Intraocular Lens Power Calculation For Combined Penetrating Keratoplasty, Extracapsular Cataract Extraction And Intraocular Lens Implantation

To reduce the surgical impact of refractive errors in patients who have undergone combined penetrating keratoplasty (PK), cataract extraction, and intraocular lens (IOL) implantation. Our objective is to identify and comprehensively discuss the factors that influence the calculation of IOL power.

This retrospective case series included patients who underwent combined PK, cataract extraction, and IOL implantation at Taipei City Hospital Zhong Xing Branch in Taipei, Taiwan. The procedures were conducted by a single surgeon between January 2006 and December 2021.

The IOL power calculation utilized hypothesized keratometry (K) readings ranging from 43.5 to 44.5 diopters (D), with a donor-recipient disparity set at 0.5 mm. The primary outcome measured the difference between the target spherical equivalent and the post-operative refraction. Post-operative K, spherical power, and cylindrical power were recorded during follow-up. Stable post-operative K was defined as K readings measured after a follow-up period exceeding 1 year.

This study comprised 23 eyes from 21 patients, with a mean age of 68.6 years at the time of the operation. The most prevalent pre-operative diagnoses were pseudophakic bullous keratopathy (43.5%), followed by corneal opacity (34.8%) and Fuchs dystrophy (17.4%). Post-operation, 86% of our patients exhibited myopia compared to the initially predicted target. A further myopic shift was observed, with a spherical equivalence of -1.27 D in the first 6 months and -2.22 D at 2 years post-operation. Patients with a graft/recipient size smaller than 8.0/7.5 mm showed a trend towards myopia compared to those with a larger-sized transplant. The average stable post-operative K was 45.05 D and was not associated with the K of the fellow eye.

The post-operative K in patients undergoing combined PK, cataract extraction, and IOL implantation is surgeon-dependent and exhibits significant variation. In the future, a hypothesized K value, approaching the stable K of the surgeon, will be employed for IOL power calculation. Patients with elevated intraocular pressure and those undergoing suture removal may experience a myopic shift. Transplants with smaller-sized grafts also demonstrate a trend of greater myopic deviation, a particularly noteworthy consideration in Asians with smaller corneal size.