The impact of donor diabetes on corneal transplant immunity

Corneal transplantation is the most common form of solid tissue grafting, with an approximately 80% to 90% success rate. However, success rates may decline when donor tissues are derived from patients with a history of diabetes mellitus (DM). To evaluate the underlying immunopathologic processes that cause graft rejection, we used streptozotocin-induced type 1 DM (DM1) and transgenic Lepob/ob type 2 DM (DM2) diabetic murine models as donors and nondiabetic BALB/c as recipients. DM resulted in an increased frequency of corneal antigen-presenting cells (APCs) with an acquired immunostimulatory phenotype. Following transplantation, recipients that received either type of diabetic graft showed increased APC migration and T helper type 1 alloreactive cells, impaired functional regulatory T cells, and graft survival. Insulin treatment in streptozotocin-induced diabetic mice led to an increased tolerogenic profile of graft APC, lower T helper type 1 sensitization, and a higher frequency of functional regulatory T cells with high suppressive capacity, reflected in increased graft survival. We conclude that both DM1 and DM2 in donors can impact corneal APC functional phenotype, rendering the tissue more immunogenic and thereby increasing the risk of graft failure.

Challenges in Assessing COVID-19 Vaccines Safety Signals-The Case of ChAdOx1 nCoV-19 Vaccine and Corneal Graft Rejection

The rapid and large-scale roll-out of new COVID-19 vaccines has led to unprecedented challenges in assessing vaccine safety. In 2021, the European Medicines Agency (EMA) processed about 1.7 million safety reports related to COVID-19 vaccines in the EudraVigilance (EV) database and identified more than 900 potential signals. Beyond the large amount of information to be processed, the evaluation of safety signals has faced several difficulties and limitations, both in the assessment of case reports and in the investigation of databases. The evaluation of a signal of corneal graft rejection (CGR) with Vaxzevria^® was no exception to this. In this commentary, we present the challenges encountered in making regulatory decisions in the context of evolving evidence and knowledge. The pandemic crisis emphasised the importance of quick and proactive communication to address the many questions and, above all, to ensure the transparency of safety data.

Corneal Adverse Events Associated with SARS-CoV-2/COVID-19 Vaccination: A Systematic Review

Vaccines against coronavirus disease 2019 (COVID-19) have played an important global role in reducing morbidity and mortality from COVID-19 infection. While the benefits of vaccination greatly outweigh the risks, adverse events do occur. Non-ocular adverse effects of the vaccines have been well-documented, but descriptions of ophthalmic effects remain limited. This systematic review aims to provide an overview of reported cases of corneal adverse events after receiving vaccination against COVID-19 and to compile existing clinical data to bring attention to these phenomena. Our review discusses corneal graft rejection, including proposed mechanisms, herpetic keratitis, and other reported corneal complications. Ophthalmologists and primary care physicians should be aware of such possible associations.

Impact of pandemic COVID-19 lockdown on penetrating keratoplasty patients

Purpose

To study the impact of the COVID-19 lockdown on the regular follow-up of keratoplasty patients.

Methods

This retrospective interventional case series included 30 patients who had immunological corneal endothelial rejection out of 190 patients who came for post-PKP follow-up between September 15, 2019, and September 30, 2020. The demographics, primary diagnosis, surgical technique, time of presentation, recovery of graft, associated ocular problems, and visual acuity at 1 month were analyzed. Forward stepwise (likelihood ratio) binary logistic regression was used to find significant variables.

Results

The study population had 19 males (63.33%) and 11 females (36.67%). The mean age of the study group was 42.83 ± 18.89 (8-80) years. Of 30 patients, 19 (63.3%) presented before and 11 (36.7%) after the COVID-19 lockdown. Overall, 23 (77%) showed a reversal of graft rejection. Logistic regression showed that preoperative indications, large-sized grafts, and deep corneal vascularization were significant risk factors for non-resolution of graft rejection. It was noted that patients who presented to the hospital late had poor recovery (P = 0.002). The delay in the presentation was a significant risk factor for non-resolution of graft rejection (P < 0.01). Z-test for proportions revealed that the difference in the non-resolution of rejection on immediate or delayed treatment in patients presenting during lockdown (P = 0.002) was significant.

Conclusion

This article is to highlight the impact of the COVID-19 lockdown on graft rejection recovery of PKP patients due to delays in follow-up. Early treatment helps in the recovery of graft transparency and the reversal of immunological graft rejection. Also, primary diagnosis, deep vascularization, and large-sized grafts were significant risk factors for non-resolution of graft rejection.

Ocular Complications Following Vaccination for COVID-19: A One-Year Retrospective

Vaccination efforts as a mitigation strategy in the corona virus disease 2019 (COVID-19) pandemic are fully underway. A vital component of understanding the optimal clinical use of these vaccines is a thorough investigation of adverse events following vaccination. To date, some limited reports and reviews have discussed ocular adverse events following COVID-19 vaccination, but a systematic review detailing these reports with manifestations and clinical courses as well as proposed mechanisms has yet to be published. This comprehensive review one-year into vaccination efforts against COVID-19 is meant to furnish sound understanding for ophthalmologists and primary care physicians based on the existing body of clinical data. We discuss manifestations categorized into one of the following: eyelid, orbit, uveitis, retina, vascular, neuro-ophthalmology, ocular motility disorders, and other.

