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R. J. McCulloh, G. P. Holley, P. E. Miller, J. M. Miller, H. F. Edelhauser, G. Leatherberry, K. B. Luetkehoelter, B. J. Christian, C. J. Murphy, T. T. Lam; Pachymetry in New Zealand White Rabbits, Beagle Dogs, and Cynomolgus Monkeys. Invest. Ophthalmol. Vis. Sci. 2008;49(13):645. doi: https://doi.org/.
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To compare pachymetric measurements obtained with an ultrasonic pachymeter, noncontact specular miscroscope, and a contact specular microscope in New Zealand White (NZW) rabbits, beagle dogs, and cynomolgus monkeys and to determine the variation between observers with ultrasonic pachymetry.
Central corneal thickness was measured in 14 NZW rabbits, 14 beagle dogs, and 10 cynomolgus monkeys using an AccuPach V ultrasonic pachymeter (PM), a Topcon SP-3000 noncontact specular microscope (NCSM), and a Keeler-Konan SP-1 contact specular microscope (CSM). To determine the variability between operators of the ultrasonic pachymeter, three measurements of each eye were taken by three different individuals for each of the same 6 dogs.
Pachymetry Measurements (microns) a: average thickness with the use of an X-Cel, 10.0 mm diameter (no power) contact lens for monkeysb: coefficient of variationAn X-Cel, 10.0 mm diameter (no power) contact lens was needed for the NCSM imaging for the monkeys. Within each species PM gave consistently the highest values in dogs and rabbits and a higher value than CSM in monkeys. Comparing the average corneal thickness obtained with the three methods (excluding the monkey NCSM measurements); dogs exhibited the largest variation while rabbits were the least variable. All three methods exhibit similar variations in the CV. The average CVs for three readings with 12 eyes (dogs) for the three observers showed minimal variations (1.34%, 0.82%, and 1.20% respectively).
The need for the use of a contact lens in the monkeys for NCSM results in artificially high pachymetry readings. Consistent with the literature values, the dogs have the thickest corneas, followed by the monkeys, with NZW rabbits having the thinnest. All three methods are viable for measuring corneal thickness in dogs and rabbits but NCSM is not suitable for use in the cynomologus monkey. PM is a robust system with minimal inter-observer differences.
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