One threat, different answers: the impact of COVID-19 pandemic on cornea donation and donor selection across Europe

Deciphering the molecular symphony: Unraveling endothelial-to-mesenchymal transition in corneal endothelial cells

Understanding the molecular complexity of this phenomenon provides innovative targets for maintaining phenotypic integrity during in vitro expansion, thereby advancing corneal endothelial tissue engineering. In this study, we established an in vitro model to simulate endothelial-to-mesenchymal transition (EndMT) in corneal endothelial cells. Through RNA sequencing, we identified 452 upregulated and 163 downregulated genes, resulting in a total of 615 differentially expressed genes. Key pathways enriched by GO and KEGG analysis include extracellular matrix (ECM) regulation and the PI3K-Akt signaling pathway. Potential hub proteins such as THBS1, ITGA5, COL1A1, and SNAI1/2 were also identified, and their dynamic changes at different time points (0, 2, 12, 24 h) were monitored. Uncovering these key pathways and genes may deepen our understanding of the mechanisms underlying EndMT in corneal endothelial cells, providing valuable insights for optimizing in vitro cultivation strategies.

Restoring the Ocular Integrity of Perforated Corneal Ulcer Using Living Surgical Donor Tissues Derived From Keratoplasty in the COVID-19 Pandemic

The coronavirus disease 2019 (COVID-19) caused an unprecedented crisis for corneal surgeons who were forced to strategize for an acute shortage of tissues. Here, we report the initial clinical outcomes of utilizing host corneal buttons derived from optical penetrating keratoplasties of pseudophakic bullous keratoplasty (PBK) patients. Two patients presented to our department with a perforated fungal corneal ulcer in one eye during the COVID-19 pandemic. One eye of each of the patients was operated on with non-vascularized host cut tissues preserved in glycerin. The tissues were secured using 10-0 nylon sutures. Good anatomical integrity was achieved in both eyes. An optical penetrating keratoplasty (PK) was done in both eyes after one year for visual rehabilitation, with a final visual acuity of 20/120 and 20/80, respectively, at six months. In conclusion, therapeutic PK using host tissues obtained from the recipients of optical PK is a safe and effective option to restore ocular integrity during a shortage of fresh or glycerol-preserved corneas. However, optical PK is required for the final visual rehabilitation.

Global impact of COVID-19 on corneal donor tissue harvesting and corneal transplantation

Introduction

The purpose of this review is to consolidate and examine the available literature on the coronavirus disease 2019 pandemic and its effect on corneal transplantation and eye banking.

Methods

A primary literature search was conducted using the PubMed (Medline) database with keywords and MeSH terms such as "corneal transplantation," "eye banks," "keratoplasty" and then were combined with COVID-19. Relevant articles through September 2022 were assessed and 25 articles were included in this review.

Results

Donor tissue volumes declined globally during lockdown periods due to a lower number of referrals and tighter tissue screening guidelines. Rates of elective surgeries decreased in the lockdown period compared to respective periods in previous years. However, changes in rates of emergency procedures were not uniform across different regions. Moreover, rates of different elective corneal grafts [i.e., penetrating keratoplasty (PK), endothelial keratoplasty (EK), or anterior lamellar keratoplasty (ALK)] were affected differently with the pattern of change being dependent on region-specific factors.

Conclusion

Both donor tissue volumes and rates of corneal transplant procedures were affected by lockdown restrictions. The underlying etiology of these changes differed by region. Examining the range of impact across many countries as well as the contributing factors involved will provide guidance for future global pandemics.

An Overview of Corneal Transplantation in the Past Decade

The cornea is a transparent avascular structure located in the front of the eye that refracts light entering the eyes and also serves as a barrier between the outside world and the internal contents of the eye. Like every other body part, the cornea may suffer insult from trauma, infection, and inflammation. In the case of trauma, a prior infection that left a scar, or conditions such as keratoconus that warrant the removal of all or part of the cornea (keratoplasty), it is important to use healthy donor corneal tissues and cells that can replace the damaged cornea. The types of cornea transplant techniques employed currently include: penetrating keratoplasty, endothelial keratoplasty (EK), and artificial cornea transplant. Postoperative failure acutely or after years can result after a cornea transplant and may require a repeat transplant. This minireview briefly examines the various types of corneal transplant methodologies, indications, contraindications, presurgical protocols, sources of cornea transplant material, wound healing after surgery complications, co-morbidities, and the effect of COVID-19 in corneal transplant surgery.

