Laser-induced primate glaucoma. II. Histopathology.

Area of Science:

• Ophthalmology
• Neuroscience
• Regenerative Medicine

Background:

• Glaucoma is a leading cause of irreversible blindness.
• Understanding the structural and axonal consequences of elevated intraocular pressure is crucial for developing effective treatments.
• Nonhuman primate models offer valuable insights into ocular disease pathogenesis.

Purpose of the Study:

• To investigate the effects of laser-induced sustained moderate intraocular pressure elevation on primate optic nerves.
• To quantify axonal loss in relation to optic disc cupping.
• To compare experimental findings with human glaucoma pathology.

Main Methods:

• Sustained, moderate intraocular pressure elevation induced via laser trabeculoplasty in 15 nonhuman primate eyes.
• Light and electron microscopy to assess structural changes in the trabecular meshwork and optic nerve head.
• Quantitative analysis of axonal count and optic disc cupping (cup-to-disc ratio).

Main Results:

• Laser treatment resulted in blunted trabecular beams and synechiae, causing sustained moderate pressure elevation.
• Observed optic nerve head damage included backward bowing of the lamina cribrosa, myelin sheath loss, and diffuse axonal loss.
• Eyes with moderate cupping (0.6-0.8) showed 38%-69% axonal loss; severe cupping (0.9-1.0) showed 10%-36% axonal loss.

Conclusions:

• Laser-induced ocular hypertension in primates causes significant structural damage to the optic nerve head and substantial axonal loss.
• The observed disc and axonal changes are comparable to those found in human glaucoma.
• This model provides a platform for studying glaucoma progression and testing therapeutic interventions.