Endothelial cell density after descemet membrane endothelial keratoplasty: 1 to 5-year follow-up

Machine Learning Analysis of Postkeratoplasty Endothelial Cell Images for the Prediction of Future Graft Rejection

Purpose

This study developed machine learning (ML) classifiers of postoperative corneal endothelial cell images to identify postkeratoplasty patients at risk for allograft rejection within 1 to 24 months of treatment.

Methods

Central corneal endothelium specular microscopic images were obtained from 44 patients after Descemet membrane endothelial keratoplasty (DMEK), half of whom had experienced graft rejection. After deep learning segmentation of images from all patients' last and second-to-last imaging, time points prior to rejection were analyzed (175 and 168, respectively), and 432 quantitative features were extracted assessing cellular spatial arrangements and cell intensity values. Random forest (RF) and logistic regression (LR) models were trained on novel-to-this-application features from single time points, delta-radiomics, and traditional morphometrics (endothelial cell density, coefficient of variation, hexagonality) via 10 iterations of threefold cross-validation. Final assessments were evaluated on a held-out test set.

Results

ML classifiers trained on novel-to-this-application features outperformed those trained on traditional morphometrics for predicting future graft rejection. RF and LR models predicted post-DMEK patients' allograft rejection in the held-out test set with >0.80 accuracy. RF models trained on novel features from second-to-last time points and delta-radiomics predicted post-DMEK patients' rejection with >0.70 accuracy. Cell-graph spatial arrangement, intensity, and shape features were most indicative of graft rejection.

Conclusions

ML classifiers successfully predicted future graft rejections 1 to 24 months prior to clinically apparent rejection. This technology could aid clinicians to identify patients at risk for graft rejection and guide treatment plans accordingly.

Translational Relevance

Our software applies ML techniques to clinical images and enhances patient care by detecting preclinical keratoplasty rejection.

Descemet membrane endothelial keratoplasty: Update on preoperative considerations, surgical techniques, and outcomes

Descemet membrane endothelial keratoplasty (DMEK) is the closest to the physiological replacement of endothelial cells. In the initial years, the technique was surgically challenging. Over the years, with better understanding and modifications in the surgical steps, the technique has evolved as an alternative to more popular procedure Descemet stripping endothelial keratoplasty. The article highlights the various preoperative, intraoperative, and postoperative nuances of DMEK. Additionally, it summarizes the various comparative and noncomparative studies on DMEK outcomes.

Delivering Endothelial Keratoplasty Grafts: Modern Day Transplant Devices

PURPOSE

To summarize the graft loading, transporting and delivery devices used for endothelial keratoplasty (EK).

METHODS

A literature search of electronic databases was performed.

RESULTS

New techniques and devices have been introduced and implemented to prepare, load, transport and transplant the grafts for EK. The advantages are not only limited to the surgical theatre but also widely spread across the eye banking field. Investigation of advanced materials and designs have been rapidly growing with continuous evolution in the field of eye banking and corneal transplantation. Innovative techniques and modern devices have been evaluated to reduce the endothelial cell loss and increase the precision of the transplant in order to benefit both surgeons and the patients.

CONCLUSIONS

It is extremely important to reduce any potential wastage and optimize the use of every available donor cornea due to the limited availability of healthy cadaveric donor corneas required for transplants. As a result, the use of pre-cut and pre-loaded grafts supplied by the eye banks in calibrated devices have been gaining momentum. Innovation in the field of bioengineering for the development of new devices that facilitate excellent clinical outcomes along with reduction in learning curve has shown promising results.

Two-year clinical outcome after Descemet membrane endothelial keratoplasty using a standardized protocol

PURPOSE

The purpose of this study is to evaluate 2-year clinical outcome after Descemet membrane endothelial keratoplasty (DMEK) in a variety of endothelial dysfunctions using a standardized protocol.

