Dry eye occurs when insufficient tears are produced or when the tears are of poor quality and the tear film does not function efficiently. Dry eye is also known as keratoconjunctivitis sicca or dry eye disease (DED).
Dry eye is common, studies estimate that up to 30% of people may experience it at some point in their life. It is more common in people over 60 - particularly women. Dry eye is not normally serious, there is no cure but most people can be kept comfortable using eye drops. In extreme cases dry eye can damage the eye and vision.
Symptoms of dry eye
- itchy or scratchy sensations in or around the eyes
- dryness, grittiness, stinging or soreness in the eyes that worsens through the day
- red eyes
- watery eyes, particularly when exposed to wind
- ocassional blurred vision and sensitivity to normal light
The Tear Film
The tear film has three layers which protect the surface of the eye, helping to create a smooth optical surface so vision stays crisp, clear and undistorted.
LIPID LAYER is composed of oils secreated by the meibomian glands. This is
the outermost layer of the tear film covering the aqueous components and providing
a hydrophobic barrier which modulates tear evaporation and retains moisture.
The lipid layer also protects the eye surface from contamination.
AQUEOUS LAYER is produced by
the lacrymal gland it is the central component of the tear film
and accounts for about 98% of tear volume. It consists mainly of
water but also contains other substances such as proteins, which
nourish the eye and electrolytes. This layer also washes away
irritants, keeping the eye healthy. It helps maintain optimum vision
by promoting spreading of the tear film across the cornea.
