Optimization of Intraocular Lens Constant Improves Refractive Outcomes in Combined Endothelial Keratoplasty and Cataract Surgery

Abstract

Purpose To evaluate the accuracy of intraocular lens (IOL) power calculations with A-constant optimization in Descemet’s stripping automated endothelial keratoplasty (DSAEK) combined with cataract extraction and intraocular lens implantation (DSAEK triple procedure). Design Retrospective case series. Participants Thirty eyes of 22 patients with Fuchs’ endothelial dystrophy who underwent the DSAEK triple procedure performed by a single surgeon. Methods Prediction errors were calculated retrospectively for consecutive DSAEK triple procedures. These prediction errors then were used to determine an IOL constant for this cohort of patients. The new optimized IOL constant subsequently was compared with the manufacturer’s IOL constant, allowing evaluation and quantification of refractive benefits of optimization. Main Outcomes Measures The error in diopters (D) of the predicted refraction with the manufacturer’s and optimized IOL constants. Results Optimization of the A constant decreased the mean absolute error (MAE) from 1.09±0.63 D (range, 0.12–2.41 D) to 0.61±0.4 D (range, 0–1.58 D; P = 0.004). Comparing the intended and final postoperative refractions calculated with the original manufacturer’s constant and the optimized constant, 20% versus 43% of all eyes were in the less than 0.5-D range and 50% versus 83% of all eyes were in the less than 1.0-D range of the target refraction. Furthermore, optimization decreased the number of eyes that were more than 1.0 D from the target refraction from 50% to 17%. Conclusions Optimization of the IOL constant showed significantly improved accuracy of predicted postoperative refraction compared with the manufacturer’s IOL constant, which may help improve the postoperative refractive outcomes in patients undergoing the DSAEK triple procedure.

Changes in Corneal Refractive Power for Patients With Fuchs Endothelial Dystrophy After DMEK

“…This hyperopic shift is very relevant after DSAEK and is described in the literature as ranging from 0.7 to 1.5 D. Many surgeons favor a more myopic postoperative outcome and aim to achieve a postoperative refraction of 21.0 to 22.0 D to reduce the chance of unintended hyperopic surprises. 18 Modern 2-variable third-generation formulas such as SRK/T, Haigis, Holladay 1, and Hoffer Q use the corneal power estimated using the anterior sagittal corneal radii, together with a fictitious refractive index and the axial length to calculate the IOL power. 19 Given the fact that no significant changes in axial length occurred after posterior lamellar keratoplasty, postoperative refractive changes must be based on changes in corneal curvature.…”

“…We know that after DSAEK different parameters such as graft thickness and lenticular graft profile contribute to the postoperative variance in refractive shift. 18 The cornea has 2 refracting surfaces, and the TCRP is the key parameter for the calculation of IOL power. To determine the TCRP, it is necessary to know the curvature not only of the front but also of the back of the cornea.…”

“…18 Modern optical biometers such as the IOL-Master (Carl Zeiss Meditec, Jena, Germany) do not measure the posterior cornea directly, but instead account for it by using an assumed value for the refractive index of the cornea combined with measurements of the anterior corneal curvature. 18 It is already known from patients undergoing laser in situ keratomileusis (LASIK) surgery that postoperative IOL calculations based on classic formulae become biased because of a change in the relationship between the anterior and posterior curvatures. 20 In contrast to patients undergoing LASIK, surgery in patients undergoing DMEK is mainly carried out on the back side of the cornea.…”

Descemet stripping automated endothelial keratoplasty in Fuchs′ endothelial dystrophy versus pseudophakic bullous keratopathy

“…There are two approaches to improve refractive outcomes after the DSAEK triple procedure including aiming for a more myopic postoperative outcome by targeting a postoperative refraction of −1.0 to −2.0 D and optimization of the IOL constant. [1142526] However, unacceptable refractive outcomes should be expected in patients who undergo DSAEK triple procedures. The four potential sources of error in IOL calculations are corneal curvature measurement, axial length measurement, effective lens position estimation, and the IOL calculation formula.…”

Simple, Inexpensive, and Effective Injector for Descemet Membrane Endothelial Keratoplasty

“…Previous steps of the procedure were performed through a 2.75-mm clear corneal keratome incision and included the scoring of the DM at 8.0 mm, removal of the DM, and scraping of the peripheral recipient stromal bed as described previously. 8 All patients underwent an intraoperative inferior peripheral iridectomy. In 6 out of 7 cases, combined phacoemulsification with intraocular lens (IOL) implantation was performed before any steps of the DMEK procedure.…”