intraocular lens power determination in 10 patients with previous radial keratotomy with or without astigmatic keratotomy: a case series

purpose : to compare results of different methods for true corneal power determination and intraocular lens (iol) power calculation formulas in 10 eyes of 7 patients with previous radial keratotomy (rk) with or without astigmatic keratotomy methods : in this case series study, we determined the corneal power of 10 eyes of 7 patients who had undergone rk with or without astigmatic keratotomy with two methods: the contact lens method (clm) and the mean keratometry of the 3 mm zone in topography. in the next step, the iol power for these eyes was calculated with the 3 formulas of srk ii, srk t, and holladay ii the latter was used for the iol selection. refractive results were determined 3 month after surgery. according to the rule that 1.5 diopter (d) change in iol power results in 1.0 d change in a patient’s refraction at the spectacle plane, we estimated the manifest refraction of these eyes with other formulas and compared them with the results achieved by holladay ii formula. results : using the clm and holladay ii formula, the postoperative manifest refraction spherical equivalent in 8 eyes ranged from -3.00 to +2.00 d. both clm and the mean keratometry of the 3 mm zone in topography lead to a greater degree of hyperopia after cataract surgery with srk ii formula than srk t, and with srk t than holladay ii. the mean spherical equivalent with mean keratometry of the 3 mm zone in topography and holladay ii formula was 0.08 d, and with clm and holladay ii formula was -0.05 d. conclusion : in this study, it seemed that after rk, the mean keratometry of the 3 mm zone in topography gives a better estimate of true corneal power compared with clm, and that the holladay ii formula brings results closer to emetropia compared with srk ii and srk t formulas.   iranian journal of ophthalmology 200820(4):10-19