The change of the extraocular muscle insertion after a slanted recession in rabbit eyes

Purpose To evaluate the change of slanting degree after slanted recession using a rabbit model. Methods A prospective, controlled study was performed in ten eyes of five rabbits with anatomically normal eyes. These eyes were divided into two groups according to the amount of slanted recession. In right eyes, slanted superior recti (SR) muscle recession was performed with 6 mm of nasal margin and 2 mm of temporal margin (4-mm slanting group), and in fellow eyes, slanted SR muscle recession was performed with 6 mm and 4 mm, respectively (2-mm slanting group). We measured both margins of superior recti from insertion, and calculated the amount of anterior creeping movement of both margins at 30, 60, and 90 postoperative days, and also compared the change of slanting degree of the SR muscle between the two groups. Results Slanting degrees showed a gradual decrease in all rabbit eyes. In the 4-mm slanting group, each margin of anterior movement was 2.4.mm (nasal) and 0.9 mm (temporal) and slanting degrees decreased in 50 -7 5%. In the 2-mm slanting group, the margins of anterior movement were 2.9 mm and 1.8 mm respectively, and slanting degrees decreased in 25 ∼ 50%. The amount of slanting degree showed a greater decrease in the 4-mm group than in the 2-mm group at postoperative 3 months ( p = 0.045). Conclusion Both margins of extraocular muscle in slanted recession showed anterior movement at postoperative 3 months; therefore, the effectiveness of slanted recession might be decreased postoperatively.