Hyunkyoo Kang1, Shin-Hyo Lee2, Chung-Sik Oh3, Hyun Jin Shin4,5, Andrew G Lee6,7,8,9,10,11,12,13. 1. Department of Mechatronics and Electronic Engineering, Konkuk University Glocal Campus, Chungju, Chungcheongbuk-do, Republic of Korea. 2. Department of Anatomy, Yonsei University College of Medicine, Seoul, Republic of Korea. 3. Department of Anesthesiology and Pain Medicine, Konkuk University Medical Center, Seoul, South Korea. 4. Department of Ophthalmology, Research Institute of Medical Science, Konkuk University Medical Center, Konkuk University School of Medicine, 120 Neungdong-ro, Gwangjin-gu, Seoul, 05030, Republic of Korea. shineye@kuh.ac.kr. 5. Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX, USA. shineye@kuh.ac.kr. 6. Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX, USA. 7. Department of Ophthalmology, Neurology, Neurosurgery, Weill Cornell Medicine, New York, NY, USA. 8. Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX, USA. 9. Department of Ophthalmology, UT MD Anderson Cancer Center, Houston, TX, USA. 10. Department of Ophthalmology, Texas A and M College of Medicine, College Station, TX, USA. 11. Department of Ophthalmology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA. 12. Department of Ophthalmology, Baylor College of Medicine and the Center for Space Medicine, Houston, TX, USA. 13. Department of Ophthalmology, University of Buffalo, Buffalo, NY, USA.
Abstract
PURPOSE: To evaluate the passive duction force (PDF) in extraocular muscles (EOMs) in patients with intermittent exotropia (IXT) using a quantitative tension-measuring device. METHODS: This prospective, case-control study enrolled 25 patients with IXT and 26 age- and sex-matched controls. PDF was measured under general anesthesia as the eyeball was rotated medially or laterally away from the direction of the force being tested. The preferred eye for fixation was determined using a cover-uncover test. RESULTS: The PDF in the IXT and control groups were 60.9 g and 52.1 g, respectively, for the lateral rectus (LR) (p = 0.046) and 53.0 g and 48.8 g for the medial rectus (MR) (p = 0.293). When the eyes were examined separately in the IXT group, the PDF of LR was larger in the nonpreferred eye for fixation than in the control group (p = 0.039), whereas there was no difference in the preferred eye for fixation (p = 0.216). Additionally, the relative PDF of LR in the nonpreferred eye compared to the ipsilateral PDF of MR was positively associated with the duration of manifest deviation (p = 0.042) and the average angle of the near and far deviations (p = 0.023). CONCLUSIONS: The PDF in the LR in patients with IXT in the nonpreferred eye for fixation was larger than normal and could increase with the duration of manifest deviation and the angle of deviation. Evaluating the PDF in EOMs could provide information that is useful for managing strabismus and understanding its pathophysiology.
PURPOSE: To evaluate the passive duction force (PDF) in extraocular muscles (EOMs) in patients with intermittent exotropia (IXT) using a quantitative tension-measuring device. METHODS: This prospective, case-control study enrolled 25 patients with IXT and 26 age- and sex-matched controls. PDF was measured under general anesthesia as the eyeball was rotated medially or laterally away from the direction of the force being tested. The preferred eye for fixation was determined using a cover-uncover test. RESULTS: The PDF in the IXT and control groups were 60.9 g and 52.1 g, respectively, for the lateral rectus (LR) (p = 0.046) and 53.0 g and 48.8 g for the medial rectus (MR) (p = 0.293). When the eyes were examined separately in the IXT group, the PDF of LR was larger in the nonpreferred eye for fixation than in the control group (p = 0.039), whereas there was no difference in the preferred eye for fixation (p = 0.216). Additionally, the relative PDF of LR in the nonpreferred eye compared to the ipsilateral PDF of MR was positively associated with the duration of manifest deviation (p = 0.042) and the average angle of the near and far deviations (p = 0.023). CONCLUSIONS: The PDF in the LR in patients with IXT in the nonpreferred eye for fixation was larger than normal and could increase with the duration of manifest deviation and the angle of deviation. Evaluating the PDF in EOMs could provide information that is useful for managing strabismus and understanding its pathophysiology.