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Consider age, residual stromal bed, percent tissue altered to improve accuracy of screening for ectasia risk

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LAS VEGAS — Using the weighted equation of age, residual stromal bed and percent tissue altered may improve the efficacy of screening ectasia risk in patients with normal topography who undergo LASIK, according to a study presented here.

“The purpose of this study was to specifically develop an ectasia risk equation considering percent tissue altered, flap percentage, residual stromal bed, ablation depth, and age all together to have a combination that would provide very high sensitivity, and with the other parameters, we would increase the specificity of our findings,” Marcony R. Santhiago, MD, said at the American Academy of Ophthalmology annual meeting.

Marcony R. Santhiago

The retrospective case-control study included 30 eyes with normal preoperative corneal topography who developed ectasia after LASIK and 174 control eyes with uncomplicated LASIK results, he said.

Santhiago and colleagues developed a modified risk formula including age, residual stromal bed and percent tissue altered (PTA). PTA is derived from an equation that factors in flap thickness, ablation depth and preoperative central corneal thickness.

With this formula, patients were correctly identified as high risk with 100% sensitivity, while 9% of control patients were misidentified with 91% specificity.

“When we perfectly matched for high PTA, we did find that the eyes that developed ectasia presented a significantly thicker flap than the eyes that did not develop ectasia. But do not get carried away here because when we specifically investigated perfectly matched eyes with thick flaps, we found that the eyes that developed ectasia actually presented a significantly higher ablation depth,” he said. — by Nhu Te

Reference:

Santhiago M. Evaluation of role of age, residual stromal bed and percent tissue altered in ectasia risk assessment for patients with normal preoperative topography. Presented at: The American Academy of Ophthalmology. Nov. 16, 2015; Las Vegas.

Disclosure: Santhiago reports he is a consultant for Ziemer.