Influence of time to procurement, incubation and release of organ cultured donor corneas on graft failure after Descemet Stripping Automated Endothelial Keratoplasty

PURPOSE

The aim of the present study was to investigate whether the time from death to procurement, to preservation or the storage time of donor corneas preserved in organ culture influenced the clinical outcome of patients undergoing Descemet stripping automated endothelial keratoplasty (DSAEK) for Fuchs endothelial keratoplasty.

METHODS

We conducted a registry-based study on 776 patients undergoing DSAEK. Data on time from donor death to cornea retrieval (DRT), time from death to preservation (DPT), the preservation time and donor cornea characteristics: age, sex and endothelial cell density (ECD) at the time of release for surgery, were extracted from The Danish Cornea Bank Registry. Data on recipient follow-up were collected from a corneal graft registry. The primary outcome was presence of graft failure within a period from 2 months to 2 years after surgery. Secondary outcomes were DRT, DPT, ECD ≤2300 and gender mismatch between donor and recipient.

RESULTS

Graft failure occurred in 26 patients. The mean preservation time for failed grafts was 34.1 ± 10.0 days (mean ± SD) and 27.3 ± 10.6 days (mean ± SD) for the clear, functional grafts at the 2-year follow-up. A preservation time of >29 days compared with ≤29 days was associated with a lower survival (HR 2.33, 95% CI on 1.06-5.14, p = 0.036) and an increased risk of graft failure (RR 1.53, 95% CI on 1.11-2.10, p = 0.009). For the secondary outcome variables, no difference in the risk of graft failure was observed and did not appear to impact the survival rate of DSAEK patients.

CONCLUSION

Preservation time of donor cornea was associated with graft survival and a prolonged preservation time of more than 4 weeks seemed to lower the 2-year survival.

Post Penetrating Keratoplasty Ectasia: Incidence, Risk Factors, Clinical Features, and Treatment Options

BACKGROUND: Corneal transplantation in keratoconus (KC) patients is generally considered to be successful with a high grade of patient satisfaction. Long-term studies suggest a 6% to 11% probability of KC recurrence manifested by keratometric instability and progressive corneal ectasia. METHODS: We propose to review the frequency, risk factors for the development, and the surgical options for the correction of high irregular astigmatism due to late graft ectasia following penetrating keratoplasty (PK). RESULTS: Post-keratoplasty ectasia is characterized by increasing corneal steepening with myopic shift and high irregular astigmatism, developing years or decades after PK, mostly occurring in KC patients. Contact lenses may adequately improve the visual acuity; however, because these patients are often elderly and intolerant to hard contact lenses, ultimately a surgical correction is proposed to the patient. Compressive suture and corneal wedge resection may improve corneal astigmatism, but the outcomes are unpredictable and often temporary. For this reason, a larger PK graft is often proposed for surgical rehabilitation with the consequence of removing more of the recipient’s healthy endothelium and exposing the patient to a renewed immunogenic stimulus and short-term graft failure for endothelial decompensation. More recently, lamellar keratoplasty using various techniques has been proposed as an alternative to PK in order to maximize the visual outcomes and minimize the complications. CONCLUSIONS: Management of advanced corneal ectasia is a significant challenge for corneal surgeons. Many surgical approaches have been developed, so there is a large arsenal of surgical operations to correct post-PK ectasia. Among them, large-diameter anterior lamellar keratoplasty may be a viable, safer, and effective alternative to PK for the correction of post-keratoplasty ectasia.

Effects of femtosecond laser-assisted trephination on donor tissue in liquid interface as compared to applanated interface

Purpose

To evaluate the effects of femtosecond laser‐assisted keratoplasty using a liquid patient interface (L‐PI) as opposed to an applanated interface (A‐PI) on graft quality and functionality markers.

Methods

Pressure measurements during femtosecond laser‐assisted trephination were performed using two groups of 10 porcine eyes. Trephination was performed either in an L‐PI or in an A‐PI setting. Pressure sensor needles placed intravitreally continuously recorded intraocular pressure during trephination. Twenty paired human donor eyes were used to test the morphological quality of donor tissue after trephination in L‐PI and A‐PI settings. Optical coherence tomography (OCT) scans were performed before and after trephination. Images were processed using ImageJ and pixel².