METHODS

: From a group of 230 eyes which underwent DMEK for Fuchs' endothelial corneal dystrophy (FECD), aphakic and pseudophakic bullous keratopathy, failed full thickness corneal transplants, ICE syndrome, failed DSEK, and TASS the clinical outcomes [best spectacle-corrected visual acuity (BSCVA), central endothelial cell density (ECD)] were evaluated before, and at 6, 12, and 24 months and the success rate, failure rate and postoperative complications were also analyzed.

RESULTS

Out of 230 eyes, 144 eyes (70%) had BSCVA 6/9 or better 2 years postoperatively. Mean donor ECD was 2692.23 (range, 2300-3436) cells/mm2 preoperatively, which was reduced to 1433.64 (range, 619.0-2272.0) cells/mm2 2 years after DMEK surgery, indicating a mean reduction of 1258 cells/mm2 (46%) in ECD.

CONCLUSION

DMEK is a highly successful surgical procedure when following a standard protocol for treating diseases of the corneal endothelium providing a near perfect anatomic restoration and a high degree of visual rehabilitation.

[Descemet membrane endothelial keratoplasty DMEK - Donor and recipient step by step]

In 2020 Descemet membrane endothelial keratoplasty (DMEK) has become the gold standard in Germany for the treatment of corneal endothelial diseases; however, the widespread use of DMEK was initially limited due to problems with donor preparation and the difficulty of correctly and gently unfolding the endothelial Descemet membrane (EDM) in the anterior chamber. Following the situational donor selection, the safe single-handed donor preparation of the cornea without tearing or even rupturing the EDM, including the indispensable peripheral semicircular orientation marking. Also presented is a step by step atraumatic loading of the glass cartridge, the introduction of the EDM roll into the anterior chamber, and its safe step by step unfolding based on (1) the sequential use of jets of fluid, (2) repeated tapping on the peripheral/central cornea, (3) controlled flattening of the anterior chamber, (4) use of air bubbles of defined size and finally, the fixation of the EDM in correct orientation to the back of the host cornea with a gas bubble. Since every wrong step with DMEK can have far-reaching consequences for patient and surgeon, this step by step pragmatic approach should minimize the incidence of donor tissue damage and failure in patient maneuvers.

Simultaneous Vitreoretinal Surgery and Penetrating Keratoplasty without a Keratoprosthesis or Endoscopy for Vitreoretinal Disease Associated with Corneal Opacity

We evaluated the visual outcome of combined penetrating keratoplasty (PKP) and 25G pars plana vitrectomy (PPV) performed without a temporary keratoprosthesis or endoscopy in a patient with vitreoretinal disease complicated by severe corneal opacity. The patient was a 68-year-old woman who had severe corneal opacity and silicone oil in her left eye after several previous intraocular surgeries for rhegmatogenous retinal detachment and proliferative vitreoretinopathy. We successfully performed a combined surgery of conventional PKP followed by 25G PPV without the use of a keratoprosthesis. At 6 months after surgery, visual acuity had not improved, and the density of corneal endothelial cells of the donor cornea had declined from 3,205 to 1,969 cells/mm². However, corneal transparency remained good, and additional surgery for vitreoretinal disease was not necessary. The combined surgical procedure designed to minimize the number of open-sky steps and to limit vitreoretinal complications thus proved to be safe and achieved stable corneal clarity in a patient with vitreoretinal disease and severe corneal opacity.

Ultrathin Descemet stripping automated endothelial keratoplasty

PURPOSE OF REVIEW

Endothelial keratoplasty has evolved tremendously since its inception. Thick Descemet stripping automated endothelial keratoplasty (DSAEK) grafts have made sway for slimmer ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK). This review discusses the recent literature comparing outcomes of UT-DSAEK, DSAEK, and Descemet membrane endothelial keratoplasty (DMEK).

RECENT FINDINGS

DMEK provides quick visual recovery and has remarkably low incidence of graft rejection. However, the learning curve is long compared to DSAEK. UT-DSAEK utilizes donor grafts less than 100-μm thick. Recent studies comparing DMEK and UT-DSAEK have shown DMEK has better visual outcomes with similar rejection rates.

