Evolution of Endothelial Keratoplasty: Where Are We Headed?

Is ultra-thin Descemet stripping automated endothelial keratoplasty a viable alternative to Descemet membrane endothelial keratoplasty? A systematic review and meta-analysis

Background

Ultra-thin Descemet stripping automated endothelial keratoplasty (UT-DSAEK) is a recently developed surgical procedure that has shown promising results for the management of various corneal endothelial diseases.

Objectives

To evaluate the outcomes of the UT-DSAEK to the Descemet membrane endothelial keratoplasty (DMEK).

Design

A systematic analysis of the studies comparing UT-DSAEK with DMEK by evaluating one or more outcomes (vision, complications, and post-operative endothelial cell counts) was performed. The meta-analysis was done if two or more studies reported a common outcome.

Methods

We used PubMed, EMBASE, and SCOPUS databases to identify articles comparing the outcomes of UT-DSAEK with DMEK and performed a meta-analysis using RevMan, version 5.4.

Results

A total of six studies were included in this review (two randomized clinical trials and four non-randomized comparative studies). Our analysis showed the patients who underwent DMEK cases showed better visual outcomes with a mean difference of 0.06 LogMAR (95% CI: 0.04-0.09) in BCVA, albeit with i ² of 52% (heterogenous values). The evidence was weak, with the most weightage on retrospective studies. UT-DSAEK showed significantly fewer complications such as graft dislocations, with an odds ratio of 0.25 (95% CI: 0.13-0.48). There was no significant difference in the endothelial cell counts with a mean difference of 86.34 (95%CI: -133.09 to -305.77).

Conclusion

Although the literature is limited on UT-DSAEK with post-operative visual acuity that could be practically at par with DMEK, lesser complication rates and comparable post-operative endothelial cells could be a suitable alternative to DMEK for corneal endothelial pathologies.

A machine learning approach to explore predictors of graft detachment following posterior lamellar keratoplasty: a nationwide registry study

Machine learning can be used to explore the complex multifactorial patterns underlying postsurgical graft detachment after endothelial corneal transplantation surgery and to evaluate the marginal effect of various practice pattern modulations. We included all posterior lamellar keratoplasty procedures recorded in the Dutch Cornea Transplant Registry from 2015 through 2018 and collected the center-specific practice patterns using a questionnaire. All available data regarding the donor, recipient, surgery, and practice pattern, were coded into 91 factors that might be associated with the occurrence of a graft detachment. In this research, we used three machine learning methods; a regularized logistic regression (lasso), classification tree analysis (CTA), and random forest classification (RFC), to select the most predictive subset of variables for graft detachment. A total of 3647 transplants were included in our analysis and the overall prevalence of graft detachment was 9.9%. In an independent test set the area under the curve for the lasso, CTA, and RFC was 0.70, 0.65, and 0.72, respectively. Identified risk factors included: a Descemet membrane endothelial keratoplasty procedure, prior graft failure, and the use of sulfur hexafluoride gas. Factors with a reduced risk included: performing combined procedures, using pre-cut donor tissue, and a pre-operative laser iridotomy. These results can help surgeons to review their practice patterns and generate hypotheses for empirical research regarding the origins of graft detachments.

Specifying Risk of Intraocular Lens Opacification After Endothelial Keratoplasty for Different Intraocular Lens Models: A Retrospective Monocentric Cohort Study

PURPOSE

The aims of this study were to calculate the specific risk of opacification for different intraocular lens (IOL) models and to determine whether differences exist, even between lenses made of similar acrylic materials.

METHODS

This is a retrospective cohort study of all patients who underwent endothelial keratoplasty (EK), either after or in conjunction with cataract surgery, from June 2009 to October 2020 at Fundación Jiménez Díaz Hospital.

RESULTS

Three hundred seventy-two eyes of 308 patients with a median follow-up of 856 days [interquartile range (IQR): 384-1570] were included, of which 128 IOLs were hydrophobic, 120 hydrophilic, and 124 unknown. 12.9% of IOLs opacified after a median of 466 days (IQR: 255-743). Visual acuity (VA) was significantly lower in the opacified IOL group [0.51 (IQR: 0.36-1.13)] compared with the nonopacified group [0.22 (IQR: 0.11-0.65)] ( P < 0.001). IOL explantation and exchange was performed in 10 eyes, in which VA improved markedly, from 1.75 (IQR: 0.99-3.00) to 0.60 (IQR: 0.36-0.86) ( P = 0.004). IOL material and opacification events were not independent ( P < 0.001). Significant differences were found between the Akreos ADAPT AO and MI60P models and the Asphina 409M model ( P = 0.022). No significant differences were found in the opacification ratio for hydrophilic IOLs in the clinical diagnosis ( P = 0.11), the type of EK ( P = 0.25), the rebubbling rate ( P = 0.44), or the tamponade used ( P = 0.36).

CONCLUSIONS

Hydrophilic lenses should be avoided in patients at risk of requiring EK. It is important to know the probability of opacification of each IOL model to balance risk and benefits when planning an EK procedure because not all lenses opacify equally. Opacification is an unwanted event with a negative impact on VA, making IOL explantation and exchange the only viable treatment, although one that is not without risks.

Topical Ripasudil for the Treatment of Primary Corneal Endothelial Degeneration in Dogs

Purpose

The purpose of this study was to evaluate the tolerability and efficacy of topical rho-kinase inhibitor ripasudil in the treatment of primary corneal endothelial degeneration (PCED) in dogs.

