Factors influencing abnormal posterior corneal surface elevation with normal corneal biomechanical parameters / 眼科新进展

ABSTRACT

Objective To investigate the influence factors of abnormal posterior corneal surface elevation of myopia patients under normal corneal biomechanical state.Methods A retrospective case-control study was conducted.A total of 99 myopia patients(99 right eyes)who were going to undergo refractive surgery in Nanjing Aier Eye Hospital from April 2022 to December 2022 were included.All patients received routine preoperative examinations,and the corneal morphologi-cal and biomechanical examinations were performed by Pentacam combined with Corvis ST.For patients with normal Cor-vis biomechanical index(CBI,corneal biomechanical indexes measured by Corvis ST),corneal back difference(BD,difference between the enhanced posterior surface elevation and the normal posterior surface elevation)obtained by BADⅢ-Belin/Ambrósio Enhanced Ectasia Display(BAD)of the Pentacam 3D anterior segment analysis system was used to di-vide the posterior corneal surface elevation into group A(BD＜12 μm,33 patients,33 eyes,control group),group B(12μm≤BD≤16 μm,32 patients,32 eyes,suspicious corneal abnormality group),and group C(BD＞16 μm,34 patients,34 eyes,corneal abnormality group).Basic information about the patients,such as gender and age,was collected;ocular pa-rameters,such as intraocular pressure,spherical equivalent(SE),thinnest pachymetry(THP)and anterior chamber depth(ACD),were included;corneal morphological parameters obtained by Pentacam,such as corneal horizontal diameter(HWTW),BD,anterior Sim Ks(ASK),posterior Sim Ks(PSK),BAD system-related indicators[including deviation of normality of the front elevation(Df),deviation of normality of pachymetric progression(Dp),deviation of normality of corneal thinnest point(Dt),and overall deviation of normality(Do)]and pachymetric progression index(PPI),were en-rolled;corneal biomechanical integration parameters obtained by Corvis ST,such as stiffness parameters,integrated radius(IR,area under the inverse concave radius curve),Ambrósio relational thickness to the horizontal profile(ARTh,THP/thickness change rate)and deformation amplitude ratio,were included.The comparison between groups was conducted with one-way ANOVA test and H test,Spearman Correlation was used to analyze the correlation between the BD and ocular parameters in each group,and a multivariate logistic regression model was used to explore the main factors affecting the classification of BD values under normal corneal biomechanical state.The probability distribution of abnormal posterior corneal surface elevation under normal corneal biomechanical state was plotted according to the logistic regression equa-tion,and then the receiver operating characteristic(ROC)curve was used to analyze the diagnostic efficiency of the logistic regression equation.Results There were statistically significant differences in THP,HWTW,PSK,Df,Dp,Dt,Do,PPImin,PPIavg,ACD,Db and ARTh among the three groups(all P＜0.05);in pairwise comparisons,only PSK(F=11.385),Db(H=87.107),Do(F=50.051)and PPImin(F=16.556)showed statistically significant differences(allP＜0.01),and the other parameters only showed statistically significant differences between Group A and Group B,Group A and Group C(all P＜0.05).The BD of the three groups were highly positively correlated with Db(r=0.957,0.914 and 0.952,all P＜0.05).In addition,the BD in Group A was slightly negatively correlated with PSK(r=-0.437,P＜0.05)and slightly positively correlated with Do(r=0.432,P＜0.05);the BD in Group C showed a low degree of negative corre-lation with SE(r=-0.399,P＜0.05)and a moderate negative correlation with HWTW(r=-0.482,P＜0.05).Using BD as the dependent variable and other parameters as covariates for multivariate logistic regression,the results showed that the influencing factors of BD in Group B were THP,HWTW and ARTh,the influencing factors of BD in Group C were THP,HWTW,ARTh and IR,and the overall percentage of model classification was 72.7％.According to ROC curve analysis,the new parameter Logistic(C)in multivariate logistic regression could improve the diagnostic efficiency of normal corneal bio-mechanical parameters with abnormal corneal posterior surface elevation,and its area under the curve(sensitivity,speci-ficity)was 0.975(100.0％,90.9％).Conclusion THP,HWTW,ARTh and IR are the main influencing factors of ab-normal posterior corneal surface elevation in myopic patients under normal corneal biomechanical state;the influence of corneal morphological and biomechanical parameters should be considered when diagnosing the abnormal posterior corneal surface elevation.