SUMMARY

UT-DSAEK remains an excellent surgical option for endothelial keratoplasty in eyes with complex anterior segment anatomy. The visual outcomes after UT-DSAEK have been shown to be superior when compared with DSAEK. Recent studies show that DMEK provides better visual outcomes compared with UT-DSAEK.

From DMEK to Corneal Endothelial Cell Therapy: Technical and Biological Aspects

The main treatment available for restoration of the corneal endothelium is keratoplasty and DMEK provides faster visual recovery and better postoperative visual acuity when compared to DSAEK. However, the technical challenges related to this technique and the steep technical learning curve seem to prevent the overcoming of DSAEK in favor of DMEK. Furthermore, the outcome of lamellar keratoplasty techniques is influenced by problems related to corneal grafting tissue availability, management, and quality. On the other hand, improvements in the field of cell engineering have opened the way for the use of stem cells-derived corneal endothelial cells with regenerative intent. In this overview, latest findings in endothelial cell engineering are reported, and perspectives of clinical application of mesenchymal stem cells for corneal endothelial replacement and regeneration are evaluated.

Outcomes of Hemi-Descemet Membrane Endothelial Keratoplasty for Fuchs Endothelial Corneal Dystrophy

PURPOSE

To report the mid-term outcomes of hemi-Descemet membrane endothelial keratoplasty (hemi-DMEK) performed for Fuchs endothelial corneal dystrophy (FECD).

METHODS

In this prospective, interventional case series, we evaluated clinical outcomes of 10 eyes from 10 patients who underwent hemi-DMEK for FECD. Main outcome measures were best-corrected visual acuity (BCVA), endothelial cell density (ECD), central pachymetry, and postoperative complications.

RESULTS

At 1 year postoperatively, 7/7 eyes (excluding 2 eyes with low visual potential) reached a BCVA of ≥20/40 (≥0.5), 6/7 (86%) ≥20/25 (≥0.8), 4/7 (57%) ≥20/20 (≥1.0), and 2/7 (29%) 20/17 (≥1.2). BCVA remained stable until 2 years postoperatively (P ≥ 0.05) and further improved thereafter (P < 0.05). Mean ECD decreased from 2740 (±180) cells/mm preoperatively to 850 (±300) cells/mm (n = 9) at 1 year (P ≤ 0.05) and showed an annual decrease of on average 6% to 7% thereafter (P ≥ 0.05 between consecutive follow-ups). Pachymetry decreased from preoperatively 745 (±153) μm to 533 (±63) μm (n = 9) and 527 (±35) μm (n = 8) at 1 and 3 years postoperatively, respectively. Within the first 6 postoperative months, 4/10 eyes underwent rebubbling for visually significant graft detachment. One eye received secondary circular DMEK for persistent graft detachment 1 month postoperatively; another eye developed secondary graft failure 2.5 years postoperatively, and 1 eye was suspected for an allograft reaction 1.5 years postoperatively.

CONCLUSIONS

Hemi-DMEK may render visual outcomes comparable to those achieved by conventional DMEK. Despite low ECD counts by 6 months, ECD levels remain fairly stable thereafter. Hence, hemi-DMEK may become a potential alternative technique for treatment of FECD while increasing the yield of the endothelial tissue pool.

Donor Tissue Preparation for Descemet Membrane Endothelial Keratoplasty: An Updated Review

PURPOSE

To provide an overview of the current literature on donor tissue preparation for Descemet membrane endothelial keratoplasty (DMEK).

METHODS

A comprehensive database search without date restrictions was performed in PubMed and in The Cochrane Library in May, 2017. Keywords included Descemet membrane endothelial keratoplasty, corneal transplantation, graft, harvest, dissection, preparation, endothelial cell, and endothelial cell density. Articles aiming to describe or evaluate a technique for DMEK graft preparation were considered eligible and were included in this review.

