Helmy Hazem, Hashem Omar
Glaucoma and Optic Nerve Disease Department, Research Institute of Ophthalmology, Giza, Egypt.
Cornea and Refractive Surgery Department, Research Institute of Ophthalmology, Giza, Egypt.
Clin Ophthalmol. 2020 Feb 21;14:509-516. doi: 10.2147/OPTH.S239329. eCollection 2020.
Corneal refractive surgery is widely used worldwide. Myopia is the most common reason for laser-assisted corneal refractive surgery (LASIK) and one of the risk factors for glaucoma. Intraocular pressure (IOP) measurement becomes variable postoperatively as the results are affected by the decrease in corneal thickness and biomechanics. This prospective clinical case study attempted to establish a simple correction formula for the calculation of IOP in post-LASIK myopic patients.
This study included 300 eyes of 150 patients with myopia and myopic astigmatism as a refractive error who underwent LASIK. IOP was measured preoperatively and 6 months postoperatively. Preoperative and postoperative corneal thickness as well as ablation depth were measured. Statistical analysis was performed to detect the relationship between ablation depth and change in IOP. An attempt was made to construct a correction formula for the calculation of post-LASIK IOP.
The age of the patients ranged between 18 and 50 (mean ± SD 34.78±8.8) years. The spherical equivalent of refractive error ranged between -1.5 and -10 diopters. The mean IOP decreased significantly from 15.72±2.37 mmHg preoperatively to 11.71±2.24 mmHg postoperatively, with a mean difference of 4±1.75 mmHg (˂0.001). A positive correlation was detected between corneal thickness and IOP difference among patients both preoperatively and postoperatively (˂0.001). A positive correlation was identified between ablation depth and IOP change (˂0.001). The correction formula for IOP was established: Real IOP=4+0.7(preoperative IOP)-0.3(ablation depth).
IOP measurements change after corneal refractive surgery with LASIK. A corrected formula may be a good option for the proper calculation of post-LASIK IOP.
角膜屈光手术在全球范围内广泛应用。近视是激光辅助角膜屈光手术（LASIK）最常见的原因，也是青光眼的危险因素之一。由于术后结果受角膜厚度和生物力学下降的影响，眼压（IOP）测量值在术后变得不稳定。本前瞻性临床病例研究试图建立一个简单的校正公式，用于计算LASIK术后近视患者的眼压。
本研究纳入了150例近视和近视散光患者的300只眼睛，这些患者接受了LASIK手术。术前和术后6个月测量眼压。测量术前和术后的角膜厚度以及消融深度。进行统计分析以检测消融深度与眼压变化之间的关系。试图构建一个用于计算LASIK术后眼压的校正公式。
患者年龄在18至50岁之间（平均±标准差34.78±8.8岁）。屈光不正的等效球镜度在-1.5至-10屈光度之间。平均眼压从术前的15.72±2.37 mmHg显著降低至术后的11.71±2.24 mmHg，平均差值为4±1.75 mmHg（˂0.001）。术前和术后患者的角膜厚度与眼压差值之间均检测到正相关（˂0.001）。消融深度与眼压变化之间存在正相关（˂0.001）。建立了眼压校正公式：实际眼压=4 + 0.7（术前眼压）- 0.3（消融深度）。
LASIK角膜屈光手术后眼压测量值会发生变化。校正公式可能是正确计算LASIK术后眼压的一个好选择。
