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Apr 2, 2008

Big girls don’t cry

Dry eye disease is a common disorder affecting mainly females, especially those in the older age group.

FIFTY years ago, Henrik Sjogren described a disease characterised by autoimmune damage to the lacrimal gland tissues (tear glands), decreased tear secretion and ocular surface disease and called it keratoconjunctivitis sicca.

Today, dry eye is defined as ocular surface disease that results from any condition or circumstance that decrease tear secretion or increase tear film evaporation.

An International Task Force of dry eye disease experts propose that the term “dry eye disease” be replaced with “ dysfunctional tear syndrome” to reflect current understanding of the condition’s pathophysiology.

Research in recent years has shown that the disease involves progressive, self-reinforcing alterations of the tear film composition that promote inflammation. Although these inflammatory changes of the ocular surface are usually not apparent in routine clinical examination, they are now understood to underlie dry eye disease.

In dry eye disease, patients feel that their eyes are tired, blurred and have difficulty in keeping them open.
Tear production in humans is divided into two parts:

# The basic secretors (goblet cells, accessory lacrimal glands and oil glands)

# The reflex secretor (controlled mainly by the main lacrimal gland) which is modulated by sensory reflex arcs and emotion.

Dry eye disease is common condition affecting mainly those above 40 years of age. Risk factors include older age, female sex, postmenopausal status and previous lasik (laser-in-situ keratomileusis) surgery for refractive errors.

Common symptoms include eye discomfort and irritation such as grittiness, scratchiness, foreign body sensation and burning sensation.

Patients feel that their eyes are tired, blurred and have difficulty in keeping them open. Very often, there is paradoxical tearing even when their eyes are dry due to reflex tearing from the main lacrimal gland.

Symptoms usually get worst as the day progresses and are aggravated by the presence of wind, smoke, air-conditioning or wearing contact lenses.

Prolonged use of video display terminals and excessive reading or watching television can worsen the condition.

Diagnostic tests

The usefulness of a diagnostic test is determined in part by its sensitivity and specificity.

Shirmer’s test makes use of a filter paper inverted into the inferior fornix of the eye, at the lateral one third of the lower lid margin. This test has been shown to be quite inaccurate in diagnosing dry eye, with a high rate of false positive and false negative results.

Rose Bengal test makes use of a vital dye to stain parts of the cornea and conjunctival epithelium. This test is particularly useful in the diagnosis of keratoconjunctivitis sicca

Dry eye disease encompasses diverse etiologies and varies in severity. Furthermore, correlations between symptoms, clinical signs and diagnostic test results are variable, rendering the diagnosis and treatment of this condition challenging and frustrating.

Treatment of dry eye disease

An individual’s quality of life can be significantly affected by this condition, reducing one’s zeal in life and even contributing to depression. Traditional treatment options available are often palliative in nature.

It has been commonly taught that the initial treatment of dry eye involves the use of artificial tears. However, artificial tears do not contain the balanced mixture of proteins, electrolytes, nutrients and growth factors that a person’s own tears contain. These nutrients and proteins are important for preventing infection and keeping the cornea nourished.

Moreover, due to the toxicity of the preservatives used and the short retention time of the drops, the use of artificial tears is frequently a frustrating experience.

More recently, newer and more viscous drops which are preservative-free are available in the market. Lubricating gels are also available as these can last longer than drops.

Punctal occlusion is therapeutic for those with dry eye disorders characterised by elevated tear film osmolarity.

Punctal occlusion can be reversible with the use of silicone punctual plugs or irreversible by cauterisation of the inferior punctum. With punctual occlusion, non-preserved artificial tears would be more effective. (The entrance to the nasolacrimal drainage channel is called the lacrimal punctum, a small opening in each of our eyelids. In punctal occlusion, a small plug is inserted in one or more puncta to slow the drainage of tears from your eyes. By slowing the rate of tear drainage, more tears stay on your eyes, relieving dry eye symptoms.)

A key recommendation in the treatment of dry eye is the application of topical anti-inflammatory agents including corticosteroids, cyclosporine A and doxycycline.

These should be used even if ocular surface inflammation is not clinically apparent as research in recent years has shown that the disease involves progressive changes in the tear film composition that promote inflammation.

Furthermore, in dry eye associated with postmenopausal status, the hormonal support that normally maintains the ocular surface in a non-inflammatory state is compromised.

The effective use of topical steroids, in short durations, to reduce the severity of the dry eye attest to the inflammatory nature of the disease. However, long term application of steroids is not advisable due to its side effects like glaucoma and steroid induced cataracts.

Longer term topical cyclosporine A therapy has been shown to normalise the tear film composition early in the clinical course of the disease and may have the potential to slow, prevent or reverse the progression of dry eye disease.

Due to its safety profile in chronic use, topical cyclosporine A has been approved by the FDA for use in the therapy of dry eye. It results in the restoration of lacrimal gland function, resulting in increased tear production and restoration of the ocular surface.

In conclusion, dysfunctional tear syndrome or dry eye disease, is a common disorder affecting mainly females, especially in the older age group. Routine treatment using artificial tears is often palliative and unrewarding.

However, with the advent of topical anti-inflammatory agents, a definitive treatment of the disorder is now possible.

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