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Density of corneal endothelial cells, corneal thickness, and corneal diameters in normal eyes of llamas and alpacas

Stacy E. AndrewDepartment of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0126 .

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A. Michelle WillisDepartment of Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.
Present address is Rowley Memorial Animal Hospital, 171 Union St, Springfield, MA 01105.

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David E. AndersonDepartment of Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.

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Abstract

Objective—To determine density of corneal endothelial cells, corneal thickness, and corneal diameters in normal eyes of llamas and alpacas.

Animals—36 llamas and 20 alpacas.

Procedure—Both eyes were examined in each camelid. Noncontact specular microscopy was used to determine density of corneal endothelial cells. Corneal thickness was measured, using ultrasonographic pachymetry. Vertical and horizontal corneal diameters were measured, using Jameson calipers.

Results—Values did not differ significantly between the right and left eyes from the same camelid. There was no significant effect of sex on density of corneal endothelial cells or corneal thickness in either species. Mean density of endothelial cells was 2,669 cells/mm2 in llamas and 2,275 cells/mm2 in alpacas. Density of endothelial cells decreased with age in llamas. Polymegathism was observed frequently in both species. Mean corneal thickness was 608 µm for llamas and 595 µm for alpacas. Corneal thickness and density of endothelial cells were negatively correlated in llamas. Older (> 36 months old) llamas had significantly larger horizontal and vertical corneal diameters than younger llamas, and older alpacas had a significantly larger vertical corneal diameter than younger alpacas.

Conclusions and Clinical Relevance—Density of corneal endothelial cells is only slightly lower in camelids than other domestic species. Density of endothelial cells decreases with age in llamas. Age or sex does not significantly affect corneal thickness in normal eyes of llamas and alpacas. Specular microscopy is useful for determining density of corneal endothelial cells in normal eyes of camelids. (Am J Vet Res 2002;63:326–329)

Abstract

Objective—To determine density of corneal endothelial cells, corneal thickness, and corneal diameters in normal eyes of llamas and alpacas.

Animals—36 llamas and 20 alpacas.

Procedure—Both eyes were examined in each camelid. Noncontact specular microscopy was used to determine density of corneal endothelial cells. Corneal thickness was measured, using ultrasonographic pachymetry. Vertical and horizontal corneal diameters were measured, using Jameson calipers.

Results—Values did not differ significantly between the right and left eyes from the same camelid. There was no significant effect of sex on density of corneal endothelial cells or corneal thickness in either species. Mean density of endothelial cells was 2,669 cells/mm2 in llamas and 2,275 cells/mm2 in alpacas. Density of endothelial cells decreased with age in llamas. Polymegathism was observed frequently in both species. Mean corneal thickness was 608 µm for llamas and 595 µm for alpacas. Corneal thickness and density of endothelial cells were negatively correlated in llamas. Older (> 36 months old) llamas had significantly larger horizontal and vertical corneal diameters than younger llamas, and older alpacas had a significantly larger vertical corneal diameter than younger alpacas.

Conclusions and Clinical Relevance—Density of corneal endothelial cells is only slightly lower in camelids than other domestic species. Density of endothelial cells decreases with age in llamas. Age or sex does not significantly affect corneal thickness in normal eyes of llamas and alpacas. Specular microscopy is useful for determining density of corneal endothelial cells in normal eyes of camelids. (Am J Vet Res 2002;63:326–329)