Methods

Twenty-one eyes of 12 client-owned, PCED-affected dogs received topical ripasudil 4 times daily. Ophthalmic examination, ultrasonic pachymetry (USP), Fourier-domain optical coherence tomography (FD-OCT), and in vivo confocal microscopy were performed at baseline and 1, 3, 6, and 12 months. Effects of treatment on corneal thickness, corneal edema extent, and endothelial cell density (ECD) were evaluated by repeated-measures ANOVA or Friedman test. Individual eyes were classified as improved, progressed, or stable at 12 months using clinical response criteria. Kaplan-Meier curves and log-rank test were used to compare ripasudil-treated eyes to age-, breed/size-, and disease stage-matched historical controls.

Results

During treatment, 12 dogs developed conjunctival hyperemia, 4 demonstrated reticular bullous epithelial edema, and 2 developed corneal stromal hemorrhage. No adverse event necessitated permanent cessation of ripasudil. Central corneal thickness measured by USP significantly progressed from baseline to 12 months. Corneal thickness by FD-OCT, ECD, and edema extent did not differ over time. Considered individually, 5 eyes improved, 8 remained stable, and 8 progressed. The log-rank test found less edema progression in ripasudil-treated eyes compared to historical controls.

Conclusions

Ripasudil was well-tolerated in PCED-affected dogs. Response to therapy varied; 62% of eyes showed improved or stable disease whereas 38% progressed. Ripasudil-treated eyes progressed more slowly than historical controls.

Translational Relevance

Topical ripasudil offered a therapeutic benefit in a subset of patients using a canine model of endothelial degeneration, which may guide future trials in humans.

“Endothelium-Out” and “Endothelium-In” Descemet Membrane Endothelial Keratoplasty (DMEK) Graft Insertion Techniques: A Systematic Review With Meta-Analysis

Background

We evaluated the visual outcomes and complications of “endothelium-out” and “endothelium-in” Descemet membrane endothelial keratoplasty (DMEK) graft insertion techniques.

Materials and Methods

Electronic searches were conducted in CENTRAL, Cochrane databases, PubMed, EMBASE, ClinicalTrials.gov. Study designs included clinical trials, comparative observational studies, and large case series (≥25 eyes). PRISMA guidelines were used for abstracting data and synthesis. Random-effects models were employed for meta-analyses.

Results

21,323 eyes (95 studies) were included. Eighty-six studies reported on “endothelium-out” techniques; eight studies reported on “endothelium-in” techniques. One study compared “endothelium-out” to “endothelium-in” techniques. Eighteen “endothelium-out” studies reported that 42.5–85% of eyes achieved best-corrected visual acuity (BCVA) ≥20/25 at 6 months; pooled proportion of eyes achieving BCVA ≥20/25 at 6 months was 58.7% (95% CI 49.4–67.7%,15 studies). Three “endothelium-in” studies reported that 44.7–87.5% of eyes achieved BCVA of ≥20/25 at 6 months; pooled proportion of eyes achieving BCVA ≥20/25 at 6 months was 62.4% (95% CI 33.9–86.9%). Pooled mean endothelial cell loss was lower in the “endothelium-in” studies (28.1 ± 1.3%, 7 studies) compared to “endothelium-out” studies (36.3 ± 6.9%,10 studies) at 6 months (p = 0.018). Graft re-bubbling rates were higher in the “endothelium-out” studies (26.2%, 95% CI 21.9–30.9%, 74 studies) compared to “endothelium-in” studies (16.5%, 95% CI 8.5–26.4%, 6 studies), although statistical significance was not reached (p = 0.440). Primary graft failure rates were comparable between the two groups (p = 0.552). Quality of evidence was considered low and significant heterogeneity existed amongst the studies.

Conclusion

Reported rates of endothelial cell loss were lower in “endothelium-in” DMEK studies at 6 months compared to “endothelium-out” studies. Outcomes of “endothelium-in” techniques were otherwise comparable to those reported in “endothelium-out” studies. Given the technical challenges encountered in “endothelium-out” procedures, surgeons may consider “endothelium-in” techniques designed for easier intra-operative DMEK graft unfolding. “Endothelium-in” studies evaluating outcomes at longer time points are required before conclusive comparisons between the two techniques can be drawn.

Thickness Measurement of Endothelium-Descemet Membrane in Descemt Membrane Detachment Patients Using High-Definition Optical Coherence Tomography

Purpose: (1) To measure the corneal endothelium-Descemet membrane (EDM) layer thickness in Descemet membrane detachment (DMD) patients in vivo using high-definition optical coherence tomography (HD-OCT), and to investigate its correlation with age. (2) To explore whether the detachment time will affect the EDM thickness. (3) To explore whether the EDM thickness of cornea with DMD was different from that without DMD. Participants: Patients with DMD were divided into three groups. Group 1 included twenty-three patients whose Descemet membrane (DM) was partial or complete detached from the corneal stroma after various ocular surgeries. Group 2 included eight patients from group 1 who underwent twice HD-OCT examination on different days before the DM reattached to the stroma. Group 3 included nine patients from group 1 who had clear grayscale boundary between the DM and stroma in HD-OCT images after DM reattachment. Methods: All patients underwent HD-OCT and EDM thickness was measured using Image -Pro Plus 6.0. In Group 1, regression analyses were used to evaluate the correlation between EDM thickness and age, and the thickness difference between the ≤50-year-old group and the >50-year-old group was analyzed by independent sample t-test. In Group 2, paired samples t-test was used to check whether detachment time would affect EDM thickness. In Group 3, paired samples t-test was used to check whether the EDM thickness of cornea with DMD was different from that without DMD. p < 0.05 was considered significant. Results: In Group 1, the EDM thickness measured on the first post-operative day was 27.8 ± 3.6 μm, and a positive correlation was found between EDM thickness and age (r = 0.619, p < 0.05). The EDM thickness of ≤50-year-old group and >50-year-old group were 23.9 ± 3.2 and 29.2 ± 2.6 μm, and there was a significant difference between the two groups (p = 0.001). In Group 2, the first measurement of EDM thickness was 27.5 ± 4.0 μm, the second measurement was 27.6 ± 4.2 μm, the interval between the two measurements was 2.1 ± 1.6 days, and there was no significant difference between the two measurements (p = 0.328). In Group 3, the EDM thickness with DM detachment was 28.3 ± 3.5 μm, with DM reattachment was 23.4 ± 2.4 μm, there was a significant difference between the two measurements (p = 0.002). Conclusions: The EDM thickness in the state of DMD is thicker than its actual thickness in normal cornea, and EDM thickness of the >50-year-old group is much thicker than that of the ≤50-year-old group.

