A study on structure of human horizontal rectus insertion by anterior segment optical coherence tomography

Abstract

Background The measurement of the extraocular muscle is critical for the diagnosis of extraocular muscle diseases,but conventional medical imaging techniques present some shortcomings because of the contact pattern.The anterior segment optical coherence tomography (OCT) is thought to be an in vivo noninvasive optical diagnostic imaging method.Objective This clinical study attempted to seek an available approach to the evaluation of the anatomic structure of human horizontal rectus insertion with Visante OCT.Methods One hundred and fourteen eyes of 58 subjects were included in this study and were divided into the low refractive power group (≤-3.00 D) with 43 eyes,moderate refractive power group(＞-3.00 D-≤-6.00 D) with 49 eyes and high refractive power group(＞-6.00 D) with 22 eyes.The horizontal rectus insertion distance to the scleral spur and its thickness were measured by Visante OCT.The correlation of the refractive power with the rectus insertion distance or thickness was analyzed.Written informed consent was obtained from each subject before medial assessment.Results The average distance from the scleral spur to the lateral and medial rectus insertion were (5.23±0.50)mm and (3.81±0.46)mm respectively.The average thickness of the lateral and medial rectus insertions were (0.39±0.06)mm and (0.39±0.06)mm respectively,showing no significant differences in comparison with those of ultrasound biomicroscopy (P=0.338,P=0.759).The lateral and medial rectus insertion distances were (5.25±0.45)mm and (3.74±0.53)mm in the low refractive power the group,(5.22±0.60)mm and (3.81±0.42)mm in the moderate group and (5.20±0.35)mm and (3.90±0.42)mm in the high refractive power group,presenting inconsiderable difference among these three groups(lateral rectus: χ2=0.054,P=0.974;medial rectus: F=0.508,P=0.604).The thickness of the lateral and medial rectus insertions were (0.41±0.06)mm and (0.40±0.06)mm in the low refractive power group,(0.40±0.07)mm and (0.37±0.07)mm in the moderate refractive power group,(0.36±0.05)mm and (0.39±0.05)mm in the high refractive power group with a significant difference among lateral rectus (F=4.922,P=0.009) but not medial rectus (F=2.152,P=0.125).The lateral rectus insertions thickness in the high refractive power group was thinner than that in low refractive power group (P＜0.05).A positive correlation was found between refractive power and the thickness of lateral or medial rectus insertions (r=0.284,P＜0.01).Conclusion Visante OCT is a uscful way in measuring the distance and thickness of the extraocular muscles.Lateral rectus insertions thickness tends to be thinner with the worsening of myopia,which is obvious in high myopia. Key words: Extraocular muscle; Rectus insertion; Anterior segment optical coherence tomography; Refractive power