目的：探讨不同角膜直径下眼表形态学参数对早期圆锥角膜的诊断价值。

方法：回顾性病例对照研究。选取2019-01/2022-03至我院就诊的患者201例201眼，分为对照组(单纯屈光不正病史的患者)135例135眼和亚临床圆锥角膜组66例66眼，均采用Pentacam眼前节分析仪检测角膜后表面3mm水平中央曲率(Kf)、垂直中央曲率(Ks)、平均曲率(Km)、I-S值、最薄点后表面高度、最佳拟合球体的最大后表面高度、最佳拟合复曲面椭圆体的最大后表面高度、角膜后表面非球面不对称指数(AAI)、角膜最薄点厚度(TCT)、角膜中央厚度(CCT)、角膜中央与最薄点厚度之差(DCT)、平均角膜厚度进展(PPIavg)、Ambrósio厚度最大变化率(ARTmax)、Belin D值。比较两组各指标的组间差异，并进行受检者工作特征(ROC)曲线分析，确定出最佳诊断界点。对照组根据角膜直径进一步分组：角膜直径≤11.0mm组； 11.1mm≤角膜直径≤11.5mm组； 11.6mm≤角膜直径≤12.0mm组； 角膜直径≥12.1mm组。比较不同角膜直径组间各参数差异。角膜直径与各参数相关性采用Pearson相关分析。

结果：亚临床圆锥角膜组与对照组I-S值、最薄点后表面高度、最佳拟合球体的最大后表面高度、最佳拟合复曲面椭圆体的最大后表面高度、AAI、TCT、DCT、PPIavg、ARTmax、Belin D值均有差异(P<0.001)。Belin D值、I-S值、PPIavg、AAI、最佳拟合复曲面椭圆体的最大后表面高度(AUC≥0.9)对亚临床圆锥角膜诊断价值较高。对照组中的四组I-S值、最佳拟合复曲面椭圆体的最大后表面高度、AAI、TCT、CCT、DCT均无差异(P>0.05)，且均与角膜直径无相关性(均P>0.05)。

结论：Pentacam眼前节分析仪获取的Belin D值、I-S值、PPIavg、AAI、最佳拟合复曲面椭圆体的最大后表面高度等参数是诊断早期圆锥角膜的敏感指标，其中I-S值、AAI、最佳拟合复曲面椭圆体的最大后表面高度等受角膜直径影响较小，对不同角膜直径下的早期圆锥角膜诊断起着重要的临床意义。

METHODS: A retrospective case-control study. A total of 201 patients(201 eyes)who were treated in our hospital from January 2019 to March 2022 were included. They were divided into 135 cases(135 eyes)in the control group(patients with history of refractive error)and 66 cases(66 eyes)in the subclinical keratoconus group. The Pentacam anterior segment analyzer was used to determine the horizontal central curvature of corneal posterior surface(Kf), posterior vertical central curvature of corneal posterior surface(Ks), average curvature of corneal posterior surface(Km), Posterior I-S ratio, corneal posterior surface height after the thinnest point(PE at the thinnest point), maximum posterior elevation from best fit sphere(MPE from BFS), maximum posterior elevation from best fit toric ellipsoid(MPE from BFTE), posterior asphericity asymmetry index(AAI), thinnest point thickness of the cornea(TCT), central corneal thickness(CCT), depressed corneal thickness(DCT), pachymetric progression index average(PPIavg), Ambrósio relational thickness maximum(ARTmax)and Belin D value. The differences of each parameter between the two groups were analyzed. Receiver operating characteristic(ROC)curves were analyzed to determine the best diagnosis point. The control group was further divided into groups according to the corneal diameter: corneal diameter ≤11.0mm, 11.1mm≤ corneal diameter ≤11.5mm, 11.6mm≤ corneal diameter ≤12.0mm, corneal diameter ≥12.1mm. The differences of each parameter among these groups were compared. Pearson correlation analysis was used to analyze the correlation between corneal diameter and other parameters.

RESULTS: There were significant differences in posterior I-S ratio, PE at the thinnest point, MPE from BFS, MPE from BFTE, posterior AAI, TCT, DCT, PPIavg, ARTmax, Belin D value between the subclinical keratoconus group and the control group(P<0.05). Sensitive index of Pentacam to diagnosis subclinical keratoconus were Belin D value, posterior I-S ratio, PPIavg, posterior AAI and MPE from BFTE(AUC≥0.9). In the control group, there was no significant difference in posterior I-S ratio, MPE from BFTE, posterior AAI, TCT, CCT, and DCT among different corneal diameter groups (P>0.05), and there was no significant correlation with corneal diameter(all P>0.05).

CONCLUSION: The Belin D value, posterior I-S ratio, PPIavg, posterior AAI, MPE from BFTE obtained by Pentacam are sensitive indicators for the diagnosis of early keratoconus, among which posterior I-S ratio, posterior AAI, MPE from BFTE are less affected by corneal diameter. They play an important role in the early diagnosis of keratoconus under different corneal diameters.