Ocular Biometry in Guinea Pigs Using Computed Tomography

OBJECTIVE: To present a consistent and reproducible method for measuring ocular structures and to establish reference ranges for ocular biometry in the adult domestic guinea pig (Cavia porcellus) without clinical or imaging evidence of ophthalmic disease, using a 64-slice multidetector computed tomography (CT) scanner. PROCEDURE: This retrospective, observational anatomical study analyzed 60 eyes from 30 guinea pigs with no history of or clinical or imaging signs of ocular disease. Head CT scans were used to measure globe length, width, and height via 3D multiplanar reconstruction. Additional measurements included lens width and length, anteroposterior lengths of the anterior and vitreous chambers, and attenuation values of the lens and vitreous. These parameters were evaluated in relation to age, sex, and weight. RESULTS: Reference values were established, with globe width being the greatest dimension (11.25 ± 1.61 mm), followed by height (10.56 ± 1.43 mm) and length (10.49 ± 1.44 mm). Increased body weight correlated significantly with greater length of the anterior chamber (p = 0.045). Older age was significantly associated with increased lens width (p = 0.044). Intra-observer reliability was excellent and interobserver reliability was good to excellent. CONCLUSIONS: Computed tomography is a reliable tool for assessing ocular biometry in guinea pigs. The established reference values can aid in detecting ocular conditions that alter globe dimensions in guinea pigs over 18 months of age.