Evaluation Of Biology Parameter Pre-and Post-laser In Situ Keratomileusis By The IOL-Master

Objective To investigate the changes of axial length(AL) and anterior chamberdepth(ACD) and the relationship between the changes with the theoretical ablation depth afterlaser in situ keratomileusis(LASIK). Meanwhile the accuracy of formula SRK/T (combinedwith clinical history) and Haigis-L for calculating the intraocular lens (IOL) diopter werecompared after LASIK.Methods120eyes of60patients who underwent LASIK were recruited. Axial lengthand anterior chamber depth were measured preoperatively and postoperatively by the use ofIOL-Master and the theoretical ablation depth were recorded as well. The changes of axiallength and anterior chamber depth were compared by paired-samples T test and therelationship between the changes with the theoretical ablation depth was performed usingPearson correlation coefficient. Two kinds of calculation formula including SRK/T (combinedwith clinical history) and Haigis-L were used to calculate the equivalent diopter differencebetween preoperative and postoperative based on the concept for “equivalent intraocular lensdiopter”. The accuracy was investigated by the χ2test.Results1. AL and ACD:1.1Comparison the AL pre-and post-laser in situ kertomileusisThe AL got shortened with significant difference between pre-operation and at1month,3months,6months after LASIK, the change of AL was bigger than the theoretical ablationdepth after LASIK and the difference was statistically significant. There was no statisticalsignificance in AL at different time points postoperatively. 1.2Comparison of corrected AL (AL*=AL-central cornea thickness) pre-and post-laserin situ kertomileusis.There was no statistical significance in corrected AL*between pre-operation and at1month,3months,6months after LASIK. However, when120eyes were divided intomild-to-moderate myopia group（0～-6.0D） and high myopia group（more than-6.0D）according to preoperative refractive diopter, there was no statistical significance in AL*between pre-operation and at1month after LASIK in mild-to-moderate myopia group, butAL*got lengthened with significant difference between pre-operation and at1month afterLASIK in high myopia group.1.3Comparison of ACD pre-and post-laser in situ kertomileusisThe ACD become shallow with significant difference between pre-operation and at1month,3months,6months after LASIK, the change of ACD was bigger than the theoreticalablation depth after LASIK and the difference was statistically significant. There was nostatistical significance in ACD at different time points postoperatively.1.4Comparison of corrected ACD (ACD*=ACD-central cornea thickness) pre-and post-laser in situ kertomileusis.The ACD*become shallow with significant difference between pre-operation and at1month,3months,6months after LASIK. There was no statistical significance in ACD*atdifferent time points postoperatively.1.5The relationship between the changes of AL and ACD with the theoretical ablationdepth after LASIKThere was no association between the changes of AL and ACD with the theoreticalablation depth after LASIK.2. The accuracy of formula SRK/T (combined with clinical history) and Haigis-L forcalculating IOL diopter after LASIK:120eyes of60myopia patients were used SRK/T (combined with clinical history) and Haigis-L to calculate the IOL diopter pre-and post-operation, respectively. Then thedifference was divided into±0.5D and±1.0D. The number of eyes which the difference is±0.5D are22eyes (18.33%) and55eyes (45.83%). The number of eyes which the differenceis±1.0D are44eyes (36.67%) and109eyes (90.83%), respectively. There were significantdifferences between the two formulas．Conclusion1. There was a trend that the axial length got shortened and anterior chamber depth becomeshallow after LASIK, but there was no association between the changes and the theoreticalablation depth.2. The formula Haigis-L is more precise than the SRK/T (combined with clinical history) forIOL diopter calculation after LASIK.