Excimer Corneal Refractive Corneal Topography And Visual Quality

ObjectiveTo analysis the changes of corneal topography after excimer laser photorefractive keratectomy; to evaluate the influence of surgery type and ablation ratio on the changes of corneal topography; to explore the relationship between the changes of subjective visual quality and corneal topography.MethodsA total of52myopic patients (103eyes) who performed excimer laser refractive surgery during2008.8-2009.2in our hospital and had completed all perioperative exams were included in the analysis. The patients were divided into L(LASIK) and and A(ASA) group according to the type of surgery. In both groups, the patients were divided into1(AD/CT≤0.15) and2(AD/CT>0.15) group by the ablation depth/corneal thickness ratio(AD/CT). The patients underwent routine examination presurgery and one week, one month and three months post-surgery, including uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), spherical diopter, cylindrical diopter, spherical equivalent (SE), intraocular pressure, slit lamp examination, corneal topography and subjective visual quality questionaire. The parameters to be recorded in corneal topography included surface regularity index(SRI), surface asymmetry index(SAI), simulated keratoscopy reading (SimK) and△SimK.Results1. In general population, the postoperative SAI increased significantly than baseline values, and was generally steady after the1st week postoperatively. The changes in SAI increased with the ablation ratio.2. In general population, SRI at the1st week postoperatively increased significantly than baseline values, but the values at the1st month returned to baseline levels. The changes in SRI increased with the ablation ratio.3. In general population,△SimK and SimK equivalent decreased significantly and progressively compared to baseline values.4. The changes in SAI and△SimK were influenced by surgery type, and the changes in LASIK group were greater than ASA group. 5. The changes in SAI, SRI,△SimK and SimK equivalent were influenced by ablation ratio, and increased with ablation ratio.6. In general population, the subjective visual quality scores at the1st month postoperatively improved compared to the1st week postoperatively, and remained stable after the1st month postoperatively. No significant changes occurred in the postoperative subjective visual quality in LASIK group. The changes in ASA group were similar with the general population.7. The postoperative subjective visual quality scores were influenced by ablation ratio and surgery type.the subjective visual quality was worse in patients with greater ablation ratio and who underwent LASIK.8. The changes in subjective visual quality scores mainly occurred between the1st week and the1st month postoperatively, consistent with the trend of SRI, SAI in L2and A2groups and△SimK in Al group during this period.Conclusions1. The postoperative corneal topographic parameters underwent a cetain degree of changes. In our research, SAI trended to increse. SRI initially incresed and then decresed.△SimK and SimK equivalent significantly and gradually decreased. The changes across the groups differed.2. In general population, the subjective visual quality scores at the1st month postoperatively improved compared to the1st week postoperatively, and remained stable after the1st month postoperatively. No significant changes occurred in the postoperative subjective visual quality in LASIK group. The changes in ASA group were similar with the general population.3. The postoperative corneal topographic parameters and the subjective visual quality were influenced by surgery type and ablation ratio. The changes of corneal topographic parameters were greater and the subjective visual quality was worse in patients with greater ablation ratio and who underwent LASIK.4. The changes in subjective visual quality scores mainly occurred between the1st week and the1st month postoperatively, consistent with the trend of SRI, SAI and△SimK during this period.