Results

During trephination, pressure measurements with an L‐PI were significantly lower than with an A‐PI (p = 0.0121). Mean pressure during trephination was 78.1 mmHg ± 37.6 mmHg with L‐PI and 188.6 mmHg ± 17.7 mmHg with A‐PI. Trephination in A‐PI produced a significantly larger increase (p < 0.00001) in donor pachymetry than trephination in L‐PI. Significantly lower areas of Descemet folds were achieved in L‐PI trephination than in A‐PI trephination (p < 0.01). There was no significant difference in circularity between A‐PI and L‐PI (p = 0.27). Total time required for trephination was comparable between L‐PI and A‐PI (p = 0.45). Time taken to reach working vacuum was achieved significantly more quickly in L‐PI (p < 0.05).

Conclusion

Femtosecond laser‐assisted L‐PI keratoplasty appears to be a promising method to decrease stress to donor and recipient tissue during femtosecond laser‐assisted trephination. Results showed favourable donor tissue morphology markers after L‐PI trephination.

Post-corneal transplant Candida keratitis - Incidence and outcome

Purpose:

To report the risk factors, clinical characteristics, and outcomes of Candida keratitis following corneal transplantation in India.

Methods:

On retrospective review of medical records of 789 patients, 31 eyes developed a graft infection following corneal transplantation or keratoprosthesis and we could identify the Candida infection in only five. These cases were operated at two tertiary care centers in India. These five records were reviewed for demographics, risk factors (local and systemic) for graft infection, characteristics of infective lesion, corneal scraping results, treatment plan, and the final outcome following management.

Results:

The median age of the subjects with the Candida graft infection was 62.4 ± 10.33 years (range, 62–71 years). All patients were males. The predominant risk factors included repeat corneal transplantation (5/5), prolonged usage of topical steroids (5/5), and epithelial defects (4/5). The clinical characteristics included infiltrates of variable configuration like powdery deposits, white plaque, fluffy white infiltrate, and crystalline keratopathy. The smear showed budding yeasts in all five cases whereas culture was positive in four out of five cases. The final outcome with antifungals (systemic [4/5] and topical [5/5]) is variable. Two eyes underwent evisceration, two eyes had scar formation in the failed grafts, and one patient succumbed to the systemic disease 1-month post-corneal infection.

Conclusion:

Candida keratitis, in India, seems to be an emerging pathology following corneal transplantation and has a varied presentation. Though the outcomes following management seem to be grim, however, such infection can easily be avoided by a timely reduction of the risk factors.

Use of biomaterials in corneal endothelial repair

Human corneal endothelium (HCE) is a single layer of hexagonal cells that lines the posterior surface of the cornea. It forms the barrier that separates the aqueous humor from the rest of the corneal layers (stroma and epithelium layer). This layer plays a fundamental role in maintaining the hydration and transparency of the cornea, which in turn ensures a clear vision. In vivo, human corneal endothelial cells (HCECs) are generally believed to be nonproliferating. In many cases, due to their nonproliferative nature, any damage to these cells can lead to further issues with Descemet’s membrane (DM), stroma and epithelium which may ultimately lead to hazy vision and blindness. Endothelial keratoplasties such as Descemet’s stripping automated endothelial keratoplasty (DSAEK) and Descemet’s membrane endothelial keratoplasty (DEK) are the standard surgeries routinely used to restore vision following endothelial failure. Basically, these two similar surgical techniques involve the replacement of the diseased endothelial layer in the center of the cornea by a healthy layer taken from a donor cornea. Globally, eye banks are facing an increased demand to provide corneas that have suitable features for transplantation. Consequently, it can be stated that there is a significant shortage of corneal grafting tissue; for every 70 corneas required, only 1 is available. Nowadays, eye banks face long waiting lists due to shortage of donors, seriously aggravated when compared with previous years, due to the global COVID-19 pandemic. Thus, there is an urgent need to find alternative and more sustainable sources for treating endothelial diseases, such as utilizing bioengineering to use of biomaterials as a remedy. The current review focuses on the use of biomaterials to repair the corneal endothelium. A range of biomaterials have been considered based on their promising results and outstanding features, including previous studies and their key findings in the context of each biomaterial.

[Nerve fiber structure after different types of corneal transplantation]

This review presents basic information about the state of corneal nerve fibers and Langerhans cells before and after keratoplasty. Keratoplasty is a common corneal surgery that carries a risk of graft rejection. The state of corneal nerve fibers can vary after different types of keratoplasty. Corneal confocal microscopy allows in vivo evaluation of the cornea, which can help assess the condition of corneal nerve fibers, as well as reveal the presence of Langerhans cells. Further research in this direction would contribute to identifying the relationship between the state of corneal nerve fibers, the presence of Langerhans cells, and graft rejection.