RESULTS

A graft dissection technique that provides consistent tissue qualities and a low risk of preparation failure is essential for surgeons and eye banks preparing DMEK tissue. Various techniques have been described aiming to facilitate DMEK graft dissection, including manual dissection, pneumatic dissection, and hydrodissection. All show a trend toward a no-touch technique, for example, without direct physical tissue manipulation during tissue harvesting, as a potential ideal approach to minimize graft damage.

CONCLUSIONS

An overview of the current harvesting techniques available for DMEK may benefit corneal surgeons and eye banks in choosing the best approach for each specific user.

Incidence and Clinical Course of Immune Reactions after Descemet Membrane Endothelial Keratoplasty: Retrospective Analysis of 1000 Consecutive Eyes

PURPOSE

To analyze the incidence and clinical course of graft rejection episodes after Descemet membrane endothelial keratoplasty (DMEK).

DESIGN

Retrospective analysis of a consecutive, interventional case series.

PARTICIPANTS

One thousand eyes that underwent DMEK from July 2011 through August 2015 at the Department of Ophthalmology, University of Cologne.

METHODS

All cases with follow-up of at least 1 month were included (mean follow-up, 18.5 months). Patients with a graft rejection episode were followed up for 1 additional year.

MAIN OUTCOME MEASURES

Incidence of graft rejection, best spectacle-corrected visual acuity (BSCVA), central corneal thickness (CCT), endothelial cell density (ECD), and need for regraft.

RESULTS

Nine hundred five cases met the inclusion criteria. A graft rejection episode developed in 12 patients (estimated probability of rejection at 1 year, 0.9%; at 2 years, 2.3%; at 4 years, 2.3%). At time of rejection, 9 of 12 patients had stopped corticosteroids. Five patients were symptomatic and 7 did not note the rejection episode. Intensified topical corticosteroid therapy was started immediately after diagnosis of rejection. Two eyes decompensated and required a regraft, whereas the remaining 10 eyes required no regraft (BSCVA, 0.27±0.28 logarithm of the minimum angle of resolution [logMAR]; CCT, 554.1±39.1 μm at last visit before rejection vs. BSCVA, 0.21±0.15 logMAR; CCT, 540.0±15.0 μm 3 months after rejection). One year after the rejection episodes, BSCVA and CCT in these eyes remained unchanged when compared with the last visit before rejection (BSCVA, 0.15±0.11 logMAR; CCT, 533.8±26.0 μm). Significant changes were observed for ECD values (1741±274.5 cells/mm² at last visit before rejection vs. 1356±380.3 cells/mm² after 3 months [P = 0.04] and 1290±359.0 cells/mm² after 1 year [P = 0.01]).

CONCLUSIONS

The risk for graft rejection after DMEK is low, and an even smaller minority requires a regraft. After intensified local corticosteroid therapy, most patients show stable visual acuity and CCT, although ECD decreases. The occurrence of immune reactions up to 2 years after surgery predominantly in patients not receiving corticosteroids supports the prolonged use of corticosteroids after DMEK.

Long-term Clinical Outcome After Descemet Membrane Endothelial Keratoplasty

PURPOSE

To evaluate the long-term clinical outcome up to 5 years after Descemet membrane endothelial keratoplasty (DMEK).

DESIGN

Retrospective, consecutive case series.

METHODS

In this single-center study, 310 consecutive DMEK operations for endothelial decompensation were reviewed; 97 eyes of 84 patients met the inclusion criterion of a minimum 3-year follow-up. Retrospective evaluation of clinical examinations occurred at 1 and 3 months and annually up to 5 years after DMEK at the Department of Ophthalmology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen (FAU), Germany. Main outcome measures were corrected distance visual acuity (CDVA), endothelial cell density (ECD), central corneal thickness (CCT), and graft survival (Kaplan-Meier analysis).

