Decrease in visual chromatic sensitivity as a potential biomarker for early detection of mild cognitive impairment – a pilot study

Abstract

Purpose Vision is essential to maintain daily activities and quality of life for the elderlies. Studies have suggested that elderlies with cognitive impairment would also face visual challenges. In particular, colour vision requires an intact visual pathway, starting from the retina to the brain, and a good brain function for colour information processing. In this pilot study, we conducted comprehensive eye examinations for elderlies of different cognitive capabilities, and revealed the possibility of utilizing chromatic sensitivity as a biomarker for the early detection of mild cognitive impairment (MCI). Method Sixty elderlies were recruited, and 56 completed all the measurements (aged 73.5 ± 8.2, range 60 – 91 years old, 44 female & 12 male). Eye examination included, but not limited to, visual acuity (VA), external and internal ocular health assessments. Additionally, contrast sensitivity (CS) and colour vision (CV) were also evaluated. To assess the cognitive function of the elderlies, the Cantonese version of the Mini-Mental State Examination (MMSE) was conducted. Results Of the participants, 42.9% had MCI based on the MMSE (cutoff score 24/25), having a mean score of 24.52 ± 4.73 out of 30. The VA and CS were significantly better in normal than MCI participants (p <0.05). Interestingly, MCI participants were subjectively more aware of a reduced vision (p <0.05). Despite the statistical insignificance, MCI participants had a consistently higher rate of having problems on ocular health issues, e.g., cataract and macular degeneration. In particular, the MMSE score was positively correlated with the CV, even after controlling for covariates, indicating that CV is an independent factor in relation to cognitive function. Conclusion MCI is difficult to detect when the symptoms are mild. On the other hand, patients are more aware of a reduced vision, which may be indicative of an impaired cognitive ability. Changes of colour vision may be a potential sign for the early detection of MCI for elderlies. Regular eye examination is recommended to the public to early reveal visual and cognitive impairments.