Abstract
Purpose: :
To measure corneal endothelial cell density (ECD, cells/mm2) in New Zealand White (NZW) rabbits, cynomolgus monkeys, and beagle dogs using noncontact specular microscopy (NCSM). Additionally, in NZW rabbits, the purpose was to compare ECDs obtained with contact and noncontact specular microscopy, and to correlate these findings with aliziran red staining of postmortem specimens.
Methods: :
Fourteen NZW rabbits, 6 beagle dogs, and 10 cynomolgus monkeys had their ECD measured under general anesthesia with the TopCon SP3000 noncontact specular microscope (NCSM). Nine eyes from the 14 rabbits were also used to compare ECDs obtained with the NCSM, the Keeler-Konan contact specular microscope (CSM), and with Alizarin Red (AR) stained corneal buttons obtained postmortem.
Results: :
NCSM was relatively easy to operate (images were readily obtained with proper eye positioning) and gave results within a short period of time for all 3 laboratory species. However, a plano contact lens (X-Cel, 10-mm) placed on the cornea was required to obtain usable images in monkeys. Of the three species, a full-field image could be obtained only for the dog while only a partial-field images could be obtained from rabbits and monkeys (with contact lens). Overall, mean ECDs with NCSM were monkey 3100.6 ± 328.0 (N=20) > rabbit 2918.5 ± 177.4 (N=28) > dog 2645.8 ± 227.3 (N=12). Mean ECD using 3 different methods in rabbits, were AR (3554 ± 295.0) > CSM (3385.4 ± 230.8) > NCSM (2935.5 ± 183.9) with coefficient of variance (CV) at 0.086, 0.071, and 0.063, respectively. However, the means were within 20% of each other. Although the average ECD from NCSM was significantly different from CSM, there was a good linear correlation between the two readings of the same eyes resulting in a R2 of 0.800.
Conclusions: :
NCSM is applicable to all three laboratory animal species provided a plano contact lens is used in cynomolgus monkeys. The dog is the easiest species to examine as full-field images for analysis can be readily obtained. In rabbits, the three methods of determining ECDs are comparable to each other in terms of mean ECDs and CVs.
Keywords: cornea: endothelium • imaging/image analysis: non-clinical • ocular irritancy/toxicity testing