A new theory for dry eye pathology may be needed

A new theory regarding the development and treatment of dry eye suggests looking at the disease as part of an interrelationship of several factors within the eye.

Issue: June 1, 2000

LAS VEGAS — While dry eye tends to be a relatively common problem in many ophthalmologists’ offices, determining the causes and treatment is often still a mystery. The symptoms are regularly non-specific; there is no one exceptional measurement system; and the range of what is a normal eye and what may be a diseased eye is broad.

William D. Mathers, MD, professor of ophthalmology at Oregon Health Services University, who delivered the Conrad Berens Lecture at the Contact Lens Association of Ophthalmologists meeting, said that while the disease crossed all racial, age and gender lines, typically it affected women in menopause and post-menopause, contact lens wearers and patients with blepharitis.

He said that about 10% of the time dry eye is the result of Sjögren’s syndrome, which occurs mostly in women.

Loss of hormone support

Problematic for many dry eyes is the loss of hormone support that Dr. Mathers believes is a function of androgen in the system. One treatment for dry eye is to prescribe prolactin, but according to Dr. Mathers, that could further inhibit the eye. He felt that prolactin may antagonize androgen and since the lacrimal gland has androgen receptors, it may cause more problems than it helps. He also noted that evaporation may cause a healthy eye to lose one-third of its moisture, whereas a dry eye can lose as much as three-quarters tears.

In terms of age-related dry eye, Dr. Mathers pointed out that there are few studies that researched that connection. But he stated that like all other tissues in the body, the tear tissues age as well. However, surprisingly, most older people do not suffer from the intense version of pain due to dry eye. Dr. Mathers believes that is the result of corneal sensitivity that declines with age.

According to Dr. Mathers, past explanations of dry eye have usually included immunal diseases, evaporation, aging and problems with the lacrimal gland — and that they all tend to be partially correct.

His belief is that doctors need to re-evaluate the corneal/lacrimal gland feedback model. Dr. Mathers believes that the relationship between the two tissues is the key. Multiple factors can cause a change in the relationship between the cornea and the lacrimal gland. There could be corneal damage, decreased corneal sensitivity or a local immune disease. He also suspects that corneal damage can alter the lacrimal gland.

Contact lens use

One of the causes of corneal damage is still contact lenses, Dr. Mathers said. He said that contact lenses still help foster decreased washout, decreased corneal sensation and decreased tear flow.

Dr. Mathers noted he has had good results from the oral pill Salagen (pilocarpine hydrochloride; MGI Pharma). “A restoration of tear flow is preferred to artificial tears,” Dr. Mathers said.

However, he also said that it was important that more studies be conducted, particularly on the global theory of the eye and the interrelationships of the tissues.

Steven C. Pflugfelder, MD, expanded on Dr. Mathers’ global theory later during the Castroviejo Society Symposium. He explained that it was his theory that dry eye is caused by a dysfunction of the integrated ocular surface and lacrimal gland unit.

He pointed to several factors that inhibit eye tearing, including delayed fluorescein clearance, any disruption of the ocular surface homeostasis, aging, surgery and contact lenses.

In his practice, Dr. Pflugfelder saw positive results when he administered tetracycline.

Gary N. Foulks, MD, agreed with Dr. Pflugfelder and offered some other alternative treatments of the disease. However he first warned doctors to avoid the temptation of permanently closing the tear evacuating ducts. He said it was important to keep the function of the eye as normal as possible and to treat the eye medically as the first line of therapy.

He said that anti-inflammatory medications like Restasis (cyclosporine; Allergan) might prove to be an excellent answer for dry eye. He also noted that P2Y2 Agonist (Inspire Pharmaceuticals) shows promise by increasing the aqueous component of the tears.

Dr. Foulks stated that the best option today is to look at a blend of two or three treatments to combat the disease.

Other treatments that were mentioned included the Boston Scleral Lens, conjunctival transplantation and limbal transplantation.

For Your Information:

William D. Mathers, MD, can be reached at the Casey Eye Institute Oregon Health Science Institute, 3375 S.W. Terwilliger Blvd., Portland, OR 97210; (503) 494-2745; fax: (503) 494-3929; e-mail: mathersw@ohsu.edu. Dr. Mathers has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Stephen C. Pflugfelder, MD, can be reached at the Bascom Palmer Eye Institute, 900 N.W. 17th St., Miami, FL 33136; (305) 326-6368; fax: (305) 326-6337; e-mail: spgflug@bpei.med.mia.edu. Dr. Pflugfelder has no direct financial interest in any of the products mentioned in this article. He is a paid consultant for Allergan.

Gary N. Foulks, MD, can be reached at the University of Pittsburgh MD/Eye and Ear Institution, 203 Lothrop St., 8th Floor, Pittsburgh, PA 15213; (412) 647-2205; fax: (412) 647-5119; e-mail: friberg@vision.eei.upmc.edu. Dr. Foulks has no direct financial interest in any of the products mentioned in this article. He is a paid consultant for Allergan and Inspire Pharmaceuticals.