目的：探讨双眼眼前节生物学参数的差值对早期圆锥角膜的诊断价值。

方法：回顾性对照研究。选取2022-03/2023-11在我院就诊的患者183例366眼，其中亚临床期圆锥角膜组40例80眼，临床期圆锥角膜组36例72眼，单纯屈光不正患者107例214眼作为对照组，均采用Pentacam眼前节分析仪检测双眼角膜后表面下方与上方3 mm屈光力差值(I-S)，角膜后表面最薄点高度(P.E.)，最佳拟合球体的最大后表面高度(MPE from BFS)、最佳拟合复曲面椭圆体的最大后表面高度(MPE from BFTE)、角膜后表面非球面不对称指数(AAI)、角膜中央厚度(CCT)、角膜最薄点厚度(TCT)、角膜平均厚度进展(PPIavg)、角膜厚度最大变化率(ARTmax)、Belin/Ambrósio增强扩张显示总偏差值(BAD-D)，并分别计算每例患者各检测指标的双眼差值。对照组根据角膜直径进一步分为：角膜直径<11.2 mm组21例42眼； 11.2 mm≤角膜直径≤11.8 mm组54例108眼； 角膜直径>11.8 mm组32例64眼。

结果：临床期圆锥角膜组与对照组双眼I-S、P.E.、MPE from BFS、MPE from BFTE、AAI、CCT、TCT、PPIavg、ARTmax、BAD-D差值均有差异(P<0.05)； 双眼I-S、P.E.、MPE from BFS、MPE from BFTE、AAI、CCT、TCT、PPIavg、BAD-D差值对圆锥角膜诊断价值较高(AUC≥0.900)，其中P.E.、BAD-D诊断能力最佳，AUC分别高达0.999和0.995。亚临床期圆锥角膜组与对照组的双眼P.E.、 ARTmax差值有差异(P<0.05)； 双眼I-S 、P.E.、BAD-D差值对亚临床期圆锥角膜诊断价值较高(AUC≥0.900)。对照组患者不同角膜直径组比较双眼角膜I-S、CCT、TCT、MPE from BFS、MPE from BFTE、AAI、PPIavg、ARTmax均无差异(均P>0.05)，且均与角膜直径无相关性(P>0.05)； 不同角膜直径组双眼P.E.、BAD-D差值比较有差异(P=0.007、0.003)，而双眼P.E.差值与角膜直径无相关性(P=0.270)，双眼BAD-D差值与角膜直径负相关(r=-0.230，P=0.017)。

结论： Pentacam眼前节分析仪可以准确测量多种角膜生物学参数，双眼I-S、P.E.、BAD-D差值是诊断亚临床期圆锥角膜的敏感指标，其中双眼I-S、P.E.差值受角膜直径影响较小，对不同直径角膜的亚临床期圆锥角膜诊断有着重要的临床意义。

METHODS: Retrospective case-control study. A total of 183 patients(366 eyes)who visited our hospital from March 2022 to November 2023 were included, including 107 cases(214 eyes)in the control group(patients with simple refractive error), 40 cases(80 eyes)in the subclinical keratoconus group, and 36 cases(72 eyes)in the clinical keratoconus group. All of the patients were examined by the Pentacam anterior segment analyzer to determine the inferior-superior 3 mm of the posterior corneal surface(I-S), corneal posterior elevation of the thinnest point(P.E.), maximum posterior elevation of the best fit sphere(MPE from BFS), the maximum posterior elevation of the best fit toric ellipsoid(MPE from BFTE), posterior aspherical asymmetry index(AAI), central corneal thickness(CCT), thinnest corneal thickness(TCT), pachymetric progression index average(PPIavg), Ambrósio relational thickness maximum(ARTmax), Belin/ Ambrósio enhanced ectasia display(BAD-D), and the binocular difference of each test was calculated separately for each patient. The control group was further divided according to corneal diameter: 21 cases(42 eyes)with corneal diameter <11.2 mm in group A, 54 cases(108 eyes)with 11.2 mm≤ corneal diameter ≤11.8 mm in group B, and 32 cases(64 eyes)with corneal diameter >11.8 mm in group C.

RESULTS: There was significant differences in the binocular I-S, P.E., MPE from BFS, MPE from BFTE, AAI, CCT, TCT, PPIavg, ARTmax and BAD-D between the clinical keratoconus group and the control group(P<0.05). The difference of binocular I-S, P.E., MPE from BFS, MPE from BFTE, AAI, CCT, TCT, PPIavg, and BAD-D were of high diagnostic value(AUC≥0.900), with the best diagnostic ability for P.E. and BAD-D, and an AUC as high as 0.999 and 0.995, respectively. The difference of binocular P.E. and ARTmax between the subclinical keratoconus group and the control group were statistically significant(P<0.05). The difference of binocular I-S, P.E. and BAD-D had high diagnostic value for subclinical keratoconus(AUC≥0.900). In the control group A, B and C, there were no significant difference in binocular I-S, CCT, TCT, MPE from BFS, MPE from BFTE, AAI, PPIavg and ARTmax(all P>0.05), and none of them had correlation with corneal diameter(P>0.05); however, there were statistical significant differences in binocular P.E. and BAD-D in the control group A, B and C(P=0.007, 0.003), while the P.E. differences had no correlation with corneal diameter(P=0.270), and binocular BAD-D differences were negatively correlated with corneal diameter(r=-0.230, P=0.017).

CONCLUSION: Pentacam anterior segment analyzer can accurately measure a variety of corneal biological parameters. Difference of binocular corneal I-S, P.E. and BAD-D are sensitive indexes for the early diagnosis of keratoconus. Among them, difference of binocular I-S and P.E. are less affected by corneal diameter, thus being significant for the early diagnosis of keratoconus with different cornea diameters.