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Xi Chen, Luis Lesmes, Jennifer Wallis, Thomas Wallis, Mary Lou Jackson, Peter Bex; Analyses of contrast sensitivity assessments over time: A pilot study. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2761.
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The contrast sensitivity function (CSF) provides a useful functional endpoint for development of ophthalmic drugs and devices. Evaluation of CSF assessment over time is critical for tracking the progression or remediation of CSF deficits. In this pilot study, we examined a series of repeated CSF assessments, to evaluate method reliability, and examine trends (such as learning) using a time-based analysis that may be useful for future evaluation of clinical therapies.
In 5 subjects with corrected-to-normal vision (ages ranging from 20 to 57), we tested contrast sensitivity weekly over a 4-8-week period with the novel quick CSF method (Lesmes et al, 2010) and established contrast sensitivity charts (Pelli-Robson and Vistech). To assess reliability, two runs of 20 quick CSF trials were collected at each session, and each run lasted approximately 3 minutes. We focused on the general contrast sensitivity assessment provided by the area under the log CSF (AULCSF).
The AULCSF values demonstrated excellent test-retest reliability (r = 0.91) between runs, averaged across weeks. The coefficient of variation (sd/mean) for within-session difference scores <12%. We applied a Bayesian hierarchical linear model to analyze the AULCSF values, with model terms that signified learning patterns: either changes across weeks or across runs in the same session. The significant differences observed between subjects were expected age-related effects, though Pelli-Robson and Vistech exhibited no difference across observers. The stability of CSF assessments between and within repeated testing sessions was confirmed by slope coefficient estimates that were not credibly different from zero at the population level.
For clinical studies using contrast sensitivity endpoints, it is critical to evaluate trends over time. The current study demonstrated that the quick CSF method provides reliable contrast sensitivity assessments using a statistical framework based on a hierarchical analysis. Together, these tools demonstrate potential for future studies that identify the progression of visual impairment, or its remediation with therapeutic intervention.
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