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Gonioscopy can briefly distort cornea, affecting IOL calculations
Following gonioscopy, corneal curvatures may appear artificially steepened when measured by surface topography-based simulated keratometry, a study found. This could, in turn, affect measurements for calculation of IOL power, the study authors said.
Mathew K. George, MD, and colleagues at Yale University prospectively compared the effects of gonioscopy on corneal curvature at different time points in 198 eyes of 99 patients. Surgeons evaluated one eye of each patient using a two-mirror gonioscope. They then evaluated each patient's fellow eye using a four-mirror gonioscope. They then obtained autokeratometry measurements and topography-based simulated keratometry, or Sim K measurements, at baseline and several time points over a 25-minute period.
Using topography-based Sim K, the researchers observed clinically and statistically significant corneal steepening up to 15 minutes after gonioscopy. No changes were detected using autokeratometry, according to the study.
No significant difference in effect was seen between the two gonioscopes, the authors noted.
Based on these findings, the authors recommended waiting at least 20 minutes after gonioscopy before using topography-based Sim K to measure IOL power.
The study is published in the online journal BMC Ophthalmology.