Dry eye and causative factors

Among the possible causes of dry eye, we must differentiate between internal and external factors. Internal factors can be subdivided into the physiological and non-physiological factors and the external factors can also be divided in external with direct action and with indirect action. Let’s have a look at each of them.

1 –. Internal physiological factors.

Internal physiological factors include age and hormonal changes, especially in women. As age increases, the secretion of the lachrymal glands is reduced, which affects the aqueous portion of the tear, as well as that of the meibomian glands, which are located in the eyelids and secrete lipids (the fat needed to lubricate the ocular surface and to prevent the rapid evaporation of tears).

Hormonal changes are fundamentally related to menopause in women but can also occur in men, with the reduction of androgens that comes with age. The hormonal changes of menopause cause a deterioration of the tear and especially of the meibomian glands, resulting in gland atrophy and the reduction of lipids secretion to the lipid layer of the tear film.



2 -. Internal non physiological factors.

They relate to diseases that may indirectly affect the eyes. The most highlighted are those of rheumatic character (such as osteoarthritis, rheumatoid arthritis or Sjogren’s disease), autoimmune diseases (such as pemphigus, Crohn’s disease or ulcerative colitis), skin diseases (such as acne rosaceous), degenerative diseases (such as primary biliary cirrhosis or diabetes) and cancerous disorders. In all these cases the disturbance of the lachrymal gland, meibomian glands and the ocular surface occurs.

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.

4 -. Indirect external factors.

In this section, we refer to some drugs and other substances which can have a negative effect of the ocular tear-ocular surface complex if administrated from the outside. Antiallergic drugs, alcohol, chemotherapy and antidepressants stand out.

The subject of diet is worth being mentioned apart. We know that nutritional balance is essential for the overall health and in cases of dry eye, we have noticed that in most of these cases there is an imbalance in the levels of hydration, vitamins, trace elements and especially in the balance of omega-3 and omega-6 fatty acids. The predominance of saturated fats is found in the diet (omega 6) due to an excess of meat and pastries, compared to unsaturated fats, rich in omega 3 fatty acids, found in cold fish, olive oil and nuts. This imbalance increases the level of free radicals having a negative action on the lachrymal – ocular surface complex.

Factors causing dry eye

  • Age, older people have more risk of dry eye.
  • Sex, dry eye is more common in women.
  • Hormonal changes with decrease in estrogen, progesterone and        testosterone specially.
  • Unbalanced diet predominantly omega-6 fatty acids relative to omega-3        unsaturated fatty acids.
  • After chemotherapy or radiotherapy
  • Dermatological disorders such as acne rosacea
  • Patients with digestive tract disorders (ulcerative colitis or Crohn’s disease)
  • Important smoking and alcohol consumption
  • Treatment with antidepressants or antiallergy
  • Contact lens wearers
  • After eye surgery (cataract or refractive surgery)
  • Infiltration of botox in the periocular area
  • Treatment of glaucoma (eye drops and surgery)
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