Assessments The Corneal Refractive Power After SBK With Pentacam

Objective: To compare the differences of using some methods toevaluate the corneal refractive power after SBK,then to improve the accuracyof corneal refractive power after SBK.Methods: Retrospectively analyzed one hundred and thirty myopiceyes of65subjects undertaken SBK.The age range of65subjects was fromnineteen to thirty-one.The mean spherical equivalent was（-4.16±1.15）Dpreoperative.These65subjects had taken examination with Pentacam pre-andpostioerative.The mean curvature radius of anterior corneal surface was（7.75±0.29）mm preoperative,and the mean curvature radius of posteriorcorneal surface was （6.31±0.20）mm preoperative. The mean curvature radiusof posterior corneal surface was （6.35±0.22）mm one month after surgery,andthe mean curvature radius of posterior corneal surface was （6.34±0.15）mmthree months after surgery.The difference of curvature radius of posteriorcorneal surface between preoperative and one month after surgery had nostatistical significance（P=0.974）. The difference of curvature radius ofposterior corneal surface between preoperative and three months after surgeryhad no statistical significance（P=0.982）.The difference of curvature radius ofposterior corneal surface between one month after surgery and three monthsafter surgery had no statistical significance（P=0.992）. The ratio between thepreoperative anterior corneal curvature radius and the preoperative posteriorcorneal curvature radius was1.22±0.02.The first method was to adjust thecorneal curvature:to correct corneal refractive power P₁with the actualmeasured corneal refractive power of posterior corneal surface. P₁was thecorneal refractive power of anterior corneal surface plus the corneal refractivepower of posterior corneal surface.The second method was Gaussian formulamethod:the total corneal refractive power postoperative P2with Gauss formula.The third method was corrected corneal refractive power by calculate-d preoperative corneal refractive power:the total corneal refractive powerpostoperative P₃with with this method.The last method was clinical historymethod:the total corneal refractive power postoperative P₄with clinical historymethod.Compared and analyzed the differences between P₁, P2,P₃andP₄.P<0.05with statistical significance.Results: The first method was to adjust the corneal curvature: to correctcorneal refractive power P₁with the actual measured corneal refractive powerof posterior corneal surface, P₁was （35.42±2.03）D. The second method wasGaussian formula method:the total corneal refractive power postoperative P2with Gauss formula, P2was （37.29±1.90）D. The third method: P₃was（39.59±0.20）D.The forth method was clinical history method:the totalcorneal refractive power postoperative P₄with clinical history method, P₄was（38.34±1.82）D. Compared and analyzed the differences between P₁, P2,P₃andP₄with variance analysis. P<0.05with statistical significance.The differencebetween P₁and P₄had statistical significance （P<0.05）. The differencebetween P2and P₄had no statistical significance （P>0.05）. The differencebetween P₃and P₄had statistical significance （P<0.05）.Conclusions:1The changes of posterior corneal curvature radius between pre-andpostoperative has no clinical significance.2The corneal refractive power postoperative by Gauss formula is moreaccurate.It has important clinical significance,especially lose the preoperativeclinical data.