Morphometric, immunohistochemical and ultrastructural examination of age-related structural alterations in optic nerve.

Age related optic nerve changes were evaluated in newborn (4 days old), prepubertal (5 weeks old), pubertal (7 weeks old), young (3 months old), adult (1 year old), and elder (2 years old) Wistar Albino rats. Optic nerves of animals of different age groups were analyzed immunohistochemically, electron microscopically and morphometrically. To determine significant morphometric data, numeric image analysis and statistical analysis were applied to all morphological results. In light of the data we obtained, while a morphometrically increase was observed in the diameter of optic nerve with growing age, changed axon numbers among the age groups were found to be statistically insignificant. In our immunohistochemical assessments, GFAP involvement was more specific with growing age, while NGF involvement was at membrane level in the newborn and was both at cellular and axonal levels parallel to growing age. In electron microscopic examinations, it was determined that myelin sheath was degenerated with aging and that these areas were filled with connective tissue. Consequently, it was concluded that one reasons of loss of vision that appeared with growing age resulted parallel to occurrence of further degenerative changes in optic nerve.