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Surgeons must be aware of glaucoma risk after refractive surgery
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ALICANTE, Spain — The risk of glaucoma after refractive surgery procedures should not be underestimated, according to one surgeon speaking here at the Alicante Refractiva International meeting.
"I have to play the part of devil's advocate by speaking about this topic in a refractive surgery meeting," said José Belda, MD, of Vissum Institute in Alicante. "Still, we have to consider that what we see is only the tip of the iceberg, and below it we may have a large quantity of patients presenting this problem in the future."
The volume of refractive surgery is constantly increasing. Figures are difficult to estimate in Europe, but in the United States, approximately 1.4 million refractive procedures are performed per year, according to Dr. Belda.
"We must take into account that the largest part of refractive surgery procedures are done in myopic patients, amongst which the prevalence of glaucoma is three to four times higher than normal, even without any surgical procedure," Dr. Belda said.
For glaucoma related to refractive surgery, surgeons must look at the causes, and these vary according to the technique used, he said.
One problem all techniques have in common is that true IOP levels are difficult to assess after surgery. IOP can be underestimated, and glaucoma can go undiagnosed for a long time, Dr. Belda said.
Surface techniques hold some advantages because no suction is applied during the procedure. But more corticosteroids are used to prevent haze, which may lead to corticosteroid-induced glaucoma, particularly in patients with high myopia, he said.
Meanwhile, suction can be a problem with LASIK. The vacuum phase is short, but pressure values are high — between 60 mm Hg and 90 mm Hg — and can reach as high as 200 mm Hg as the blade presses against the cornea, according to Dr. Belda.
"Time is also surgeon-dependent. Inexperienced surgeons might prolong this stage and cause damage to the optic nerve," he said.
There is no evidence to prove that this risk applies to normal eyes, but nobody has yet proved that this pressure increase is safe in eyes with underlying glaucoma or ocular hypertension, he noted.
Even less is known when femtosecond lasers are used for LASIK, he said.
"We know that suction is lower, pressure is lower, but since the procedure is longer, we are going to flatten the cornea for a longer time than with mechanical microkeratomes, and so some damage can still be caused to the optic nerve," Dr. Belda said.
He believes, however, that most cases of glaucoma after refractive surgery are related to the increase in IOP induced by the use of corticosteroids.