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Altered tissue percentage may not be risk for ectasia after LASIK
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LISBON, Portugal — The currently recommended percentage of tissue altered did not demonstrate to be an independent risk factor for post-LASIK ectasia in a multicenter study.
Percentage of tissue altered (PTA) is a possible new risk factor for iatrogenic ectasia recently described by Marcony Santhiago, MD, and currently at the center of a hot debate among cornea and refractive surgery specialists.
“Santhiago did a great job trying to identify independent risk factors for iatrogenic ectasia, and he and his co-authors found in a large series of cases that eyes with normal Placido topography but PTA above 44 had a higher risk of developing iatrogenic ectasia after LASIK surgery. We wanted to evaluate and validate this risk factor in an external group because, so far, all the studies describing PTA have come from the same population,” Alain Saad, MD, said at the European Society of Cataract and Refractive Surgeons meeting.
The preoperative topography and tomography maps of 31 eyes that developed iatrogenic ectasia were compared with those of more than 500 patients who had LASIK and did not have this complication after 2 years of follow-up.
“We calculated and compared the PTA values in the two groups. Twenty-one percent of the normal cases had a PTA greater than 44, and 17% of the eyes that developed iatrogenic ectasia had a PTA greater than 44. Our results suggest that, based on the current available data, PTA greater than 44 cannot be considered as an independent risk factor of iatrogenic ectasia and should not be used as a screening method for refractive surgery candidates,” Saad said.
Today, LASIK surgeons are experiencing less ectasia because of the rigorous preoperative screening of potential LASIK candidates.
“By increasing our understanding of corneal biomechanics, improving our topographic and tomographic screening methods, and perhaps modifying the current PTA calculation, we should hope to further reduce the incidence of post-LASIK ectasia,” he said. – by Michela Cimberle
Reference:
Saad A. Percentage tissue altered (PTA) for predicting post-LASIK ectasia risk. Contra. Presented at European Society of Cataract and Refractive Surgeons meeting; Oct. 7-11, 2017; Lisbon, Portugal.
Disclosure: Saad reports he is a consultant for Bausch + Lomb.