Accuracy of intraocular lens power calculation after phototherapeutic keratectomy using different methods of determining corneal refractive power

Purpose: To evaluate the predictability of intraocular lens (IOL) power calculation after phototherapeutic keratectomy (PTK). Methods: In this study, 12 eyes of 8 patients who underwent cataract surgery after PTK (PTK group), and 63 eyes of 55 patients who underwent only cataract surgery (control group) were compared. The main outcome measure was the difference between the target and actual refraction achieved 1 month after cataract surgery. IOL power was determined using 4 measurements for the PTK group: standard keratometric power, total optical power and total axial power (central 3mm) analyzed using a slit-scan corneal topographic analysis system, and pre-PTK measurements of keratometric power. Results: Measurements of corneal power by the 4 different methods in the PTK group did not differ significantly, nor did errors in postoperative refractive power differ for the different methods. The refractive errors after cataract surgery were within ±1.0 D of the targeted value in about 50% of the PTK groups using any measurement method, and all of the predicted values were lower than values in the control group. There was no significant difference in predictability of achieving the target refraction as a function of the 4 different keratometric values used to calculate IOL power. Conclusions: The predictability of IOL power needed to achieve postoperative refraction within a target range is lower for eyes undergoing both PTK and cataract surgery than for eyes undergoing cataract surgery alone, which suggests that informed consent to cataract surgery with IOL implantation should include the information that the range of possible refractive error after cataract surgery is greater in eyes that have undergone PTK.