Thickness of the lamina cribrosa and peripapillary sclera in Rhesus monkeys with nonglaucomatous or glaucomatous optic neuropathy

Abstract

Purpose: To measure the thickness of the lamina cribrosa and peripapillary sclera in monkeys with a nonglaucomatous optic nerve damage and to compare that with those of monkeys with glaucomatous optic neuropathy.

Methods: The study included 22 monkey eyes (Macaca mulatta) which had undergone a temporary experimental central retinal artery occlusion (CRAO) and seven monkey eyes in which experimental glaucoma was unilaterally produced. We measured histomorphometrically the thickness of the lamina cribrosa and peripapillary sclera.

Results: The lamina cribrosa was significantly thicker in the CRAO group than in the glaucoma group (central region: 212 ± 46 μm versus 167 ± 17 μm; p = 0.009). The thickness of the peripapillary sclera at the optic disc border (253 ± 39 μm versus 192 ± 21 μm; p = 0.001) and outside of the optic nerve meninges (408 ± 70 μm versus 314 ± 64 μm; p = 0.006) was significantly greater in the CRAO group.

Conclusions: In monkey eyes with a temporary CRAO as a model for nonglaucomatous optic nerve damage, the lamina cribrosa is significantly thicker than in monkey eyes with experimental glaucomatous optic nerve damage. It may suggest that the loss of optic nerve fibres might not be the reason for the thinning of the lamina cribrosa in eyes with advanced glaucoma. The thinner peripapillary sclera in the glaucomatous eyes may suggest that the monkey sclera is more vulnerable to stretching with increased intraocular pressure than the human eye for which no glaucoma-related lengthening of the eyeball and thinning of the peripapillary sclera have been observed.