Distance of muscle insertions in the corneal limbus

Abstract

During the last 3 years (1983 to 1985) accurate measurements of the distance between rectus muscle insertions and the corneal limbus were made on strabismus patients during surgery. After dissection of a muscle the distance from the posterior limbus (gray-white line) to the insertion line of the muscle was measured with calipers both at the midpoint and at each end of the insertion. A limbal incision was employed without exception. Statistical analysis was performed on a personal computer, using the Lotus 1-2-3 program. In contrast to the traditionally popular values determined by Fuchs, which are already over 100 years old (in parentheses), we found the following mean values: medial rectus insertion 4.5 mm (5.5), in 675 eyes operated on; inferior rectus insertion 5.67 mm (6.5), in 22 eyes operated on; lateral rectus insertion 6.20 mm (6.9), in 493 eyes operated on; and superior rectus insertion 6.64 (7.7), in 21 eyes operated on. The reasons for these differences are discussed. Because of the large size of the samples for the horizontal muscles it was possible to narrow down the confidence limits for the true mean values considerably; however, it is clear from the great differences between the lowest and highest values observed that the distance from the muscle insertions to the corneal limbus varies widely.