Cost analysis of eye bank versus surgeon prepared endothelial grafts

Background

Selective lamellar corneal transplantation (keratoplasty) has overtaken full thickness penetrating keratoplasty as the graft choice for endothelial failure. Even more recently eye bank prepared tissues are becoming increasing popular as a way to reduce the risks of tissue loss and stress during endothelial keratoplasty preparation in the surgical theatre. This study compares costs between surgeon and eye bank prepared tissues for Descemet’s stripping automated endothelial keratoplasty (DSAEK) and Descemet’s membrane endothelial keratoplasty (DMEK).

Methods

Retrospective study conducted at the Royal Liverpool University Hospital including endothelial keratoplasties with a minimum of 6 months follow-up time. Cost analysis included surgical expenses, tissue acquisition fees, cost of patient’s ward admission and out-patient expenses, including cost of re-bubbling procedures, costs of visits, anterior segment imaging and optometrist visits within the first 6 months follow-up.

Results

Ninety-eight eyes of 98 patients were included in the study of which 42 underwent DSAEK surgery and 56 DMEK surgery. Cost analysis of surgical expenses in the DSAEK group showed a significant difference between using surgeon prepared and eye bank prepared tissue (£3866 ± 296 and £4389 ± 360, respectively; p < 0.01) and the same was found in the DMEK group (£3682 ± 167 and £4162 ± 167 for surgeon prepared and eye bank prepared tissues, respectively; p < 0.01). Cost of out-patient visits did not differ significantly in either group.

Conclusions

At the Royal Liverpool University Hospital, eye bank prepared tissues had higher surgical expenses compared to those prepared by the surgeon, while the post-operative care expenses were similar between the two groups.

Challenges in corneal endothelial cell culture

Corneal endothelial cells (CECs) facilitate the function of maintaining the transparency of the cornea. Damage or dysfunction of CECs can lead to blindness, and the primary treatment is corneal transplantation. However, the shortage of cornea donors is a significant problem worldwide. Thus, cultured CEC therapy has been proposed and found to be a promising approach to overcome the lack of tissue supply. Unfortunately, CECs in humans rarely proliferate in vivo and, therefore, can be extremely challenging to culture in vitro. Several promising cell isolation and culture techniques have been proposed. Multiple factors affecting the success of cell expansion including donor characteristics, preservation and isolation methods, plating density, media preparation, transdifferentiation and biomarkers have been evaluated. However, there is no consensus on standard technique for CEC culture. This review aimed to determine the challenges and investigate potential options that would facilitate the standardization of CEC culture for research and therapeutic application.

Complications and Management of Prestripped Descemet Membrane Endothelial Keratoplasty Grafts

Prestripped Descemet membrane endothelial keratoplasty is a relatively new technique that offers advantages in reduced surgical time and reduced tissue wastage compared with surgeon-stripped graft. Here, we report the following 2 types of prestripped Descemet membrane endothelial keratoplasty graft complications and their management: 1 free floating in the transport media and the other graft mispositioned.

Refractive outcome and tomographic changes after Descemet membrane endothelial keratoplasty in pseudophakic eyes with Fuchs' endothelial dystrophy

Purpose

To analyze refractive and topographic changes secondary to Descemet membrane endothelial keratoplasty (DMEK) in pseudophakic eyes with Fuchs’ endothelial dystrophy (FED).

Methods

Eighty-seven pseudophakic eyes of 74 patients who underwent subsequent DMEK surgery for corneal endothelial decompensation and associated visual impairment were included. Median post-operative follow-up time was 12 months (range: 3–26 months). Main outcome measures were pre- and post-operative manifest refraction, anterior and posterior corneal astigmatism, simulated keratometry (CA_SimK) and Q value obtained by Scheimpflug imaging. Secondary outcome measures included corrected distance visual acuity (CDVA), central corneal densitometry, central corneal thickness, corneal volume (CV), anterior chamber volume (ACV) and anterior chamber depth (ACD).

Results

After DMEK surgery, mean pre-operative spherical equivalent (± SD) changed from + 0.04 ± 1.73 D to + 0.37 ± 1.30 D post-operatively (p = 0.06). CDVA, proportion of emmetropic eyes, ACV and ACD increased significantly during follow-up. There was also a significant decrease in posterior corneal astigmatism, central corneal densitometry, central corneal thickness and corneal volume over time (p = 0.001). Only anterior corneal astigmatism and simulated keratometry (CA_SimK) remained fairly stable after DMEK.

Conclusion

Despite tendencies toward a hyperopic shift, changes in SE were not significant and refraction remained overall stable in pseudophakic patients undergoing DMEK for FED. Analysis of corneal parameters by Scheimpflug imaging mainly revealed changes in posterior corneal astigmatism pointing out the relevance of posterior corneal profile changes during edema resolution after DMEK.

Corneal endothelial cell density in patients receiving chemotherapy

PURPOSE

This study aimed to determine if the corneal endothelium was affected by chemotherapy.

METHODS

Chemotherapy patients were recruited to undergo specular microscopy before treatment and again at 1- and 2-year follow-up visits. One eye per patient, per follow-up, was selected for comparison to baseline.

