Descemet Membrane Endothelial Keratoplasty (DMEK), which is used to treat conditions such as pseudophakic bullous keratopathy and Fuchs corneal dystrophy, is often paired with concurrent cataract surgery to improve visual outcomes. In this retrospective chart review, we investigated the effect of various corneal parameters on the accuracy of preoperative prediction of final refraction at 6 months postoperatively in DMEK combined with cataract surgery.

Methods

Patients who had undergone DMEK combined with cataract surgery between January 2014 – February 2018 were selected. Patients were excluded if they had less than 3 months of follow-up. The Mann Whitney U test was then used to compare preoperative parameters such as axial length, steep and mean K, and pachymetry of patients who achieved a final refraction within 0.5 diopters of the target refraction with those of whom achieved a final refraction outside of that range. A Wilcoxon signed-rank test was used to compare means of repeated measurements.

Results

68 eyes of 68 patients underwent DMEK combined with cataract surgery between Jan 2014 – Feb 2018. The mean patient age was 66.5 ± 8.6 years. Mean target refraction was -0.69 D (IQR: -0.8 to -0.50), and an average 0.55 D hyperopic shift was found. 47% of patients achieved a refraction within 0.5 D of the target refraction 6 months postoperatively.  Preoperative central corneal thickness, topography, and axial length were not found to be significantly different between patients whose predicted refraction was within 0.5 D of their final refraction as opposed to those who were outside that range. Mean refractive shift was significantly greater among eyes with preoperative pachymetry ≥640 μm than in those with preoperative pachymetry <640 μm (1.20 ± 0.92 D vs. 0.4 ± 0.99 D, p = 0.02).

Conclusion

Patients with hyperopic shift may have greater preoperative corneal edema that reverses after DMEK. Further examination of the effects of preoperative CCT on hyperopic surprise and the accuracy of power calculations in DMEK among different formulae is recommended.

IOL calculation accuracy in patient undergoing cataract extraction and IOL implantation in conjunction with Descemet membrane endothelial keratoplasty (DMEK)

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