A quantitative analysis of optic nerve axons in elderly control subjects and patients with Alzheimer's disease.
OBJECTIVE
To study the density and cross-sectional area of axons in the optic nerve in elderly control subjects and in cases of Alzheimer's disease (AD) using an image analysis system.


METHODS
Sections of optic nerves from control and AD patients were stained with toluidine blue to reveal axon profiles.


RESULTS
The density of axons was reduced in both the center and peripheral portions of the optic nerve in AD compared with control patients. Analysis of axons with different cross-sectional areas suggested a specific loss of the smaller sized axons in AD, i.e., those with areas less that 1.99 microm2. An analysis of axons >11 microm2 in cross-sectional area suggested no specific loss of the larger axons in this group of patients.


CONCLUSIONS
The data suggest that image analysis provides an accurate and reproducible method of quantifying axons in the optic nerve. In addition, the data suggest that axons are lost throughout the optic nerve with a specific loss of the smaller-sized axons. Loss of the smaller axons may explain the deficits in color vision observed in a significant proportion of patients with AD.
Syed
Anila B
AB
Vision Sciences, Aston University, Birmingham B4 7ET, United Kingdom.
Armstrong
Richard A
RA
Smith
Christopher U M
CU
D000368:Aged; D000544:Alzheimer Disease / Q000473:pathology*; D001369:Axons; D002452:Cell Count; D006801:Humans; D007091:Image Processing, Computer-Assisted; D009900:Optic Nerve / Q000166:cytology* / Q000473:pathology*; D015203:Reproducibility of Results