Optic neuropathy induced by experimentally reduced cerebrospinal fluid pressure in monkeys

Abstract

Purpose: To examine the influence of experimentally reduced cerebrospinal fluid pressure (CSFP) on retinal nerve fiber layer (RNFL) thickness and neuroretinal rim area of the optic nerve head.

Methods: This experimental study included nine monkeys that underwent implantation of a lumbar-peritoneal cerebrospinal fluid (CSF) shunt. In the study group (n = 4 monkeys), the shunt was opened to achieve a CSF of approximately 40 mm H2O, while the shunt remained closed in the control group (n = 5 monkeys). At baseline and in monthly intervals thereafter, optical coherence tomographic and photographic images of the optic nerve head and RNFL were taken of all monkeys.

Results: Two out of four monkeys in the study group showed bilaterally a progressive reduction in RNFL thickness between 12% and 30%, reduction in neuroretinal rim area and volume, and increase in cup-to-disc area ratios. A third monkey developed a splinter-like disc hemorrhage in one eye. The fourth monkey in the study group did not develop morphologic changes during follow-up, nor did any monkey in the control group.

Conclusions: Experimental and chronic reduction in CSF in monkeys was associated with the development of an optic neuropathy in some monkeys.

Keywords: cerebrospinal fluid pressure; glaucoma; glaucomatous optic neuropathy; intraocular pressure; normal-pressure glaucoma; trans-lamina cribrosa pressure difference.