The Test-Retest Variability of the COMPlog System in Participants with Induced Non-Normal Visual Acuity.

Aim: The aim of this study was to determine and compare test-retest variability (TRV) of the computerised visual acuity (VA) COMPlog system on participants with normal vision and non-normal vision induced by bangerter foils (BFs).

Methods: Twenty adult volunteers with VA of 0.100 logMAR or better in each eye and no eye conditions were included. Monocular VA data using the COMPlog system under five conditions-with plain Plano glasses (visually normal condition) and four pairs of Plano glasses with BF strengths of 0.6, 0.3, 0.2 and 0.1 (induced non-normal vision conditions)-were collected on two separate visits. To reduce bias, the eye tested and order of the BFs assessed were randomised. Data comparison was analysed using 2-factor ANOVA and paired t-tests and Bland Altman analysis to assess TRV.

Results: Mean VA score from the two visits was -0.072 ± 0.1 logMAR for Plano, 0.106 ± 0.1 logMAR for BF 0.6, 0.428 ± 0.1 logMAR for BF 0.3, 0.662 ± 0.09 logMAR for BF 0.2 and 0.850 ± 0.08 logMAR for BF 0.1. As BF density increased, VA score significantly worsened (p < 0.0001). Overall mean VA score from the first and second visit was 0.410 ± 0.4 logMAR and 0.379 ± 0.4 logMAR, respectively. This improvement was significant (p < 0.009). The 95% limits of agreement of the VA scores between testing conditions had a range of ±0.120 to ±0.220 logMAR.

Conclusions: Increase in BF strength led to a worsened VA score. However, the COMPlog TRV under the visually normal and induced non-normal vision conditions were within a similar range (±0.120 to ±0.220 logMAR). VA significantly improved on the second visit, suggesting a possible learning effect, which could have a clinical impact.