RESULTS

Forty-six volunteers completed baseline and at least one follow-up assessment. From 51 eyes, there was no significant change in endothelial cell density for 41 eyes assessed at one year (M_D = 0.73%, 95% CI -1.33 to 2.78%) and 18 eyes at two years (M_D = 0.31%, 95% CI -3.53 to 4.15%).

CONCLUSION

Although other studies have shown that chemotherapy can adversely affect the corneal epithelium, this study showed no measurable change in endothelial cell density.

Intraoperative optical coherence tomography guided corneal sweeping for removal of remnant Interface fluid during ultra-thin Descemet stripping automated endothelial keratoplasty

BACKGROUND

Remnant interface fluid following Descemet stripping automated endothelial keratoplasty (DSAEK) is associated with postoperative detachments. The aim of this study was to assess outcomes of intraoperative optical coherence tomography (iOCT) guided meticulous peripheral corneal sweeping for removal of interface fluid during ultra-thin (UT) DSAEK.

METHODS

This retrospective study included all eyes underwent iOCT guided UT-DSAEK from October 2016 to February 2018 at the Hanusch Hospital, Vienna, Austria. Peripheral meticulous corneal sweeping was performed to remove excess fluid. Central graft thickness (CGT) was measured prior to surgery, after graft bubbling and after corneal sweeping. Remnant interface fluid rates were compared between eyes that underwent rebubbling and those that did not.

RESULTS

Overall, 28 eyes of 28 patients with a mean age of 73.9 ± 10.0 years were included. An iOCT guided meticulous peripheral sweeping was performed in 89.3% (n = 25) of the cases. Following 84% (n = 21) of the peripheral sweeping performed, remnant fluid was no longer identified. Following peripheral sweeping the interface fluid height was reduced from 17.31 ± 15.96 μm to 3.46 ± 9.52 μm (p < 0.001) and CGT was reduced by 7% (p < 0.001). Rebubbling was performed in 17.9% (n = 5) of the cases. The rebubbling group had a greater proportion of patients that had remnant fluid identified with iOCT at the end of surgery despite meticulous peripheral sweeping (60.0% versus 4.4%, p = 0.01).

CONCLUSION

The iOCT identified subclinical remnant fluid in nearly 90% of UT-DSAEK cases. An iOCT guided peripheral corneal sweeping led to resolution of interface fluid in a majority of cases. Eyes with persistent remnant fluid despite peripheral corneal sweeping are more likely to require subsequent rebubbling.

Influence of rebubbling on anterior segment parameters and refractive outcomes in eyes with DMEK for Fuchs endothelial dystrophy

PURPOSE

To evaluate the potential impact of rebubbling on the anterior segment parameters and refractive outcomes in patients with graft detachment following uneventful DMEK for Fuchs endothelial dystrophy (FED).

METHODS

Retrospective institutional cohort study of comparing 34 eyes of 31 patients with rebubbling for graft detachment following Descemet membrane endothelial keratoplasty (DMEK) to 33 eyes of 28 patients with uneventful DMEK. Main outcome parameters were various corneal parameters obtained by Scheimpflug imaging, refractive outcome, corrected distance visual acuity (CDVA), and endothelial cell density (ECD).

RESULTS

Anterior and posterior corneal astigmatism, corneal densitometry, central corneal thickness, and anterior chamber depth and volume showed no significant differences. Preoperative distribution of astigmatism axis orientations showed a high proportion of anterior corneal with-the-rule astigmatism (71%) in eyes requiring rebubbling. Mean postoperative cylinder in the rebubbling group (1.21 ± 0.85 D) was significantly higher compared to the controls (p = 0.04), while differences in spherical equivalent (SE) were insignificant (p = 0.24). Postoperative CDVA was 0.11 ± 0.11 in the control group compared to 0.21 ± 0.17 in the rebubbling group (p = 0.03). Eyes with subsequent rebubbling demonstrated a significantly higher endothelial cell loss (56% versus 37%) (p < 0.001).

CONCLUSION

Apart from higher cylinder values, refractive outcome and corneal parameters assessed by Scheimpflug imaging were comparable in eyes with rebubbling and controls. However, a reduced visual acuity and an increased endothelial cell loss should be taken into consideration prior to rebubbling especially in eyes with circumscribed graft detachment.

Evolution of therapies for the corneal endothelium: past, present and future approaches

Corneal endothelial diseases are leading indications for corneal transplantations. With significant advancement in medical science and surgical techniques, corneal transplant surgeries are now increasingly effective at restoring vision in patients with corneal diseases. In the last 15 years, the introduction of endothelial keratoplasty (EK) procedures, where diseased corneal endothelium (CE) are selectively replaced, has significantly transformed the field of corneal transplantation. Compared to traditional penetrating keratoplasty, EK procedures, namely Descemet's stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK), offer faster visual recovery, lower immunological rejection rates, and improved graft survival. Although these modern techniques can achieve high success, there are fundamental impediments to conventional transplantations. A lack of suitable donor corneas worldwide restricts the number of transplants that can be performed. Other barriers include the need for specialized expertise, high cost, and risks of graft rejection or failure. Research is underway to develop alternative treatments for corneal endothelial diseases, which are less dependent on the availability of allogeneic tissues - regenerative medicine and cell-based therapies. In this review, an overview of past and present transplantation procedures used to treat corneal endothelial diseases are described. Potential novel therapies that may be translated into clinical practice will also be presented.

Descemet Membrane Endothelial Keratoplasty Using a Pull-Through Technique With Novel Infusion Forceps

PURPOSE

To describe a surgical technique of Descemet membrane endothelial keratoplasty (DMEK) using an endothelium-in pull-through technique with novel infusion forceps and report 6-month clinical outcomes.

