Abstract
PurposeThis study aimed to evaluate the shape of the extraocular muscles (EOMs) in normal subjects using the en-face images of anterior segment optical coherence tomography (AS-OCT). The EOM insertion and the direction of the muscle fibers were investigated.Subjects and methodsA total of 97 healthy normal subjects (194 eyes) at Okayama University Hospital (age, 47.1±21.5 years; range, 8–79 years) participated in the study. A series of 256 tomographic images of the rectus EOMs were captured using the C-scan function of the AS-OCT (CASIA2, TOMEY Co., Japan), and the images were converted to en-face images in multi-TIFF format. The anterior chamber angle to EOM insertion distance (AID) and the angle of the muscle fibers from the insertion site (angle of muscles) were measured from the images. The correlations of AID and angle of muscles with age and axial length were investigated and evaluated.ResultsAID and angle of muscles were significantly correlated with age or axial length in some EOMs. The AIDs of medial rectus (MR) (P = 0.000) and superior rectus (SR) (P = 0.005) shortened with age. The AIDs of MR (P = 0.001) and inferior rectus (IR) (P = 0.035) elongated with axial length, whereas lateral rectus (LR) (P = 0.013) shortened. The angles of MR (P = 0.001) and LR (P = 0.000) were found to have a more downward direction toward the posterior in older subjects.ConclusionEn-face images can be created by AS-OCT, and the shape of the EOMs in normal subjects using these image measurements was available. With the ability to assess the EOMs, AID and angle of muscles are expected give useful information for treating and diagnosing strabismus-related diseases.
Highlights
Recent advances in anterior segment optical coherence tomography (AS-OCT) have made it possible to visualize the cornea, anterior chamber, and iris and the extraocular muscles (EOMs) [1,2,3,4,5,6,7,8,9]
A series of 256 tomographic images of the rectus EOMs were captured using the C-scan function of the AS-OCT (CASIA2, TOMEY Co., Japan), and the images were converted to en-face images in multiTIFF format
angle to EOM insertion distance (AID) and angle of muscles were significantly correlated with age or axial length in some EOMs
Summary
Recent advances in anterior segment optical coherence tomography (AS-OCT) have made it possible to visualize the cornea, anterior chamber, and iris and the extraocular muscles (EOMs) [1,2,3,4,5,6,7,8,9]. These reports only involved the evaluation of tomographic images of the EOMs, and most of them were related to muscle insertion. The direction of muscle fibers from the insertion site of the EOM may be important for pathogenesis and diagnosis and may change with age and eye size, but no findings have been analyzed using AS-OCT
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