Absence of detectable SARS-CoV-2 replication in ex vivo cultured cornea and cornea-derived epithelial cells

PURPOSE

To study the possibility of SARS-CoV-2 to infect human corneal cells and tissues under standard corneal culture conditions using explants of COVID-19 donors and primary cornea-derived epithelial cells.

METHODS

Cornea isolated from deceased COVID-19 donors was cultured for 4 weeks, and SARS-CoV-2 replication was monitored by qRT-PCR. Furthermore, primary corneal epithelial cells from healthy donors were cultured ex vivo and infected with SARS-CoV-2 and human cytomegalovirus (HCMV) as a control. Infection status was assessed by western blotting and reporter gene expression using green fluorescent protein-expressing viral strains. ACE2 and TMPRSS2 receptor expression levels in cornea and epithelial cells were assessed by qRT-PCR.

RESULTS

We did not detect SARS-CoV-2 replication in 10 corneas isolated from deceased COVID-19 patients and cultured for 4 weeks, indicating absence of infection under natural conditions. Furthermore, high-titer SARS-CoV-2 infection of ex vivo cultured cornea-derived epithelial cells did not result in productive virus replication. In contrast, the same cells were highly permissive for HCMV. This phenotype could potentially be explained by low ACE2 and TMPRSS2 transcriptional activity in cornea and cornea-derived epithelial cells.

CONCLUSIONS

Our data suggest that cornea and limbal epithelial cells are refractory to productive SARS-CoV-2 infection. This could be due to the absence of robust receptor expression levels necessary for viral entry. This study adds further evidence to support the very low possibility of transmission of SARS-CoV-2 from an infected corneal transplant donor to a recipient in corneal organ cultures.

Effect of Covid-19 on Eye Banks and Corneal Transplantations: Current Perspectives

The coronavirus disease 2019 (COVID-19) pandemic exerted a great impact on medical practice, which was reframed according to the actual needs. Ophthalmological services and procedures including corneal transplantation did not represent an exception. The adoption and implementation of new standard operating procedures as well as of new technologies for remote consultation and smart-working reshaped daily activities of both eye bankers, physicians, researchers, and patients. Regulatory restrictions were issued redefining corneal donor eligibility criteria, as well as handling and harvesting procedures of donor ocular tissues. Surgical schedules underwent an abrupt contraction with prioritization of urgent procedures. Local lockdowns and confinement strategies resulted in both a reduction and redirection of research activities. The evaluation of SARS-CoV-2 colonization of ocular tissues, long-term corneal storage techniques, new disinfection strategies, split corneal transplants and cell-based therapies for the treatment of corneal disease peaked in the pipeline. Aim of this article is to summarizes the overall impact of the pandemic on the corneal transplantation machinery, and the current and future perspectives for the corneal transplant community.

A Review of Corneal Transplantation: An Insight on the Overall Global Post-COVID-19 Impact

The coronavirus disease 2019 (COVID-19) pandemic made us reframe a lot of the strategies followed in medical practice and ophthalmological services and procedures were also not spared, including corneal transplantation or keratoplasty, the most routine procedure performed worldwide. The prevalence of viral presence in the ocular tissue necessitates a focus on the handling of donor ocular tissue and the functioning of eye banks, ensuring it doesn't risk the patient and the doctor's safety. Restrictions in the movement of people during the pandemic limited the number of donations, causing a shortage of tissues, with a large number of people already waitlisted for tissue needs. The lesson from the COVID-19 pandemic directs us to look for long-term corneal storage techniques taking into consideration the tissue viability time and the possibility of post-pandemic shortages. Although there is not a significant number of reports, the cases of corneal graft rejection post-vaccination against COVID-19 are highlighted and thus should form a part of the lookout while evaluating the possible cause of rejection of grafts. This article summarises the overall impact of the pandemic on corneal transplantation and the possible future of storage techniques, which need to evolve and be adapted.