METHODS

This is a retrospective case series of 33 cases with Fuchs endothelial corneal dystrophy who underwent either DMEK alone (n = 5), DMEK combined with phacoemulsification (n = 27), or DMEK combined with intraocular lens exchange (n = 1) performed by surgeons at the beginning of the DMEK learning curve. Best-corrected visual acuity (BCVA), manifest refraction, central corneal thickness, endothelial cell density, intraoperative and postoperative complications, and need for additional surgeries including rebubbling were evaluated through 6 months postoperatively.

RESULTS

Preoperative BCVA was 0.37 ± 0.34 logarithm of the minimum angle of resolution and improved to 0.09 ± 0.10 logarithm of the minimum angle of resolution at 6 months (P < 0.001). Eighty-two percent of eyes obtained a BCVA of 20/25 or better. Central corneal thickness decreased significantly at 6 months (P < 0.001). Endothelial cell loss was 29.1% at 6 months (available for 20 of 33 eyes). All surgeries were uneventful. Six eyes required rebubbling for graft detachments. There were no primary or secondary graft failures at 6 months.

CONCLUSIONS

DMEK with infusion microforceps is efficacious and safe in eyes with Fuchs endothelial corneal dystrophy and could offer a more controlled surgery, making it suitable for both novice and experienced DMEK surgeons.

Surface quality and endothelial cell viability after femtosecond laser-assisted donor lenticule preparation for endothelial keratoplasty - An in-vitro study

Purpose

To compare surface quality and endothelial cell viability of descemet stripping automated endothelial keratoplasty (DSAEK) donor lenticules prepared with femtosecond laser (FSL) or microkeratome (MK).

Methods

Experimental ex-vivo evaluation of 15 DSAEK donor lenticules prepared from optical quality donor corneas using 200 KHz FSL (9 eyes) or MK (6 eyes). Surface quality and smoothness of the cut were assessed using atomic force microscopy and endothelial cell viability was assessed using transmission electron microscopy.

Results

Mean lenticule thickness was 121.89 ± 17.13 μm in FSL group and 112.67 ± 5.89 μm in MK group (P = 0.33). Average roughness of stromal surface (RMSavg) [FSL- 30.51 ± 4.55 nm, MK-22.37 ± 1.83 nm; P = 0.02] and root mean square roughness (RMSrough) [FSL-31.39 ± 5.75 nm, MK-23.08 ± 0.40 nm; P = 0.012] was significantly more in FSL group. Increased granular and linear irregularities were observed in the FSL group. Endothelial cell disruption was more in FSL group (FSL- 29.49 ± 6.91% MK-13.28 ± 3.62%; P < 0.001) with decreased mean nucleus length (FSL-5.56 ± 0.17 μm, MK-7.52 ± 0.65 μm; P < 0.001).

Conclusion

Automated MKs are still the standard of care for donor lenticule preparation and MK-assisted donor lenticules have smoother surface with less endothelial cell disruption than FSL. Further research is mandatory before FSL platforms can be considered a viable alternative to the MK.

A Novel Approach of Harvesting Viable Single Cells from Donor Corneal Endothelium for Cell-Injection Therapy

Donor corneas with low endothelial cell densities (ECD) are deemed unsuitable for corneal endothelial transplantation. This study evaluated a two-step incubation and dissociation harvesting approach to isolate single corneal endothelial cells (CECs) from donor corneas for corneal endothelial cell-injection (CE-CI) therapy. To isolate CECs directly from donor corneas, optimization studies were performed where donor Descemet’s membrane/corneal endothelium (DM/CE) were peeled and incubated in either M4-F99 or M5-Endo media before enzymatic digestion. Morphometric analyses were performed on the isolated single cells. The functional capacities of these cells, isolated using the optimized simple non-cultured endothelial cells (SNEC) harvesting technique, for CE-CI therapy were investigated using a rabbit bullous keratopathy model. The two control groups were the positive controls, where rabbits received cultured CECs, and the negative controls, where rabbits received no CECs. Whilst it took longer for CECs to dislodge as single cells following donor DM/CE incubation in M5-Endo medium, CECs harvested were morphologically more homogenous and smaller compared to CECs obtained from DM/CE incubated in M4-F99 medium (p < 0.05). M5-Endo medium was hence selected as the DM/CE incubation medium prior to enzymatic digestion to harvest CECs for the in vivo cell-injection studies. Following SNEC injection, mean central corneal thickness (CCT) of rabbits increased to 802.9 ± 147.8 μm on day 1, gradually thinned, and remained clear with a CCT of 385.5 ± 38.6 μm at week 3. Recovery of corneas was comparable to rabbits receiving cultured CE-CI (p = 0.40, p = 0.17, and p = 0.08 at weeks 1, 2, and 3, respectively). Corneas that did not receive any cells remained significantly thicker compared to both SNEC injection and cultured CE-CI groups (p < 0.05). This study concluded that direct harvesting of single CECs from donor corneas for SNEC injection allows the utilization of donor corneas unsuitable for conventional endothelial transplantation.

Long-term Results of Corneal Wedge Resection for High Postkeratoplasty Astigmatism

PURPOSE

To present the results of corneal wedge resection in postkeratoplasty astigmatism, performed by the same surgeon using the same nomogram over a 25-year period.

METHODS

This is a retrospective observational study. The sample was obtained from the medical records of all patients who underwent penetrating or deep lamellar keratoplasty, performed by a single surgeon from 1993 to 2018. All surgeries were performed using a diamond knife, on the flat meridian, involving the keratoplasty scar and closed with five 10-0 nylon sutures.

