INTRAOCULAR LENS POWER CALCULATION AFTER DOUBLE KERATOREFRACTIVE PROCEDURES - CASE REPORT

To report the results of challenging intraocular lens (IOL) power calculation cases in patients who received two sequential keratorefractive procedures, radial keratotomy (RK) followed by laser assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK).

Refractive Surgery Unit of Ophthalmology Department of Centro Hospitalar Universitário do Porto, Oporto, Portugal

Patient chart review

A 55-year-old woman had received refractive surgery for myopia with RK on her right eye, later enhanced by PRK more than 20 years ago. A 68-year-old man had received refractive surgery for myopia with RK on both eyes, later enhanced by LASIK on the right one more than 30 years ago. Both patients presented at our department with complains of reduced visual acuity, having a best-corrected visual acuity (BCVA) of 20/60 and 20/100, respectively. At slit-lamp examination, radial keratotomies and cortical cataracts were the main findings and the patients were proposed for cataract phacoemulsification with in-the-bag intraocular monofocal single-piece acrylic lens implantation with an A-constant of 118.7 and 119.26, respectively. The IOL power calculation was made using several formulae available at the American Society of Cataract and Refractive Surgery (ASCRS) online calculator, including IOL calculation formulas for post-LASIK/PRK condition (Shammas, Haigis-L and Barrett True K no history), formulas for post-RK condition (Double K-modified Holladay 1 based on Oculus Pentacam and IOL Master, and Barrett True K) and Kane formula. The Double K-modified Holladay and Kane formulae were found to be most accurate in predicting IOL power for the first patient while the Barrett True K for post-RK conditions was the most accurate for the male patient. After the surgery, the patients presented an BCVA of 20/30 and 20/40 with spherical equivalents of +0.125 and +0.625 diopters, respectively.

The IOL power calculation for patients with past history of keratorefractive surgery remains a challenge. The difficulty of this task is increased for patients with more than one procedure and there is still lack of evidence and consensus for these scenarios. In these two cases, no formula was found to be accurate for both patients. Thus, it is important to deal properly with preoperative patients’ expectations and to inform of the risk of miscalculation.