Morlet N, Maloof A, Wingate N, Lindsay P
Department of Ophthalmology, Prince of Wales Hospital, UNSW, Sydney, Australia.
Br J Ophthalmol. 1998 Jan;82(1):35-8. doi: 10.1136/bjo.82.1.35.
Some surgeons consider hand held surgical keratometers unreliable. This may be due to incorrect use through not realising that the distance that the keratometer is held from the cornea influences the shape of the image. When a keratometer is held closer to the astigmatic cornea, the elliptical image will appear more circular, particularly for larger degrees of astigmatism. However, the keratoscopic astigmatic ruler (KAR) has design features that correct the hitherto unrecognised problems with the use of a hand held keratometer. This study assesses the reliability and accuracy of measurement of astigmatism using the KAR.
The KAR and the Bausch & Lomb keratometer (B&L) were compared using six back surface toric cut contact lens blanks representing 1 to 6 dioptres of astigmatism. Two observers (one experienced in the use of the keratometers, the other a novice) took eight randomly repeated "masked" measurements of each lens blank with the KAR and four measurements with the B&L in a similar fashion.
There was no difference between the measurements with either instrument by each of the observers (p = 0.95, ANOVA). The standard error of measurement for the KAR was 0.59 D, for the B&L, 0.31 D. The intraclass correlation coefficient of reliability for the KAR was 0.90 and for the B&L it was 0.97. The coefficient of repeatability for the KAR was plus or minus 0.83 D, and for the B&L plus or minus 0.77 D. The interobserver reliability for the KAR was 0.898, and for the B&L, 0.975.
These results suggest that the KAR has good reliability and reproducibility and compares favourably with the B&L keratometer. Inexperience with use does not affect reliability.
一些外科医生认为手持式手术角膜曲率计不可靠。这可能是由于使用不当，未意识到角膜曲率计与角膜的距离会影响图像形状。当角膜曲率计靠近散光角膜时，椭圆形图像会显得更圆，尤其是散光度数较大时。然而，角膜镜散光尺（KAR）的设计特点纠正了手持式角膜曲率计使用中迄今未被认识到的问题。本研究评估了使用KAR测量散光的可靠性和准确性。
使用六个代表1至6屈光度散光的后表面复曲面切割隐形眼镜毛坯，将KAR与博士伦角膜曲率计（B&L）进行比较。两名观察者（一名有角膜曲率计使用经验，另一名是新手）以类似方式对每个镜片毛坯用KAR进行八次随机重复的“盲法”测量，用B&L进行四次测量。
每位观察者使用两种仪器测量的结果之间无差异（p = 0.95，方差分析）。KAR的测量标准误差为0.59 D，B&L为0.31 D。KAR的可靠性组内相关系数为0.90，B&L为0.97。KAR的重复性系数为±0.83 D，B&L为±0.77 D。KAR的观察者间可靠性为0.898，B&L为0.975。
这些结果表明，KAR具有良好的可靠性和可重复性，与B&L角膜曲率计相比具有优势。使用经验不足不会影响可靠性。