RESULTS

A total of 39 eyes were included. The keratometry measured cylinder improved from 7.99 ± 0.25 to 2.5 ± 0.3 D at 12 months and remained stable thereafter (a mean follow-up of 76.3 months). Best spectacle corrected visual acuity increased from 0.35 ± 0.01 to 0.57 ± 0.02 at 12 months and remained stable thereafter. There was a coupling ratio of 0.08 ± 0.03 D at 12 months. There were no corneal graft rejections or loss of best spectacle corrected visual acuity on this series.

CONCLUSIONS

Corneal wedge resection is a valuable resource for the management of high postkeratoplasty astigmatism. It is a safe and reproducible procedure, with stable results at 12 months and thereafter.

Outcome of Descemet membrane endothelial keratoplasty for graft failure after Descemet stripping automated endothelial keratoplasty

Purpose

To investigate the efficacy and safety of Descemet membrane endothelial keratoplasty (DMEK) for corneal decompensation following primary Descemet stripping automated endothelial keratoplasty (DSAEK).

Methods

This was a retrospective case series of 15 patients that underwent DMEK surgery for corneal decompensation after failed DSAEK. Main outcome parameter was corrected distance visual acuity (CDVA) after DMEK and DSAEK. Secondary outcome measures included central corneal thickness (CCT), endothelial cell density (ECD), rebubbling rate, and primary graft failure after DMEK. Explanted DSAEK grafts were evaluated by light microscopy.

Results

The mean (±SD) time period between DSAEK and DMEK surgery was 15±8 months (range, 6–31 months). Preoperative CDVA was 1.72±0.62 (logMAR). After DMEK, CDVA improved significantly to 0.78±0.48 at 1 month and to 0.23±0.24 after 12 months (P=0.022). Visual acuity data after DMEK were significantly better compared to preoperative values. The average CCT after DMEK decreased significantly from 869±210 µm (preoperative) to 505±45 µm (1 month postoperative) (P<0.001) and remained stable over 12 months. The ECD decreased from 2,589±209/mm² (preoperative) to 1,691±589/mm² (12 months postoperative). Rebubbling DMEK was required in three patients (=20%).

Conclusion

DMEK represents a feasible and safe procedure in achieving better functional results compared to DSAEK. Visual acuity and optical quality can be effectively reestablished after unsuccessful primary DSAEK surgery even in patients with long-standing corneal decompensation. Further investigations are required to validate the preliminary clinical findings.

Bio-Orthogonally Crosslinked, In Situ Forming Corneal Stromal Tissue Substitute

In this study, an in situ forming corneal stromal substitute based on collagen type I crosslinked by bio-orthogonal strain-promoted azide-alkyne cycloaddition (SPAAC) is presented. The crosslinked collagen gel has greater transparency compared to non-crosslinked collagen gels. The mechanical properties of the gels are controlled by changing functional group ratios and conjugated collagen concentrations. Higher concentrations of conjugated collagen yield enhances mechanical properties, where the storage modulus increases from 42.39 ± 8.95 to 112.03 ± 3.94 Pa after SPAAC crosslinking. Encapsulated corneal keratocytes grow within the SPAAC-crosslinked gels and corneal keratinocytes are supported on top of the gel surfaces. SPAAC-crosslinked gels support more favorable and stable keratinocyte morphology on their surface compared to non-crosslinked gels likely as a result of more optimal substrate stiffness, gel integrity, and resistance to degradation. SPAAC-crosslinked collagen gels with and without encapsulated keratocytes applied to rabbit corneas in an organ culture model after keratectomy exhibit surface epithelialization with multilayered morphology. The novel in situ forming gel is a promising candidate for lamellar and defect reconstruction of corneal stromal tissue.

Long-term Outcomes of Repeated Corneal Transplantations: A Prospective Dutch Registry Study

PURPOSE

To compare long-term outcomes of repeated corneal transplantations (CT), based on primary indication (Fuchs endothelial dystrophy [FED] vs pseudophakic bullous keratoplasty [PBK]), surgical technique (penetrating keratoplasty [PK] vs endothelial keratoplasty [EK]), and indication for repeated grafting.

METHODS

In this nonrandomized treatment comparison with national registry data (Netherlands Organ Transplantation Registry, NOTR), data on all consecutive repeated CT following primary PK or EK for FED and PBK between 1994 and 2015 were analyzed, with a maximal follow-up of 5 years. Regraft survival was analyzed using Kaplan-Meier survival curves and univariable and multivariable Cox regression analysis. Secondary outcomes best-corrected visual acuity, spherical equivalent, and refractive astigmatism were compared using linear mixed-model analysis.

RESULTS

A total of 332 repeated CT were analyzed. The number of regrafts increased significantly between 2007 and 2015 (P = .001). Overall 5-year regraft survival was 60% and was higher for FED vs PBK (77% vs 45%, HR = 0.40, P = .001), and re-EK vs re-PK (81% vs 55%, HR = 0.51, P = .041). However, multivariable analysis showed no significant difference in survival based on primary indication, surgical technique, and indication for regrafting. Corrected for baseline, secondary outcomes also did not differ between groups.

CONCLUSIONS

We found a significant increase in repeated CT, coinciding with the introduction of EK in the Netherlands. While univariable analysis suggested better overall regraft survival for FED and (re-)EK, multivariable analysis showed no such difference. This may be owing to allocation of favorable cases to undergo (re-)EK. Similarly, secondary outcomes were determined by the primary CT technique.

Visual outcome of penetrating keratoplasty, deep anterior lamellar keratoplasty and Descemet membrane endothelial keratoplasty

PURPOSE

A single-center, cross-sectional study was designed to assess and compare objective and subjective quality of vision of patients intervened with penetrating keratoplasty (PK), deep anterior lamellar keratoplasty (DALK) and Descemet membrane endothelial keratoplasty (DMEK).

