Identification of the preoperative and perioperative factors that predict postoperative endothelial cell density after Descemet membrane endothelial keratoplasty: A retrospective cohort study

Principal Component Analysis of a Real-World Cohort of Descemet Stripping Automated Endothelial Keratoplasty and Descemet Membrane Endothelial Keratoplasty Cases: Demonstration of a Powerful Data-Mining Technique for Identifying Areas of Research

PURPOSE

Principal component analysis (PCA) is a descriptive exploratory statistical technique that is widely used in complex fields for data mining. However, it is rarely used in ophthalmology. We explored its research potential with a large series of eyes that underwent 3 keratoplasty techniques: Descemet membrane endothelial keratoplasty (DMEK), conventional Descemet stripping automated endothelial keratoplasty (ConDSAEK), or ultrathin-DSAEK (UT-DSAEK).

METHODS

All consecutive DMEK/DSAEK cases conducted in 2016 to 2022 that had ≥24 months of follow-up were included. ConDSAEK and UT-DSAEK were defined as preoperative central graft thickness ≥130 and <130 μm, respectively. Seventy-six patient, disease, surgical practice, and temporal outcome variables were subjected to PCA, including preoperative anterior keratometry, the use of sulfur hexafluoride gas (SF6) versus air for primary tamponade, and postoperative best corrected visual acuity and endothelial cell density. Associations of interest that were revealed by PCA were assessed with the Welch t test or Pearson test.

RESULTS

A total of 331 eyes were treated with DMEK (n = 165), ConDSAEK (n = 95), or UT-DSAEK (n = 71). PCA showed that ConDSAEK and UT-DSAEK clustered closely, including regarding postoperative best corrected visual acuity, and were clearly distinct from DMEK. PCA and follow-up univariate analyses suggested that in DMEK, 1) flatter preoperative anterior keratometry (average, K1, and K2) associated with more rebubbling (P = 0.004-0.089) and graft detachment (P = 0.007-0.022); 2) graft marking did not affect postoperative ECD; and 3) lower postoperative endothelial cell density associated with SF6 use (all P > 0.001) and longer surgery (P = 0.005-0.091). All associations are currently under additional investigation in our hospital.

CONCLUSIONS

PCA is a powerful technique that can rapidly reveal clinically relevant associations in complex ophthalmological datasets.

Corneal endothelial validation in the eye bank: differences in automated methods and repeatability

PURPOSE

To evaluate reproducibility of endothelial cell density (ECD) measurements using the Konan Cell Check D in donor corneas by two different ophthalmologists and to compare the two automated cell count methods (center and flex-center) available in the software of this specular microscope.

METHODS

ECD values were quantified in 54 donor corneas by two independent investigators using the Cell Check D (Konan Medical USA Inc) with both automated cell count methods. In the center method, at least 30 contiguous cells are marked. For the flex-center method, an area is delineated and only the cells within the designated area are counted.

RESULTS

The mean ECD was 2473.81±378.22 cells/mm2. Good ECD intergrader reproducibility for the center (ICC=0.821) and the flex-center method (ICC=0.784) were noted. Poor reliability was observed for coefficient of variation and hexagonality (ICC≤0.265). When both methods for ECD analysis were compared, a moderate correlation for the two independent graders using the two manual (center and flex-center) methods was detected (correlation coefficient of 0.678 and 0.745 for each of the investigators). Comparison between methods yielded significantly higher ECD with the flex-center method (P=0.013). When corneas were divided by ECD, those under 2200 cells/mm2 and those between 2200 and 2700 cells/mm2 also had significantly higher ECD with the flex-center method (P<0.022).

CONCLUSIONS

ECD values are reproducible with both methods, although the flex-center method ECDs tend to be higher, particularly in cases of low ECD. Eye banks and surgeons should exercise caution in making decisions based only on small differences in ECD.

Performance outcomes from a DMEK peeling and preparation wet lab

OBJECTIVE

To evaluate the Descemet membrane endothelial keratoplasty (DMEK) preparation performance of trainee surgeons in an ex vivo human donor cornea DMEK wet lab simulation setting.

METHODS

Human donor corneoscleral rims unsuitable for transplantation were obtained from Moorfields Lions Eye Bank. At the wet lab, graft stripping was performed by scoring the peripheral endothelium. The trypan blue positive cells (TBPC) and cell density (cells/mm2-reticule count) were counted manually before and after stripping. The procedural time, peripheral and central tears and complete peel-off were also recorded and analysed.

RESULTS

Eight trainee surgeons attended the wet lab each attempting three DMEKs. Between the first and last attempts a significant decrease was seen in the procedural time (17.6 min vs 10.6 min (p<0.05)) and the TBPC % (12.9% vs 3.8% (p<0.05)). The percentage of tears peripherally and centrally also reduced between the first and the last trials (50% vs 13% (p=0.2226) and 38% vs 0% (p=0.1327)). A significant correlation was found between longer peeling times and higher TBPC % (p<0.001) with a 0.7% endothelial mortality increase for each additional minute required to complete the peel.

