角膜地形图分析准分子激光原位角膜磨削术偏心切削

Corneal topographic evaluation of decentration in laser insitu keratomileusis-treatment displacement vs intraoperative drift

目的用即时角膜地形图评估准分子激光原位角膜磨削术（ＬＡＳＩＫ）后偏心切削——治疗偏移和漂移。方法对ＬＡＳＩＫ术后１个月的１００只眼（５２例）的即时角膜地形图进行分析，确定角膜切削中心偏移入射瞳孔中心的距离及在切削过程中眼球运动引起的漂移程度，并与最佳矫正视力进行比较。结果平均治疗偏移量为 ０ ５３ ｍｍ±０． ２８ｍｍ。 ４９眼（４９％）切削中心位于入射瞳孔中央０．５ ｍｍ范围内，切削中心向上方偏移的 ６８眼（６８％）。平均漂移指数为０ ．２５ ±０． ２２。漂移指数与最佳矫正视力有正相关关系。治疗偏移与最佳矫正视力无统计学意义。结论即时角膜地形图可用于评估和鉴别ＬＡＳＩＫ术中角膜切削中心的定位偏移与切削过程中眼球运动引起的漂移。高漂移会对术后视功能造成消极影响。

Objective To evaluate the treatment displacement and movement during operation (drift) after laser insitu keratomileusis(LASIK) using instantaneous topographic maps. Methods 100 eyes of 52 patients were evaluated to determine the treatment displacement of the ablation center of LASIK from the center of the entrance pupil. The drift index (DI) was calculated to determine the relative degree of movement(drift) during treatment. The treatment displacement and drift index were compared with the mean best-corrected logMAR visual acuity. Results Mean treatment displacement from the center of the entrance pupil was 0. 53 ± 0. 28 mm. 49eyes (49% ) had ablations within 0. 50 mm from the center of entrance pupil. Downward displacement in 4 eyes(4% ) and upward displacement in 68 eyes(68% ) were observed. Mean drift index was 0. 25 ± 0. 22. The drift index showed a positive, statistically significant correlation with best-corrected visual acuity(r = 0. 36, P < 0. 01). It showed that there was no statistically significant correlation between the treatment displacement and the best-corrected visual acuity(r = 0. 024,P > 0. 05 ). Conclusion instantaneous comeal topography is valuable in evaluating and differentiating the treatment displacement from movement during treatment (drift). Patients with high drift index have worse visual outcomes than those exhibiting high treatment displacement after LASIK.