INTRAOCULAR-LENS POWER CALCULATION FOR CATARACT-SURGERY AFTER PHOTOREFRACTIVE KERATECTOMY FOR HIGH MYOPIA

OBJECTIVE: To assess intraocular lens (IOL) power calculations in pati ents undergoing cataract surgery after excimer laser photorefractive k eratectomy (PRK) for myopia. METHODS: Four eyes of two patients underw ent phacoemulsification with IOL implantation after PRK for myopia. Th e estimated refractive error that would have been induced had the IOL predicted for emmetropia been implanted was calculated using SRK-II, S RK/T, Holladay, and Binkhorst formulas. Manual keratometry and videoke ratography-simulated keratometry values measured before surgery were u sed. Keratometry values calculated by subtracting the refractive chang e induced by the excimer laser PRK from the manual keratometry or vide okeratography-simulated keratometry values measured before PRK were al so used. Both spectacle and corneal plane calculations were performed. RESULTS: Manual keratometry and videokeratography-simulated keratomet ry values underpredicted the IOL power. Corneal plane manual or videok eratography refraction-derived keratometry calculations were most accu rate using the SRK/T formula, while spectacle plane calculations were most accurate using the SRK-II formula. In both methods the calculated refractive error was within 0.52 diopters (D) for the emmetropic lens power predicted. Statistical analysis was not performed. CONCLUSIONS: Refraction-derived keratometric values provided the most accuracy in calculating IOL powers. Our results suggest the SRK/T formula was the most accurate for corneal plane calculations, while the SRK-II formula was the most accurate for spectacle plane calculations.