Physiological transpalpebral sonographic eye measurements from healthy adult horses

Background: Relevant ophthalmic lesions affecting vision occur in 5%–10% of all horses. Thus, knowledge of anatomy, physiology, clinical and imaging is essential for the discernment of a healthy and a pathological eye. Ultrasonography is an important diagnostic tool for ocular diseases, providing information on lesion site, extension and severity. In addition, it is possible to monitor the treatment efficiency and prognosis. Objectives: This study aimed to provide biometric data about the ocular globe structures of healthy horses in order to establish a normal ultrasonographic pattern. Methods: Ocular globes (n = 40) from 20 healthy horses were evaluated by transpalpebral B-mode ultrasonography, using an 11 MHz linear transducer. Results: The biometrics found in this study were: globe length: 37.78 ± 0.65 mm; anterior chamber: 5.01 ± 0.27 mm; vitreous chamber: 19.19 ± 0.54 mm; lens: 12.82 ± 0.93 mm; cornea: 0.88 ± 0.11 mm. Main limitations: The obtained results can be more safely applied to medium-sized horses (350 ± 43 kg). Conclusions: This study provides normal ocular biometrics that can be used as a reference for the diagnosis of ocular diseases, especially when the lesions are bilateral and nontranslucent cornea hinder internal structures evaluation.