Characterization of scleral rupture of canine globes following compression via mechanical testing unit.

Purpose: To determine the load at failure of canine intact cadaveric eyes and to describe the anatomic location and length of the rupture following external compression.

Animals studied: Sixty-six canine cadaveric globes.

Procedures: Globes were subjected to an axial force impacting the cornea or equator using a commercially available mechanical testing unit. Following rupture, eyes were inspected to document the anatomical site and length of rupture.

Results: The mean ± SD force necessary to induce scleral rupture was 310 ± 120 N OD and 294 ± 113 N OS. Increasing body weight (OD p = .000015, OS p = .0074) as well as cranial-to-caudal (OD p = .000045, OS p = .0075) and medial-to-lateral (OD p = .00027, OS p = .0083) globe diameter were associated with a higher force necessary to induce rupture. The median (25%, 75%) length of the scleral rupture was 8.5 (7.0, 11.0) mm OS and 10 (7.0, 12.5) mm OD. The median location was 8.0 (5.0, 10.0) mm posterior to the limbus at the most cranial extent OS and 6.5 (3.3, 10.0) mm OD. Rupture orientation in relation to the limbus was perpendicular (n = 35), parallel (n = 13), or other (n = 16). Globe laterality (i.e., OD or OS), sex, and age did not have a significant influence on the force necessary to induce rupture (p > .05).

Conclusions: Following external compression, the canine globe frequently ruptures in a region approximating the equator extending 1 cm posteriorly, which may not be readily apparent on clinical examination.