Early Experience with Descemet’s Stripping Automated Endothelial Keratoplasty Combined with Phacoemulsification: Clinical and Refractive Outcome University of Texas Southwestern Medical Center Department of Ophthalmology Marvin Hsiao, MD, Pawan Prasher, MD, R. Wayne Bowman, MD, James P. McCulley, MD, V. Vinod Mootha, MD No financial relationships involved in this presentation.

Purpose Descemet’s stripping automated endothelial keratoplasty (DSAEK) has recently gained popularity as an alternative to the full thickness penetrating keratoplasty (PK) for treatment of endothelial dysfunction. This is due to the shorter healing time and the advantage of avoiding a full thickness graft offered by the DSAEK procedure. When a cataract coexists with the corneal endothelial dysfunction, either a combined or sequential procedure for keratoplasty and cataract extraction is indicated. For the combined procedure of PK, cataract extraction, and intraocular lens (IOL) implant (PK triple), the resultant post-operative corneal keratometry is difficult to predict, leading to problems with IOL power determination and post-operative refractive surprises.

Purpose In DSAEK, previous studies have shown that the post-op corneal keratometry is much more predictable than PK, although usually associated with a hyperopic shift in refraction. A pilot study has also shown that when combining DSAEK with phacoemulsification and IOL implantation, the refractive result can be predictable, along with rapid visual recovery. In this study we present our early experience with the combined phaco/DSAEK procedure.

Methods The study was a retrospective chart review of noncomparative surgical cases. Patients who underwent combined phacoemulsification, IOL implantation, and DSAEK for treatment of cataract and corneal endothelial dysfunction were included in the study. Patients with co-morbid conditions that preclude post-op best-corrected visual acuity (BCVA) of better than 20/60 were excluded from the study. Preoperative measurements of axial length, keratometry, anterior chamber depth, and white-to-white by IOL Master were recorded for each eye. Outcome measures included IOL power implanted, BCVA and manifest refraction at post-operative months 1, 3, and 6 when available.

Methods Due to the observation of hyperopic shift associated with DSAEK, the IOL power implanted was increased from the calculated emmetropic value to account for this observation. The true emmetropic IOL power based on post-op refraction was back-calculated and compared to the calculated emmetropic IOL for each eye based on either the SRK/T or the Holladay II formula. This comparison generated an IOL error for each eye. In 3 eyes, preoperative keratometry was not possible due to significant epithelial edema. In one of these eyes, keratometry from the contralateral eye was used. For the other two eyes, keratometry from the contralateral eye was not possible, and a keratometry value of 44.0 D was used.

Results A total of 13 eyes of 11 patients that underwent combined phaco/DSAEK were included in the initial stages of the study. There were 4 males and 7 females. Average age at the time of surgery was 64. Post-op month 1 BCVA ranged from 20/25 to 20/200 (average log MAR 0.38, 20/50+1), with spherical equivalent (SE) refractive error ranging from -1.625 D to +3.375 D (average +0.78  1.17 D). Post-op month 3 BCVA ranged from 20/20-1 to 20/50-2 (average log MAR 0.21, 20/32-), with SE ranging from -0.75 D to +2.50 D (average +0.68  0.83 D). Post-op month 6 BCVA and refraction are still partially pending.

Results Based on post-op month 3 or month 6 (if available) refraction, the true emmetropic IOL power was calculated by using the formula IOL emmetropia = IOL implanted + (post-op SE x 1.4) This true emmetropic IOL power was then compared not to the IOL power implanted, but to the emmetropic IOL power predicted by either the SRK/T or the Holladay II formula. IOL error = IOL emmetropia (back calculation) – IOL emmetropia (predicted) IOL error ranged from +0.25 D to +3.80 D (average +2.33  1.04 D), illustrating the hyperopic shift with DSAEK involving all eyes in this study.

Conclusion The advantages of DSAEK include faster visual recovery, avoiding complications inherent to a full thickness corneal button such as wound dehiscence and suture related problems, limited amount of surgically induced corneal astigmatism, and the potential to either repeat the DSAEK procedure for graft failure versus subsequent PK. In this study, visual recovery is rapid, with over 75% of the eyes achieving vision better than 20/40 at post-op month 3, and 100% better than 20/60. Disadvantages of DSAEK include graft dislocation, pupillary block, possible secondary glaucoma, endothelial cell loss, and a graft-host interface that may limited final BCVA.

Conclusion In PK, the unpredictable post-operative keratometry may result in refractive errors leading to significant anisometropia, irregular astigmatism, and the need for contact lens correction. Visual recovery with PK is a lengthy process, with suture and wound issues adding to the increased risk of infection and wound instability. The hyperopic shift in post-operative refraction associated with DSAEK necessitates implanting a higher IOL power than predicted by IOL formulas to avoid a hyperopic result. In this study, the average IOL error is +2.33 diopters with standard deviation of 1.04 diopters. Despite increasing the IOL power implanted, 10 out of 13 eyes (76.9%) still resulted in a hyperopic refraction at post-op month 3.

Conclusion This hyperopic shift is thought to be from the donor graft decreasing the posterior radius of curvature of the cornea due to its concave shape, which in effect decreases the refractive power of the cornea as a whole. It would be advantageous to be able to predict the amount of hyperopic shift based on pre-op data. More eyes would be needed than available in this study to conduct a regression analysis to find this relationship. Whether DSAEK will eventually prove to be the preferred choice of keratoplasty for corneal endothelial dysfunction, the rapid recovery and more predictable post-operative refractive outcome offers an exciting new method of combining keratoplasty with cataract surgery.