Keratoplasty Rejection After the BNT162b2 messenger RNA Vaccine

PURPOSE

The aim of this report was to report 2 patients who presented with acute corneal graft rejection 2 weeks after receiving the BNT162b2 messenger RNA (mRNA) vaccine for severe acute respiratory syndrome coronavirus 2.

METHODS

Case report.

RESULTS

Two men, aged 73 and 56 years, with a history of penetrating keratoplasty due to keratoconus were noted to have acute corneal graft rejection 2 weeks after receiving a first dose of the BNT162b2 mRNA vaccine. Both patients were treated with hourly dexamethasone 0.1% and oral prednisone 60 mg per day with prompt resolution of keratoplasty rejection.

CONCLUSIONS

The BNT162b2 mRNA vaccine may be have been associated with a low-risk corneal graft rejection that responded well to topical and systemic steroids. Treating physicians should be aware of this potential complication and patients should be advised to report any visual changes after vaccination.

Acute Corneal Endothelial Graft Rejection With Coinciding COVID-19 Infection

PURPOSE

To report a case of acute corneal endothelial graft rejection with the concurrent onset of coronavirus disease 2019 (COVID-19) symptoms.

METHODS

Case report.

RESULTS

A 31-year-old African American woman with a history of asthma, sleep apnea, obesity (body mass index of 40), and bilateral keratoconus was noted to have acute corneal endothelial graft rejection 3 months after uncomplicated penetrating keratoplasty of the left eye. The patient developed dysgeusia and subjective fever on the same day as ocular discomfort, and she was subsequently diagnosed with COVID-19 with only these 2 classic symptoms of the viral infection.

CONCLUSIONS

Severe acute respiratory syndrome coronavirus 2 is known to cause conjunctivitis and has demonstrated transmissibility through ocular secretions. Acute immune and inflammatory dysregulations have been seen in cases of COVID-19 through various mechanisms. COVID-19 infection may potentially compromise ocular immune privilege contributing to acute corneal graft rejection.

Incidence of Ultrathin Descemet Stripping Endothelial Keratoplasty Corneal Graft Rejection following Steroid Discontinuation

Purpose/Aims: To determine the incidence of corneal graft rejection in patients with approximately 1 year of steroid therapy following uDSEK. A shortened course of corticosteroids may be beneficial and a viable option in Ultrathin Descemet's Stripping Endothelial Keratoplasty (uDSEK).Materials and Methods: This retrospective cohort study evaluated corneal graft rejection rate in 170 cases of uDSEK that met inclusion criteria with approximately 1 year of steroid therapy. Corneal graft rejection was defined by anterior chamber cell/flare, keratic precipitates with/without corneal edema, and/or a rejection line. The following were collected retrospectively from January 1, 2005 through January 1, 2013: gender, age, race, indication for uDSEK, length of follow-up, length of steroid therapy. Continuous data were compared using Wilcoxon Rank Sum Test and categorical data were compared using Fisher's Exact Test.Results: The included eyes had an average length of steroid therapy of 431 days (range 85-720 days) with an average follow-up of 1274 days (range 395-3186 days). During the follow-up period without steroid, 5 of the 170 eyes were diagnosed with rejection (2.94%). Of the five eyes that experienced rejection, four eyes resolved after topical prednisone was reinstituted alone and did not require repeat uDSEK. The other eye was lost to follow-up. The cumulative probability of rejection after steroid cessation was calculated at 0.67% after 12 months, 2.20% after 18 months, 3.08% after 24 months, and 4.55% after 36 months.Conclusion: Discontinuation of topical steroid at approximately 1 year after uDSEK results in a low rate of corneal graft rejection and may prove extended use unnecessary.

Comparison of endothelial/Descemet's membrane complex thickness with endothelial cell density for the diagnosis of corneal transplant rejection

Purpose:

This study compared the effectiveness of endothelial/Descemet’s membrane complex thickness obtained using high-definition anterior segment optical coherence tomography with endothelial cell density obtained using confocal microscopy as diagnostic tools in predicting corneal transplant rejection.

Methods:

This observational, prospective, cross-sectional study evaluated penetrating keratoplasty grafts. Slit lamp examination organized the grafts into healthy or rejecting grafts. Grafts were scanned using both high-definition anterior segment optical coherence tomography and confocal microscopy. Central corneal thickness, endothelial/Descemet’s membrane complex thickness, endothelial cell density, and coefficient of variation were each compared with the clinical status. Descemet’s rejection index, defined by endothelial/Descemet’s membrane complex thickness divided by central corneal thickness multiplied by 33, further compared endothelial/Descemet’s membrane complex thickness with central corneal thickness.