RESULTS

Mean follow-up was 53 ± 13 months. CDVA improved from 0.62 ± 0.42 logMAR before DMEK to 0.13 ± 0.12 logMAR (P < .001); 57% of eyes without ocular comorbidities reached ≥20/25 at 5 years after DMEK. ECD was stable after the initial postsurgical decrease (42% at 1 month, 44% at 5 years), from 2602 ± 243 cells/mm(2) before DMEK to 1460 ± 179 cells/mm(2) at 5 years. CCT decreased from 644 ± 67 μm before DMEK to 557 ± 49 μm at 5 years, with a minimum (530 ± 54 μm) at 3 months. Cumulative probability of 5-year graft survival was 95%.

CONCLUSIONS

The long-term sustainability of DMEK was confirmed. DMEK not only provides fast visual rehabilitation but maintains its clinical outcome within a follow-up of 5 years. Visual acuity and endothelial cell loss remain stable between 3 months and 5 years after DMEK.

Impact of Donor Age on Corneal Endothelium-Descemet Membrane Layer Scroll Formation

OBJECTIVE

To correlate corneal endothelium-Descemet membrane (EDM) layer parameters of scroll tightness with donor age, endothelial cell density (ECD), and history of diabetes.

METHODS

Endothelium-Descemet membrane layer scrolls were harvested from 26 corneoscleral buttons using the SCUBA technique by a cornea-fellowship trained ophthalmologist masked to donor age. Two independent outcome parameters were used to characterize the scrolling severity of successfully harvested tissue: scroll width and tendency for EDM scroll formation (referred to as scroll rating on a 1-4 scale: incomplete scroll formation to tightly scrolled).

RESULTS

Mean donor age was 59 ± 17 (15-69) years. Mean ECD of EDM scroll was 2,451 ± 626 (range: 1,307-3,195) cells per square millimeter. Using stepwise linear regression, a significant correlation was found between scroll width and donor age (R=0.497, P<0.05). Additionally, a significant inverse correlation was found between scroll width and ECD (R=-0.605, P<0.05). There was no statistically significant correlation between a donor history of diabetes and the parameters of scrolling tendency.

CONCLUSIONS

Our data suggest that using older donors reduces EDM scroll tightness.

Descemet membrane endothelial keratoplasty

Descemet membrane endothelial keratoplasty (DMEK) allows for selective replacement of damaged endothelial cells, using only donor Descemet's membrane with endothelium. However, early adoption by corneal surgeons has been limited (illustrated by graft registry reports: 0.7% all corneal transplants in the USA; 0.4% in Australia for 2011) due to challenges in donor preparation and surgical technique. Recently, innovative donor preparation techniques may improve availability of pre-stripped DMEK donors from eye banks. The refinement of donor insertion and manipulation techniques has also improved outcomes and reduced graft detachment rates-still, the most common postoperative complication following DMEK. Randomised studies are needed to compare clinical practices and surgeon preferences, such as intraoperative use of long-acting gas, early versus late intervention of graft detachments and postoperative steroid management. A review of current literature reveals that most publications to date are reports from similar study cohorts by surgeons who pioneered and advocate this technique. Thus, more long-term clinical studies in other tertiary centres are required in order to confirm if the purported advantages of DMEK such as improved visual outcomes and reduced graft rejection are replicable among most corneal surgeons.

Clinical outcome of 500 consecutive cases undergoing Descemet's membrane endothelial keratoplasty

PURPOSE

To evaluate the clinical outcome of 500 consecutive cases after Descemet's membrane endothelial keratoplasty (DMEK) and the effect of technique standardization.

DESIGN

Prospective, interventional case series at a tertiary referral center.

PARTICIPANTS

A total of 500 eyes of 393 patients who underwent DMEK for Fuchs' endothelial corneal dystrophy, bullous keratopathy, or previous corneal transplant failure.

METHODS

Best-corrected visual acuity (BCVA), endothelial cell density (ECD), pachymetry, and intraoperative and postoperative complications were evaluated before and 1, 3, and 6 months after DMEK.

