Addressing higher-order aberrations necessary to determine true astigmatism before photoablation
ROME — When treating astigmatism by photoablation, higher-order aberrations should be addressed first to unmask the true astigmatic axis and power, according to one surgeon.
“Sometimes what looks like astigmatism is a combination of higher-order aberrations. After those are treated, it might turn out that there is actually no astigmatism,” Daniel Epstein, MD, said at the joint Refractive.online and SICCSO meeting.
“In other cases, after treating higher-order errors, the astigmatism shows a different pattern and even axis compared to what was seen previously,” Epstein said.
Addressing higher-order aberrations is a prerequisite for successful astigmatic treatment because every astigmatism has a component of higher-order aberrations, according to Epstein.
“If you ignore the fact that you need to unmask the astigmatism by treating [higher-order aberrations], you get everything you don’t want to get: decentration, residual astigmatism, residual refractive error, results on visual acuity and quality of vision,” he said.
Correcting astigmatism is difficult because every astigmatism is unique but the software for astigmatic correction assumes that one size fits all. And astigmatism is unforgiving when treatment errors are involved. Misalignment of just 10° leads to 30% less correction of the astigmatism and an even higher undercorrection of higher-order aberrations, with 50% uncorrected trefoil and 65% uncorrected tetrafoil, Epstein said.
- Disclosure: Epstein has no relevant financial disclosures.