Clinical utility of the Barrett keratoscope with astigmatic dial

Intraoperative keratometry allows some degree of control over corneal astigmatism during cataract surgery. I describe the clinical use of the Barrett keratoscope combined with an astigmatic dial that quantifies the information obtained by this simple, inexpensive, hand-held surgical keratometer. Based on a comparison of intraoperative measurements with those taken after extracapsular cataract surgery with an automated keratometer, I conclude that intraoperative keratometry reliably predicted the postoperative astigmatism. For those who had the intraocular pressure (IOP) set between 15 and 20 mm Hg intraoperatively, the mean deviation of the first postoperative measurement from the intraoperative measurement of astigmatism was +/- 1.03 D (standard error, 1.56 diopters; 95% confidence interval 0.712 to 1.35 D). When the IOP was not set, the postoperative astigmatism differed from the intraoperative reading by more than 2.00 D for 50% of the cases. Setting the IOP prior to intraoperative keratometry significantly improved the reliability of the measurement. Intraoperative keratometry by the simple device used in this study is of sufficient utility to allow the surgeon to adjust for the predicted changes in the corneal astigmatism at the time of surgery.