Guber Ivo, McAlinden Colm, Majo François, Bergin Ciara
Department of Ophthalmology, University of Geneva, Geneva, Switzerland.
Department of Ophthalmology, Glangwili Hospital, Hywel Dda University Health Board, Carmarthen, UK.
Eye Vis (Lond). 2017 Oct 25;4:24. doi: 10.1186/s40662-017-0089-3. eCollection 2017.
Reaching a consensus on which parameters are most reliable at detecting progressive keratoconus patients with serial topography imaging is not evident. The aim of the study was to isolate the parameters best positioned to detect keratoconus progression using the Pentacam HR® measures based on the respective limits of repeatability and range of measurement.
Using the Pentacam HR®, a tolerance index was calculated on anterior segment parameters in healthy and keratoconic eyes. The tolerance index provides a scale from least to most affected parameters in terms of measurement noise relative to that observed in healthy eyes. Then, based on the "number of increments" from no disease to advanced disease, a relative utility (RU) score was also calculated. RU values close to 1 indicate parameters best positioned to detect a change in keratoconic eyes.
The tolerance index values indicated that 36% of ocular parameters for keratoconic eyes had repeatability limits which were wider than normative limits (worse), but 28% of the ocular parameters were narrower than normative limits (better). Considering only those parameters with a RU greater than 0.95, a small number of parameters were within this range, such as corneal curvature and asphericity indices.
This study demonstrates that measurement error in keratoconic eyes is significantly greater than healthy eyes. Indices implemented here provide guidance on the levels of expected precision in keratoconic eyes relative to healthy eyes to aid clinicians in distinguishing real change from noise. Importantly maximal keratometry (Kmax), central corneal thickness (CCT) and thinnest corneal thickness (TCT) were highlighted as problematic indices for the follow-up of keratoconus in terms of repeatability.
对于在连续地形图成像中检测圆锥角膜进展患者，哪些参数最为可靠，目前尚未达成共识。本研究的目的是基于重复性各自的限度和测量范围，利用Pentacam HR®测量结果分离出最适合检测圆锥角膜进展的参数。
使用Pentacam HR®，计算健康眼和圆锥角膜眼眼前节参数的耐受指数。该耐受指数提供了一个从受测量噪声影响最小到最大的参数量表，与健康眼中观察到的情况相对比。然后，基于从无疾病到晚期疾病的“增加数量”，还计算了相对效用（RU）得分。接近1的RU值表明该参数最适合检测圆锥角膜眼的变化。
耐受指数值表明，圆锥角膜眼36%的眼部参数重复性限度比正常限度更宽（更差），但28%的眼部参数比正常限度更窄（更好）。仅考虑那些RU大于0.95的参数，在此范围内的参数数量较少，如角膜曲率和非球面指数。
本研究表明，圆锥角膜眼中的测量误差显著大于健康眼。此处实施的指数为圆锥角膜眼中相对于健康眼的预期精度水平提供了指导，以帮助临床医生区分真实变化与噪声。重要的是，最大角膜曲率（Kmax）、中央角膜厚度（CCT）和最薄角膜厚度（TCT）在重复性方面被突出显示为圆锥角膜随访中的问题指数。
