CALCULATION OF INTRAOCULAR-LENS POWER AFTER RADIAL KERATOTOMY WITH COMPUTERIZED VIDEOKERATOGRAPHY

PURPOSE: Because standard methods to determine intraocular lens power are not adequate in eyes that have had radial keratotomy, we under too k this study to evaluate the corneal power derived from computerized v ideokeratography for use in intraocular lens power calculations. METHO DS: We examined four eyes of three patients who had radial keratotomy and who underwent phacoemulsification cataract surgery with implantati on of a posterior chamber intraocular lens, We used a computerized vid eokeratography-derived corneal curvature value in the Holladay formula for intraocular lens calculations, We determined the ideal intraocula r lens power and the keratometric value that would have led to the ide al intraocular lens power from the postoperative refraction at 6.1 +/- 1.1 months after cataract extraction. The ideal keratometric value wa s compared with the keratometric values derived from computerized vide okeratography, standard keratometry, contact. lens overrefraction, and refractions before and after radial keratotomy. RESULTS: The postoper ative refraction at approximately six months averaged -0.32 +/- 0.63 d iopter (range, -0.88 to +0.75 diopter) different than the aim. The mea n power in ring 3, which was the closest keratometric value to the ide al, disclosed only 0.09 +/- 0.73 diopter and -0.10 +/- 0.72 diopter of deviation from the ideal keratometric and intraocular lens powers, re spectively, One to two weeks after phacoemulsification cataract surger y with implantation of a posterior chamber intraocular lens, the video keratographic differential map disclosed steepening at the wound site with variable regression by six months in all patients. CONCLUSION: Re sults suggest that, after radial keratotomy, using the keratometric va lue derived from computerized videokeratography in intraocular lens ca lculations is more accurate than using keratometric values measured by routine methods.