METHODS

Forty-six patients previously intervened with PK (22 eyes), DALK (7 eyes) and DMEK (17 eyes) were recruited. Visual evaluation included spherical and cylindrical refraction, distance corrected visual acuity (DCVA), photopic contrast sensitivity (CS), optical quality, measured with the HD Analyzer (objective scattering index [OSI], MTF cut-off and Strehl ratio), and ocular and corneal aberrometry, measured with the KR-1W Wavefront Analyzer.

RESULTS

Statistically significant between-group differences were found in age (p=0.006, DMEK patients were older) and time since surgery (p<0.001, longest time for PK patients). No statistically significant differences were found in DCVA between the techniques. Between-group differences were encountered in CS at 12 (p=0.007) and 18 (p<0.001) cycles per degree, with DMEK and DALK obtaining the best and worst outcomes, respectively. Differences in optical quality were found between the techniques (OSI, p=0.004; MTF cut-off, p=0.048; Strehl ratio p=0.022), with DMEK displaying the best outcomes. Highest and lowest values in ocular and corneal aberrations were for DALK and DMEK patients, respectively. Between-group differences were found in corneal astigmatism (p<0.001; -3.31±2.00 D in PK; -2.68±0.94 D in DALK; -1.09±0.62 D in DMEK).

CONCLUSION

Overall, DMEK proved superior over PK and DALK in terms of quality of vision, with PK offering slightly better outcomes than DALK in most visual function parameters under evaluation.

Rates of Intraocular Pressure Elevation and Use of Topical Antihypertensive Medication After Descemet Stripping Automated Endothelial Keratoplasty

PURPOSE

To investigate intraocular pressure (IOP) elevation and medication augmentation after Descemet stripping automated endothelial keratoplasty (DSAEK) in those with and without glaucoma.

METHODS

The records of 379 patients who underwent DSAEK at the Cleveland Clinic Foundation between January 2009 and 2014 were retrospectively reviewed. Postoperative IOP elevations were considered significant if IOP was ≥22 mm Hg on at least 1 follow-up visit or if it increased by ≥10 mm Hg from baseline.

RESULTS

The incidence rate of IOP elevation was 4% per person-month (confidence interval [CI], 3%-6%) in patients with preexisting glaucoma and 3% (CI, 2%-4%) in those without. Rates of medication augmentation were 4% per person-month (CI, 3%-5%) in patients with glaucoma and 1.8% (CI, 1.4%-2.4%) in those without. Incidence rates for both outcomes peaked at 1 month. Whites had nearly a 47% lower incidence of IOP elevation compared with nonwhites (P = 0.004); patients with pseudophakic bullous keratopathy had a 54% higher incidence of IOP elevation (P = 0.024); and those with Fuchs endothelial corneal dystrophy had a 36% lower incidence (P = 0.024). Patients with glaucoma had over a 2-fold higher incidence of medication augmentation compared with those without (hazard rate ratio = 2.08, P < 0.001).

CONCLUSIONS

The incidence of post-DSAEK IOP elevation did not significantly differ by glaucoma status, although patients with glaucoma were more likely to have escalation of topical antihypertensive therapy. The incidence of IOP elevation was significantly associated with pseudophakic bullous keratopathy and nonwhite race. These patients should be followed closely in the early postoperative period, as elevated IOP can be a serious consequence of DSAEK.

Promoting the expansion and function of human corneal endothelial cells with an orbital adipose-derived stem cell-conditioned medium

BACKGROUND

Corneal endothelial dysfunction causes severe impairment of vision. The only solution is corneal transplantation. However, this treatment is hampered by a worldwide shortage of donor corneas. New therapies may replace the conventional donor corneal transplantation alongside the developments in regenerative medicine and tissue engineering, but sufficient functional corneal endothelial cells (CECs) are essential. The aim of this study was to promote the expansion and function of human corneal endothelial cells (HCECs) in vitro and in vivo.

METHODS

The phenotypes of human orbital adipose-derived stem cells (OASCs) were detected by flow cytometry and immunofluorescence. HCECs were isolated and cultured using a conditioned medium obtained from OASCs (OASC-CM) in vitro. Related cell markers of HCECs were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and immunofluorescence. The cell counting kit-8 (CCK-8) assay and the wound healing assay were performed to evaluate the proliferation ability of the cells. The cultured HCECs were then transplanted into rabbit and monkey corneal endothelial dysfunction models by cell injection.

RESULTS

CD29, CD105, CD49e, CD166, and vimentin were highly expressed in cultured human OASCs. The CEC-relative markers zonula occludens-1 (ZO-1), Na⁺/K⁺ ATPase, N-cadherin, Col8a2, and SLC4A4 were expressed in HCECs cultured by OASC-CM. The HCECs were able to maintain polygonal cell morphology and good proliferative capacity. In animal experiments, corneal transparency was achieved after the injection of HCECs, which demonstrated the good repair capacity of the cells.

CONCLUSIONS

The proliferation abilities of the cells were significantly enhanced, and related functional markers were strongly positive, while HCEC morphology was maintained using OASC-CM. HCECs obtained some stem cell-like properties. This preclinical study confirmed the therapeutic ability of the HCECs in vivo. Our findings demonstrated that cultured HCECs with OASC-CM might be a promising source for research and clinical treatment.

Trends in corneal transplant surgery in Ireland: indications and outcomes of corneal transplant surgery and intraocular lens opacification following Descemet's stripping automated endothelial keratoplasty

PURPOSE

To evaluate the indications for corneal transplantation, the procedures carried out, and the postoperative outcomes and to compare these with previous Irish corneal transplant studies.

METHODS

A retrospective review of the case notes of all patients who underwent corneal transplantation under the care of a single surgeon, from 2008 to 2015, was performed. The risk factors for postoperative complications including transplant failure were examined.

