Abstract
Purpose: :
Retinal imaging has revealed relatively narrow retinal venules in patients with early Alzheimer’s Disease (AD). The purpose of this study was to determine if this narrowing is detectable in individuals without dementia but who possess a genetic risk factor, apolipoprotein epsilon 4 (apoE4), for Alzheimer’s disease.
Methods: :
For this prospective, cross-sectional study, a pool of healthy participants was recruited from another study and had undergone a complete neuropsychological assessment. All had well-controlled blood pressure and HbA1c of 6.1 or less; none smoked or had dementia, diabetes, glaucoma, retinal defects, ocular inflammation, diplopia, or history of intraocular surgery other than uncomplicated cataract surgery.An examiner blind to the apoE4 status of the participants conducted a clinical exam including dilation with 0.5% tropicamide, A-scan, and acquisition of two 45-degree digital fundus photographs from each eye. A reader blind to apoE4 status determined central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) from fundus photographs using a semi-automated, published protocol (IVAN, University of Wisconsin, Madison). Relatively high AD risk was defined by the presence of the apoE4 allele.
Results: :
8 of 26 participants were positive for apoE4. Neither CRVE nor CRAE was significantly associated with apoE4. Post-hoc analysis showed CRAE was positively associated with performance on two tests of executive function, the Stroop test (p = 0.0022) and category fluency (p = 0.0025).
Conclusions: :
Retinal venular caliber was not associated with AD risk or cognition in healthy individuals. Retinal arteriolar caliber was associated with two measures of executive function, which is more typically affected early in vascular cognitive impairment. The ophthalmic artery originates near those supplying regions of the brain that mediate executive function. To our knowledge, this is the first study showing an association between generalized retinal vessel narrowing and cognitive function in healthy individuals. Further research is needed to determine whether generalized retinal arteriolar narrowing may be an early marker for risk of vascular dementia.
Keywords: retina • blood supply