What is Dry Eye?

chillibreeze writer — Dr Vinay Agarwal

Keratoconjunctivitis sicca (KCS) or dry eye disease is one of the most common complaints seen by ophthalmic specialists. In the current scenario of an ageing population and increasing environmental factors it is becoming even more prevalent. Dry eye is not a trivial complaint. The symptoms cause significant discomfort and substantially reduce the sufferer’s quality of life.

Dry Eye in Clinical Practice
May 2007
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The dry eye disease

Normal sight is dependent on a moist ocular surface. This moisture is maintained by a complex interplay of various factors: sufficient quantity of tears, normal composition of the tear film, normal lid closure, and regular blinking of the lids. The tear film and the ocular surface form a stable system, which can lose its equilibrium through numerous disturbing factors.

Our understanding of the causes and pathology of the dry eye has improved significantly in the recent years. We now know that the dry eye is a multifactor disease that exhibits primary and secondary changes in the ocular surface. Also, we now understand the tear film and the ocular surface are interdependent on each other.

Definition of dry eye disease

The modern definition of dry eye disease is based on the concept of the three layers of the tear film devised by Holly and Lemp.i Also, secondary factors such as pathological changes to the eyelids, cornea, or conjunctiva, can themselves disturb the normal function of the tear film. Neurotransmitters, hormones, and immunological processes play an important role in the regulation of tear production by the lacrimal gland. Various environmental factors like contact lenses, pollution, working at video display terminals can affect the tear film.

This multiplicity of causes and effects makes a global definition difficult. However, the following definition has been proposed: Dry eye is a disease of the ocular surface attributable to different disturbances of the natural function and protective mechanism of the external eye, leading to an unstable tear film during the open eye state. Recent studies have shown that immunologic changes play a role in the pathogenesis of the dry eye even in post infectious and age-related conditions.ii In addition to the term dry eye, which is established worldwide, the term ocular surface and tear disorder has been suggested.iii

Prevalence

How widespread is dry eye disease in the community?
Is it a disease seen in the general population that it needs the attention of the general ophthalmologists?

Data on the epidemiology of dry eye is sparse even in the western literature. Adding to the confusion is the difference in the definition and inclusion criteria in different studies.

Available data suggests that it is a significant problem in the older age group. In a community study in Sweden the prevalence rate of 15% was found in the general population aged 55-72 years. This was done on the basis of symptoms of dry eye disease and positive findings on Schirmer’s test, tear film break-up time, or rose Bengal staining.iv A recent Japanese study revealed a 17% rate of positive symptoms of dry eye.v Most other studies reveal a prevalence rate of between 11 and 17%. These studies found that symptoms of dry eye disease are more frequent in individuals above 50 years of age, however, they found no association of symptoms with sex or age.

The prevalence of dry eye disease in the community may increase in the future as the proportion of individuals over the age of 60 years of age grows. It would thus be fair to state that the individual ophthalmologist has to acquire the knowledge to both manage and educate the patients about the condition in the best possible way.

iHolly FJ, Lemp MA: Tear physiology and dry eyes. Surv Ophthalmol 22: 69-87, 1977

iiStern ME, Buerman RW, Fox RE, et al: The pathology of dry eye: the interaction between the ocular surface and lacrimal glands. Cornea 17:584-9, 1998

iiiTseng SC, Tsubota K: Important concepts for treating ocular surface and tear disorders. Am J Ophthalmol 124: 825-35, 1997

ivJacobson Lt, Axell TE, Hansen BU, et al: Dry eyes of mouth- an epidemiological study in Swedish adults, with special reference to primary Sjorgrens syndrome. J Autoimmun 2: 521-7, 1989

vHickichi T, Yoshida A, Fukui Y, et al: Prevlence of dry eye in Japanese Eye centers. Graefes Arch Clin Exp Ophthlamol 233: 555-8; 1995

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—About our writer:

Dr. Vinay Agarwal is a Mumbai based cornea surgery specialist.

What is Dry Eye?

chillibreeze writer — Dr Vinay Agarwal

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