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Optic nerve head morphology of the Eastern gray squirrel, Sciurus carolinensis.
Lindsay A Kuester1, András M Komáromy, Dennis E Brooks
1Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32601, USA. Lindsay7@ufl.edu
Veterinary Ophthalmology
|April 20, 2004
Summary
The Eastern gray squirrel optic nerve head displays a unique horizontal elongation, differing from other mammals. This study provides the first detailed morphological description of this unusual structure.
Area of Science:
- Ophthalmology
- Comparative Anatomy
- Neuroscience
Background:
- The optic nerve head (ONH) morphology varies across mammalian species.
- Understanding species-specific ONH anatomy is crucial for comparative ophthalmology and neuroscience.
Purpose of the Study:
- To characterize the morphology of the Eastern gray squirrel optic nerve head.
- To compare squirrel ONH structure with that of other mammalian species.
Main Methods:
- Histochemical techniques (hematoxylin and eosin, Gomori's trichrome stain) and light microscopy.
- Field emission scanning electron microscopy for surface evaluation.
- Analysis of optic nerve axon bundle diameter, lamina cribrosa dimensions, and pore size.
Main Results:
- The Eastern gray squirrel ONH is horizontally elongated anteriorly, becoming more rounded post-exit.
- Lamina cribrosa dimensions: 363 µm (D-V) x 3.60 mm (N-T); thickness: 125 µm (A-P).
- Mean laminar pore size: 45 ± 12 µm; collagen present in the lamina cribrosa.
Conclusions:
- This study presents the first detailed morphological description of the Eastern gray squirrel optic nerve head.
- The ONH exhibits an unusual, dramatic horizontal elongation among mammals, with its functional significance yet to be determined.
- Extracellular matrix composition, indicated by collagen presence, is similar to other species.