Comparison of different optometric tests to measure refraction before LASIK

Objective To compare the accuracy and reliability of refraction with different optometric tests before laser in situ keratomileusis (LASIK).Methods It was a prospective clinical study.Two hundred and forty one eyes of 122 myopes with a spherical range of-0.75～-13.25 D,average,-5.57±2.40 D and cylinder range of-0.25～-5.50 D,average,-0.96-±0.66 D.Four different optometric tests were used before the excimer laser surgery: cycloplegic retinoscopy,autorefraction,subjective refraction and Orbscan Ⅱ.Subjective refraction was performed on the patients 1 year postoperatively.Data were analyzed using one-way ANOVA,a paired samples t test and Pearson correlation.Results The mean spherical results with cycloplegic retinoscopy,autorefraction and subjective refraction were-5.20±2.61 D,-5.64±2.71 D and-5.57±2.40 D,respectively.These were significantly different (F=38.586,P＜0.01).The mean cylinder results with cycloplegic retinoscopy,autorefraction and subjective refraction were-0.99±0.66 D,-1.03±0.73 D and-0.96±0.66 D.These were significantly different (F=15.147,P＜0.01).The cylinder measured by Orbscan Ⅱ was-1.16±1.84 D,which was significantly different from the result by subjective refraction (t=3.190,P＜0.01).A Pearson correlation showed a high correlation for the results from the different optometric tests (r＞0.9 for all,P＜0.01 for all).Conclusion It is important to note in clinical practice,comprehensive optometric tests are necessary for the success of excimer laser surgery. Key words: Excimer laser surgery ;  Cycloplegic retinoscopy ;  Autorefraction ;  Subjective refraction ;  Orbscan Ⅱ