Effect of reduced visual acuity on the Montreal Cognitive Assessment.

Abstract

Purpose : Cognitive assessments have visual components that assume intact sensory ability, however, adults may show a decline in visual acuity with increasing age. Cognitive scores of adults with visual impairments are typically lower than adults with normal vision. But, we do not know if lower scores are due to the assessments relying on visual stimuli, or if individuals with visual impairments are actually more likely to have cognitive impairments. Therefore, we simulated reduced acuity in adults to determine how this impacts cognitive screening measure.

Methods : Participants (19) viewed one of the three version of the Montreal Cognitive Assessment (MoCA) under three conditions (20/20, simulated 20/80, simulated 20/200). The MoCA was administered following the clinical protocols. Only participants that scored >26 (i.e., normal cognitive function) at 20/20 were included in the analysis. For comparison, we included MoCA data from a sample of older adults with normal vision (n=19, M_age=74, Acuity M=.04 logMAR, SD=.16) or visual impairment (n=19, M_age=79, Acuity M=.35 logMAR, SD=.3).

Results : Acuity of participants at 20/20 (M=.06 LogMAR, SD=.1), simulated 20/80 (M=.63, SD.18) and simulated 20/200 (M=.88, SD=.19) showed that the participants experienced simulated acuity loss with the goggles. For the MoCA scores, we found a main effect of acuity (F=16.22, p<.001, η ²=.375, BF₁₀=5618). Planned post hoc comparisons showed a significant difference between scores with a 20/20 acuity (M=27.26, SD=.93) and 20/80 (M=24.74, SD=1.66, t=5.62, p_tukey<.001, d=1.88), and between 20/20 and 20/200 (M=25.63, SD=1.46, t=3.63, p_tukey=.002, Cohen’s d=1.33). However, no difference was observed between 20/80 and 20/200 (t=-1.99, p_tukey =.125, d=.572). The MoCA scores in older adults with normal vision (M=27.32, SD=2.41) and with visual impairment (M=26.68, SD=2.52), did not differ significantly (t₃₆=-.787, p=.436, d=.26, BF₁₀=.4).

Conclusions : Our findings show a simulated reduction in visual acuity can lead to lower cognitive scores, but that older adults that have a real impairment may have developed an adaptation to this loss of acuity. We would, therefore, recommend conducting cognitive testing by re-scoring the test without the visual components (as in the MoCA Blind), magnifying the visual components to make them more visible, or replacing the visual components with auditory substitutes (e.g., auditory tail-making and clock tasks).

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.