Increased vascular permeability in disc swelling produced by ocular hypotony

Area of Science:

• Ophthalmology
• Neuroscience
• Vascular Biology

Background:

• Optic disc swelling, a critical clinical sign, can lead to vision loss.
• Understanding the underlying mechanisms of optic disc swelling and associated vascular changes is crucial for effective treatment.

Purpose of the Study:

• To investigate the vascular permeability changes in monkey eyes with experimentally induced chronic hypotony and optic disc swelling.
• To identify the primary source of extravascular fluid leakage in the optic nerve head.

Main Methods:

• Chronic hypotony and optic disc swelling were induced in monkey eyes via ciliary body freezing.
• Horseradish peroxidase (HRP) was used as a tracer to assess vascular integrity and detect extravascular leakage.
• HRP distribution was examined in various layers of the optic nerve head and surrounding tissues.

Main Results:

• Extravascular HRP infiltration was observed in multiple optic nerve head regions, including the lamina retinalis, lamina choroidalis, lamina scleralis, and retrolaminar nerve head.
• HRP was present in perivascular connective tissue and interaxonal spaces in the anterior lamina retinalis.
• The choriocapillaris was identified as the major source of extravascular HRP leakage into the optic nerve head.

Conclusions:

• Ciliary body freezing effectively models chronic hypotony and optic disc swelling.
• Vascular leakage in the optic nerve head during swelling originates mainly from the choriocapillaris.
• Perineural connective tissues play a significant role in the transport of leaked fluid within the optic nerve head.