Presence of SARS-CoV-2 RNA in human corneal tissues donated in Italy during the COVID-19 pandemic

Objective

To analyse corneal tissues from asymptomatic donors with a postmortem nasopharyngeal swab tested positive for the presence of SARS-CoV-2 RNA, and therefore, understand the role that corneal transplantation may have in viral transmission.

Methods and analysis

Between March 2020 and October 2021, 101 corneas (out of 8154 collected in Italy) from 51 donors (out of a total of 4155 Italian donors) positive for SARS-CoV-2 after postmortem nasopharyngeal swab tests were analysed for the presence of SARS-CoV-2 RNA through real-time RT-PCR. When available, the corneal tissue storage media were also assessed. Corneas and/or storage media with confirmed presence of SARS-CoV-2 RNA were further investigated by isolating SARS-CoV-2 virions, which were used to infect VeroE6 target cells.

Results

Only N=4 corneas and/or storage media out of 101 showed presence of SARS-CoV-2 RNA. No VeroE6 cell infection was detected with viral isolates, thus suggesting no presence of SARS-CoV-2 virions in corneal specimens and storage media.

Conclusions

The presence of SARS-CoV-2 in cornea specimens would seem to be more likely due to prolonged detection of RNA rather than to active viral replication, with very low risk of infectivity and transmission through keratoplasty.

COVID-19 and the eye: alternative facts The 2022 Bowman Club, David L. Easty lecture

In addition to catastrophic loss of life, and dramatic and unwanted alterations to the daily lives of those left behind, the COVID-19 pandemic has fostered the publication and dissemination of an unprecedented quantity of peer-reviewed medical and scientific publications on a single subject. In particular, the ophthalmic literature is now replete with clinical and laboratory studies on putative eye involvement by SARS-CoV-2, the aetiologic agent of COVID-19. In this review, we critically appraise the published literature on COVID-19, and suggest that the quality of scientific peer review and editorial decision-making also suffered during the COVID-19 pandemic.

Impact of the COVID-19 Pandemic on Corneal Transplantation: A Report From the Italian Association of Eye Banks

Purpose

To analyze the impact of COVID-19 on Italian corneal transplantation from March-2020 to February 2021 compared to the same timeframe of the 2 previous years, in order to identify potential consequences of a global pandemic on corneal procurement and transplantation services during this time.

Methods

This national, multicentric, retrospective cohort study evaluated data collected from 12 (100%) Italian eye banks from March 2020 to February 2021 (Group A). The number of tissues collected, distributed and discarded were compared with the same time-frame of the 2 previous years: 2019 and 2018 (group B and C, respectively). The different type of transplants performed were reported. Data were analyzed using a non-parametric Friedman test.

Results

Corneal procurement and the percentage of distributed tissues reduced in 2020 by more than 30 and 15%, respectively, compared to the 2 previous years. During the pandemic corneal transplant surgery showed only a modest drop: the number of the penetrating keratoplasties (PKs) and the anterior lamellar keratoplasties (ALKs) decreased by about 30 and 20% in comparison with groups B and C, respectively; between the Endothelial Keratoplasties (EKs), the Descemet membrane endothelial keratoplasty (DMEK) increased slightly from March 2020 to February 2021.

Conclusions

Italy was one of the first countries most affected by the outbreak of COVID-19, and the Italian government adopted severe measures to limit viral transmission. The pandemic generated several implications in corneal transplant activity during the first lockdown. Then an efficacious reaction with constant, vigorous work led to a resumption of transplant surgery to a near-normal standard. The increase of EKs, despite the pandemic, is a sign that the advance in corneal transplantation has gone ahead and it continues to evolve.

