CLINICAL PROBLEMS OF DRY EYE CONTACT LENS WEAR
Dry eye is the most
frequent condition seen in ophthalmology,
Ophthalmologists treat more and more contact lens wearers with tear deficiencies. This reflects the increasing number of people who attempt contact lens wear.
Tears are a major factor in maintaining the physiological and biochemical equilibrium in the vessel-free cornea. The basic research of Holly (1986) Marquardt and Lemp (1991) and Roth (1991) has become obvious of the interaction between tears and the surface of the anterior segment, and that the primary problems associated with a dry eye are metabolic disturbances of the conjunctiva and cornea.
Table 1 Iists the various vital roles which tears play in problem-free contact lens wear results (table 1). Adequate tear flow is necessary for successful contact lents wear. Tears minimize friction between hard lenses and the lid during the blink, and acts as a cushion between it and the corneal surface during movement. This tear layer fills the region between lens and cornea; this contributes to the total focusing power, and in addition it can compensate optically for corneal surface irregularities.
Inadequate tears result in inadequately wetted contact lenses which act as an irritating foreign body (table 2). In addition, poor tear flow lessens the cleaning action of tears with a resultant with a more rapid coating of the lens requiring more frequent removal from the eye. This problem is often precipitated by the dry environment in cars during long winter trips or in jet planes; it is also caused by poor blinking of those working long hours at computer terminals.
Numerous tear components are adsorbed to a lens surface this is worsened when the component concentration is increased because of decreased tear volume; decreased tear flow diminished the surface washing effect. On slit lamp examination of a lens under these conditions one sees increased deposition of tear albumin and lipids as well as desquamated epithelial cells (Roth 1986). The problem is worse with gel lenses because these substances provide nourishment for bacteria and fungi.
The problems of the dry-eyed contact lens wearer develops gradually over years the etiology differs markedly from non-lens wearing dry eyed persons. When initially developing tear deficiency problems, patients complain of matter, burning or of rubbing of their eyes after periods of wear. When taking the patient's history the first clue about tear problems are complaints that the lids are pasted together and are hard to open.
Contact lens wear is facilitated if a spray of liposomes (Lipo Nit) is put on the lid skin. The content of liposomes (fatty acids, vitamines) flows on over the skin into the lower meniscus and tear film, without blurring the vision. The beneficial effect lasts for many hours (Roth 1996).
When using conventional eye drops the dosage should be adjusted to the patient. This can be done by determining the duration of comfort follows the instillation of a single drop. For mild cases a single drop in the morning will maintain the patient symptom-free for the day. Excessive instillation of drops will result in a vicious cycle which can worsen the dry eye status. Each instilled drop of artificial tears can interfere with the existing regulation of lacrimal gland tear secretion and also may rinse off mucin. One result can be a decreased output of natural tears, a worsening of the dry eye signs and symptoms and a decreased lens wearing time.
The therapy of a dry-eyed contact lens wearer is an extra-ordinary situation which needs the involvement of the ophthalmologist if the patient is to continue lens wear. It requires the prescribing of an appropriate therapy determined after a careful assessment with adequate follow-up visits to assess the effectiveness of the therapy based on the condition of the anterior segment and the lens. Because of the consequences, one should prescribe treatment for a dry-eyed contact lens wearer with the same care one would use in the selection of a treatment for glaucoma.