Anterior collateral circulation in the primate eye.

Area of Science:

• Ophthalmology
• Vascular Anatomy
• Corrosion Casting Microscopy

Background:

• Understanding collateral arterial blood flow to the anterior uvea is crucial for ophthalmic surgery.
• Previous knowledge on the specific anatomical basis of these collateral pathways is limited.

Purpose of the Study:

• To determine the anatomical basis of collateral arterial blood flow to the anterior uvea in primates.
• To identify and characterize the arterial anastomoses contributing to ocular vascular supply.

Main Methods:

• Sequential microdissection of primate ocular lumenal methyl methacrylate corrosion castings.
• Scanning electron microscopy was utilized to visualize the microvasculature.
• Detailed examination of arterial connections at the episclera, ciliary muscle, and iris root.

Main Results:

• Three main sites of collateral anastomoses were identified: the episcleral circle, the intramuscular circle, and the major arterial circle at the iris root.
• The intramuscular circle, formed by anterior ciliary and long posterior ciliary arteries, is the most extensive arterial ring.
• The major arterial circle at the iris root was found to be the most discontinuous of the observed collateral systems.

Conclusions:

• A multilevel collateral arterial system supplies the anterior uvea in primates.
• This extensive vascular network, particularly the intramuscular and episcleral circles, likely provides significant redundancy.
• The identified collateral pathways probably account for the low incidence of anterior segment ischemia following extraocular muscle surgeries.