Exploration of the ocular surface infection by SARS-CoV-2 and implications for corneal donation: An ex vivo study

BACKGROUND

The risk of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) transmission through corneal graft is an ongoing debate and leads to strict restrictions in corneas procurement, leading to a major decrease in eye banking activity. The aims of this study are to specifically assess the capacity of human cornea to be infected by SARS-CoV-2 and promote its replication ex vivo, and to evaluate the real-life risk of corneal contamination by detecting SARS-CoV-2 RNA in corneas retrieved in donors diagnosed with Coronavirus Disease 2019 (COVID-19) and nonaffected donors.

METHODS AND FINDINGS

To assess the capacity of human cornea to be infected by SARS-CoV-2, the expression pattern of SARS-CoV-2 receptor angiotensin-converting enzyme 2 (ACE-2) and activators TMPRSS2 and Cathepsins B and L in ocular surface tissues from nonaffected donors was explored by immunohistochemistry (n = 10 corneas, 78 ± 11 years, 40% female) and qPCR (n = 5 corneas, 80 ± 12 years, 40% female). Additionally, 5 freshly excised corneas (80 ± 12 years, 40% female) were infected ex vivo with highly concentrated SARS-CoV-2 solution (106 median tissue culture infectious dose (TCID50)/mL). Viral RNA was extracted from tissues and culture media and quantified by reverse transcription quantitative PCR (RT-qPCR) (viral RNA copies) 30 minutes (H0) and 24 hours (H24) after infection. To assess the risk of corneal contamination by SARS-CoV-2, viral RNA was tested by RT-qPCR (Ct value) in both corneas and organ culture media from 14 donors diagnosed with COVID-19 (74 ± 10 years, 29% female) and 26 healthy donors (79 ± 13 years, 57% female), and in organ culture media only from 133 consecutive nonaffected donors from 2 eye banks (73 ± 13 years, 29% female). The expression of receptor and activators was variable among samples at both protein and mRNA level. Based on immunohistochemistry findings, ACE-2 was localized mainly in the most superficial epithelial cells of peripheral cornea, limbus, and conjunctiva, whereas TMPRSS2 was mostly expressed in all layers of bulbar conjunctiva. A significant increase in total and positive strands of IP4 RNA sequence (RdRp viral gene) was observed from 30 minutes to 24 hours postinfection in central cornea (1.1 × 108 [95% CI: 6.4 × 107 to 2.4 × 108] to 3.0 × 109 [1.4 × 109 to 5.3 × 109], p = 0.0039 and 2.2 × 107 [1.4 × 107 to 3.6 × 107] to 5.1 × 107 [2.9 × 107 to 7.5 × 107], p = 0.0117, respectively) and in corneoscleral rim (4.5 × 109 [2.7 × 109 to 9.6 × 109] to 3.9 × 1010 [2.6 × 1010 to 4.4 × 1010], p = 0.0039 and 3.1 × 108 [1.2 × 108 to 5.3 × 108] to 7.8 × 108 [3.9 × 108 to 9.9 × 108], p = 0.0391, respectively). Viral RNA copies in ex vivo corneas were highly variable from one donor to another. Finally, viral RNA was detected in 3 out of 28 corneas (11%) from donors diagnosed with COVID-19. All samples from the 159 nonaffected donors were negative for SARS-CoV-2 RNA. The main limitation of this study relates to the limited sample size, due to limited access to donors diagnosed with COVID-19 and concomitant decrease in the procurement corneas from nonaffected donors.

CONCLUSIONS

In this study, we observed the expression of SARS-CoV-2 receptors and activators at the human ocular surface and a variable increase in viral RNA copies 24 hours after experimental infection of freshly excised human corneas. We also found viral RNA only in a very limited percentage of donors with positive nasopharyngeal PCR. The low rate of positivity in donors diagnosed with COVID-19 calls into question the utility of donor selection algorithms.

TRIAL REGISTRATION

Agence de la Biomédecine, PFS-20-011 https://www.agence-biomedecine.fr/.

