Date Posted: 04 November 2009
Researchers based at the Rotterdam Eye Hospital in the Netherlands have announced the first ever results reporting an association between the thickness of the retinal nerve fiber layer (RNFL) and cognitive functioning. The research results showed that a better cognitive performance was significantly associated with a thicker RNFL.
A large population based sample ranging from 18 to 85 years of age were assessed for cognitive functioning using the Dutch Adult Reading Test, the Rey Auditory Verbal Memory Test, semantic fluency, the Trail-Making Test, the Stroop Colour-Word Test and Block Design. RNFL thickness was measured by scanning laser polarimetry (SLP) and the association between cognitive functioning and SLP measurements was studied with linear regression analyses adjusting for a number of factors including age, sex and refractive error. The R2 of the multiple-regression model ranged from 0.16 to 0.37 while RNFL thickness alone explained up to 2.8% of the variance in cognitive test scores. Despite the statistical significance the authors caution that the SPL measurement is "by no means a precise predictor of cognitive ability" and that "inferences about cognitive functioning or decline by easily and safely measuring RNFL thickness is therefore not realistic at the present time".
Previous reports of an increased prevalence of glaucoma in Alzheimer's disease (AD) patients in addition to studies demonstrating retinal ganglion cell loss in patients with AD have prompted inquiry into whether any generalised association exists across a broader physiological spectrum. Recent improvements in bio-imaging tools providing for a resolution of 2 to 3um may permit more accurate RNFL thickness measurements and further exploration of association with cognitive functioning [IOVS, Oct. 2009, Vol. 50, No. 10 pp 4576-4580].
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