Extraocular Anatomic Relationships of Muscle Insertions in the Rhesus Monkey

Abstract

Abstract: : Purpose: To identify important extraocular anatomic relationships of muscle insertions in the rhesus monkey eye. Methods: Ten Rhesus macaque eyes preserved in 10% formalin were dissected to expose the insertion of extraocular muscles. Specific anatomic relations of the pertinent muscle insertions, and the relationship to the optic nerve and fovea were measured. Results: The center of the fovea (F) lies between the optic nerve (ON) and the posterior-superior border of the inferior oblique insertion (IO). The distance (in millimeters ± standard deviation) from ON to F in rhesus is 2.6±0.2. The distance from the F to the IO is 0.5±0.4. The distance from the ON to the posterior-inferior border of the IO is 2.8±0.3. The horizontal axial plane (H) of the eye (defined by the long posterior ciliary artery), to the IO is 0.5±0.4. The IO insertion forms an arc (apex superior) just inferior to H with an anterior to posterior cord insertion width of 7.7±0.3. The IO’s angle of insertion (θ; H to the line generated by the IO insertion) is 25-30°. The distance from H to F is 0.4±0.3 in the rhesus eye. Conclusions: Precise topographic measurements of extraocular muscles and fovea provide landmarks for designing juxtascleral drug delivery targeting the macular area. Rhesus macaque is a reasonable animal model for investigation, but is limited by the proximal IO insertion relative to the fovea. .

Keywords: anatomy • animal model • extraocular muscles: structure