Targeting NF-κB c-Rel in regulatory T cells to treat corneal transplantation rejection

The relevance of Tregs in the induction of tolerance against corneal allografts has been well established. Although it is well known that the conversion of Tregs into effector-like cells contributes to the loss of corneal immune privilege, the underlying mechanism is still not fully understood. Using heterologous penetrating keratoplasty model, we found that Tregs from corneal allograft rejected mice (inflam-Tregs) exhibit impaired function and characteristics of effector T cells. Further study showed that the expression of NF-κB c-Rel, a key mediator of effector T cell function, was significantly increased in inflam-Tregs. Mechanistic study revealed that elevated NF-κB c-Rel level in inflam-Tregs impaired Treg function through the promotion of inflammatory cytokine production and glycolysis. More importantly, we demonstrated that targeting NF-κB c-Rel was able to improve the immune suppressive function of inflam-Tregs in vitro and enhance the potential of them to suppress corneal transplantation rejection. Therefore, our current study identified NF-κB c-Rel as a key mediator of the conversion of Tregs into effector-like cells when under inflammatory environment.

Candida keratitis and endopthalmitis after corneal transplantation; two case reports, a novel regimen and literature overview of therapeutic options

PURPOSE

To evaluate treatment options for candida keratitis and endopthalmitis after corneal transplantation.

METHODS

Case reports and literature review.

RESULTS

Two patients with keratitis due to Candida glabrata/parapsilosis after corneal transplantation were successfully treated with a combination of topical voriconazole, intracameral voriconazole and amphotericin B, and systemic treatment with flucytosine.

CONCLUSIONS

Natamycine and voriconazole topically are preferred therapeutic options for the treatment of fungal keratitis. Systemic flucytosine is a useful alternative additive, particularly for countries where natamycine is not registered as a pharmaceutical agent.

Analysis of Cryopreservation Protocols and Their Harmful Effects on the Endothelial Integrity of Human Corneas

Corneal cryopreservation can partially solve the worldwide concern regarding donor cornea shortage for keratoplasties. In this study, human corneas were cryopreserved using two standard cryopreservation protocols that are employed in the Tissue Bank of the Teresa Herrera Hospital (Spain) to store corneas for tectonic keratoplasties (TK protocol) and aortic valves (AV protocol), and two vitrification protocols, VS55 and DP6. Endothelial viability and general corneal state were evaluated to determine the protocol that provides the best results. The potential corneal cryopreservation protocol was studied in detail taking into consideration some cryopreservation-related variables and the endothelial integrity and stroma arrangement of the resulting cryopreserved corneas. TK corneas showed mostly viable endothelial cells, while the others showed few (AV) or none (DP6 and VS55). The corneal structure was well maintained in TK and AV corneas. TK corneas showed endothelial acellular areas surrounded by injured cells and a normal-like stromal fiber arrangement. Cryoprotectant solutions of the TK protocol presented an increasing osmolality and a physiological pH value. Cooling temperature rate of TK protocol was of 1 °C/min to −40 °C and 3 °C/min to −120 °C, and almost all of dimethyl sulfoxide left the tissue after washing. Future studies should be done changing cryopreservation-related variables of the TK protocol to store corneas of optical grade.

Trends in Corneal Transplantation and Characteristics of Donors in the Chongqing Eye Bank, China: A Retrospective Study, 1999-2018

Aim: This study aimed to analyze corneal transplantation trends and voluntary donor characteristics at the Chongqing Eye Bank in China.

Methods: We retrospectively reviewed and analyzed data from January 1, 1999, to December 31, 2018, covering 5,397 preregistered voluntary donors, 1,955 actual donors, 3,910 donated tissues, and 2,374 corneal transplantations.

