Tears keep the corneal surface moist and lubricated. They are produced by the tear glands and reach the eye surface through the tear ducts. Decrease in the production of tears or increased evaporation leads to dry eyes.
If untreated severe dry eyes may lead to ocular surface damage, ulceration of the cornea, infection, visual impairment and blindness. Thus, proper diagnosis of the cause of dry eyes and its timely treatment is very important.
Normally Tears form a continuous film on the corneal surface. Less tears resulting from increased evaporation or decreased production causes instability of the tear film which leads to dry patches on the corneal surface. Moreover, tears apart from water also contain salts. Decreased tear production and increased evaporation increases the salt content of the tears i.e. their osmolality which further pulls water from the corneal surface. This causes discomfort and abrasion on the surface of cornea further leading to inflammation. Decrease in the production of tears can occur due to many reasons:
Sjogren’s syndrome is an autoimmune disease where antibodies are made by the body against its various tissues. Inflammation occurs in the tear glands and salivary glands leading to decreased secretion from the glands resulting in symptoms of dry eyes and dry mouth (primary Sjogren’s syndrome). Sjogren’s syndrome may occur with other autoimmune diseases like rheumatoid arthritis, systemic lupus erythematosus, scleroderma, polymyositis (secondary Sjogren’s syndrome).
Other factors- presence of certain factors apart from Sjogren’s syndrome that lead to reduced production of tears are sarcoidosis, vitamin A deficiency, trachoma, trauma, previous eye surgery involving corneal incision, long term contact lens wear, working on the computer for long hours, past herpes infection, diabetes and aging.
Increased evaporation of the tears may occur due to environmental factors such as dry weather, wind, air pollution, use of hair dryer, being in air-conditioned environment.
Other factors that cause dry eyes include Inflammation of the eyelid as in the case of Blepharitis, Rosea and Meibomian gland dysfunction.
Dry eyes may occur as a side effect of taking certain medicines such as birth control pills and allergy medications.
Retraction of the upper eye lid due to thyroid disorder also causes dry eyes.
Patients suffering from dry eyes usually complain of sandy sensation as if something has fallen in the eye, discomfort in wearing lenses, eye irritation in air-conditioned place and in wind, tired eyes, redness, blurring of vision, and discomfort from glaring light. Sometimes, when there is eye irritation, it may lead to production of more tears also.
Diagnosis may involve one of these tests:
Although dry eyes can be diagnosed based on the symptoms, your doctor may perform certain simple tests to assess your condition.
Schirmer’s eye test-A very small filter paper strip is kept touching the lower eye lid for some specific time. Wetting value of less than 5mm of the filter paper strip in 5 minutes is considered as dry eyes.
Tear break up time
A strip of fluorescein will be applied to the lower eyelid and removed. Then, you will be told to blink your eyes three times and look front without blinking. The tear film formed is observed under slit lamp microscope and the breakup time of the film is recorded. Break up time of 10 seconds or less indicates dry eyes.
Another more accurate and patient friendly test measures tear break up time using tear scope. In this test, values of less than 15 seconds indicate dry eyes.
There is no cure for dry eyes. Depending upon whether the problem is temporary or lifelong the treatment strategy will be decided.
Two main arms of these strategies will involve either to replace the natural tears with artificial tears or to let the tears stay in the eye for long rather than being drained by the lacrimal duct into the nose.
Artificial tears-Natural tears contain water, electrolytes, lipids and proteins with functions of enzymes. No artificial tears can replace natural tears, they can just increase the volume of the tear film, only when they are in contact with the eye surface. Thus, hydrogels are added to the artificial tears to increase their viscosity so that they can stay in the eye for long. Artificial tears contain preservative to increase their shelf life. Tears with preservatives more gentle on the eye should be preferred. Some artificial tears also contain substances that confer additional surface healing and surface protective properties to them. Anti-inflammatory eye drops are also given. Topical corticosteroids are given as short-term pulse therapy for quick relief. (2-4 weeks) Corticosteroid drops cause cataract and glaucoma if given for long so Cyclosporin drops are given simultaneously. Cyclosporin drops require several weeks sometimes even 6 months for the clinical effect. To conserve tears the opening of the tear ducts are plugged with punctal plugs. Tear duct is there one in lower eyelid and another in the upper eye lid. One or both can be plugged. Temporary punctal plugs may be collagen or silicone based. Other treatment options include use of windless sun glasses that protect from wind dust and pollen by sealing the eye space from the outside environment much like swimming goggles.
Meibomian Gland Dysfunction results in changes in the lipids secreted by the gland which leads to increased. evaporation of the tears. It is treated by prescribing oral antibiotics, lipid containing eye drops and warm compresses to provide symptomatic relief.
Decreasing or avoiding the caffeine and alcohol and drinking more water helps. Omega-3 fatty acids rich food such as fish and flaxseed oil or oral supplements reduces dryness.
Environmental factors promoting dryness should be kept under control.
Humidifiers should be used in dry weather conditions to increase humidity in the room.
Avoid use of room heaters.
Give rest to eyes in between, when working for long on the computer. Prefer working on a laptop then the monitor. Since in laptop upper eye lid covers half of the eye while looking down at the laptop screen.
Avoid going in smoke and dust.