Morphological and functional retinal impairment in Alzheimer's disease patients

Objective: Our study aims to assess the optic nerve fiber layer thickness i n vivo, the function of the innermost retinal layer and whether a correlati on exists between morphological and functional parameters in patients affec ted by Alzheimer's Disease (AD). Methods: Seventeen AD patients (mean age 70.37 +/- 6.1 years, best correcte d visual acuity >8/10 with refractive error between +/-3 sf, intra-ocular p ressure (IOP) < 18 mmHg) were enrolled. They were compared to 14 age-matche d controls. Nerve fiber layer (NFL) thickness was measured by optical coher ence tomography (OCT). Three different measurements in each quadrant (super ior, inferior, nasal, and temporal) were taken and averaged. The data in al l quadrants (12 values averaged) were identified as NFL Overall. Retinal fu nction was assessed by pattern electroretinogram (PERG) recordings using hi gh-contrast (80%) checkerboard stimuli subtending 15 min of the visual are and reversed at the rate of two reversals/s. Results: In AD eyes, there was a significant (P < 0.01) reduction in NFL th ickness in each quadrant and in the NFL Overall evaluation compared with th e values observed in control eyes. PERGs showed a significant (P < 0.01) de lay in N35, P50 and N95 implicit times, and reduction in N35-P50 and P50-N9 5 amplitudes. NFL Overall values were significantly correlated (P < 0.01) t o the PERG P50 and N95 implicit times and P50-N95 amplitude. No correlation s (P > 0.01) between NFL values and other PERG parameters (N35 implicit tim e, N35-P50 amplitude) were found. Conclusions: Our results suggest that in AD patients, there is a reduction of NFL thickness evaluated in vivo by OCT and this morphological abnormalit y is related to a retinal dysfunction as revealed by abnormal PERG response s. (C) 2001 Published by Elsevier Science Ireland Ltd.