AS-OCT to Assess Extraocular Muscle Insertion
Ana C. Almeida, MD; Ana R. Azevedo, MD; Fabio L. Gaudencio; Rita D. Gama, MD
Hospital Beatriz Angelo
Introduction: Anterior Segment Optical Coherence Tomography (AS-OCT) is a fast, noninvasive technique for high-resolution imaging that can be performed in the outpatient setting without use of sedation or anesthesia on cooperative patients.
Recent studies have found that AS-OCT can image horizontal extraocular muscle insertion distance with good level of agreement between AS-OCT imaging and intraoperative measurement with a caliper and excellent inter- and intraexaminer reproducibility.||We aim to demonstrate the usefulness AS-OCT to assess the insertion of extraocular rectus muscles in a case of penetrating trauma to the eye.
Methods: Seventy-five year old female patient observed in the emergency after penetrating trauma to the right eye (OD). Upon observation, visual acuity was 0.8 on her right eye and 0.63 on the left; pupils were brisk with no afferent pupillary defect and color vision was maintained. Ocular movements were full with no apparent restriction or diplopia.
A penetrating vertical wound on the nasal conjunctiva OD was observed on slit lamp and subsequently sutured. No significant findings were identified on fundoscopy. The following day the patient reported diplopia and a 45Diopters right exotropia was found with limited adduction OD.
Results: AS-OCT identified right medial rectus insertion and magnetic resonance imaging (MRI) revealed an increase in the size of the right medial rectus with hyperintensity on STIR probably related to muscle edema.
Discussion: Several techniques can be used to image the extraocular muscles, such as MRI, computed tomography and ultrasound biomicroscopy. However these methods are costly and not always available.
Conclusion: AS-OCT is a noninvasive, accessible technique for high-resolution imaging that can be used not only for the preoperative study of strabismus patients but also to identify extraocular rectus muscle insertion in cases of trauma and suspected muscle slippage.
References: Park KA, et al. Reproducibility of horizontal extraocular muscle insertion distance in anterior segment optical coherence tomography and the effect of head position. J AAPOS. 2014 Feb;18(1):15-20
De-Pablo-Gómez-de-Liaño L, et al. Spectral domain optical coherence tomography to assess the insertion of extraocular rectus muscles. J AAPOS. 2016 Jun;20(3):201-5
Ngo CS, et al. The accuracy of anterior segment optical coherence tomography (AS-OCT) in localizing extraocular rectus muscles insertions. J AAPOS. 2015 Jun;19(3):233-6