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D.A. Samuelson, A. Travers, P.A. Lewis, J.H. Young; Corneal Angiogenesis in the Florida Manatee . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4805.
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Purpose: This study is a continued investigation of corneal angiogenesis of the Florida manatee (Trichechus manatus latirostris). We have consistently found the presence of blood vessels within the corneas and their anterior epithelia of every animal that has been examined. In all specimens, no signs of infection or injury were present. In order to determine the amount of angiogenesis that has occurred in these individuals and observe possible vascular patterns within the anterior stroma and adjacent epithelium, that may or may not result in visual hindrance, numerous corneas were assessed histologically and by three–dimensional (3–D) reconstruction. Methods: 26 eyes from 22 manatees including fetus, preserved in 10% formalin, were provided by the Florida Marine Research Institute (FMRI) in St. Petersburg, FL along with additional information, including gender, size, location and time when the animal was found. Corneal specimens were measured and notched for orientation and were serially sectioned having used a frontal approach. Sections were stained with Masson’s trichrome and 3–D reconstructions of the vasculature where performed, all at 25X and 3 at 200X, the latter having been divided into dorsal, ventral, medial and lateral quadrants. Vessels were morphometrically evaluated for percent volume of total tissue. Results: Blood vessels were found in all corneas, having varied in location and to a lesser extent in shape and size even between corneas of the same individual. A network of vessels was observed in both corneas of the fetus. Vasculature at 200X was similar to that at 25X in that the vessels did not form repeating patterns and appeared randomly distributed in the examined region. The vascular patterns at 200X occupied more volume, 0.1–5.3% vs 0.1–1.2%, and were smaller in average diameter, 27 um vs. 84 um. Additionally, vessels could be observed frequently penetrating the anterior epithelium from the stroma with the higher magnification reconstructions. The level of detailed vascularization could not be detected at 25X. Conclusions: In the absence of edema, inflammation, or any other abnormalities and the presence of blood vessels in all specimens including the fetus, corneal vascularization in the Florida manatee may be a developmental process. The greater amount of vessels detected at the highest magnification was due to the ability to visualize and trace small vessels. The size and density of the small vessels were most likely too small to interfere with light transmission and are most likely not affecting manatees’ ability to survive in their different aquatic environments.
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