雷射屈光手術後其影響角膜後表面前移之因子

Factors Affecting the Forward Shift of Posterior Corneal Surface after Myopic Laser Refractive Surgery

王馨儀(Shing-I Wang) ； 鄭惠川(Huey-Chuan Cheng)

《中華民國眼科醫學會雜誌》 43卷4期 (2004/12) Pp. 307-317

https://doi.org/10.30048/ACTASOS.200412.0004

摘要

Purpose: To determine the relationships between posterior corneal surface shift and preoperative IOP, preoperative corneal thickness, corrected refractive power, ablated corneal thickness, and postoperative corneal thickness after laser refractive surgery. Differences in ablation positions in LASIK and PRK were also compared to evaluate their effects in posterior corneal surface shift.
Methods: 101 myopic eyes (-3.5D~-13.25D) received LASIK between January and June, 2003 were collected. The mean preoperative spherical equivalence is -7.04±2.15D. Corneal pachymeter and topograph (Orbscan Ⅱ) were used to measure preoperative corneal thickness, ablated corneal thickness, postoperative corneal thickness, and anterior shift of posterior corneal surface before and 1 month after surgery. Multiple regression analysis is used to assess the data. In addition, 25 low-to-moderate myopic eyes after LASIK and 25 low-to-moderate myopic eyes after PRK were collected to compare the effects of anterior shift of posterior corneal surface measured before and 1 month after surgery. The data were analyzed by t-test.
Results: In the 101 eyes received LASIK, there were statistically significant relationships between the posterior corneal surface shift measured 1 month after surgery (mean 31.40±17.62 μm) and postoperative residual corneal stromal thickness (mean 316.10±45.73μm), postoperative corneal thickness (mean 456.10±45.73μm), ablated corneal thickness (mean 82.26+20.97μm), and corrected myopic power (R^2=0.687, P＜0.0001; R^2=0.345, P＜0.0001; R^2=0.286, P＜0.0001; R^2=0.175, P＜0.0001). There was no statistically significant relationship between the posterior corneal surface shift and preoperative corneal thickness (mean 551.30±28.46μm), and preoperative IOP (mean 14.25±2.20mmHg). In low and moderate myopia (＜-6.0D) the anterior shift of posterior corneal surface is observed in both LASIK and PRK groups. Anterior shift of posterior corneal surface is more prominent in LASIK group than PRK group with statistical significance.
Conclusions: In this study, anterior shift of posterior corneal surface will be observed in patients receiving either LASIK or PRK in early postoperative period, especially in LASIK group. The posterior corneal surface shift is well correlated to postoperative corneal thickness, ablated corneal thickness, and corrected myopic power. If we preserve more corneal thickness when performing refractive surgery, the incidence of corneal posterior surface ectasia will be lower and thus the risk of subsequent keratoconus. Besides, in low and moderate myopic eyes, the less prominent anterior shift of corneal posterior surface after PRK makes it an advisable procedure for patients with possibly flap complication or thin corneal thickness.

並列摘要

Purpose: To determine the relationships between posterior corneal surface shift and preoperative IOP, preoperative corneal thickness, corrected refractive power, ablated corneal thickness, and postoperative corneal thickness after laser refractive surgery. Differences in ablation positions in LASIK and PRK were also compared to evaluate their effects in posterior corneal surface shift.
Methods: 101 myopic eyes (-3.5D~-13.25D) received LASIK between January and June, 2003 were collected. The mean preoperative spherical equivalence is -7.04±2.15D. Corneal pachymeter and topograph (Orbscan Ⅱ) were used to measure preoperative corneal thickness, ablated corneal thickness, postoperative corneal thickness, and anterior shift of posterior corneal surface before and 1 month after surgery. Multiple regression analysis is used to assess the data. In addition, 25 low-to-moderate myopic eyes after LASIK and 25 low-to-moderate myopic eyes after PRK were collected to compare the effects of anterior shift of posterior corneal surface measured before and 1 month after surgery. The data were analyzed by t-test.
Results: In the 101 eyes received LASIK, there were statistically significant relationships between the posterior corneal surface shift measured 1 month after surgery (mean 31.40±17.62 μm) and postoperative residual corneal stromal thickness (mean 316.10±45.73μm), postoperative corneal thickness (mean 456.10±45.73μm), ablated corneal thickness (mean 82.26+20.97μm), and corrected myopic power (R^2=0.687, P＜0.0001; R^2=0.345, P＜0.0001; R^2=0.286, P＜0.0001; R^2=0.175, P＜0.0001). There was no statistically significant relationship between the posterior corneal surface shift and preoperative corneal thickness (mean 551.30±28.46μm), and preoperative IOP (mean 14.25±2.20mmHg). In low and moderate myopia (＜-6.0D) the anterior shift of posterior corneal surface is observed in both LASIK and PRK groups. Anterior shift of posterior corneal surface is more prominent in LASIK group than PRK group with statistical significance.
Conclusions: In this study, anterior shift of posterior corneal surface will be observed in patients receiving either LASIK or PRK in early postoperative period, especially in LASIK group. The posterior corneal surface shift is well correlated to postoperative corneal thickness, ablated corneal thickness, and corrected myopic power. If we preserve more corneal thickness when performing refractive surgery, the incidence of corneal posterior surface ectasia will be lower and thus the risk of subsequent keratoconus. Besides, in low and moderate myopic eyes, the less prominent anterior shift of corneal posterior surface after PRK makes it an advisable procedure for patients with possibly flap complication or thin corneal thickness.

並列關鍵字

Myopia ； Photorefractive Keratectomy PRK ； Laser in situ keratomileusis LASIK ； Posterior corneal surface