MAIN OUTCOME MEASURES

Comparison between 2 groups (group I: cases 1-250, outcome of "early surgeries" during transition to technique standardization; group II: cases 251-500, outcome of "late surgeries" after technique standardization).

RESULTS

At 6 months, 75% of eyes reached a BCVA of ≥20/25 (≥0.8), 41% of eyes achieved ≥20/20 (≥1.0), and 13% of eyes achieved ≥20/18 (≥1.2) (n=418) when excluding eyes with ocular comorbidities (n=57). When including all available eyes at 6 months (n=475), 66% of eyes reached a BCVA of ≥20/25 (≥0.8), and 36% of eyes achieved ≥20/20 (≥1.0). Mean ECD decreased by 37% (±18%) to 1600 (±490) cells/mm2 (n=447) at 6 months (P<0.001). Postoperative pachymetry averaged 525 (±46) μm compared with 667 (±92) μm preoperatively (P<0.001). None of these parameters differed among the 2 groups (P>0.05). (Partial) graft detachment presented in 79 eyes (15.8%), and 26 eyes (5.2%) required a secondary surgery within the first 6 months (re-bubbling in 15, secondary keratoplasty in 11). With technique standardization, the postoperative complication rate decreased from 23.2% to 10% (P<0.001) and the rate of secondary surgeries decreased from 6.8% to 3.6% (P=0.10).

CONCLUSIONS

In comparison with earlier endothelial keratoplasty techniques, DMEK may consistently give higher visual outcomes and faster visual rehabilitation. When used for the extended spectrum of endothelial pathologies, DMEK proved feasible with a relatively low risk of complications. Technique standardization may have contributed to a lower graft detachment rate and a relatively low secondary intervention rate. As such, DMEK may become the first choice of treatment in corneal endothelial disease.

Repeat Descemet membrane endothelial keratoplasty after complicated primary Descemet membrane endothelial keratoplasty

PURPOSE

To describe the clinical outcome and complications of repeat Descemet membrane endothelial keratoplasty (re-DMEK).

DESIGN

Retrospective case series study at a tertiary referral center.

PARTICIPANTS

From a series of 550 consecutive DMEK surgeries with ≥ 6 months follow-up, 17 eyes underwent re-DMEK for graft detachment after initial DMEK (n = 14) and/or endothelial graft failure (n = 3). The outcomes were compared with an age-matched control group of uncomplicated primary DMEK surgeries.

METHODS

The re-DMEK eyes were evaluated for best-corrected visual acuity (BCVA), densitometry, endothelial cell density (ECD), pachymetry, and intraoperative and postoperative complications.

MAIN OUTCOME MEASURES

Feasibility and clinical outcome of re-DMEK.

RESULTS

In all eyes, re-DMEK was uneventful. At 12 months, 12 of 14 eyes (86%) achieved a BCVA of ≥ 20/40 (≥ 0.5); 8 of 14 eyes (57%) achieved ≥ 20/25 (≥ 0.8), 3 of 14 eyes (21%) achieved ≥ 20/20 (≥ 1.0), and 1 eye (7%) achieved 20/17 (1.2); 5 eyes were fitted with a contact lens. Average donor ECD decreased from 2580 ± 173 cells/mm(2) before to 1390 ± 466 cells/mm(2) at 6 months after surgery, and pachymetry from 703 ± 126 μm to 515 ± 39 μm, respectively. No difference in densitometry could be detected between re-DMEK and control eyes (P = 0.99). Complications after re-DMEK included primary graft failure (n = 1), secondary graft failure (n = 2), graft detachment requiring rebubbling (n = 1), secondary glaucoma (n = 2), cataract (n = 1), and corneal ulcer (n = 1). One eye received tertiary DMEK.