Results: The 5,397 preregistered donors included 13 ethnic groups, with an overall mean age of 39.6 years (SD 21.5) and 3,010 were women (55.8%). The most prevalent education level was college and above (2,546, 47.2%), and the most common ethnic group was Han (5,335, 98.85%). Of the 1,955 actual donors, the male-to-female ratio was 3.3, and the mean age was 57.1 (SD 23.0 years). Based on population size in 2018, Jiangbei county was the most active in donation willingness, with ~60 × 10⁻⁶ per capita, and the Yuzhong county was the most active in cornea donations, with ~451 × 0⁻⁶ per capita. Of the 3,910 donated corneas, 2,540 (65.0%) were clinically used. Of those not used, 978 (71.4%) were rejected for poor corneal quality. The 2,374 (93.5%) corneal transplantation procedures were done at the Department of Ophthalmology of the First Affiliated Hospital of Chongqing Medical University and the rest (n = 166, 6.5%) were performed in other centers. Of those 2,374 corneal transplantations, there were 1,671 penetrating keratoplasty (70.39%), 700 anterior lamellar keratoplasty (29.49%), and three corneal endothelial transplantations in our center (0.13%). The number of annual corneal transplantations increased by nearly 10 times, from 35 cases in 1999 to 327 cases in 2018. Among them, cases of penetrating keratoplasty and anterior lamellar keratoplasty increased from 27, and eight cases in 1999 to 230 and 94 cases in 2018, respectively. Infectious keratitis (37.0%) was the leading indication for keratoplasty, followed by corneal scar (19.8%). Over the study period, corneal scars dropped from the first (41.1% in 1999–2003) to the second indication (20.5% in 2014–2018), while infectious keratitis advanced to take the lead, ranging from 12.2% in 1999–2003 to 26.3% in 2014–2018.

Conclusion: Our study reports corneal donation and transplantation trends in Chongqing over 20 years, showing that infectious keratitis is a leading indication for keratoplasty and that penetrating keratoplasty and anterior lamellar keratoplasty show upward trends. The analysis further suggests that a potential preregistered cornea donor is a female Han, with a higher education level.

Elevated Cytokine Levels in Aqueous Humor Are Associated with Peripheral Anterior Synechiae after Penetrating Keratoplasty

Peripheral anterior synechiae (PAS) after corneal transplantation leads to refractory glaucoma and permanent loss of vision. However, the exact mechanism remains elusive. This study aimed to evaluate the association between cytokine levels in the aqueous humor (AqH) and the progression of PAS after penetrating keratoplasty (PKP). We measured 20 cytokine levels in AqH and assessed the correlation with PAS progression after PKP in 85 consecutive patients who underwent PKP. We also evaluated age-dependent alterations in PAS and cytokine levels in DBA2J mice. PAS developed in 38 (44.7%) of 85 eyes after PKP. The incidence of intraocular pressure increase after PKP was significantly greater in eyes with PAS (26.3%) than in those without PAS (2%, p = 0.0009). The PAS area at 12 months after PKP was significantly positively correlated with the preoperative levels of interleukin (IL)-6, interferon (IFN)-γ and monocyte chemotactic protein (MCP)-1 (p ≤ 0.049). In the DBA2J mice, an experimental glaucoma model that developed PAS at 50 weeks, the AqH levels of IL-2, IL-6, IL-10, IFN-γ, tumor necrosis factor-α, MCP-1 and granulocyte-macrophage colony-stimulating factor (GM-CSF) significantly increased at 50 weeks compared to 8 weeks (p ≤ 0.021). In conclusion, inflammatory alterations in the AqH microenvironment, such as high preoperative specific cytokine levels, can lead to PAS formation and glaucoma.

Quality of vision and vision-related quality of life after Descemet membrane endothelial keratoplasty: a randomized clinical trial

Purpose

To compare quality of vision and vision‐related quality of life (QOL) in patients undergoing Descemet membrane endothelial keratoplasty (DMEK) or ultrathin Descemet stripping automated endothelial keratoplasty (DSAEK).

Methods

Fifty‐four eyes of 54 patients with Fuchs' dystrophy from six corneal clinics in the Netherlands were randomized to DMEK or ultrathin DSAEK and examined preoperatively, and 3, 6 and 12 months postoperatively. Main outcome measures were corneal higher‐order aberrations (HOAs), contrast sensitivity, straylight and vision‐related QOL.

Results

Posterior corneal HOAs decreased after DMEK and increased after ultrathin DSAEK (p ≤ 0.001) 3 months after surgery and correlated positively with best spectacle‐corrected visual acuity (12 months: r = 0.29, p = 0.04). Anterior and total corneal HOAs did not differ significantly between both techniques at any time point. Contrast sensitivity was better (p = 0.01), and straylight was lower (p = 0.01) 3 months after DMEK compared with ultrathin DSAEK; 95% confidence interval [CI] of log(cs) 1.10–1.35 versus 95% CI: 0.84 to 1.12, and 95% CI: log(s) 1.18 to 1.43 versus 95% CI: 1.41 to 1.66, respectively. Both were comparable at later time points. Vision‐related QOL (scale 0–100) did not differ significantly between both groups at any time point and improved significantly at 3 months (β = 12 [95% CI: 7 to 16]; p < 0.001), and subsequently between 3 and 12 months (β = 5 [95% CI: 0 to 9]; p = 0.06).

