Echographic study of extraocular muscle thickness in children and adults

Background Echobiometric evaluation of extraocular muscles in normal subjec ts has been performed previously, but only in adults. We determined extraoc ular muscle thickness in normal subjects in three age groups. Methods Extraocular muscle thickness was studied in 75 normal subjects divi ded into three age groups (5-10, 11-15 and 2837 years) using a Biovision B- scan-S instrument in standardized A-mode (frequency, 10 MHz; biometry resol ution, 0.15 mm; depth, 40-60 mm; points on X axis, 512; levels on Y axis, 2 56). All measurements were performed by the same operator and repeated five times. The reproducibility of the technique was determined using the coeff icient of variation. The one-way ANOVA test was used to compare the three g roups, and the two-tailed unpaired t-test was used to compare subjects aged 5-10 years and those aged 11-15 years, and subjects aged 11-15 years with those aged 28-37 years. Results The technique showed good reproducibility. In subjects 5-10 years o ld, the coefficient of variation was 8%; in subjects 11-15 years and 28-37 years old, it was 5%. Increased muscle thickness was observed with age (p < 0.001). A statistically significant difference between the medial and infe rior recti muscles in subjects 11-15 years and 28-37 years old was found (p < 0.001). Conclusions The increased thickness of all recti muscles may be influenced by growth (primarily during puberty), and the variations in thickness of th e extraocular muscles may be attributable to near-vision stimulus of the in ferior and medial recti muscles.