RT-PCR Testing of Organ Culture Medium for Corneal Storage Fails to Detect SARS-CoV-2 Infection Due to Lack of Viral Replication

Concerns of possible transmission of SARS-CoV-2 from donors to patients by corneal transplantation have caused a decline in corneal transplantations. Graft culture media are routinely tested for infectious risks, but it is unclear whether this constitutes a viable means to avoid transmitting SARS-CoV-2 via keratoplasty. We found that SARS-CoV-2 RNA was not present in the medium after seven days of organ culture of corneas from donors (n = 4), who were SARS-CoV-2-positive upon tissue procurement. These medium samples showed no presence of viral RNA. To pursue this question under controlled conditions and further exclude the possibility of productive infection in corneal grafts, we inoculated corneoscleral discs from healthy donors (n = 8) with infectious SARS-CoV-2 and performed PCR testing of the culture medium at various time points. After seven days of culture, we also tested for SARS-CoV-2 RNA within the inoculated corneal tissue. The medium from tissue samples inoculated with SARS-CoV-2 showed no increase in viral RNA, which may indicate lack of viral replication in these corneal grafts. SARS-CoV-2-RNA was, however, detected on or in corneal tissue seven days after inoculation. Our data suggest that corneal grafts may not be permissive for replication of SARS-CoV-2 and demonstrates that PCR testing of culture media cannot safely exclude that tissue has been exposed to SARS-CoV-2. It also demonstrates the difficulty to differentiate between virus adherence and virus replication by PCR testing in SARS-CoV-2 exposed tissue.

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.

The impact of the COVID-19 pandemic on microbial keratitis presentation patterns

BACKGROUND

Microbial keratitis (MK) is the most common non-surgical ophthalmic emergency, and can rapidly progress, causing irreversible sight-loss. This study explored whether the COVID-19 (C19) national lockdown impacted upon the clinical presentation and outcomes of MK at a UK tertiary-care centre.

METHODS

Medical records were retrospectively reviewed for all patients with presumed MK requiring corneal scrapes, presenting between 23rd March and 30th June in 2020 (Y2020), and the equivalent time windows in 2017, 2018 and 2019 (pre-C19).

RESULTS

In total, 181 and 49 patients presented during the pre-C19 and Y2020 periods, respectively. In Y2020, concurrent ocular trauma (16.3% vs. 5.5%, p = 0.030) and immunosuppression use (12.2% vs 1.7%, p = 0.004) were more prevalent. Despite proportionately fewer ward admissions during the pandemic (8.2% vs 32.6%, p<0.001), no differences were observed in baseline demographics; presenting visual acuity (VA; median 0.6 vs 0.6 LogMAR, p = 0.785); ulcer area (4.0 vs 3.0mm2, p = 0.520); or final VA (0.30 vs 0.30 LogMAR, p = 0.990). Whilst the overall rates of culture positivity were similar in Y2020 and pre-C19 (49.0% vs. 54.7%, p = 0.520), there were differences in the cultures isolated, with a lower rate of poly-microbial cultures in Y2020 (8.3% vs. 31.3%, p = 0.022).

CONCLUSIONS

Patient characteristics, MK severity and final visual outcomes did not appear to be affected in the first UK lockdown, despite fewer patients being admitted for care. Concurrent trauma and systemic immunosuppression use were greater than in previous years. The difference in spectra of isolated organisms may relate to behavioural changes, such as increased hand hygiene.

Approaches for corneal endothelium regenerative medicine

The state of the art therapy for treating corneal endothelial disease is transplantation. Advances in the reproducibility and accessibility of surgical techniques are increasing the number of corneal transplants, thereby causing a global deficit of donor corneas and leaving 12.7 million patients with addressable visual impairment. Approaches to regenerate the corneal endothelium offer a solution to the current tissue scarcity and a treatment to those in need. Methods for generating corneal endothelial cells into numbers that could address the current tissue shortage and the possible strategies used to deliver them have now become a therapeutic reality with clinical trials taking place in Japan, Singapore and Mexico. Nevertheless, there is still a long way before such therapies are approved by regulatory bodies and become clinical practice. Moreover, acellular corneal endothelial graft equivalents and certain drugs could provide a treatment option for specific disease conditions without the need of donor tissue or cells. Finally, with the emergence of gene modulation therapies to treat corneal endothelial disease, it would be possible to treat presymptomatic patients or those presenting early symptoms, drastically reducing the need for donor tissue. It is necessary to understand the most recent developments in this rapidly evolving field to know which conditions could be treated with which approach. This article provides an overview of the current and developing regenerative medicine therapies to treat corneal endothelial disease and provides the necessary guidance and understanding towards the treatment of corneal endothelial disease.