Conclusions

Descemet membrane endothelial keratoplasty (DMEK) results in lower posterior corneal HOAs compared with ultrathin DSAEK. Contrast sensitivity and straylight recover faster after DMEK but reach similar levels with both techniques at 1 year. Vision‐related QOL improved significantly after surgery, but did not differ between both techniques.

Complete anterior segment reconstruction: Corneal transplantation and implantation of an iris prosthesis and IOL in a single surgery

PURPOSE

Patients who have suffered an ocular trauma may present with varying degrees of injury to the anterior segment. In this retrospective interventional case series, we report the outcome of seven patients who underwent complete anterior segment reconstruction in a single surgery.

METHODS

All patients with posttraumatic corneal decompensation or scar, aphakia, and iris defect underwent human donor corneal graft transplantation and implantation of an intraocular lens combined with a flexible silicone iris prosthesis. Postoperative examinations included assessment of best corrected distance visual acuity, objective refraction, and intraocular pressure. Sensitivity to glare and subjective discontent with the eye's appearance was rated on a scale from 1 to 10, with 1 standing for low and 10 for high severity.

RESULTS

Mean best corrected distance visual acuity (BCDVA) was 1.51 ± 0.26 logMAR preoperatively and 1.29 ± 0.36 logMAR postoperatively. Mean IOP was 15.71 ± 8.94 mmHg pre-surgery and 13.57 ± 6.52 mmHg post-surgery. The mean sensitivity to glare was reduced from 7.17 ± 2.91 to 3.80 ± 3.43 and subjective cosmetic disfigurement was reduced from 5.33 ± 3.35 to 1.80 ± 1.60.

CONCLUSIONS

A single surgery technique for entire anterior segment reconstruction in trauma patients can effectively reduce glare and patient discontent with the eye's appearance.

Novel adaptation of a running suture technique in a mouse model of corneal transplantation

Several murine models of corneal transplantation have been developed over the years to study the immunopathological processes that lead to the failure of grafted corneas. In all of them, the classic eight interrupted sutures technique is utilized for transplanting the donor cornea on the host bed. However, in clinical practice, a single continuous suture with a single knot is generally performed for corneal transplantation. Here, we describe the adaptation of the single continuous suture technique in a mouse model of corneal transplantation.

Role of Immune Cell Diversity and Heterogeneity in Corneal Graft Survival: A Systematic Review and Meta-Analysis

Corneal transplantation is one of the most successful forms of solid organ transplantation; however, immune rejection is still a major cause of corneal graft failure. Both innate and adaptive immunity play a significant role in allograft tolerance. Therefore, immune cells, cytokines, and signal-transduction pathways are critical therapeutic targets. In this analysis, we aimed to review the current literature on various immunotherapeutic approaches for corneal-allograft rejection using the PubMed, EMBASE, Web of Science, Cochrane, and China National Knowledge Infrastructure. Retrievable data for meta-analysis were screened and assessed. The review, which evaluated multiple immunotherapeutic approaches to prevent corneal allograft rejection, showed extensive involvement of innate and adaptive immunity components. Understanding the contribution of this immune diversity to the ocular surface is critical for ensuring corneal allograft survival.

Patient-Reported Outcomes After Corneal Transplantation

PURPOSE

To characterize vision-related quality of life after penetrating keratoplasty (PKP), deep anterior lamellar keratoplasty (DALK), Descemet stripping automated endothelial keratoplasty (DSAEK), and Descemet membrane endothelial keratoplasty (DMEK) using the National Eye Institute Visual Function Questionnaire (NEI-VFQ 9).

METHODS

Using the Sight Outcomes Research Collaborative ophthalmology electronic health record repository, questionnaire responses were obtained from 103 PKP patients, 24 DALK patients, 42 DSAEK patients, and 50 DMEK patients undergoing postoperative examination. No exclusions were made based on preoperative diagnosis, age, complications, or comorbidities. Associations between clinical characteristics and vision-related quality of life were analyzed using nonparametric and linear regression methods.

