经上皮准分子激光屈光性角膜切削术（TPRK）及飞秒激光辅助的准分子激光原位角膜磨镶术（FS-LASIK）后眼轴长度及角膜光密度的变化

目的　观察经上皮准分子激光屈光性角膜切削术（transepithelial photorefractive keratectomy，TPRK）及飞秒激光辅助的准分子激光原位角膜磨镶术（femtosecond laser-assisted in situ keratomileusis，FS-LASIK）手术前后眼轴长度及角膜光密度（corneal density，CD）的变化，并探讨二者间相关性。方法　回顾性分析。使用IOL Master 500测量TPRK组（72眼）和FS-LASIK组（42眼）患者术前及术后3个月的眼轴长度，同时使用Pentacam进行角膜厚度测量及CD分析。对手术前后眼轴差与角膜消融厚度之间的差异性、相关性及一致性进行分析，同时分析IOL Master眼轴测量偏差（眼轴差与角膜消融厚度间差值）与CD变化的相关性。结果　TPRK组及FS-LASIK组手术前后眼轴差分别为（0.09±0.04）mm、（0.11±0.05）mm，角膜消融厚度分别为（0.09±0.02）mm、（0.09±0.03）mm，二者之间显著正相关（r=0.486、0.494，均为P<0.01），差异均无统计学意义（t=1.534、1.995，均为P>0.05)，Bland-Altman 分析显示二者一致性好。TPRK组角膜前层（120 μm）及全层的CD术后低于术前，中间层及后层（60 μm）的CD术后高于术前。FS-LASIK组眼轴测量偏差仅与0~2 mm前层的CD中等相关（r=0.356，P<0.05）。结论　TPRK及FS-LASIK术后患者眼轴长度均较术前短，二者差值与角膜消融厚度相符。TPRK及FS-LASIK术后3个月CD略有降低，但IOL Master眼轴测量偏差与CD的变化基本不相关。

Changes in axial and corneal density after transepithelial photorefractive keratectomy and femtosecond laser-assisted in situ keratomileusis

Objective　To observe the changes in axial length and corneal density (CD) values before and after transepithelial photorefractive keratectomy (TPRK) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and to assess their correlation.Methods　Retrospective analysis was conducted. The axial length of 72 eyes undergoing TPRK (TPRK group) and 42 eyes undergoing FS-LASIK (FS-LASIK group) was measured using IOL master 500 before surgery and 3 months after surgery. The corneal thickness and CD values were measured using Pentacam. The difference, correlation and consistency between axial difference and corneal ablation thickness were analyzed, and the correlation between IOL master axial measurement deviation (the difference between axial difference and corneal ablation thickness) and the change in CD was analyzed.Results　In the TPRK group and FS-LASIK group, the difference in axial length was（0.09±0.04）mm and （0.11±0.05）mm before and after the operation, and the corneal ablation thickness was（0.09±0.02）mm and （0.09±0.03）mm, respectively. There was a positive correlation between the two (r=0.486,0.494, both P<0.01), but there was no significant difference in axial difference and corneal ablation thickness between groups (t=1.534, 1.995, both P>0.05). Bland-Altman analysis showed good consistency. In the TPRK group, the CD values of the anterior layer (120 μm) and the whole layer were lower than those before surgery, and the middle layer and the posterior layer (60 μm) were higher than before surgery. In the FS-LASIK group, the deviation of axial measurement was moderately correlated with the CD difference in the 0-2 mm anterior layer (120 μm ) (r=0.356, P< 0.05).Conclusion　The axial length is found to be shorter after both TPRK and FS-LASIK, and the difference between the two surgeries was consistent with the thickness of the corneal ablation. After 3 months, the CD decreased slightly, but the deviation between the axial difference measured by IOL master and the corneal ablation thickness is found to be not related to the change in CD.