# Ocular Motility Abnormalities in Ehlers-Danlos Syndrome: An Observational Study
## 1 Introduction
Conjunctival abnormalities observed in EDS are severe conjunctivchalasis, recurrent subconjunctival hemorrhages and conjunctival irritation with chemosis and foreign body sensation [7]. Orbital and ocular adnexa alterations such as blepharochalasis, palpebral ptosis, floppy eyelid, ectropion, hypertelorism, epicanthal folds, orbital pain and periorbital hemorrhages or swelling have been described [8; 9; 10]. Moreover, in EDS, tear film instability and deficiency, blue sclera, myopia and degenerative myopia have been reported, oftentimes associated with vitreous-retinal degenerations and abnormalities due to scleral thinning and bulging in consequence of abnormal collagen deposition. High myopia can lead to the development of myopic staphyloma, choroidal thinning, retinal atrophy and lacquer cracks [11; 12]. Strabismus was reported in this clinical condition, mostly due to craniofacial bone asymmetry with orbital misalignment, and to abnormal collagen deposition in the extraocular muscles. Ocular imbalance due to orbital discrepancy can also cause diplopia, amblyopia and stereopsis reduction [7; 13; 14]. A higher incidence of open angle glaucoma associated with altered development of the aqueous outflow tract has been reported. This complication is mostly detected in vEDS, because collagen type III is a fundamental component of the juxtacanicular meshwork and Schlemms canal [15]. Regarding retinal involvement, this condition is characterized by vessel fragility and malformation that may lead to vitreous hemorrhages. In particular, vEDS is linked to a higher incidence of rheematogenous retinal detachment and angioid streak formation [16]. Moreover, EDS patients suffering from cardiovascular and valvular diseases are more likely to develop retinal ischemic perivascular lesions, recognizable with ocular coherence tomography [17]. Lens involvement occurs less frequently compared to other heritable connective tissue disorders, particularly Marfan Syndrome. Ectopia lentits and dislocation have rarely been described [18; 19]. Interestingly, a higher incidence of small lens opacities has been found among young EDS patients [12]. Furthermore, in patients with important scleral thinning, cases of spontaneous globe rupture have been described. A secondary cause of vision loss can be linked to systemic and cerebrovascular complications, such as cervical artery dissection or aneurysms, which can determine ischemic/hemorrhagic brain injury. These events can manifest with visual symptoms such as nystagmus, visual field loss, visual acuity reduction, diplopia and ocular motility disorders. Carotid cavernous fistula has also been described in EDS patients, potentially responsible for relative afferent pupillary defects, episcleral vein congestion, pulsating exophthalmos and retinal thromboembolism [7]. The most recent EDS classification includes the brittle cornea syndrome. This pathology has an autosomal recessive inheritance and patients present mostly ocular signs. Pathognomonic characteristics of this syndrome are a thin cornea associated with an elevated risk of developing keratoglobbus or keratoconus in early life. This condition can cause corneal rupture, perforation and infections as consequences of mild injuries in young patients. Progressive corneal thinning may result in corneal opacities and scarring, potentially vision-threatening. Central corneal thickness is often <400 \(\upmu\)m. These patients are prone to high myopia due to an elevated ocular axial length, associated with blue sclera. In these cases, patients can also be subjected to retinal complications such as retinal detachment or secondary glaucoma. Additionally, this pathology presents a systemic involvement with deafness, hypercompliant tympan membrane, hip dysplasia, scoliosis, arachodactylly, joint hypermobility, finger contractures and hyper-extensible and fragile skin [3; 7; 20]. Moreover, in BCS patients, altered ECM protein expression in [PERSON]'s membrane has been demonstrated.