目的:比较计算法和试戴镜法在确定硬性透氧性角膜接触镜（RGP）屈光度时的差异,阐明用试戴镜法验配RGP的优越性。方法:用试戴镜法验配的16例31眼近视和近视散光患者,在戴片验光结合顶点换算确定RGP屈光度后,再用已经确定的RGP基弧结合SAM(steep add minus,即陡加负)和FAP(flat add plus,即平加正)原则与顶点换算,计算出RGP的屈光度。结果:（1）计算法确定RGP屈光度的31只镜片中,除2只的度数与试戴镜法相同外,其余29只全部过矫,半数以上（18/31）过矫≥-0.50D。（2）根据试戴镜法确定屈光度订制的RGP给患者配戴后,除1眼矫正远视力为0.8外,其余30眼的矫正远视力均≥1.0。结论:在确定RGP屈光度时,计算法可导致近视过矫。用试戴镜法确定的RGP屈光度普遍低于计算法。

AIM:To compare the calculation method with diagnostic method in determining the power of rigid gas permeable contact lens (RGP), and to notice that diagnostic method is superior to calculation method.METHODS:Sixteen cases(31 eyes) with myopia or myopic astigmatism were fitted by diagnostic method, after wearing optometry combined with vertex conversion to determine the RGP diopter, then using the determined RGP base curves combined with steep add minus(SAM), flat add plus(FAP) principle and the vertex conversion to calculate the RGP refraction.RESULTS:In 31 eyes determined by calculating the RGP refraction, except 2 eyes' diopter were similar with diagnostic method, the other 29 eyes were all overcorrected, more than half (18/31) eyes were overcorrected ≥-0.50D. 30 eyes have corrected VA≥1.0 with RGP fitted with diagnostic method, while only 1 eye has corrected VA as 0.8.CONCLUSION:Calculation method can cause over correction of myopia in determining RGP power. The RGP power determined by diagnostic method is lower than that determined by calculation method.