Yang Kaili, Xu Liyan, Fan Qi, Ren Shengwei
Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Henan University People's Hospital, Zhengzhou 450003, China.
J Ophthalmol. 2020 Dec 2;2020:6667507. doi: 10.1155/2020/6667507. eCollection 2020.
The study aimed to evaluate the character of corneal stiffness parameter at the first applanation (SP-A1) in normal and keratoconus eyes and explore the association between SP-A1 and keratoconus severity indicators.
A total of 351 normal and 351 keratoconus eyes were included in the current study. Keratoconus was diagnosed according to the corneal topography map and slit-lamp examination. The severity of keratoconus was classified to mild (steep keratometry (Ks) < 48D), moderate (48 ≤ Ks < 55D), and severe (Ks ≥ 55D). The SP-A1 was measured using the Corvis ST software. The correlation analyses and receiver operating characteristic (ROC) curve were performed in the current analysis.
The SP-A1 values of keratoconus were lower than that of normal eyes (72.11 (57.02, 83.08) mmHg/mm vs 110.89 (100.45, 122.47) mmHg/mm, < 0.001). With the severity of keratoconus increasing, the SP-A1 decreased and the value of SP-A1 was 79.54 (70.30, 90.93) mmHg/mm, 65.11 (53.14, 77.46) mmHg/mm, and 47.59 (37.50, 62.14) mmHg/mm in mild, moderate, and severe keratoconus eyes, respectively ( < 0.001). The negative association between SP-A1 and Ks was found in mild, moderate, and severe keratoconus eyes (r = -0.171, = -0.317, = -0.288, all < 0.05). A positive association between SP-A1 and the thinnest corneal thickness (TCT) was found in all eyes (r = 0.687, = 0.519, = 0.488, = 0.382, all < 0.05). SP-A1 was found to be statistically positively associated with intraocular pressure (IOP), biomechanical corrected IOP (bIOP), time from the initiation of air puff until the first applanation (A1T), corneal velocity at the second applanation (A2V), and negatively associated with deformation amplitude (DA), peak distance (PD), corneal velocity at the first applanation (A1V), time from the initiation of air puff until the second applanation (A2T), and DA Ratio Max [2 mm] both in normal and keratoconus eyes (all < 0.05). The ROC analysis indicated that the AUC (95% CI) of SP-A1 was 0.952 (0.934-0.967) and 0.930 (0.904-0.951) in detecting keratoconus eyes and mild keratoconus eyes from normal eyes, respectively.
The SP-A1 value decreased while the keratoconus severity increased. It was lower in keratoconus than that in normal eyes and could be helpful in identifying keratoconus eyes from normal eyes. Further researches would be warranted to expand the clinical utility of SP-A1.
本研究旨在评估正常眼和圆锥角膜眼首次压平（SP-A1）时的角膜硬度参数特征，并探讨SP-A1与圆锥角膜严重程度指标之间的关联。
本研究共纳入351只正常眼和351只圆锥角膜眼。根据角膜地形图和裂隙灯检查诊断圆锥角膜。圆锥角膜的严重程度分为轻度（陡峭角膜曲率（Ks）＜48D）、中度（48≤Ks＜55D）和重度（Ks≥55D）。使用Corvis ST软件测量SP-A1。在当前分析中进行相关性分析和受试者工作特征（ROC）曲线分析。
圆锥角膜的SP-A1值低于正常眼（72.11（57.02，83.08）mmHg/mm对110.89（100.45，122.47）mmHg/mm，P＜0.001）。随着圆锥角膜严重程度的增加，SP-A1降低，轻度、中度和重度圆锥角膜眼的SP-A1值分别为79.54（70.30，90.93）mmHg/mm、65.11（53.14，77.46）mmHg/mm和47.59（37.50，62.14）mmHg/mm（P＜0.001）。在轻度、中度和重度圆锥角膜眼中均发现SP-A1与Ks呈负相关（r分别为-0.171、-0.317、-0.288，均P＜0.05）。在所有眼中均发现SP-A1与最薄角膜厚度（TCT）呈正相关（r分别为0.687、0.519、0.488、0.382，均P＜0.05）。发现SP-A1在正常眼和圆锥角膜眼中均与眼压（IOP）、生物力学校正眼压（bIOP）、从吹气开始到首次压平的时间（A1T）、第二次压平时的角膜速度（A2V）呈正相关，与变形幅度（DA）、峰值距离（PD）、首次压平时的角膜速度（A1V）、从吹气开始到第二次压平的时间（A2T）以及DA Ratio Max[2mm]呈负相关（均P＜0.05）。ROC分析表明，SP-A1在从正常眼中检测圆锥角膜眼和轻度圆锥角膜眼时的AUC（95%CI）分别为0.952（0.934-0.967）和0.930（0.904-0.951）。
圆锥角膜严重程度增加时SP-A1值降低。圆锥角膜中的SP-A1值低于正常眼，有助于从正常眼中识别圆锥角膜眼。有必要进一步研究以扩大SP-A1的临床应用。
