Predictability of Postoperative Corneal Astigmatism in DMEK: Advisability of Toric IOL Implantation at Time of DMEK
Narrative Responses:
Purpose
To compare pre and postoperative Pentacam measures in DMEK cases, in order to determine the predictability of postoperative corneal astigmatism and the clinical utility of primary Toric IOL implantation at the time of transplantation.
Methods
This is a retrospective review of 44 patients who had undergone DMEK surgery. Pre and postoperative Pentacam imaging was utilized to evaluate corneal tomography. The focus was postoperative change in the magnitude and degree of measured preoperative astigmatism. Patients were then stratified by degree of preoperative astigmatism to determine the characteristics of each sub group as follows: Minimal (0-0.9D, n=23), Mild (1-1.9D, n=13) and Moderate (2-4D, n=8) astigmatism. Further analysis was completed to evaluate the role of preoperative corneal thickness in the predictability of postoperative astigmatism.
Results
The overall mean change in corneal astigmatism was 0.38D (SD= 0.28D), with an average axis change of 18’ (SD= 17’). Sub analysis by degree of preoperative astigmatism was as follows: Minimal (0-0.9D) mean change 0.31D (SD= .21D) and axis 22’ (SD= 18’), Mild (1-1.9D) mean change 0.39D (SD= .46D) and axis 13’ (SD= 15’), Moderate (2-4D) mean change 0.55D (SD= .46D) axis 14’ (SD= 15’). Stratification of those patients with clinically significant preoperative astigmatism (>1D) by corneal thickness of greater (n=10) or less (n=11) than 630um demonstrated no significant difference with respect to change in magnitude (p= 0.78) or axis (p=0.94) of postoperative astigmatism.
Conclusion
Preoperative astigmatism, measure by Pentacam, does not adequately predict the magnitude or axis of postoperative astigmatism in DMEK, and is not significantly affected by preoperative corneal thickness. Unpredictable postoperative astigmatism in DMEK limits the clinic utility of Toric lens implantation at the time of endothelial transplantation.