CONCLUSIONS

DMEK wet labs provide a controlled risk-free learning opportunity for trainee surgeons to improve confidence and competence. Wet labs improve the success rate of DMEK graft preparation as well as flatten the learning curve. This emphasises the importance of continued support for the expansion of this valuable learning resource, promoting wider uptake of DMEK surgery.

Main issues in deep anterior lamellar keratoplasty: A systematic narrative review

Deep anterior lamellar keratoplasty (DALK) has emerged as a transformative approach in managing corneal pathologies, notably keratoconus (KC), providing a viable alternative to penetrating keratoplasty (PK). This systematic review explores the intricacies of DALK, comparing its preoperative, intraoperative, and postoperative considerations with PK. Extensive literature searches revealed a wealth of data regarding DALK's advantages and challenges, with an emphasis on graft survival, visual outcomes, and complications. In the preoperative phase, DALK showcases its versatility, catering to a wide spectrum of patients, including those with KC and ocular surface disorders. Intraoperatively, it offers innovative techniques to address emphysema, bubble formation, and Descemet's membrane perforation, all while maintaining a strong focus on patient-centered outcomes. Postoperatively, DALK's lower rejection rates and decreased complications underscore its potential superiority over PK, although unique challenges such as graft failure from nonimmunologic factors demand vigilant management. This comprehensive review not only serves as a valuable resource for ophthalmic surgeons but also sheds light on the evolving landscape of corneal transplantation, highlighting DALK's role as a transformative force in the field.

New forceps free injection technique for delivering descemet membrane endothelial keratoplasty preloaded endothelium-in grafts

PURPOSE

To describe a new method for delivering DMEK grafts into the recipient's eye with endothelium inward configuration using a no-forceps injection technique.

METHODS

We retrospectively review 11 patients that underwent DMEK surgery at our institution using a no-forceps injection technique. The graft was preloaded into an intraocular lens (IOL) cartridge and connected to an anterior chamber maintainer (ACM). A 5 ml non luer lock syringe was inserted into the other end of the ACM to create a one-flow system. The cartridge was inserted into the posterior end of an injector, and the graft was successfully delivered into the recipient's eye.

RESULT

Twelve eyes of 11 patients were included. Mean follow-up was 9.16 ± 1.3 months. At baseline, mean best corrected visual acuity (BCVA) was 0.76 ± 0.13 logMAr and mean endothelial cell density (ECD) was 2619.00 ± 115.89 cells/mm2. At follow-up, BCVA significantly improved to 0.22 ± 0.05 logMAR (p = 0.003). Although we observed a significant reduction in ECD at follow-up (1688 ± 182.20, p = 0.002), our patients lost only 35.69 ± 6.36% of endothelial cells.

CONCLUSION

Our technique can help surgeons safely deliver an endothelium-in graft into the recipient's eye. The method doesn't require the use of a forceps, minimizing the risk of endothelial cell loss or graft damage.

Postoperative, but not preoperative, central corneal thickness correlates with the postoperative visual outcomes of Descemet membrane endothelial keratoplasty

Descemet membrane endothelial keratoplasty (DMEK) restores visual acuity in patients with progressive corneal endothelial diseases such as Fuchs endothelial corneal dystrophy (FECD). However, patients often prefer to delay the surgery as long as possible, even though outcomes are poorer in advanced FECD. A recent study proposed that preoperative central corneal thickness (CCT) of ≥625 μm associated with worse best spectacle-corrected visual acuity (BSCVA) after DMEK for FECD. Since this threshold could signal to both surgeons and patients when to perform DMEK, we further explored the relationship between CCT and BSCVA with a retrospective cohort study. The cohort consisted of all patients with FECD who underwent DMEK in a tertiary-care hospital in 2015-2020 and were followed for 12 months. Extremely decompensated corneas were not included. Relationships between preoperative CCT and BSCVA on days 8 and 15 and months 1, 3, 6, and 12 were examined with Pearson correlation analyses. Eyes with preoperative CCT <625 or ≥625 μm were also compared in terms of postoperative BSCVA. Relationships between postoperative CCT and final BSCVA were also explored. The cohort consisted of 124 first-operated eyes. Preoperative CCT did not correlate with postoperative BSCVA at any timepoint. Eye subgroups did not differ in postoperative BSCVA. However, postoperative CCT at 1-12 months correlated significantly with 12-month BSCVA (r = 0.29-0.49, p = 0.020-0.001). Thus, postoperative, but not preoperative, CCT correlated with postoperative BSCVA. This phenomenon may reflect factors that distort preoperative CCT measurements but disappear after surgery. This observation and our analysis of the literature suggest that while there is a relationship between CCT and post-DMEK visual acuity, preoperative CCT measurements may not always adequately reflect that relationship and may therefore not be a reliable predictor of DMEK visual outcomes.