Porcine sclera: thickness and surface area.

PURPOSE: To assess the thickness and surface area of porcine sclera. METHODS: One hundred twenty-eight porcine globes were sectioned from the center of the cornea to the region of the optic nerve. Photographs of the sectioned sclera including a millimeter scale were taken. Photographic slides were projected onto blank paper, and the scleral silhouette was traced. Perpendicular thickness measurements were taken at 1-mm intervals from the limbus to the optic nerve. The sclera of 18 porcine eyes were cut into small pieces, and the surface area was calculated with computerized digital tracing software. RESULTS: The scleral thickness near the corneal scleral limbus was 0.83 +/- 0.2, 0.91 +/- 0.17, and 1.12 +/- 0.23 mm in the small-, medium-, and large-sized pigs, respectively. Thickness decreased to minimum of 0.31 +/- 0.07, 0.35 +/- 0.1, and 0.43 +/- 0.16 mm at a distance of 5 mm from the limbus in the small- and medium-sized pigs and 6 mm in the large-sized pigs, respectively. The mean scleral surface area was 7.78 +/- 0.66, 9.66 +/- 0.75, and 11.92 +/- 1.57 cm(2) in the small-, medium-, and large-sized pigs, whereas the corneal surface area was 1.09 +/- 0.07, 1.15 +/- 0.09, and 1.40 +/- 0.19 cm(2), respectively. CONCLUSIONS: Porcine scleral thickness is very similar to human scleral thickness. The porcine model is an excellent model for studying transscleral drug delivery.