The causes for the “dry eye“ – allegedly more than 60 percent of the office workers suffer from it – are manifold. On one hand the production of tears decreases with age, on the other hand there are external factors promoting the drying out such as for example smoking. In addition there are chronic diseases like diabetes, rheumatism and inflammatory vessel diseases where the symptom appears frequently. And drugs as well might affect the production of tears, e. g. Thiazid-diuretics, beta-blockers, tetra- and tricyclic antidepressants, estrogens and neuroleptics. Other potential causes might be the ozone and fumes in addition to working on the screen in rooms with low humidity which promotes an increased evaporation of the tear film. But there is no proof for the assumption mentioned time and again, that nutrition might have something to do with the disease.
Not enough attention paid to: the Meibom-gland
It increasingly becomes clear that not only the lacrimal glands but also the Meibom-glands have a significant function during the development and the course of the “dry eye”. This large sebaceous gland named after the German anatomist Heinrich Meibom produces the outer lipid phase of the tear film and thus are necessary to avoid a too high evaporation of the tear fluid and to preserve the stability of the tear film. Function disorders of the Meibom-glands are one of the major causes for wetting disorders of the eye since they lead to an insufficient lipid layer. Supposedly more than three-quarters of the patients with “dry eyes” suffer from disorders of the lipid phase of the tear film and in two thirds of those patients this is a result of a dysfunction of the Meibom-glands.
Unfortunately the dysfunction of the Meibom-glands (also called blepharitis posterior) is not paid enough attention. Mostly it occurs as an obstructive disorder caused mainly by an increased cornification and/or changes of the secretion. Age has a large influence on the function of the Meibom-glands. The average number of active glands decreases between the age of twenty and eighty by 50%. According to recent studies, wearing contact lenses is also associated with a decrease of active gland numbers – depending on how long they are worn but independent from the material the lenses are made of.
Androgens good, estrogens bad
Many research results point in this direction: A lack of androgens like it shows during menopause, in older years and during anti-androgenic therapy or also with testicular feminization, leads to a dysfunction of glands, because androgens control the development, differentiation and lipid production of the sebaceous glands in the entire body. Primarily they work at the epithelia acinar cells of the sebaceous glands where they – among others – lead to an increased transcription of certain genes and produce proteins necessary for lipid synthesis and –secretion. In contrast, an anti-androgenic therapy inhibits activity and secretion of the gland.
While androgens rather stimulate the function of the Meibom-glands, estrogens have a negative effect – similar to the tear gland, although type and magnitude of the estrogenic effect on the tear gland are not quite clear yet and still are discussed controversially. Contrary to the androgen influence, research results point to the fact that a hormone replacement therapy leads to a Meibom-gland dysfunction and a “dry eye”. From the point of view of Dr. Frank Schirra at the hospital for ophthalmology of the university hospital Saarland and his colleagues “this estrogen influence first of all is based on a suppression of the Meibom-glands”. As a result the size, activity and lipid production of the sebaceous glands decrease.
Thus estrogens had been used for many years to suppress sebum production. Since estrogens antagonize the androgenic effect in the sebum they were – according to Schirra – considered the “major therapeutic agent for reduction of androgenic effects in sebum”. The ant-androgenic effect depends on the dose and can be revoked with physiological amounts of androgens. Androgens also reduce the number of estrogenic binding sites in sebaceous glands. Thus it is comprehensible that estrogens lead to a Meibom-gland dysfunction and a “dry eye” in women during the menopause since they already lack androgens.
The Meibom-Therapy: Swabs, drops, tetracyclines
But how does the therapy look like for the “dry eye” caused by a dysfunction of the Meibom-gland? It has proven to go by a tuned step-by-step plan depending on severity code and symptoms. Surgical interventions are hardly ever necessary.
1. Eyelid hygiene
Eyelid hygiene is recommended as a basic treatment and has proven itself for most patients. They should put moist, warm compresses or swabs on the closed eyelids twice a day for about 5 minutes and then remove incrustations from the edge of the eyelid.
2. Tear film replacement
Also tear replacement solutions are helpful. For high drop frequency it is recommended to use solutions free of preservatives in order not to further damage the surface epithelia. It can be of advantage if those replacement solutions contain lipids in various pharmaceutical forms (drops, gel, spray).
3. Improving the secretion quality
For serious forms of the obstructive dysfunction, a long-term therapy with systemic tetracyclines has proven itself. Those are taken in a dose below the effective antibiotic quantity over a period of several weeks, or perhaps even months. Tetracyclines inhibit the lipases which are produced by the increased commensal bacterial flora of the eyelid and turn the composition of the Meibom-lipids to the negative. In addition they inhibit the activity of tissue destroying matrix metalloproteinases as well as the genesis of inflammatory cytokines and thus potential inflammatory processes which might occur with a dysfunction of the glands.
4. Punctum Plugs
If the ”dry eye“ is solely the result of a disorder of the aqueous layer of the tear film, an atrophy or closure of the punctum plugs might help.