Dry eye affects millions of people worldwide and is a common problem leading patients to consult ophthalmologists. There are many causes of dry eye, which results ultimately from abnormalities of the tear film and/or ocular surface. The tear film is composed of three layers, the outermost lipid layer, the middle aqueous layer and the inner mucin layer. Each layer is being derived from a different part of the eye. Hence, any abnormalities of any layer will cause a defective tear film mechanism, as does any abnormality of the ocular surface (example, the cornea, eyelids).
As with any disease, an accurate diagnosis is important in determining appropriate treatment and resolving patients’ complaints. A thorough history and physical examination are essential in making a proper diagnosis. Laboratory evaluation can provide further information to support the diagnosis.
The symptoms are variable and range from burning and foreign body sensation to severe pain and irritation out of proportion to clinical signs. Symptoms are often made worse by smoke, wind, or prolonged use of the eyes. Paradoxical tearing may be present. This is similar to such insult like exposure to chopping onions, which also causes reflex tearing to the eyes. One may complain of ropy mucus, vision that fluctuates with blinking, and photophobia.
History may often disclose the cause of the dry eye. Most types of dry eye are more common in women, and postmenopausal women are more likely to have aqueous tear deficiency than premenopausal women. Contact lens wearers after many years of extended wear are made worse with air condition exposure. This is further precipitated when blinking is reduced with constant staring at the computer. Many commonly prescribed medications that are taken orally and topically can affect tear film and should be eliminated.
Ask about specific systemic complaints that might suggest an underlying systemic disorder associated with dry eyes, particularly autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosus, thyroid disease, sarcoidosis, graft-versus-host disease and lymphoma. Dry eyes have been associated with certain dermatologic diseases as well. Congenital condition may also be the cause in rarer cases. Irradiation, chemical burns, or mechanical trauma to the lacrimal gland produces hyposecretion as well. A history of factors leading to vitamin A deficiency must be elicited because this is a common cause of dry eye worldwide.
Thorough examination to evaluate the lid structure such as in growing eyelashes, inverted or outward turning, and irregularity of the lids must be evaluated. Previous history of stroke can also cause constant exposure of the eyes or failure to respond to sensation leading to severe dryness. Surgical repair can be undertaken accordingly. Further examination of the eyes include the conjuntival which is the membrane covering the white part can indicate the underlying cause such as chemical burn and Stevens-Johnson syndrome. Biopsy and cell study can also pinpoint more specific diseases. Tear volume, characteristics and surface staining using different dyes and paper strip will further determine the severity of the disease.
After establishing the diagnosis of dry eye, a logical stepwise manner of treatment is implemented. Lid and eye surface abnormalities may be surgically corrected and inflammation of the lids is controlled. Underlying systemic conditions are treated medically and control the associated inflammation and immune processes by local and systemic immunosuppression as needed.
The mainstay of dry eye treatment is artificial tear replacement. Tear supplement is broadly available in either liquid, gel, semi liquid-gel or ointment form, with some even in the form of preservative free form for very allergic individual. Gel and oil form are longer lasting but are generally quite sticky. Hence they are more suited for night use. The inconvenience of constant lubricants may be overcome by inserting punctal plugs into the drainage system to withhold the tear in the eye much longer.
Patients should decrease external factors that increase the evaporation of the tear film or exacerbate symptoms. As a rule, extended contact lens wear, direct exposure to air condition, fan, long exposure to reading, computer and smoky atmosphere should be avoided. The efficacy of therapy may be assessed by regular examination, but the most important gauge is the patient’s symptoms.