RESULTS

Patients were surveyed an average of 1.5 years postoperatively (range 24 d to 4.4 yrs). Participants who had undergone DALK, DMEK, DSAEK, and PKP had median composite VFQ scores of 77.8, 84.2, 76.1, and 70.6, respectively (P= 0.002). There were no significant differences in VFQ scores between patients treated with DMEK versus DSAEK (P = 0.440) or between patients treated with PKP versus DALK (P = 1.000). Higher postoperative acuities in the operative and fellow eyes were associated with higher VFQ scores (P < 0.001 and P < 0.001). When controlling for postoperative acuity by regression modeling, surgery type was not associated with patient-reported composite VFQ scores.

CONCLUSIONS

In this study, patient-reported vision-related quality of life was similar among DMEK and DSAEK participants and also among DALK and PKP participants. When controlling for postoperative acuity, vision-related quality of life was similar among all study participants, irrespective of the keratoplasty technique.

The Association between Diabetes Mellitus and Keratoplasty in Poland in the Years 2013-2017

BACKGROUND

The aim of this study is to assess the incidence and characteristic of corneal grafts and its association with diabetes mellitus in Poland in the years 2013-2017.

METHODS

The retrospective survey of the National Database of Hospitalizations was performed to identify all the corneal transplantations in Poland between January 2013 and December 2017. The comorbid diseases, in particular diabetes mellitus, were verified in the patients' medical history. The logistic regression was applied to demonstrate the factors related to urgent surgeries.

RESULTS

In total, 5069 corneal grafts in 4710 patients were reported in the years 2013-2017. The number of CTs gradually increased by 37% from 914 (2.37 surgeries per one hundred thousand population) in the year 2013 to 1250 (3.25 surgeries per one hundred thousand population) in 2017, the final year of the study. CT incidence was the highest in subjects aged 70 years or older: 13.18 per one hundred thousand population in the year 2017. On average, about 22.43% of procedures were performed in patients with DM. The chance of urgent surgery was mostly correlated with full thickness CT and patients' age.

CONCLUSIONS

Despite the relatively low value of CT in Poland, there was an increasing number of CTs in the analyzed period.

Tectonic Deep Anterior Lamellar Keratoplasty to Treat Corneal Perforation and Descemetocele from Microbial Keratitis

Purpose

To evaluate the result of tectonic deep anterior lamellar keratoplasty (DALK) for keratitis with perforation and descemetocele.

Patients and Methods

A prospective clinical study of 36 patients (36 eyes) treated with tectonic DALK for corneal perforation or descemetocele from microbial keratitis managed at the Vietnam National Eye Hospital over a two-year period. The surgical technique was manual lamellar dissection. The grafts were harvested from the anterior corneal cap of pre-cut donor tissues used for DSAEK or donor corneas with a low endothelial cell count.

Results

A mean age was 55.36 ± 13.98 years (ranged from 25 to 75 years). Female gender represented 52%. causative agents were herpes simplex virus (58.3%), bacteria (22.2%), fungi (13.9%) and microsporidia (5.6%). There were 24 eyes with descemetocele (66.7%) and 12 with perforation (33.3%). There were 33 successful cases (91.7%) and 3 failed cases (8.3%). Best corrected visual acuity (BCVA) improved in 28 eyes (84.8%). The range of post-operative BCVA was from hand motions to 20/70. Eleven eyes (33.3%) attained vision 20/200 and higher. Clear graft was obtained in 15 eyes (45.5%), while mild or severe graft opacity was observed in 14 eyes (42.4%), and 4 eyes (12.1%), respectively. Surgical complications included descemet rupture (20.8%), pseudo anterior chamber (41.6%), persistent corneal epithelial defects (8.3%), reinfection (11.1%), glaucoma or ocular hypertension (5.6%) and cataract (8.3%).

Conclusion

The study demonstrates that DALK is an effective procedure to treat corneal descemetocele, especially when an urgent penetrating keratoplasty (PKP) cannot be performed.

Three-quarter DMEK in eyes with glaucoma draining devices to avoid secondary graft failure

PURPOSE

To present a case series of a modified three-quarter Descemet's membrane endothelial keratoplasty (3/4-DMEK) technique to treat pseudophakic bullous keratopathy in the presence of a glaucoma drainage device (GDD) tube in the anterior chamber by reducing the risk of donor endothelial damage due to absence of donor endothelial cells overlying the GGD tube area.

METHODS

In this prospective case series, four eyes of three patients with stable glaucoma underwent 3/4-DMEK surgery for pseudophakic bullous keratopathy after GDD insertion. The patients were followed up to 24 ± 2.5 months postoperatively.

