People with a certain low level of tear production are more likely to develop chronic dry eye syndrome after Lasik laser refractive surgery to correct near- and far-sightedness than those with more plentiful tears. The finding is reported by scientists at Schepens Eye Research Institute whose study is published in the January issue of Investigative Ophthalmology and Vision Science. The study may offer reliable prescreening criteria for ophthalmologists and patients.
Dr. Darlene Dartt, director of the Military Vision Research Program at Schepens and the principal investigator of the study, said the findings should help ophthalmologists determine if pretreatment is necessary before surgery or if surgery is appropriate at all for an individual.
One of the most common problems treated by eye physicians, dry eye syndrome affects more than 10 million Americans. It is caused by problems with the tear film responsible for lubricating the eye. It does not cause vision loss, but can be painful for victims who look for relief with artificial tears and other medications.
Lasik surgery may cause some patients to experience dry eyes after surgery. This is especially true if there was tendency toward dry eyes before the procedure. During the Lasik procedure, a thin layer of tissue is created, called a flap, under which the actual laser energy is applied to reshape the cornea to correct nearsightedness, farsightedness and astigmatism.
When the flap is created, the very fine cornea nerves may be severed as part of the Lasik procedure. But these nerves are required in order to "signal"? the Lacrimal Gland to produce tears. Sometimes, the temporary interruption of the corneal nerve impulses can actually cause a lesser amount of tears to be produced, resulting in dry eyes after Lasik surgery.
Dartt and her team found a way to prescreen for the chronic condition so surgeons could prepare patients in advance with preventative artificial tears or opt against surgery for some patients. Their method was arrived at after evaluating the eyes of 24 patients about to undergo Lasik surgery at the Massachusetts Eye and Ear Infirmary. The team discovered that if a patient had a presurgical tear production value greater than a predetermined amount, they were not likely to develop dry eye syndrome. Patients who produced less were more likely to develop the condition.
The team's next step is to expand the study to a larger group of individuals and examining patients who have the PRK (photorefractive keratectomy) type of refractive surgery, which has the same goal as Lasik surgery but different procedures.