Validity of digital measurement of visual acuity and contrast sensitivity in Parkinson's disease.

Purpose: The Senaptec Sensory Station (SSS) is a device that can measure visual acuity (VA) and contrast sensitivity (CS), but validity has not been established in clinical populations. Therefore, we examined analytical and initial clinical validation of VA and CS measured via the SSS in Parkinson's disease (PD).

Methods: SSS was used in 34 PD (aged 69.6 (SD = 9.4) years old) to measure VA (via visual clarity outcome) and CS (via SSS-CS6 and SSS-CS18 outcomes). Analytical validation was performed through comparison to reference VA and CS eye-charts (ETDRS VA, MARS CS), and clinical validation was performed through correlation with clinical measures.

Results: Difference in VA LogMar score between the reference eye chart and the SSS was - 0.03 (0.23); e.g., approximately a single letter on the eye chart. There was moderate agreement between the SSS and eye chart VA measurement in PD (ICC = 0.42). Additionally, there was moderate correlation between SSS and eye chart (0.8 cpd) CS measurement in PD, specifically for SSS-CS6 (6 cpd) (r = 0.46). However, there was poor correlation between eye chart and SSS-CS18 (18 cpd). SSS VA and CS measures correlated moderately with cognitive function, disease duration and severity, providing clinical validation evidence.

Conclusion: VA and CS can be measured with SSS in PD with moderate comparability to reference eye charts (dependent on cpd for CS), and digital outcomes may provide clinically meaningful outcomes to use in PD trials. A range of human, technological and protocol factors may impact validity of VA and CS measurement via SSS, which should be further examined in future studies.