discovering dry eye
LASIK and the Dry Eye Patient
BY BARBARA CAFFERY, OD, MS
As the number of LASIK procedures performed annually continues to grow, practitioners remain pleased with the percentage of successful cases and learn more about the complications. One of the minor complications of laser surgery is persistent symptoms of dryness and ocular irritation that often last only a few weeks. This complication becomes major when the symptoms persist and the patient becomes a chronic sufferer of dry eye symptoms. Unfortunately, the percentage of patients who suffer from this long-term result is unknown.
Even more troubling is the fact that we don't know which patients will experience this complication. What are their risk factors? Are these marginal dry eye patients, early Sjögren's syndrome patients or contact lens-intolerant patients? In order to counsel our patients prior to surgery, we need to investigate the mechanism of this complication and to warn candidates about this potential complication.
Many candidates for LASIK come from a group of patients who have been deemed as contact lens intolerant. A large percentage of these patients have symptoms of dryness when they wear their contact lenses, so they decide that laser refractive surgery is the best option for them. The practitioner's dilemma is how to advise these patients about their chances of success with laser refractive surgery.
One of the contraindications for laser surgery is severe dry eye, especially that associated with autoimmune disease. The logic here appears simple. Patients with Sjögren's syndrome and severe sicca syndrome have poor corneal epithelial health. Clinical wisdom is that these unhealthy corneal cells, which are best observed with flourescein staining, produce the gritty, dry and burning symptoms of dry eye disease. Since LASIK procedures require cutting the cornea with subsequent healing, it's unlikely that these patients will heal properly.
How does this logic apply to mild to moderate dry eye disease, or those patients who have dryness symptoms only when wearing their contact lenses? Many of these patients have little corneal staining and perhaps their symptoms don't arise solely from corneal sensation. Do they have increased risk for complications with laser procedures? This is not known. Clinicians recognize patients with prolonged post LASIK dry eye symptoms, but we need to know the source of these symptoms.
Points to Ponder
Does the procedure change the sensitivity of the cornea and produce symptoms of irritation unrelated to dry eye? Is this the same mechanism as those post cataract patients who have significant symptoms of dryness? Has a change in corneal sensitivity reduced the reflex production of tears from the lacrimal gland? Or is there a much more mechanical explanation here of a marginal dry eye that was once protected by spectacles or contact lenses, now exposed to the elements and sending signals of irritation to the brain? These are questions that require study.
In the meantime, clinicians must screen patients who are considering LASIK, and give them the best advice about their chances of success. Topography, refraction and corneal thickness are standard measurements for this work-up. Laser surgery can teach us about dry eye disease. Pre- and post-surgical tear film work-ups including questionnaires and objective testing may help us to better choose our LASIK patients, and to better understand the pathophysiology of dry eye symptoms.
Dr. Caffery has practiced optometry in Toronto, Canada, in a group setting dedicated to contact lens and tear film research since 1977.