Differential Effects on the Axonal Population in Human HIV Optic Nerves With and Without CMV Retinitis

Abstract

Purpose: : This is a prospective clinical pathological correlation of human HIV optic nerves with morphometric analysis of axonal counts, spectra, and axonal degeneration to compare optic nerves with and without CMV retinitis.

Methods: : Eight eyes from four HIV patients who had CMV retinitis on examination were studied. We included two sets of controls: four eyes were from three HIV patients with ophthalmological examination free of CMV retinitis, and four eyes were from four age matched healthy humans. Optic nerves were immersion fixed and embedded into epon blocks. Sections were cut at 1 micron on an ultramicrotome and stained with p–phenylene diamine (PPD) highlighting the myelin of each axon. Morphometric analysis was performed on light microscopic images captured via a Spot II digital camera with Zeiss Standard microscope. For each optic nerve, myelinated axonal counts were obtained in 32 sectors mapped across its area at a magnification of 1,250x.

Results: : Morphometric analysis of optic nerves from HIV patients affected by CMV retinitis, HIV positive patients without a history of CMV, and normal age matched controls revealed that the average number of axons for CMV affected HIV was 536,239 ± 237,771; HIV without CMV was 841,980 ± 103,677; and healthy human optic nerve controls was 1,032,750 ± 187,885(P value<0.05).Thus the optic nerves of CMV affected HIV patients had lower total axon counts compared to the optic nerves of HIV patients without CMV, and they were both less in total axon counts compared to the healthy optic nerves.

Conclusions: : Previous studies have shown that chronic infection with HIV can result in optic nerve axonal degeneration and visual field loss. This data reveals that HIV infection results in the loss of optic nerve axons, and CMV retinitis is associated with greater axonal degeneration. Further studies associating location of the axonal degeneration and retinal injury will help establish the site of CMV induced injury

Keywords: neuro-ophthalmology: optic nerve • AIDS/HIV • cytomegalovirus