Total keratometry versus simulated keratometry for intraocular lens power calculation in adult patients with traumatic aphakia and corneal scar

Background Traumatic aphakia with corneal scarring constitutes a major cause for vision loss following open globe injury. Accurate intraocular lens (IOL) power calculation is important to avoid postoperative refractive surprises making vision rehabilitation difficult. Purpose To compare the accuracy of total versus simulated keratometry for IOL power calculation in adult patients suffering from traumatic aphakia and corneal scarring following open globe injury repair. Patients and methods Patients were randomized into two groups: group A where IOL power was calculated using total keratometry and the Haigis formula and group B where IOL power was calculated using simulated keratometry and Haigis formula. Prediction error in both groups was assessed and compared at 1 and 3 months postoperatively. A secondary analysis was performed in group A to compare combinations of total keratometry with vergence formulas other than Haigis (Hoffer Q, Holladay 1, SRK-T) to the Haigis formula and to compare biometry of the sound eye with biometry of the injured eye. Results The study included 30 eyes in group A and 30 eyes in group B. Mean absolute prediction errors were significantly lower in group B than in group A at 1 month 1.24±0.81 D versus 2.28±1.67 D ( P =0.017) and at 3 months 1.19±0.83 D versus 2.27±1.72 D ( P =0.018). Group B contained significantly higher percentage of eyes within±1D (50 vs 20%) ( P =0.014) and within±2D (80 vs 50%) ( P =0.015). In group A, using the vergence formulas (Hoffer Q, Holladay 1, and SRK-T) did not improve prediction accuracy compared with the Haigis formula. Biometry of the sound eye was not significantly better than the injured eye and exhibited a wider range of prediction errors. Conclusion In patients with traumatic aphakia and corneal scarring, simulated keratometry by corneal topography gives more accurate refractive results for IOL power calculation than total keratometry. Biometry of the sound eye may provide a broader range of prediction errors than biometry of the injured eye.