Background

Ocular biometry is essential for diagnosing eye diseases that alter globe dimensions, yet reference values for guinea pigs using computed tomography (CT) have not previously been established. Guinea pigs are commonly affected by ocular conditions such as cataracts, and CT imaging is increasingly used in veterinary practice. This study aimed to develop a standardized CT-based method and establish reference ranges for ocular structures in healthy adult guinea pigs.

Methods

This retrospective observational study analyzed CT scans from 30 adult guinea pigs (60 eyes) without clinical or imaging evidence of ocular disease. A 64-slice multidetector CT scanner was used, and multiplanar reconstruction enabled precise measurement of globe dimensions, lens size, anterior and vitreous chamber lengths, and tissue attenuation values. Associations with age, sex, and weight were assessed, along with inter- and intra-observer reliability.

Results

Reference values were established, with globe width being the largest dimension (~11.25 mm), followed by globe length and height (~10.5 mm each). The vitreous chamber was substantially longer than the anterior chamber. Strong correlations were observed between left and right eyes for all measurements. Lens width increased significantly with age, while anterior chamber length showed a positive association with body weight. No significant associations were found with sex. Measurement reliability was excellent overall, with slightly lower but still good agreement for smaller structures.

Limitations

Limitations included the retrospective design, absence of full ophthalmologic examinations, and lack of validation against histopathology or cadaveric measurements. CT resolution constraints and reliance on visual estimation may introduce measurement variability. Additionally, attenuation measurements may be affected by imaging artifacts, and findings are limited to adult guinea pigs (>19 months).

Conclusions

Computed tomography provides a reliable and reproducible method for assessing ocular biometry in guinea pigs. The reference ranges established in this study offer a valuable clinical tool for identifying ocular abnormalities and advancing diagnostic capabilities in exotic animal veterinary medicine.

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