Navigating the learning curve in Descemet membrane endothelial keratoplasty – Insights from fellowship training

Descemet membrane endothelial keratoplasty (DMEK) has revolutionized the management of corneal endothelial disorders, offering unmatched visual recovery, anatomical restoration, and reduced rejection rates. However, its steep learning curve poses significant challenges for corneal fellows in the early phase of surgical training.[1] Our recent retrospective study of 65 DMEK surgeries performed by eight fellows highlights how surgical exposure—not just fellowship duration—shapes outcomes. All fellows had prior experience of ≥40 therapeutic penetrating keratoplasties (TPKs), ≥10 optical penetrating keratoplasties (PKPs), and ≥10 Descemet stripping automated endothelial keratoplasties (DSAEKs). Each fellow completed at least 10 DMEK graft preparations and received structured wet lab training using nontransplantable donor tissue. An experienced DMEK surgeon (S.K.S) supervised all aspects of training, including wet laboratory sessions, graft preparation, surgeries, and postoperative management. Primary graft failure was defined as persistent corneal edema within 12 weeks or need for repeat surgery within 3 months. Rebubbling was performed within 4 weeks for ≥30% graft detachment confirmed on anterior segment OCT. We categorized fellows as “Beginner” (≤6 independent DMEK cases) or “Experienced” (>6 cases), based on literature suggesting improvement after 5–10 cases and aligned with institutional training patterns [Table 1]. Fellows generally gain surgical independence around five cases, with consistency and confidence improving beyond the sixth. This cutoff also allowed for balanced group comparisons and robust statistical evaluation.Table 1: Demographic and Clinical Characteristics of the Study CohortInterestingly, surgical duration was longer among fellows with >180 days of training compared to those with shorter tenure. While counterintuitive, this may reflect assignment of complex cases to more experienced fellows or more meticulous surgical pacing as confidence grows. Surgical efficiency, however, improved with case volume, suggesting that hands-on exposure plays a more pivotal role than time alone.[2] Graft detachment occurred in 33.8% of cases, consistent with published literature where rates range from 20% to 40% during initial training phases.[3] This emphasizes that case complexity, intraoperative decisions (e.g., tamponade strategy), and postoperative care equally influence outcomes. Notably, detachments were detected later in experienced fellows, likely due to delayed-onset separation in cases with initially well-centered grafts. A key observation was the exclusive occurrence of fibrin formation in beginners—a complication that prolongs surgical time and impairs visualization. This underscores the importance of minimizing intraocular manipulation and adopting standardized, gentle unfolding techniques early in training.[4] Conversely, positive pressure complications were seen only in experienced fellows, perhaps reflecting aggressive air fill strategies. Primary graft failure, though not statistically different between groups, was more common among beginners. This pattern echoes prior literature linking early surgical inexperience with higher manipulation-related trauma. Importantly, visual outcomes showed a clear benefit with greater experience—78.9% of fellows with >180 days training achieved ≤0.3 logMAR CDVA, compared to 21.1% in those with less experience. These findings align with prior studies suggesting that outcomes improve significantly after 6–10 cases, with graft handling and postoperative care evolving alongside confidence and skill.[5] Although the ≥180-day group had a higher mean logMAR CDVA (1.10 vs. 0.61), this likely reflects the higher proportion of complex cases assigned to late-phase fellows—such as failed DMEKs, ICE syndrome, and eyes with limited preoperative visual potential. In contrast, early-phase fellows primarily performed DMEK for less complex indications like pseudophakic bullous keratopathy and Fuchs’ endothelial dystrophy, which are typically associated with more favorable visual outcomes [Fig. 1 and Table 2]. We also noted that final CDVA improved with increasing surgical experience (1.36 in beginners vs. 0.80 in experienced fellows; P = 0.995), reinforcing the positive impact of hands-on case volume.Figure 1: Mirrored histogram displaying a: the distribution of surgical duration (in minutes) across two fellowship categories: with fellows having <180 days of training (blue) and those with ≥180 days (green). Mean ranks for each group are shown (26.41 vs. 35.33); b: the distribution of surgical duration (in minutes) across two experience categories: fellows with ≤6 cases performed (blue) and those with >6 cases (green). Mean ranks for each group are shown (32.51 vs. 33.83); c: the distribution of graft detachment follow-up duration (in days) across two fellowship categories: fellows with <180 days of training (blue) and those with ≥180 days (green). Mean ranks for each group are shown (17.25 vs. 12.38); d: the distribution of graft detachment follow-up duration (in days) across two experience categories: fellows with ≤6 cases performed (blue) and those with >6 cases (green). Mean ranks for each group are shown (14.35 vs. 11.89); e: the distribution of corrected distance visual acuity (CDVA) at follow-up across two fellowship categories: fellows with <180 days of training (blue) and those with ≥180 days (green). Mean ranks for each group are shown (27.29 vs. 35.02); f: the distribution of CDVA at follow-up across two experience categories: fellows who have performed ≤6 cases (blue) and those who have performed >6 cases (green). Mean ranks for each group are shown (32.99 vs. 33.02)Table 2: Comparison of Surgical Performance, Outcomes, and Complications in DMEK Based on Fellowship Duration and Surgical ExperienceThe findings advocate for competency-based, rather than time-based, training models. Structured mentorship, wet lab simulations, and progressive autonomy appear critical to optimizing surgical performance. Fellowship curricula must evolve to balance volume with quality, ensuring that trainees gain sufficient, graded experience in graft preparation, chamber maintenance, and unfolding techniques. While limitations such as retrospective design and limited endothelial cell data exist, this study provides valuable evidence that supports revisiting how DMEK training is structured across corneal fellowships in India. With DMEK becoming the preferred modality for endothelial dysfunction, ensuring high-quality training is essential—not only for surgical excellence but also for patient safety. In conclusion, surgical expertise rather than fellowship duration independently predicts DMEK outcomes in training. Programs should incorporate early hands-on exposure, simulation tools, and feedback-based milestones to flatten the learning curve. As DMEK adoption expands, tailored fellow training can bridge the gap between complexity and competence. Ethics statement This study involves human participants and was approved by the Institutional Ethics Committee (IEC-2025-223-BHR-14) of LV Prasad Eye Institute, Bhubaneswar, Odisha, India. Authorship statement All the authors included in this paper fulfil the criteria of authorship recommended by ICMJE. Consent to publish All the authors included in this paper consent to publish. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.