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Neuroretinal basis of visual impairment in the very elderly
John Vincent Lovasik1, Marie-Jeanne Kergoat, Lisette Justino
1School of Optometry, University of Montreal, CP 6128, Succursale Centre-Ville, H3C 3J7, Montreal, Quebec, Canada.
Purpose:
To evaluate the effects of senescence on the morphology and neural function of the retinal nerve fiber layer (NFL) in the very elderly.
Methods:
The NFL thickness about the optic nerve head and the neural activity of its neurons were quantified by scanning laser polarimetry and pattern reversal electroretinograms (PERGs), respectively, in a group of young healthy volunteers ( n=27; mean ocular refraction -1.59+/-0.45 D) between 20 and 31 years of age, and a group of healthy elderly volunteers ( n=27; mean ocular refraction +0.11+/-0.40 D) between 75 and 88 years of age.
Results:
Relative to the young group, the elderly subjects showed an overall thinning of the NFL of some 22.5%; however, the superior quadrant was attenuated by about 30.0%. The function of the ganglion cell axons in the NFL as reflected by the N95 component of the PERG was reduced by about 28.8% in the elderly compared with the young.
Conclusion:
Aging caused a thinning of the NFL, particularly in the superior quadrant. The evoked potentials from the neurons comprising this layer were attenuated by near equivalent amount. These findings have clinical implications in the differential diagnosis of normal aging versus disease-related alterations in the structure and function of the NFL in the very elderly sector of our population.