Dry eye disease in strabismus patients: Does eye deviation harm ocular surface?

Dry eye disease is a multifactorial disease which affects the ocular surface system, and determines ocular discomfort symptoms and visual disturbance. Various types of ocular surgery, including strabismus one, represents a recognized cause for iatrogenic dry eye. However, it is not uncommon that strabismus patients, even not undergone to surgery, report symptoms of ocular discomfort and dryness. Hypothesis We hypothesize that two possible mechanisms may determine dry eye in strabismus patients by setting up a specific vicious circle: firstly, the increased exposure of the area of the bulbar conjunctiva located on the opposite side compared to the deviation may cause the thinning of the tear film lipid layer, with increased tear film instability; secondly, the dysfunctional lubricity secondary to the altered relationship between the eyelids and the deviated globe may cause blinking-related microtrauma, and thus inflammation and tear hyperosmolarity. These two entry points into the vicious circle of dry eye may determine a cascade of detrimental mechanisms, leading to further damage of the tear film, thus closing the disease circle.Strabismus patients may be affected by signs and symptoms of dry eye syndrome. The increased exposure of the bulbar conjunctival area along with the dysfunctional lubricity between the eyelids and the deviated eye could be the main underlying pathophysiological mechanisms acting as entry points into the vicious circle of dry eye disease. If our hypothesis was to be confirmed, ocular surface parameters should be routinely investigated in strabismus patients, whilethe use of tear substitutes with the aim of moistening and nourishing the ocular surface could help in reducing dry eye signs and symptoms.