CONCLUSIONS

In the management of persistent graft detachment and graft failure after primary DMEK, re-DMEK proved a feasible procedure. Acceptable BCVA may be achieved, albeit lower than after DMEK in virgin eyes, and some cases may benefit from contact lens fitting. Complications after re-DMEK may be better anticipated than after primary DMEK because graft detachment and graft failure tended to recur, suggesting that intrinsic properties of the host eye play a role in graft adherence and graft failure.

Donor age and factors related to endothelial cell loss 10 years after penetrating keratoplasty: Specular Microscopy Ancillary Study

OBJECTIVE

To examine the effect of donor age and other perioperative factors on long-term endothelial cell loss after penetrating keratoplasty (PKP).

DESIGN

Multicenter, prospective, double-masked clinical trial.

PARTICIPANTS

We included 176 participants from the Cornea Donor Study cohort who had not experienced graft failure ≥ 10 years after PKP for a moderate risk condition (principally Fuchs' dystrophy or pseudophakic/aphakic corneal edema).

METHODS

Corneas from donors 12 to 75 years old were assigned to participants using a randomized approach, without respect to recipient factors. Surgery and postoperative care were performed according to the surgeons' usual routines. Images of the central endothelium were obtained preoperatively and at intervals for 10 years postoperatively. Images were analyzed by a central image analysis reading center to determine endothelial cell density (ECD).

MAIN OUTCOME MEASURES

Endothelial cell density at 10 years.

RESULTS

Among study participants with a clear graft at 10 years, the 125 who received a cornea from a donor 12 to 65 years old experienced a median cell loss of 76%, resulting in a 10-year median ECD of 628 cells/mm(2) (interquartile range [IQR], 522-850 cells/mm(2)), whereas the 51 who received a cornea from a donor 66 to 75 years old experienced a cell loss of 79%, resulting in a median 10-year ECD of 550 cells/mm(2) (IQR, 483-694 cells/mm(2); P adjusted for baseline ECD = 0.03). In addition to younger donor age, higher ECD values were significantly associated with higher baseline ECD (P<0.001) and larger donor tissue size (P<0.001). Forty-two of the 176 participants (24%) had an ECD of <500 cells/mm(2) at 10 years and only 24 (14%) had an ECD of >1000 cells/mm(2).

CONCLUSIONS

Substantial cell loss occurs in eyes with a clear graft 10 years after PKP, with the rate of cell loss being slightly greater with older donor age. Greater preoperative ECD and larger donor tissue size are associated with higher ECD at 10 years.

Descemet stripping endothelial keratoplasty--rapid recovery of visual acuity

BACKGROUND

Technical innovations in corneal transplantation have now made it possible to replace only the diseased part of the cornea, rather than the entire cornea as in penetrating keratoplasty (PKP). Patients with endothelial insufficiency due to Fuchs endothelial dystrophy, bullous keratopathy, or endothelial failure after keratoplasty can be treated with the new methods of posterior lamellar corneal transplantation: Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK). It remains unclear which of these methods is better in the individual case.

METHODS

We review the pertinent literature retrieved by a selective search in Medline and the Cochrane Library employing the terms "DMEK," "DSAEK," "DSEK," and "posterior lamellar keratoplasty." The publications considered in this article are those that contain important clinical information on the operative techniques.

RESULTS

No randomized controlled trials of these techniques have been published to date. Numerous case series have shown that patients who undergo DSAEK (postoperative visual acuity ≥0.5 in 38-100%), and especially those who undergo it in early or intermediate stages of endothelial insufficiency, achieve a better functional result more rapidly than patients treated with PKP (postoperative visual acuity ≥0.5 in 47-61%). Only 23-47% of DSAEK patients achieve a visual acuity of 0.8 or more, compared to 36-79% of DMEK patients. Moreover, transplant rejection is seen in only 1-3% of cases of DMEK, compared to 0-8% after DSAEK and 1-23% after PKP.

CONCLUSION

Numerous case series show clear advantages of DMEK over DSAEK, which, in turn, has better results than PKP. Nonetheless, randomized controlled trials are needed to determine which operative method is best in each stage of corneal disease.