Corneal biomechanics may pave way for personalized refractive surgery

Take-home message: Developments in the field of corneal biomechanics will enable refractive surgeons to perform more precise surgery in the future.

 Reviewed by William J. Dupps Jr., MD, PhD

Cleveland-Advances in corneal biomechanics will continue to lead to better and more personalized results in refractive surgery, said William J. Dupps Jr., MD, PhD.

“The corneal biomechanical link between the structure and optical function of the cornea is exquisite,” said Dr. Dupps, staff, ophthalmology, biomedical engineering and transplant, Cole Eye Institute, Cleveland Clinic, Cleveland, and founder, OptoQuest Inc.

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“Small changes in elevation or curvature make an enormous difference in optical properties,” Dr. Dupps said. “It’s important not to ignore it.”

The relationship between corneal biomechanics and the practice of refractive surgery continues to evolve, Dr. Dupps said.

He reviewed its early central role in incisional refractive surgery, then its less well-recognized effects in photoablative surgery in the 1980s, then a resurgence in awareness of the importance of biomechanics with the recognition of postoperative ectasia in the 1990s.

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“Then in the early 2000s, we saw the first publication¹ demonstrating the ability of corneal stiffening treatments to alter the course of keratoconus,” he said. “A few years later, the first commercially available tool for measuring corneal biomechanical properties was introduced.”

More recently, computer-based biomechanical models are helping leverage the potential of existing tools to transform diagnosis and surgery, Dr. Dupps said.

Although refractive surgeons have a number of precise, sophisticated tools for corneal measurement and treatment delivery at their fingertips, tools for leveraging this precision in treatment planning have not kept pace.

Current paradigms vs Future possibilities

For examples, nomograms incorporate very little patient-specific information from the preoperative exam and are lacking altogether for newer, off-label, or combined refractive treatments. Corneal biomechanics may eventually help fill that gap, he said.

“Current paradigms are more retrospective, probabilistic, and population-based,” Dr. Dupps said. “In the future, they will be more prospective, deterministic, and more personalized. The way to get there is through simulation-based medicine.”

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In refractive surgery, simulation can help surgeons and researchers test hypotheses, simulate treatments in a pre-clinical setting without putting patients at risk, and evaluate novel treatment designs and personalized optimizations.

“If we can predict refractive outcomes more precisely in a virtual domain, this can help us to select right procedure for a patient or optimize it appropriately,” he said. “For screening, it provides feedback on the likely structural response and may help reduce ectasia risk. It will also be a new tool for designing and refining the next generation of corneal refractive treatments.”

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Examples of applications include evaluating how a refractive surgery candidate might fare from a structural risk standpoint with LASIK, PRK or SMILE, for example, or assessing how a patient with a particular keratoconus geometry might respond to various crosslinking patterns.

To drive the predictive simulations, surgeons will be able to capture patient-specific information from devices they are already using, such as Scheimpflug tomography or optical coherence tomography, and then eventually include information from emerging corneal biomechanical characterization tools.

The goal of developing a software interface that can combine this information, simulate the outcome of a procedure, and produce a report for the surgeon is becoming a reality with the help of National Institutes of Health support and a commercialization grant from the State of Ohio, Dr. Dupps said.

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Reference

1. Wollensak G, Spoerl E, Seiler T. Riboflavin/ultraviolet-a-induced collagen crosslinking for the treatment of keratoconus. Am J Ophthalmol. 2003;135:620-627.

William J. Dupps Jr., MD, PhD

E: bjdupps@sbcglobal.net

This article was adapted from Dr. Dupps’ keynote presentation at Refractive Surgery Subspecialty Day at the 2015 meeting of the American Academy of Ophthalmology. Dr. Dupps is founder of OptoQuest Inc. and has intellectual property through Cleveland Clinic Innovations related to computational modeling and biomechanical measurement in ophthalmology.