METHODS: In this prospective study, keratometry was performed using an IOL Master(IM), a Bausch & Lomb manual keratometer(Man)and TOPCON KR-8800 autokeratometer(Top)on 252 eyes of patients recruited from camps for cataract surgery. The average keratometry values were recorded and compared. The agreements between the instruments were analyzed using the Bland-Altman statistical method. The main outcome measure was average keratometry values.

RESULTS:1)IOL Master and Manual keratometer: the mean corneal power was 44.62±1.52 D with the IOL Master and 44.60±1.52 D with the Manual keratometer. The paired t-test demonstrated a statistically significant difference in the mean corneal power between the IOL Master and Manual keratometer(P=0.001). The 95% LOAs of the two devices were -0.22 to 0.22 as shown in the Bland-Altman plot; 2)IOL Master and autokeratometer: the mean corneal power was 44.62±1.52 D with the IOL Master and 44.46±1.53 D with the autokeratometer. The paired t-test demonstrated a statistically significant difference in the mean corneal power between the IOL Master and autokeratometer(P<0.0001). The 95% LOAs of the two devices were -0.24 to 0.55 as shown in the Bland-Altman plot; 3)Autokeratometer and Manual keratometer: the mean corneal power was 44.60±1.52 D with Manual keratometer and 44.46±1.53 D with the autokeratometer. The paired ttest demonstrated a statistically significant difference in the mean corneal power between the autokeratometer and Manual keratometer(P<0.0001). The 95% LOAs of the two devices were -0.30 to 0.57 as shown in the Bland-Altman plot.

CONCLUSION: Keratometry data obtained with different instruments may not be interchangeable, a fact that has important implications for cataract surgeons with respect to both surgical planning and outcomes auditing.