3 -. Direct external factors.
This section ranges from excessive contact lens wear until air conditioners, fans, windy environments, excessive exposure to sunlight, ultraviolet radiation, smoke, snuff or toxic environments.
In some cases we have seen the presence of dry eye by affecting the eyelid margin and meibomian gland, due to changes in the microbial flora of this region or the presence of Demodex in the eyelashes follicles, which makes its viewing and treatment difficult.
It is important to consider the harmful action of the majority of drops, due to the preservatives used, plus we know they are toxic to the eye surface, especially drops for glaucoma treatment.
Refractive laser surgery is also one of the factors that can cause dry eye more frequently, especially in cases of hyperopia. We are currently seeing an increase in dry eye after facelift as in blepharoplasty or after injections of botox, if not correctly performed or when they are used too often, when blinking is altered, it is not complete and not a tear film efficient forms or is part of the ocular surface exposed to the action of air.
Radiation therapy can cause a deterioration of the lachrymal and meibomian glands and trophic impairment of the ocular surface, initiating or aggravating dry eye.