Proliferation Increasing Genetic Engineering in Human Corneal Endothelial Cells: A Literature Review

The corneal endothelium is the inner layer of the cornea. Despite comprising only a monolayer of cells, dysfunction of this layer renders millions of people visually impaired worldwide. Currently, corneal endothelial transplantation is the only viable means of restoring vision for these patients. However, because the supply of corneal endothelial grafts does not meet the demand, many patients remain on waiting lists, or are not treated at all. Possible alternative treatment strategies include intracameral injection of human corneal endothelial cells (HCEnCs), biomedical engineering of endothelial grafts and increasing the HCEnC density on grafts that would otherwise have been unsuitable for transplantation. Unfortunately, the limited proliferative capacity of HCEnCs proves to be a major bottleneck to make these alternatives beneficial. To tackle this constraint, proliferation enhancing genetic engineering is being investigated. This review presents the diverse array of genes that have been targeted by different genetic engineering strategies to increase the proliferative capacity of HCEnCs and their relevance for clinical and research applications. Together these proliferation-related genes form the basis to obtain a stable and safe supply of HCEnCs that can tackle the corneal endothelial donor shortage.

Eye Banks: Future Perspectives

Technological progress and societal change are transforming medicine, and cornea banks are no exception. New infectiological factors, statutory requirements, management concepts, globalisation and digitalisation are also influencing how such facilities will operate in the future. The goal of providing high quality material to patients with corneal disease remains unaltered. The present article seeks to shed light on the type of material this will involve and under what circumstances it is to be obtained.

Amniotic membrane transplantation for infectious keratitis: a systematic review and meta-analysis

Infectious keratitis (IK) is the 5th leading cause of blindness globally. Broad-spectrum topical antimicrobial treatment is the current mainstay of treatment for IK, though adjuvant treatment or surgeries are often required in refractory cases of IK. This systematic review aimed to examine the effectiveness and safety of adjuvant amniotic membrane transplantation (AMT) for treating IK. Electronic databases, including MEDLINE, EMBASE and Cochrane Central, were searched for relevant articles. All clinical studies, including randomized controlled trials (RCTs), non-randomized controlled studies and case series (n > 5), were included. Primary outcome measure was time to complete corneal healing and secondary outcome measures included corrected-distance-visual-acuity (CDVA), uncorrected-distance-visual-acuity (UDVA), corneal vascularization and adverse events. A total of twenty-eight studies (including four RCTs) with 861 eyes were included. When compared to standard antimicrobial treatment alone, adjuvant AMT resulted in shorter mean time to complete corneal healing (− 4.08 days; 95% CI − 6.27 to − 1.88; p < 0.001) and better UDVA (− 0.26 logMAR; − 0.50 to − 0.02; p = 0.04) at 1 month follow-up in moderate-to-severe bacterial and fungal keratitis, with no significant difference in the risk of adverse events (risk ratio 0.80; 0.46–1.38; p = 0.42). One RCT demonstrated that adjuvant AMT resulted in better CDVA and less corneal vascularization at 6 months follow-up (both p < 0.001). None of the RCTs examined the use of adjuvant AMT in herpetic or Acanthamoeba keratitis, though the benefit was supported by a number of case series. In conclusion, AMT serves as a useful adjuvant therapy in improving corneal healing and visual outcome in bacterial and fungal keratitis (low-quality evidence). Further adequately powered, high-quality RCTs are required to ascertain its therapeutic potential, particularly for herpetic and Acanthamoeba keratitis. Future standardization of the core outcome set in IK-related trials would be invaluable.

