屈折矯正手術後における角膜形状が眼圧計測におよぼす影響

Abstract

Corneal configuration change due to recent keratorefractive surgery such as photorefractive keratectomy (PRK), photherapeutic keratectomy (PTK), and laser in- situ keratomileusis (LASIK) reduce the corneal rigidity, and will result in significant underestimation of postoperative intraocular pressure (IOP) measurement. So we have analyzed the relation between corneal cofiguration change and postoperative measurement of IOP in keratorefractive surgery (PRK PTK, and LASIK). Actual IOP was controlled using a manometer inserted into the anterior chamber of enucleated pig eyes. Clinical IOP was measured with electronic applanation tonometer (Tono-Pen XL, Menter) at several heights of manometer, central corneal thickness (CCT) was measured with ultrasonic pachymeter (SP-2000, Tome.) before and after IOP measure- ment, and anterior corneal curvature with Orbscan (Orbtech). Each measured IOP was analyzed statistically with linear regression and paired t-test. Measured IOP of the group of normal eyeball with various CCT was increased in every experimentation as CCT increased. And measured IOP of automated lamellar keratoplasty (ALK) performed group was significantly reduced as CCT reduced. Linear correlation was established between set up IOP and measured IOP, with correlation coefficients close to unity. Correlation between CCT and the measured IOP, CCT and the difference of the measured IOP to each sample was statistically highly significant (P＜0.001). Measured anterior corneal curvature at 3 mm diameter of central cornea of the ALK performed group was decreased as IOP increased. Results of our investigation show that CCT has a larger effect on the measurement of IOP than central corneal curvature and corneal hydration. We should take into consideration the corneal configuration change for proper assessment of postoperative IOP measurement in recent keratorefractive surgery.