Causes of Dry Eyes and How to Investigate Them?

Most people suffer from the syndrome of dry itchy eyes at some time or another in their lives. However the dry eyes may in fact be a reflection of something more systemic such as vitamin deficiency. In may in fact be associated with dry skin, dry hair and brittle nails.

Symptoms

•  Irritation of eyes
• Burning
• Grittiness
• Difficulty in focusing or reading for long times
• Excessive tearing

Causes and pathophysiology of Dry eyes

The function of the tear film of the eyes actually depends on three layers of fluid

• Mucus layer which also has anti-microbial property
• Slightly alkaline watery layer
•  Oily layer that prevents rapid evaporation of the tears
• In addition to these three layers blinking of the eyes is important and a normal blinking cycle has to be maintained .Normally a person blinks 10-12 blinks per minute. Blinking less than this leads to dry tired eyes
• Disruption in the production of tears is known as ‘aqueous tear-deficient dry eye’. This occurs when the lacrimal glands do not produce enough tear fluid.
• ‘Evaporative dry eye’ occurs when there is a dysfunction of the membobian gland, which may result from meibomian gland inflammation.
• LASIK surgery and Inflammation of the eyelids can also cause dry eyes
• Systemic diseases like –Diabetes ,rheumatoid arthritis ,Hypothyroidism , Sjogrens disease can also cause dry eyes
• Age: The symptoms of dry eyes are increased as the increase in the age
• Hormonal changes also cause variation in the production of the tears. When the oestrogen levels are high the tear production is low and the symptoms of dry eyes are more . Similarly during pregnancy the symptoms of dry eyes are more
• Post-menopause the meimbobian gland function is reduced and the symptoms of dry eyes also increases
• Smoking, drinking a lot of coffee, wearing contact lenses, being in air-conditioning or heated places with low humidity also increases the possibility of dry eyes
• Vitamin D deficiency is also associated with abnormal film formation and with dry eyes
• Antibiotics such as Antidepressants ,Antihistamines ,Appetite suppressants, Birth control pills, Blood pressure medications, and Diuretics also cause disruption of the normal tear formation

Investigations in the diagnosis of dry eyes

•  The first step that needs to be taken is to visit the ophthalmologist to get the eyes checked. The doctor will do a number of tests to diagnose the problem and to diagnose which layers of  the tear film are causing the problem. Some of the tests are

Schirmer tear test

Tear film break-up time (10 seconds)

Conjunctival impression cytology

Rose Bengal staining pattern

Tear Osmolarity

Tear protein levels (lactoferrin and lysozyme)

Presence of corneal filaments

Evaluation of debris in tear film

Other than these tests some of the laboratory tests that can rule out other systemic causes of the disease are

1. Complete blood count to rule out systemic infection and anaemia
2. Blood sugar fasting and post 75 gms glucose to rule out diabetes
3. HbA1c to rule out diabetes
4. Thyroid function tests including T3,T4 and TSH to rule out any thyroid abnormalities
5. Thyroid antibodies to rule out thyroiditis
6. Auto immune profile to rule out the systemic conditions like SLE , Rheumatoid arthritis , and Sjogrens syndrome – these tests include ANA, dsDNA