Abstract
Purpose :
The distances of the extraocular rectus muscle insertions from the limbus and corneal diameters are clinically relevant in surgical ophthalmology. It is widely accepted that the corneal diameters are about 11.7 x 10.6 mm and that the medial, inferior, lateral, and superior recti muscles on average insert 5.5, 6.5, 6.9, and 7.7mm, respectively, from the limbus. This descriptive cadaveric study investigates the measurements of the Spiral of Tillaux and corneal diameters.
Methods :
Thirty cadavers were included for a total of 60 eyes. For each eye, a lateral canthotomy and cantholysis followed by a peritomy were performed. Muscle hooks were used to isolate the rectus muscles. Corneal diameters and distances from the midpoint of recti muscle insertions to the limbus were measured using calipers (Fig. 1). Using mixed effects modeling, the mean distance from the limbus to each rectus muscle was found.
Results :
Of the 30 cadavers, 50% were female, with a mean age of 81.9 years. Table 1 reports the measurements from the limbus to the rectus muscle insertion (medial rectus = 5.28 mm, inferior rectus = 5.72 mm, lateral rectus = 6.40 mm, superior rectus = 6.78 mm). When compared to the historical benchmarks, nearly all of these measurements in this study were shorter (p < 0.01). No meaningful heterogeneity was identified across ages or by right and left eye (p > 0.05). Women tended towards approximately half a millimeter shorter measurements on average (limbus to rectus: t (45.35) = -1.91, p = 0.0624). Mean corneal diameters were found to be 11.7 mm horizontally and 10.7 mm vertically, and were not found to be significantly different from the expected values (p> 0.05).
Conclusions :
Nearly all measurements from the limbus to rectus muscle insertions demonstrated variations from the accepted Spiral of Tillaux measurements, particularly with females having shorter distances. However, we found that the recti muscles followed the same pattern to the historical Spiral of Tillaux measurements, with the medial rectus inserting most closely to the limbus and the inferior, lateral, and superior rectus inserting successively farther from the limbus. We found no significant differences in the expected corneal diameter measurements.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.