No more tears?
DIPTI A GOGATE
That’s actually a cause for concern since you may be suffering from dry eyes.
Crying helps: Dry eye tends to affect women more often.
Normal vision requires a moist healthy ocular surface. A sufficient quantity of tears, a normal composition of the tear film, normal lid closure, and regular blinking are among the prerequisites to maintain a healthy ocular surface.
The eye surface is always kept wet by tears, which are produced by tear glands. Tears also lubricate blink for comfort and allow lens movement and wash debris. Tears supply oxygen and nutrients to the cornea and the enzymes in the tears prevent infection. Dryness could be either due to deficient tear formation or loss of tears from the ocular surface through evaporation.
How it happens
Dry eye is actually a group of conditions with certain common elements. In the majority of cases, the primary feature is one or more symptoms of dryness, irritation, foreign body sensation, burning and stinging, and photophobia (sensitivity to light), as well as variants of these. These symptoms may be present either with or without objective signs of either tear insufficiency or eye surface damage.
Often people are working indoors in air conditioned offices, commute long distance in cars or travel by air planes. All these are low humidity environments, which aggravate tear evaporation rate.
Also people now tend to consume more caffeine through coffee or other beverages. Consumption of OTC medications like anti-histaminic, anti depressants and oral contraceptives has also increased. These can cause dryness in the eye. There are some inflammation conditions of the eye lid margins, which can cause dryness.
The eye becomes dry either because enough tears are not being produced (Aqueous Tear Deficiency or ATD), which is caused by a lack of secretion from the lachrymal gland or because there is an abnormally high rate of evaporation of tears (Evaporative Tear Deficiency or ETD), characterised by the lipid layer of the tear film evaporating too rapidly. This is most commonly caused by an infection of the glands in the upper lid.
Causes of dry eye may be divided into internal and external causes. Examples of internal causes include systemic disease such as Sjogren’s syndrome, congenital and or autoimmune disease that affects the lachrymal glands, corneal surface disease leading to tear film disruption, and any problems with the lids or the blinking mechanism.
External causes would include side effects of systemic or ocular medication, contact lens, ocular surgery (particularly refractive surgeries like LASIK), seasonal allergy, and environmental factors such as dry, windy conditions, excessive air conditioning, or decreased blinking during computer use.
Most dry eye patients tend to be older and tend to be female. Severe cases may be associated with some auto-immune disease, of which Sjogren’s syndrome is the most well known example. In the elderly, many other conditions may also produce symptoms of dry eye, either directly or as a side-effect of systemic medication. Various reports have indicated that medication for blood pressure, allergies, hormone replacement, and even preserved ocular medication for glaucoma have a significant damaging effect on the lachrymal system and the ocular surface.
Medications, which can cause tear deficiency and associated dryness in the mouth, include oral diuretics, oral antihistamines prescribed for sedation or control of nausea. Drugs with anti-cholinergic action prescribed for gastro-intestinal upset or travel sickness and antidepressants for insomnia, also cause dry eye.
Eye doctors often ask questions about sensitivity to windy or smoky conditions, air conditioning, and specific visual tasks such as computer work. It has been established that computer users not only blink less frequently than those engaged in other tasks, but also more of their ocular surface is exposed due to the partial up-gaze nature of computer terminal work as compared with other near tasks such as reading.
Tear Film stability depends on many factors including the correct quantity and quality of various components of the tears. Decrease in superficial lipid layer of the tear film, results in increased evaporation of the underlying layers which finally results in dryness on the surface of the eye. Even in normal patients, a small of amount of tear fluid is lost passively by evaporation. Tear evaporation is found to be lowest on awakening.
The dryness in the eye due to contact lens is also referred as contact lens induced Dry eye (CLIDE). The symptoms and clinical findings of patient with CLIDE are different from that of a true dry eye patient. Contact lens wearers frequently complain of sensations of eye discomfort, blurry vision and dryness associated with wearing their lenses.
The longer the same pair of contact lens is worn, the greater the number of surface deposits and compromised surface qualities that de-stabilizes the tear film, again contributing to dryness in the eye. Contact lens users feel very comfortable when they wear disposable contact lenses which have special property to retain moisture within and around the lenses.
The writer is an Associate Professor in Optometry based in Pune.
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