The eye is an amazing camera, and few man made cameras even begin to compare with the incredible human eye. Like the front surface of a photographic camera, the front surface of the eye also must have an exquisitely smooth, “polished” surface for crisp and clear images. The tear film is the critical front surface of the eye for high quality images. In addition to its optical function, the tear film serves an important nutrient role for maintaining the health of the cornea. While there are many other star players in the eye’s visual pathway (cornea, lens, retina, optic nerve, visual pathways in the brain), the tear film is an absolutely critical support player with a vital function often taken for granted… until it doesn’t function optimally.
Dry eye is the term used when the tear film is inadequate. Normally, the surface of the eye is constantly covered with a uniform layer of constantly produced tears replenished by normal and automatic frequent blinking. When the tear film dries, vision immediately becomes blurry as this is equivalent to roughing the normal smooth front surface of a camera lens. Patients with dry eye or ocular surface disease complain of tearing, burning, stinging, redness, irritation, blurred vision, inability to wear contacts comfortably, and general foreign body sensation.
Often patients remark, “But my eyes are not dry. They run water all the time.” In fact, excess tearing, known as epiphora, is a common symptom of dry eye. When the corneal surface dries, the eye responds with reflex tearing to try and reestablish adequate lubrication. This is demonstrated by the tearing that sometimes results in daily activities when excess wind dries the cornea (for example, when walking out into a windy day, riding in a boat, driving with the windows down or with air vents blowing straight into one’s face, etc.) Unfortunately, this reflex tearing does not sufficiently compensate for a constantly inadequate tear film.
Dry eye is more common with advancing age, but can occur at any age and in both sexes. Causes besides aging include hormonal change, auto-immune disease, medications, poor blinking and past ocular injuries among others.
The tear film consists of three layers:
- an inner mucous layer which helps the tears to adhere to the surface of the eye
- a middle lubricating water layer secreted by the lacrimal gland
- an outer oil layer, secreted by oil glands on the lid margin, which stabilizes the tear film and slows evaporation
Treatments for dry eye may be specifically designed depending on which layers are primarily deficient. Therapy usually begins with over-the-counter artificial tears, but may also include oral supplements (fish oil, omega-3s), prescription drops to increase tear production (Restasis), punctal plugs to slow drainage of the natural tears produced, antibiotics and/or hygiene regimens to treat lid margin/oil (Meibomian) gland dysfunction, or even surgery if eyelid malpositions are a factor.
Live Oak Ophthalmology uses a step-wise approach to treat ocular surface disease. Call today at 910-251-8200 for an appointment.