Results:

Endothelial/Descemet’s membrane complex thickness, central corneal thickness, and Descemet’s rejection index were all able to differentiate between clear and rejected corneal grafts (p < 0.0001, p = 0.001, and p = 0.012, respectively). Endothelial cell density and coefficient of variation did not correlate with the clinical status (p = 0.054 and p = 0.102, respectively). Endothelial/Descemet’s membrane complex thickness had the largest area under the curve using receiver operating characteristic curves (p < 0.0001). Endothelial/Descemet’s membrane complex thickness had a sensitivity of 86% and specificity of 81% with a cutoff value of >16.0 µm (p < 0.0001). The sensitivity and specificity of endothelial cell density were both 71% with a cutoff value of ⩽897 cells/mm² (p = 0.053). There was a high correlation between endothelial/Descemet’s membrane complex thickness and both Descemet’s rejection index and central corneal thickness (p < 0.0001).

Conclusion:

Endothelial/Descemet’s membrane complex thickness measured by high-definition anterior segment optical coherence tomography is a useful parameter for the diagnosis of corneal graft rejection. The diagnostic performance of endothelial/Descemet’s membrane complex thickness was significantly better than that of endothelial cell density and central corneal thickness. Endothelial cell density and the coefficient of variation were unable to diagnose corneal graft rejection in our cross-sectional study.

Long-lasting corneal endothelial graft rejection successfully reversed after dexamethasone intravitreal implant

Graft rejection is the most significant complication corneal transplantation and the leading indication for overall corneal transplantation. Corticosteroid therapy represents the mainstay of graft rejection treatment; however, the optimal route of administration of corticosteroid remains uncertain. We report herein for the first time the multimodal imaging of a case of long-lasting corneal endothelial graft rejection successfully reversed 3 months after dexamethasone intravitreal implant. A 29-year-old Asian female presented with a long-lasting corneal endothelial graft rejection in her left phakic eye. She underwent penetrating keratoplasty for advanced keratoconus 24 months before presentation. Hourly dexamethasone eyedrops, daily intravenous methylprednisolone, and one parabulbar injection of methylprednisolone acetate were administered during the 5 days of hospitalization. However, the clinical picture remained approximately unchanged despite therapy. By mutual agreement, we opted for the off-label injection of dexamethasone 0.7 mg intravitreal implant in order to provide therapeutic concentrations of steroid for a period of ~6 months. No other concomitant therapies were prescribed to the patient. Visual acuity measurement, slit lamp biomicroscopy, anterior segment photography, confocal microscopy, anterior segment optical coherence tomography, laser cell flare meter, intraocular pressure measurement, and ophthalmoscopy were performed monthly for the first postoperative 6 months. Three months after injection, both clinical and subclinical signs of rejection disappeared with a full recovery of visual acuity to 20/30 as before the episode. Currently, at the 12-month follow-up visit, the clinical picture remains stable without any sign of rejection, recurrence, or graft failure. Dexamethasone intravitreal implant seems to be a new potential effective treatment for corneal graft rejection, particularly in case of poor compliance or lack of response to conventional treatment. In addition, it could be especially useful in diabetic patients unable to receive systemic steroids.

[Risk factors, clinical presentations, prevention, and treatment of corneal graft rejection]

Corneal transplantation is the most common and successful type of allotransplantation surgery. Post-transplant immune response in keratoplasty is less pronounced than that in other transplantation procedures, which is accounted for by anatomical features of the cornea and, also, its low antigenic potential and active immunosuppression. However, the immune privilege of the cornea can be violated by neovascularization, inflammation, or trauma. Patients who require keratoplasty to restore their sight and whose immune privilege is disturbed, fall into a high-risk group and are likely to demonstrate tissue incompatibility and non-transparent engraftment. Two approaches exist as to how graft rejection can be prevented. One of them involves induction of donor-specific tolerance, the other - non-specific suppression of the recipient's immune response. To avoid tissue incompatibility, measures can be taken to restore the immune privilege of the cornea as well as to induce antigen-specific tolerance, which is considered a promising, thought yet experimental, area of modern transplantology. In clinical practice, one pays most attention to improvement of non-specific immune suppression methods based on interfering in the metabolism of immunocompetent cells. Thus, timely prescriptions and proper immunosuppressive tactics with account to possible risk factors determine the outcome in high-risk patients undergoing corneal transplantation surgery.

Evaluation of corneal graft rejection in a mouse model

Corneal graft rejection presents clinically and in experimental models as opacification and is considered to be the result of endothelial cell dysfunction or loss. However, recovery from opacification can occur suggesting either (a) that new endothelial cells can regenerate if the original cells were lost, or (b) that sufficient numbers of original cells can regain function if the opacification was due to temporary dysfunction. In this perspective, previous experimental studies of allograft rejection plus some new data are reviewed to support the latter mechanism.