Dry eye is here to stay but all treatments not equal

New York-It's more an evolution than a revolution, but ophthalmologists' stance on dry eye is unquestionably changing. Definitions and treatments are being revised, and this process will continue as ongoing research yields new findings.

"Dry eye is out of the closet. We now recognize it as a significant problem, and it is perhaps one of the most common reasons that a patient seeks eye care. That may have always been true, but in the past many of us ignored it, thinking either it was not too important or we didn't have much to offer, so there wasn't too much we were going to do about it," said Penny A. Asbell, MD, FACS, MBA, professor of ophthalmology and director, cornea and refractive surgery, Mount Sinai School of Medicine, New York.

"I think what has changed is that we recognize it is a common problem, and from the patient's point of view it's significant in terms of interfering with quality of life," she added.

Dry eye and functional vision

Recent data on dry eyes show that while vision often seems to be excellent based on chart readings in the office, patients' functional vision may in fact be decreased. "When the tear film dries out between blinks, the quality of the image degrades, and patients don't see well," Dr. Asbell explained. Patients may have poor quality vision for 60% to 70% of their waking time, yet this will not necessarily be evident in an office setting.

In addition to the understanding that dry eye is not a trivial matter to thousands of patients, clinicians have gained a new, broader perspective about the condition. Dr. Asbell traced the path from a focus on replacement of tears to the use of punctal plugs to keep the tears in the eye for a longer time to current views representing a paradigm shift from the idea that dry eye is strictly a matter of tear quality or quantity.

The study of the pathogenesis of dry eye has led to the current understanding of this condition as a fundamental change in the ocular unit that causes a complex and chronic inflammatory process affecting the ocular surface, the lacrimal glands, the nervous system, and the brain, Dr. Asbell said.

However, the inflammatory process in dry eye is different from what ophthalmologists are accustomed to seeing in patients with corneal ulcers or bacterial conjunctivitis, conditions marked by extremely red eyes and a lot of pus. Dry eye is rarely characterized by a full-blown inflammation, but research studies show increased inflammatory cells on the ocular surface and increased cytokines and mediators of inflammation in the tear film.

Another revision to attitudes about dry eye is greater understanding of the components of the tear film, including mucins, electrolytes and other proteins, and lipids.

"Any one or a combination of these may be out of kilter so that when we look ahead, we're going to be looking at all aspects of the tear film to improve the ocular function," Dr. Asbell said. Treatment for one patient may consist of a lipid, for another a mucin stimulator, and for others a combination, in addition to inflammatory mediators such as cyclosporine ophthalmic emulsion 0.05% (Restasis, Allergan), the only immune mediator currently approved for dry eye treatment.

Several other immune modulators as well as mucin stimulators are currently being investigated in various stages of clinical trials. Hormone therapy and topical steroids are a few of the other approaches also under study.

"There are many ways that people are thinking about how to reapproach dry eye," Dr. Asbell said. "There's probably not one way for every patient, and there may be a particular combination that works for a particular patient. There will be different causes and different treatments."