Stereological Evaluation of the Optic Nerve Volume in Alzheimer Disease

Optic nerve damage occurs in Alzheimer disease (AD) related to the loss of the retinal ganglion cells that contribute fibers to the optic nerve and reduction of the density of axons of the optic nerve. In this study the authors evaluated optic nerve volume changes and the relation between the cerebrum and optic nerve volumes in AD patients. The study evaluated the volumetric measurements of optic nerve by applying the stereological method on magnetic resonance images (MRI). It included age-matched study and control groups, which were composed of 20 patients with probable AD and 20 healthy subjects, respectively. MRIs were analyzed by using the point-counting approach holding Cavalieri principle. There were statistically significant optic nerve volume reduction and cerebral atrophy in AD patients when compared with the age-matched control subjects (P = 0.013, P < 0.001, respectively) but there was no correlation between the optic nerve volume and cerebral volume in AD patients (r = 0.326, P = 0.160). There was a difference between optic nerve volumes of AD and control subjects. The stereological evaluation of optic nerve volume is of importance for both clinicians and anatomists and it can provide valuable information in the evaluation of morphological changes of AD in vivo.