Comparison of IOL Powers by Different Formulae Used in Corrected Method at Cataract Surgery in Eyes after PRK

ABSTRACT

PURPOSE: By statistical analysis, to evaluate the comparison of the intraocular lens (IOL) powers by different formulae in patients who have been treated with excimer laser photorefractive keratectomy (PRK) for mild to moderate myopia. METHODS: A total of 38 consecutive eyes of 23 patients who were treated with PRK for mild to moderate myopia have been followed up for more than 6 months. IOL powers by SRK-II, SRK/T, Binkhorst-II, HofferQ, Holladay formula using autorefractokeratometer measured keratometric (K) values by autorefractokeratometer (RK-2, Canon, Japan) and refraction derived K values were compared . RESULTS: The mean IOL powers using autorefractokeratometer measured K values and refraction derived K values were 20.46+/-0.92 and 20.57+/-0.86 diopter (D) by SRK-II, 20.69+/-0.93 and 20.81+/-0.88 D by SRK/T, 21.27+/-0.94 and 21.40+/-0.95 D by Binkhorst-II, 20.93+/-0.09 and 21.05+/-0.06 D by Hoffer Q, and 20.65+/-0.90 and 20.76+/-0.87 D by Holliday respectively. The mean IOL powers using autorefractokeratometer measured K values and refraction derived K values were high in oder of Binkhorst-II, HofferQ, SRK/T, Holladay, and SRK-II, but there was no significant statistical difference between the IOL powers by SRK/T and those by Holladay (p>0.05). In all formulae, the mean IOL powers using refraction derived K values were higher than the mean IOL powers using autorefractokeratometer measured K values, but there was no statistically significant difference (p>0.05). CONCLUSIONS: In patients with excimer laser PRK treatment for mild to moderate myopia, refractive error after cataract surgery is caused by IOL calculation formula as well as its method for IOL power. IOL powers by Binkhorst-II using refration derived keratometric values of all formulae were statistically highest.