RESULTS

No intraoperative or postoperative complications were noted. The average central endothelial cell density (ECD) was 1093 ± 74 cells/mm² at 12 months postoperatively, corresponding to an ECD decrease of 58 (±6)% as compared to preoperative values. Average best-corrected visual acuity increased from finger counting before surgery to 20/60 (logMar 0.5) at 12 months after 3/4-DMEK and remained stable up to 24 months postoperatively. All corneas remained clear at the last available follow-up.

CONCLUSION

This case series demonstrates the technical feasibility of 3/4-DMEK in eyes with pseudophakic bullous keratopathy in the presence of a GDD tube. The absence of a donor DM and donor cells above the silicone tube excludes direct tube contact with the graft. Longer term studies are needed to show the effect of this modified graft pattern and dimensions on transplant survival.

Corneal supply and the use of technology to reduce its demand: A review

Recovery and access to end-of-life corneal tissue for corneal transplantation, training and research is globally maldistributed. The reasons for the maldistribution are complex and multifaceted, and not well defined or understood. Currently there are few solutions available to effectively address these issues. This review provides an overview of the system, key issues impacting recovery and allocation and emphasises how end-user ophthalmologists and researchers, with support from administrators and the wider sector, can assist in increasing access long-term through sustaining eye banks nationally and globally. We posit that prevention measures and improved surgical techniques, together with the development of novel therapies will play a significant role in reducing demand and enhance the equitable allocation of corneas.

Lymphatic Trafficking in the Eye: Modulation of Lymphatic Trafficking to Promote Corneal Transplant Survival

(Lymph)angiogenesis into the cornea prior to and after corneal transplantation is a critical risk factor for allograft rejection. Lymphatic vessels even more than blood vessels seem important in mediating immune responses, as they facilitate allograft sensitization in the draining lymph nodes. Thus, the concept of modulating lymphatic trafficking to promote corneal graft survival seems promising. A variety of approaches has been developed to inhibit progressive lymphangiogenesis in experimental settings. Recently, additionally to pharmacological approaches, clinically available techniques such as UVA-based corneal collagen crosslinking and fine needle diathermy were reported to be effective in regressing lymphatic vessels and to experimentally promote graft survival. Clinical pilot studies also suggest the efficacy of blocking antigen presenting cell trafficking to regional lymph nodes by regressing corneal lymphatic vessels to enhance allograft survival in high-risk eyes. In this article, we will give an overview of current strategies to modulate lymphatic trafficking with a special focus on recently reported strategies, which may be easy to translate into clinical practice. This novel concept of temporary, pretransplant regression of lymphatic vessels at the site of transplantation to promote subsequent corneal transplant survival (“lymphangioregressive preconditioning”) may also be applicable to other transplantation sites later.

Advances in corneal graft rejection

PURPOSE OF REVIEW

Immune rejection after corneal transplantation is a major risk for graft failure. We aim to summarize recent advances in the understanding and management of graft rejection.

RECENT FINDINGS

Immune rejection remains the leading cause of graft failure in penetrating keratoplasty (PKP). While ABO blood type and sex match between donor and recipient may reduce rejection, human leucocyte antigens class II matching in a randomized study did not reduce the risk of rejection in high-risk PKP. Compared with PKP, deep anterior lamellar keratoplasty, descemet stripping automated endothelial keratoplasty, and descemet membrane endothelial keratoplasty have lower immune rejection rates of 1.7-13%, 5-11.4%, and 1.7-2.8%, respectively, based on long-term (5 years and more) studies. Whether immune rejection is a major risk factor for graft failure in these lamellar keratoplasties is unclear. While there have not been major advances in the systemic management of graft rejection, topical nonsteroid agents such as tacrolimus and anti-vascular endothelial growth factor have shown promise in high-risk cases.

SUMMARY

Immune rejection remains the leading cause of graft failure in PKP. Lamellar keratoplasties have significantly lower rejection rates compared with PKP. The significance of rejection in the failure of lamellar grafts warrants further investigation.

Why a dedicated section on keratoconus in the European Journal of Ophthalmology?

Keratoconus is emerging as a new subspecialty in ophthalmology. The literature is booming with publications on the topic as we have better understanding of the pathophysiology, treatment and prognosis of the disease over the past two decades. Advances in diagnostic tools as well as genuine increase in prevalence have shifted perspective of the disease from being a rare one. Early diagnosis is of public health interest as early treatment arrests progression. With the view to encourage research, increase awareness and to reflect the evolution of knowledge related to keratoconus, the European Journal of Ophthalmology has dedicate a special section on keratoconus in its journal.