Ophthalmic Outpatient and Inpatient Care Under Pandemic Conditions: Hygiene, Triage and New Challenges

BACKGROUND

The progression of the COVID-19 pandemic has caused significant changes in the environment for outpatient and inpatient care in ophthalmology, with limitations on access to medical care but also new observations and challenges. We now describe major developments in recent months and provide an outlook on the expected consequences.

METHODS

PubMed literature search, clinical survey.

RESULTS

To date, the course of the COVID-19 pandemic has been characterised by several new but overall rare ocular manifestations, the ophthalmological shared management of COVID-19 patients on intensive care units, and a significant decrease in case numbers, associated with an increase in case severity and relative proportion of emergencies, as a result of delayed presentation of patients and reduced treatment adherence. With the introduction of hygiene measures and infection control procedures, ophthalmic patient care was maintained - including emergencies and urgent treatments. Due to the extensive postponement of elective surgeries, scarce therapeutic and health care professional resources, and the prioritisation of critically ill patients from other specialties, there is a reasonable likelihood that urgent treatments will be delayed as infection rates rise.

CONCLUSION

Outpatient and inpatient care in ophthalmology during the COVID-19 pandemic is primarily accompanied by additional organisational or medical challenges and a decline in case volume. Although to date emergency and urgent ophthalmic treatments have been maintained, long-term persistence of pandemic conditions will require additional strategies to provide continuation of ophthalmic care at the required level.

Ocular Involvement in COVID-19: Conjunctivitis and More

Since the beginning of 2020, SARS-CoV-2, the pathogen of COVID-19, has led to a global pandemic that also affects ophthalmology. Ophthalmologists can be confronted at any time with potentially COVID-19 associated ocular symptoms or manifestations in patients and also become infected through close patient contact. Even without systemic infection, the ocular surface can come into direct contact with aerosols or liquids containing SARS-CoV-2 particles. A smear infection through hand-to-eye contact is also possible. A purely isolated ocular infection has not yet been shown. Rather, it seems that ocular complications occur in the context of a systemic infection. However, ocular symptoms can also be the first symptom of COVID-19. The most common ocular complication of COVID-19 is mild follicular conjunctivitis. Haemorrhagic conjunctivitis, dry eye disease, episcleritis, or retinal involvement can also occur less frequently. There are currently no evidence-based therapy recommendations for COVID-19 associated diseases of the ocular surface. Artificial tears might be helpful for symptom relief. There is no evidence for antiviral, antibiotic, or anti-inflammatory therapies, but these medications might be used in individual cases. Potential intraocular complications include retinal artery occlusions and haemorrhages, as well as cotton wool spots caused by complement-mediated thrombotic angiopathy. Neuro-ophthalmological complications including Miller-Fisher syndrome or infarct-related central blindness can also occur in very rare cases. Knowledge of potential transmission routes and personal protective equipment is just as essential for each ophthalmologist as a basic knowledge of potential ocular symptoms and complications.

The Transmission of SARS-CoV-2 Infection on the Ocular Surface and Prevention Strategies

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global health problem. Although the respiratory system is the main impaired organ, conjunctivitis is one of its common findings. However, it is not yet understood if SARS-CoV-2 can infect the eye and if the ocular surface can be a potential route of SARS-CoV-2 transmissions. Our review focuses on the viral entry mechanisms to give a better understanding of the interaction between SARS-CoV-2 and the eye. We highlighted findings that give evidence for multiple potential receptors of SARS-CoV-2 on the ocular surface. Additionally, we focused on data concerning the detection of viral RNA and its spike protein in the various ocular tissues from patients. However, the expression level seemed to be relatively low compared to the respiratory tissues as a result of a unique environment surrounding the ocular surface and the innate immune response of SARS-CoV-2. Nevertheless, our review suggests the ocular surface as a potential route for SARS-CoV-2 transmission, and as a result of this study we strongly recommend the protection of the eyes for ophthalmologists and patients at risk.