Chan Ben, Cho Pauline, Mountford John
School of Optometry, The Hong Kong Polytechnic University, Hong Kong SAR, China.
Clin Exp Optom. 2010 Jul;93(4):237-42. doi: 10.1111/j.1444-0938.2010.00489.x. Epub 2010 Jun 23.
To investigate the relationship between the change in the manifest refractive error (DeltaM), the change in apical corneal power (DeltaACP) and initial corneal asphericity (Q) in overnight orthokeratology (ortho-K).
One hundred and twenty-eight clinical records of children undergoing ortho-K from a university optometry clinic were reviewed. The refractive and topographical data at baseline and at two-week visit of 58 patients who fulfilled the inclusion criteria were retrieved and analysed.
Significant differences (p < 0.001) between the change in manifest refractive error and changes in the apical corneal power or the maximum change in corneal power (DeltaMCP) within the treatment zone were found. Linear regression analysis was used to describe the change in manifest refractive error and the change in apical corneal power, and the change in manifest refractive error and the maximum change in corneal power, with the equations: DeltaM = 0.91DeltaACP + 0.57 (r = 0.78, p < 0.001) and DeltaM = 0.93DeltaMCP + 0.01 (r = 0.79, p < 0.001) respectively. On average, the change in apical corneal power underestimated the change in manifest refractive error by 0.34 +/- 0.57 D; whereas on average, the maximum change in corneal power overestimated the change in manifest refractive error by 0.23 +/- 0.57 D (paired-t-tests, p < 0.001). A low but significant correlation between initial corneal asphericity and the change in manifest refractive error (Spearman r = -0.33, p = 0.01) was observed.
The change in apical corneal power underestimates the change in manifest refractive error in ortho-K, whereas the maximum change in corneal power overestimates this parameter. Compared with retinoscopy and autorefraction, the change in apical corneal power is still useful for estimation of the change in manifest refractive error. Although the maximum change in corneal power appears to give a closer estimation of the change in manifest refractive error than the change in apical corneal power, there is no advantage in the use of maximum corneal power (manually located) instead of apical corneal power (a default given by the topographer) to estimate the change in manifest refractive error, as there is no significant difference in the estimations by either parameter. Initial corneal asphericity measured by the Medmont E300 corneal topographer has limited usage in predicting the change in manifest refractive error in overnight ortho-K.
研究夜间角膜塑形术（ortho-K）中明显屈光不正的变化（DeltaM）、角膜顶点屈光力的变化（DeltaACP）与初始角膜非球面性（Q）之间的关系。
回顾了一所大学验光诊所128例接受ortho-K治疗儿童的临床记录。检索并分析了符合纳入标准的58例患者基线及两周随访时的屈光和地形图数据。
发现明显屈光不正的变化与角膜顶点屈光力的变化或治疗区内角膜屈光力的最大变化（DeltaMCP）之间存在显著差异（p < 0.001）。采用线性回归分析来描述明显屈光不正的变化与角膜顶点屈光力的变化，以及明显屈光不正的变化与角膜屈光力的最大变化，方程分别为：DeltaM = 0.91DeltaACP + 0.57（r = 0.78，p < 0.001）和DeltaM = 0.93DeltaMCP + 0.01（r = 0.79，p < 0.001）。平均而言，角膜顶点屈光力的变化低估明显屈光不正的变化0.34 +/- 0.57 D；而平均而言，角膜屈光力的最大变化高估明显屈光不正的变化0.23 +/- 0.57 D（配对t检验，p < 0.001）。观察到初始角膜非球面性与明显屈光不正的变化之间存在低但显著的相关性（Spearman r = -0.33，p = 0.01）。
在ortho-K中，角膜顶点屈光力的变化低估了明显屈光不正的变化，而角膜屈光力的最大变化高估了该参数。与检影验光和自动验光相比，角膜顶点屈光力的变化对于估计明显屈光不正的变化仍然有用。尽管角膜屈光力的最大变化似乎比角膜顶点屈光力的变化能更接近地估计明显屈光不正的变化，但使用最大角膜屈光力（手动定位）而非角膜顶点屈光力（地形图仪给出的默认值）来估计明显屈光不正的变化并无优势，因为这两个参数的估计值没有显著差异。通过Medmont E300角膜地形图仪测量的初始角膜非球面性在预测夜间ortho-K中明显屈光不正的变化方面用途有限。
