LASIK: specialists debate the flap about glaucoma

July 14, 2008

Performing LASIK in patients with glaucoma should be carefully considered before making the commitment because of changes in the eye that might result in lower IOP measurements, according to two ophthalmologists. PRK, however, might be a better option for this subgroup of patients, suggests one surgeon.

Key Points

LASIK in an individual suspected of having glaucoma or with glaucoma is a controversial topic. Two specialists, Thomas W. Samuelson, MD, and Richard A. Lewis, MD, examined the pros and cons at the annual meeting of the American Society of Cataract and Refractive Surgery and provided their recommendations.

"Should LASIK be denied to patients with glaucoma?" asked Dr. Samuelson, clinical associate professor, Department of Ophthalmology, University of Minnesota, and attending surgeon, Phillips Eye Institute, both in Minneapolis. "No prospective study has evaluated this point. However, my belief is that all patients should be presented with all the options, the risks, and the benefits, and then be permitted to make an informed choice."

Choices for the patient should include carefully performed LASIK as well as PRK and, more importantly, thoughtful follow-up, he said. He said he would discourage from undergoing LASIK those with advanced glaucoma and uncontrolled glaucoma. Dr. Samuelson also said that some patients with advanced glaucoma may be exceptions to the rule.

Although the latter part of that statement may be surprising, Dr. Samuelson cited several relevant factors-i.e., glaucoma can require surgical intervention, bleb-related endophthalmitis is a lifelong risk, contact lens wear is a risk for infection, and young patients with myopia often do not want to wear glasses.

"In the presence of a bleb, the surgeon has to consider what carries more risk-wearing contact lenses or correcting the refractive error with LASIK or PRK," he said. "Refractive surgery may be safer for some patients with glaucoma than contact lenses if the refractive procedure is performed carefully and with informed consent."

In his own practice, Dr. Samuelson said, he does not take these patients lightly. He cited a study that his group published that looked at virtually every psychophysical and functional test that was available for assessing glaucoma performed before and after LASIK.

"We did this trial in response to a published study that I did not agree with," he said. "The paper suggested that the brimonidine [Alphagan, Allergan] is neuroprotective in refractive surgery. Because I do not think that refractive surgery causes damage, the obvious question is how any drug could protect against damage."

When they compared patients who underwent LASIK and either took or did not take brimonidine, Dr. Samuelson and colleagues found no structural or functional differences between the two groups of patients.

When considering a refractive procedure for a patient with glaucoma, he underscored it is important to evaluate two primary factors: the risk of the procedure and the implications for long-term follow-up.

High pressure

"An ongoing question is whether the high IOP that the patients are subjected to during LASIK is a cause of concern. IOP probably rises to between 80 and 90 mm Hg," he said. "The highest pressure probably occurs during applanation with the microkeratome or with the docking cone of the femtosecond laser."

An important consideration is that the elevated IOP remains so for an average of 11 seconds.

"What is the likelihood that the elevated IOP can cause a neuroretinal injury in that period?" Dr. Samuelson asked rhetorically.

A similar example is that of digital ocular massage, which patients are instructed to perform four times daily for about 10 seconds for a failing trabeculectomy. During this practice, IOP reaches about 90 to 100 mm Hg, according to published reports. Passage of a microkeratome requires about 10 seconds. The femtosecond laser may expose the eye to a slightly lower IOP than a keratome, but no definitive data are available. He urged surgeons to explain to patients that damage is probably unlikely although no study has proved that point.