Impact of keratorefractive surgery type on the interpretation of intraocular pressure measurements: the role of corneal topographic and biomechanical remodeling

Abstract

   Background. Keratorefractive surgery is widely used to correct myopia; however, surgery-induced changes in corneal shape inevitably affect corneal biomechanical properties. These changes reduce the accuracy of intraocular pressure measurements used in glaucoma assessment and complicate the evaluation of the risk of iatrogenic corneal ectasia in patients who have undergone surgery.    Purpose: to evaluate how the relationships between corneal topographic and biomechanical parameters vary according to the type of keratorefractive surgery and to determine their implications for the interpretation of intraocular pressure measurements.    Materials and methods. A total of 61 participants (121 eyes) aged 21–60 years were examined. The control group included 16 participants (31 eyes) with no history of ocular surgery. The study group included 45 patients (90 eyes) who had undergone LASIK (26 eyes), femtosecond laser-assisted LASIK; 32 eyes), or photorefractive keratectomy (32 eyes). The examination included corneal topography using the Pentacam, assessment of corneal biomechanical parameters using the Ocular Response Analyzer, including corneal hysteresis and corneal resistance factor, and elastotonometry.    Results. Following LASIK and FS-LASIK, IOP measurements were underestimated: corneal-compensated intraocular pressure was 1.69–2.62 mm Hg lower and Goldmann-correlated intraocular pressure was 3.23–4.18 mm Hg lower than in the control group. After photorefractive keratectomy, corneal-compensated intraocular pressure and Goldmann-correlated intraocular pressure values were comparable to those in the control group. Procedures involving corneal flap creation were characterized predominantly by inverse correlations between corneal biomechanical parameters and corneal curvature. The strongest correlations were observed for corneal resistance factor and corneal hysteresis in the central and inner paracentral zones (|r| up to 0.6; p < 0.01). After photorefractive keratectomy and in intact corneas, direct correlations between these parameters and corneal curvature predominated.    Conclusion. Different keratorefractive surgery techniques affect corneal biomechanical remodeling differently. These effects should be considered when interpreting tonometry results and assessing the risk of iatrogenic complications.