Busin M, Madi S, Santorum P, et al. Ultrathin Descemet's stripping automated endothelial keratoplasty with the mi- crokeratome double-pass technique: two- ...
Ultra Thin Descemet Stripping Automated Endothelial Keratoplasty: Single Pass Microkeratome for Thinner Grafts and Improved Outcomes Nicholas Bottaro OMS-3 , Neel R. Desai M.D. §
Introduction
Keratoplasty techniques have advanced tremendously over the past two decades, improving patient satisfaction and visual rehabilitation in patients with corneal pathologies. Studies continue to show that using less donor tissue yields greater outcomes . However, with de1 creased tissue comes increased surgical difficulty. By using Nanocut® ultra-thin corneal grafts created with a single pass microkeratome technique, we have found the balance between surgical difficulty and optimal results. Corneal pathologies such as Fuch’s dystrophy and bullous keratopathy were initially treated with penetrating keratoplasty, transplanting full thickness corneas. In pursuing a procedure that would yield better outcomes, DSAEK became the most commonly preferred treatment. This replaces only the posterior side of the cornea resulting in increased globe integrity, rapid healing 2-4 and better acuity. DMEK has improved on these results by transplanting only Descemet’s membrane, eliminat5-7 ing refraction and rejection caused by the stroma. Although superior, DMEK has not found favor among surgeons because of its steep learning curve, difficulty of intraocular manipulation of the graft, and increased graft 1 detachment and loss. Most recently, studies have shown that performing DSAEK with grafts less than 120 microns 8,9 have improved outcomes but are still inferior to DMEK. This study shows that a Nanocut® ultra-thin DSAEK grafts can achieve results comparable to DMEK grafts using the same preferred DSAEK surgical techniques.
Materials and Methods
A single pass 6-second translational speed cut with the Amadeus II microkeratome over a pressurized cornea greater than 90mmHg resulted in an average graft thickness of 80um with negligible endothelial loss. Grafts were transported in Optisol-GS cold storage media and transplanted using traditional DSAEK techniques within 24 hours of preparation. Patients were followed at 3, 6, and 12 months. Postoperative examinations included UDVA, CDVA, manifest refraction, slit-lamp biomicroscopy, and Goldmann applanation tonometry. At the one month appointment, the donor thickness was measured using OCT. Specular Endothelial Micrography was used to determine endothelial survivability at varying intervals.
Best corrected visual acuity at 12 months was converted to logMAR for statistical analysis. Percentage of patients reaching final BCVA at each interval was also recorded.
Figure 1: Nanocut® single pass microkeratome technique resulting in a thinner, more viable graft.
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termed our Nanocut® Ultra Thin group. By study conclusion, 28 grafts were included in the single-pass Nanocut® UTDSAEK group. The remaining 37 eyes with UT-DSAEK grafts >100um, averaging 125um, were followed and 30 were included in the study. OCT pictures representative of each group is shown in Figures 3 & 4.
Figure 3: OCT of 166 micron single pass DSAEK graft and donor cap before transplant
Figure 4: OCT of 66 micron single pass Nanocut® UT-DSAEK graft and donor cap before transplant.
Figure 2: folding of Nanocut® graft in preparation of insertion
Results
Donor grafts averaging 80um are shown to have excellent results when used in DSAEK. Final visual acuity and total rehabilitation time are improved over grafts thicker than 100um, as typically used in UT-DSAEK. These thinner grafts allow results comparable to DMEK while still having the surgical advantages of DSAEK. Additionally, with no complications reported in the eyes studied, patients were very pleased to only require one procedure and a short recovery. 131 eyes from 119 patients that received single-pass DSAEK between 08/2011 and 11/2014 were analyzed for 3, 6, and 12 month BCVA and healing time. After accounting for exclusion criteria, data from 73 grafts were included in the study. Of those, 36 were single-pass microkeratome graphs of 100um DSAEK group: average logMAR 0.222 v. 0.276 respectively (P=0.037) Final BCVA of DSAEK and Nanocut® UT-DSAEK Grafts logMAR > 100 microns 0.276 (n=30)
< 100 microns (n=28)
0.222 P= 0.037
Table 1: statistical comparison of final visual acuity between Nanocut® ultra thin and thicker grafts
By 6 months post-op, 20% of the Nanocut® group and only 10% of the thicker group had achieved 20/30 acuity. By 1 year, 60% of the Nanocut® group achieved 20/30 or better acuity, with only 33% of the thicker group having similar results.
Conclusion
In our study, graft preparation using a single pass technique with a standard microkeratome was able to yield grafts averaging 80 microns. Nanocut® ultra thin grafts are thought to result in improved visual acuity that is comparable to DMEK while providing surgeons a procedure with fewer complications and a shorter learn7 ing curve. Neff et al. was first to report a significant improvement in BCVA with thinner 110um grafts over 9 thicker 160um grafts. Additionally, Busin and Albe showed UT-DSAEK of 100um to be comparable to DMEK 10 in BCVA and visual recovery. However, Terry et al. and others have reported there is minimal positive correlation between graft thickness and acuity outcomes between 100-200um. This study is the first to our knowledge that compares visual acuity outcomes for grafts less than 80um prepared with a single-pass method. Here we show statistically significant improvement in visual acuity for single pass prepared ultra thin tissue of 80um or less. The peak visual acuities were achieved faster than patients receiving thicker grafts presumably because of less graft stroma deturgescence prior to host stroma deturgescence. This also suggests that peak visual acuities were preserved for at least 1 year during the study period and single pass graft preparation does not generate any further cell loss compared to traditional methods but may have a 11 decreased cell loss as previous studies have reported.
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