# Ocular Motility Abnormalities in Ehlers-Danlos Syndrome: An Observational Study
## 4 Discussion
In detail, considering the diagnostic gaze position in the right lateroversion, the left MR had severe hypofunction in 19.5% and the right LR had moderate-mild hyperfunction in 26.8% of cases. On the other hand, in the left lateroversion, moderate-mild hypofunction was observed in the right MR in 29% and hyperfunction of the same degree in the left LR in 28.4% of cases. Considering the diagnostic gaze position up and to the right, we found moderate-mild hypofunction in the right SR in 24.4%, with contralateral synergistic muscle hyperfunction (left IO) in 19.5% of cases. The last gaze position in which the OM examination revealed deficits was up and to the left, where the left SR showed moderate-mild hypofunction in 36.8% and the right IO showed moderate-mild hyperfunction in 34.2% of cases. The two horizontal gaze positions to the right and left were associated with the presence of eye pain and diplopia. The presence of diplopia shows how oculomotor alteration appeared after the plastic period (0-6 years) as a consequence of the EDS progression. These orthoptic alterations suggest that the ligamentous laxity observed in EDS tends to involve the extraocular muscles. Our findings suggest that ligamentous laxity and muscular fiber alterations can in fact affect the ocular district, determining functional changes over the years. Ophthalmological and orthoptic evaluation should be considered as part of the regular diagnostic assessment in this pathology. In our cohort, only a minority of patients presenting ocular motility disorders reported diplopia. These data suggest that an important part of ocular muscular dysfunction remains subclinical and underdiagnosed. An early diagnosis of this muscular involvement might be crucial in these patients to monitor the evolution of the disease over time. Moreover, the ocular muscular district offers the possibility of an easy clinical evaluation and can mirror the condition of the systemic muscular apparatus. Furthermore, EDS children during the plastic period should be closely checked, because the development of subclinical strabismus can represent an important cause of amblyopia. In children, the occurrence of subtle forms of strabismus is not associated with the onset of double vision, but can lead to silent sight suppression. [PERSON] et al. studied the structures of the fibrils of the dermal collagen and the fibrils of the extraocular muscles and the conjunctivae of both eyes of a child affected by EDS. They observed that in the reticular dermis, 48% of fibrils presented a normal diameter, 23% were enlarged and 29% were thinner than normal. In the extraocular muscle, they found that 77% of fibrils were of normal size, 14.5% of larger size and 8.5% of smaller size. In the conjunctivae, 73% of the fibrils were of normal size, 22% were enlarged and 5% were smaller. In healthy controls, no small fibrils were found in the extraocular muscles [14]. To the best of our knowledge, this is the first study that analyzes specifically the extraocular muscle abnormalities in EDS through a complete and accurate orthoptic assessment. Furthermore, the previous studies that described OM alterations in EDS had by far a smaller sample compared to ours. [PERSON] et al. reported OM disorders in 15 (71.4%) of 21 patients affected by EDS, with convergence insufficiency in 13 of them [22]. [PERSON] et al. reported, among 467 patients with confirmed EDS, 17 cases that underwent strabismus correction surgeries, out of which 14 (82.4%) underwent surgery before receiving their EDS diagnosis [13]. Other authors reported strabismus in EDS patients in combination with particular craniofacial features such as down-slanting palpebral fissures, palatine alterations, microretrognathia or protruding jaw and crowded teeth, contributing to congenital contractures and malocclusion [23; 24]. It can be hypothesized that bone craniofacial alterations, malocclusion and frequent orthopedic spine issues, leading to incorrect posture, might represent an additional risk factor for the development of strabismus [25; 26].