RESULTS

During the period studied, 42 corneal transplant surgeries were carried out on 40 eyes of 38 patients, 24 of whom were male (63%), median age at surgery was 62 years (range 23-96 years). The most common indication for transplantation was pseudophakic corneal decompensation associated with Fuch's endothelial dystrophy (FED) (n = 13). Seventeen penetrating keratoplasties, 23 lamellar keratoplasties, and two amniotic membrane transplant procedures were carried out. Transplant failure resulting in corneal oedema or repeat corneal transplant surgery (n = 4, 10%), was associated with previous transplant failure in the eye; odds ratio (OR) = 1.58 (p = 0.05), and with comorbid FED, OR = 1.50 (p = 0.02). Intraocular lens opacification occurred in one lens following DSAEK, giving an incidence rate of 7%.

CONCLUSIONS

Pseudophakic corneal decompensation is the commonest indication for corneal transplant surgery, with lamellar keratoplasty the most frequent approach in our cohort, reflecting developments observed in corneal transplant surgery elsewhere. Prior corneal transplant failure and Fuch's dystrophy remain important risk factors for failure. The risk of intraocular lens opacification and its potential effects on vision should be elaborated prior to endothelial keratoplasty.

Evaluation of Visual Quality in Patients With Fuchs Endothelial Corneal Dystrophy

Fuchs endothelial corneal dystrophy (FECD) is a bilateral corneal endothelial dystrophy characterized by the deposition of extracellular matrix (guttae), thickening of Descemet membrane, and progressive loss of corneal endothelial cells. Progressive endothelial cellular loss leads to corneal edema and impairs visual function. In eyes with FECD, corneal edema begins in the central cornea and expands into the periphery. FECD is the most common dystrophic reason for corneal transplantation in many countries. Some patients with FECD report visual discomfort despite the absence of corneal edema. Intraocular forward light scatter impairs patients' quality of vision (QOV), and corneal guttae associated with FECD may cause intraocular light scatter and glare, which can be extremely debilitating despite the absence of edema. We recently investigated the effect of the severity of corneal guttae on QOV in patients with mild FECD. It was shown that corneal guttae increased forward light scatter that negatively affected QOV in eyes with mild FECD without severe corneal edema. Therefore, quantification of corneal guttae would be useful to determine surgical indications for eyes with mild FECD. This review discusses QOV in patients with FECD.

Descemet stripping automated endothelial keratoplasty versus descemet membrane endothelial keratoplasty: a meta-analysis

PURPOSE

To evaluate the efficacy and safety of descemet stripping automated endothelial keratoplasty (DSAEK) compared with descemet membrane endothelial keratoplasty (DMEK).

METHODS

Databases including PubMed, EMBASE, and Cochrane Library were searched to find studies that compared DSAEK and DMEK outcomes. Efficacy parameters were the postoperative best-corrected visual acuity (BCVA) and spherical equivalent (SE). Safety parameters were postoperative endothelial cell loss (ECL), air injection (rebubbling), graft failure, graft rejection, and high intraocular pressure (IOP). Results from last visit were pooled for the analyses because the follow-up ranged from 3 to 24 months.

RESULTS

A total of 7 trials including 433 eyes were selected for this meta-analysis. BCVA was reported in all 7 studies, ECL% and rebubbling rate were reported in 6, and the remaining outcomes were reported in only 3 or 2 studies. Postoperative logMAR BCVA was significantly better for DMEK than that for DSAEK (P < 0.00001). More patients achieved the postoperative BCVA ≥ 20/25 and 20/20 in DMEK group than that in DSAEK (P > 0.001), whereas the proportion of patients whose postoperative BCVA ≥ 20/40 and the amount of SE did not differ statistically (P = 0.32 and P = 0.50, respectively). The DSAEK group has a significantly lower frequency of rebubbling than the DMEK group (P < 0.0001). The postoperative ECL%, graft failure, graft rejection, and high IOP were comparable between the 2 groups (all P values >0.05).

CONCLUSIONS

Our meta-analysis suggests that DMEK provided better visual outcomes with similar safety when compared to DSAEK. Given the limited sample size, further investigations are needed to validate these findings.

Systemic Immunomodulatory Strategies in High-risk Corneal Transplantation

The cornea is the most commonly transplanted tissue in the body. Although corneal grafts generally have high success rates, transplantation onto inflamed and vascularized host beds, or so-called high-risk corneal transplantation, has a high rate of graft rejection. The management of this high-risk corneal transplantation is challenging and involves numerous measures. One of the key measures to prevent graft rejection in these cases is the use of systemic immunosuppressive agents. In this article, we will review the systemic immunosuppressive agents most commonly used for high-risk corneal transplantation, which include corticosteroids, cysclosporine A, tacrolimus, mycophenolate mofetil, and rapamycin. Benefits, risks, and published data on the use of these medications for high-risk corneal transplantation will be detailed. We will also summarize novel immunoregulatory approaches that may be used to prevent graft rejection in high-risk corneal transplantation.

Management of high-risk corneal transplantation

The cornea is the most commonly transplanted tissue in medicine. The main cause of corneal graft failure is allograft rejection. The incidence of graft rejection depends on the presence of high-risk characteristics, most notably corneal neovascularization. Although corneal grafting has high success rates in the absence of these risk factors, high-risk keratoplasty is associated with low success rates because of a high incidence of immune-mediated graft rejection. To improve the survival of high-risk corneal transplantation, various preoperative, intraoperative, and postoperative measures can be considered; however, the key step in the management of these grafts is the long-term use of local and/or systemic immunosuppressive agents. Although a number of immunosuppressive agents have been used for this purpose, the results vary significantly across different studies. This is partly due to the lack of an optimized method for their use, as well as the lack of a precise stratification of the degree of risk in each individual patient. New targeted biologic treatments, as well as tolerance-inducing methods, show promising horizons in the management of high-risk corneal transplantation in near future.