To the Editor.
—A major problem with the measurement of large muscle recessions is the accurate measurement of the amount of recession on the globe. The currently popular technique for the management of congenital esotropia is to measure the amount of recession of the medial rectus from the limbus,1 thus avoiding an error inherent in the variable insertion of the medial rectus in infants.2 Such recession measurements are usually about 10 to 11 mm. Measurements made with standard squint calipers of 10 mm or more are inaccurate, because they measure the chord, not the arc of curvature of the globe.3,4The previously reported curved ruler was designed for use in large recessions, because it measured along the curvature of the globe. That ruler has now been modified for easier use by incorporating a swivel joint at the junction of the 70-mm friction handle with the ruler (Figure).
Scott WE, Gole GA. A Modified Curved Ruler for Strabismus Surgery. Arch Ophthalmol. 1985;103(5):625. doi:10.1001/archopht.1985.01050050015002