computerised Test Chart 2000 Xpert are comparable with those obtained with the Pelli-Robson chart. A significant difference was found between the scores from the two tests and the Test Chart 2000 Xpert consistently generated a higher contrast sensitivity threshold. This study did not assess test–retest variability. It is acknowledged that further studies with a larger sample size and repeat testing on two visits are required to assess repeatability.

Abstract licence: CC BY

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