In Vitro Evaluation and Transplantation of Human Corneal Endothelial Cells Cultured on Biocompatible Carriers

Corneal transplantation is currently the only effective treatment option for dysfunctional corneal endothelial cells (CEC). In this study, we test in vitro the surgical potential of cultivated human corneal endothelial cells (hCEC) on human anterior lens capsule (HALC), LinkCell™ bioengineered collagen sheets of 20-µm thickness (LK20), and denuded Descemet membrane (dDM) as tissue-engineered grafts for Descemet membrane (DM) endothelial keratoplasty (DMEK) to bypass the problem of donor tissue availability. Primary hCEC cultured on all carriers formed a monolayer of tightly packed cells with a high cell viability rate (96% ± 4%). hCEC on HALC and LK20 showed unremarkable expression of zonula occludens-1 (ZO-1) and Na⁺/K⁺-adenosine triphosphatase (ATPase), while Na⁺/K⁺-ATPase expression of cells seeded on dDM was mainly cytoplasmic. All hCEC-carrier constructs were evaluated by simulating DMEK surgery in vitro using a human donor cornea without DM mounted on an artificial anterior chamber (AC) and a regular DMEK-graft used as a surgical reference model. During in vitro surgery, hCEC-HALC constructs behaved most similarly to a DMEK-graft during implantation and unfolding, showing good adhesion to the bare stroma. On the other hand, hCEC-LK20 and hCEC-dDM constructs required some additional handling because of challenges related to the surgical procedure, although they were both successfully unfolded and implanted in the artificial AC. The hCEC-dDM constructs showed similar graft adherence as hCEC-HALC constructs, while adherence of hCEC-LK20 constructs was less effective. After the in vitro surgery, the estimated area populated by viable cells on the hCEC-HALC and hCEC-LK20 constructs was ∼83% and ∼67%, respectively. Overall, hCEC-HALC constructs behaved most similarly to a DMEK-graft during in vitro DMEK surgery, while graft adhesion and surgical handling, respectively, are parameters still requiring optimization for hCEC-LK20 and hCEC-dDM constructs.

Ex Vivo-Induced Bone Marrow-Derived Myeloid Suppressor Cells Prevent Corneal Allograft Rejection in Mice

Purpose

To investigate the effects of ex vivo-induced bone marrow myeloid-derived suppressor cells (BM-MDSCs) on allogeneic immune responses in corneal transplantation.

Methods

Bone marrow cells from C57BL/6J (B6) mice were cultured with IL-6 and GM-CSF for four days. The ex vivo induction of the BM-MDSCs was assessed using flow cytometry, inducible nitric oxide synthase (iNOS) mRNA expression using reverse transcription-quantitative polymerase chain reaction, and nitric oxide (NO) production in allogeneic stimulation. T-cell proliferation and regulatory T-cell (Treg) expansion were investigated on allogeneic stimulation in the presence of ex vivo-induced BM-MDSCs. IFN-γ, IL-2, IL-10, and TGF-β1 protein levels were measured using enzyme-linked immunosorbent assays. After subconjunctival injection of ex vivo-induced BM-MDSCs, the migration of the BM-MDSCs into corneal grafts, allogeneic corneal graft survival, neovascularization, and lymphangiogenesis were assessed using flow cytometry, slit-lamp microscopy, and immunohistochemistry.

Results

The combination of GM-CSF and IL-6 significantly induced BM-MDSCs with increased iNos mRNA expression. The ex vivo-induced BM-MDSCs promoted NO release in allogeneic stimulation in vitro. The ex vivo-induced BM-MDSCs inhibited T-cell proliferation and promoted Treg expansion. Decreased IFN-γ and increased IL-2, IL-10, and TGF-β1 production was observed in coculture of ex vivo-induced BM-MDSCs. Injected ex vivo-induced BM-MDSCs were confirmed to migrate into the grafts. The injected BM-MDSCs also prolonged corneal graft survival and prevented angiogenesis and lymphangiogenesis.

Conclusions

The ex vivo-induced BM-MDSCs have suppressive effects on allogeneic immune responses and prolong corneal allograft survival via the iNOS pathway, indicating that they may be a potential therapeutic tool for corneal transplantation.