Cornea

Millions of people worldwide are bilaterally blind due to corneal diseases including infectious etiologies, trauma, and chemical injuries. While corneal transplantation can successfully restore sight in many, corneal graft survival decreases in eyes with chronic inflammation and corneal vascularization. Additionally, the availability of donor cornea material can be limited, especially in underdeveloped countries where corneal blindness may also be highly prevalent. Development of methods to create and implant an artificial cornea (keratoprosthesis) may be the only option for patients whose eye disease is not suitable for corneal transplantation or who live in regions where corneal transplantation is not possible. The Boston Keratoprosthesis (B-KPro) is the most commonly implanted keratoprosthesis worldwide, having restored vision in thousands of patients. This article describes the initial design of the B-KPro and the modifications that have been made over many years. Additionally, some of the complications of surgical implantation and long-term care challenges, particularly complicating inflammation and glaucoma, are discussed.

PURPOSE: To assess clinical outcomes of patients with severe, cicatricial ocular surface disease (OSD) implanted with the currently marketed design of the Boston keratoprosthesis type II (BK2). DESIGN: Retrospective cohort study. METHODS: Records of consecutive patients undergoing BK2 implantation from June 2009 to March 2021 were assessed for postoperative visual acuity, postoperative complications, device replacement, and additional surgeries. RESULTS: Fifty-six eyes of 53 patients with a mean follow-up of 45.8 months (range, 0.2-134.7 months) were included. Stevens-Johnson syndrome/toxic epidermal necrolysis was the most common indication (49.1%), followed by mucous membrane pemphigoid (39.6%) and other OSD (11.3%). Visual acuity improved from logMAR 2.2 ± 0.5 preoperatively to 1.5 ± 1.2 at final follow-up. Of 56 eyes, 50 saw ≥20/200 at some point postoperatively. Of the eyes with a follow-up of more than 5 years, 50.0% retained a visual acuity of ≥20/200 at their final follow-up. The most common complications over the entire postoperative course (mean ∼4 years) were de novo or worsening glaucoma (41.1%), choroidal effusions (30.3%), retinal detachment (25.0%), and end-stage glaucoma (25.0%). In a univariate analysis, patients who experienced irreversible loss of ≥20/200 visual acuity were more likely to have been previously implanted with an older design of BK2, less likely to be on preoperative systemic immunosuppressive therapy, and less likely to have undergone concurrent glaucoma tube implantation, compared to patients who retained ≥20/200 acuity (P < .04 for all). CONCLUSIONS: Advances in device design and postoperative care have made implantation of BK2 a viable option for corneal blindness in the setting of severe cicatricial OSD.

PURPOSE: To determine the prevalence, clinical characteristics, and risk factors associated with neurotrophic keratopathy (NK) in patients with chronic ocular graft-versus-host disease (oGVHD). DESIGN: Retrospective cohort study. METHODS: We performed a chart review of patients diagnosed with chronic oGVHD between January 2015 and December 2018 at a single academic institution and recorded demographic data, systemic and ocular comorbidities, history of hematologic malignancy, transplant characteristics, oGVHD severity scores, and adnexal and ocular examination findings. We determined the prevalence of NK and clinical characteristics associated with NK in these patients. A multivariate logistic regression analysis was performed to determine the risk factors associated with NK in these patients. MAIN OUTCOME MEASURE: Prevalence of NK in chronic oGVHD. RESULTS: We identified 213 patients diagnosed with chronic oGVHD following hematopoietic stem cell or bone marrow transplantation from our electronic patient database, and the prevalence of NK was 14%. The mean age of oGVHD patients with NK was 62.6 ± 12.9 years; 48% were women, 19 had unilateral NK, and ten had bilateral NK. In the cohort, 56%, 20%, and 24% eyes of the patients had grades 1, 2, and 3 of NK, respectively. The mean time to diagnose NK after transplantation was 52.9 ± 45.4 months. oGVHD patients diagnosed with NK had a significantly higher NIH oGVHD severity score (p = 0.04) and a lower corneal sensation score (p = 0.0001) than those without NK. Our analyses showed a significantly higher CFS score (p = 0.01) and a trend toward lower Schirmer test scores (p = 0.16) and tear break-up times (p = 0.08) in oGVHD patients with NK. Additionally, we observed a significantly higher prevalence of persistent epithelial defect (p = 0.0001), corneal ulceration (p = 0.0001), and corneal perforation (p = 0.005) in oGVHD patients diagnosed with NK. A logistic regression analysis to determine factors associated with NK showed that a higher NIH oGVHD score (odds ratio [OR] = 2.03, p = 0.026) and history of cataract surgery (odds ratio [OR] = 5.03, p = 0.001) are significant risk factors for NK in oGVHD patients. CONCLUSIONS: The prevalence of NK in chronic oGVHD patients was 14% during the study period. Our analysis shows that oGVHD patients with a higher NIH oGVHD severity score and previous history of cataract surgery are at a higher risk of developing NK and may develop severe sequelae such as persistent epithelial defect or corneal ulceration.

The anterior segment of the eye consists of the cornea, iris, ciliary body, crystalline lens, and aqueous humor outflow pathways. Together, these tissues are essential for the proper functioning of the eye. Disorders of vision have been ascribed to defects in all of them; some disorders, including glaucoma and cataract, are among the most prevalent causes of blindness in the world. To characterize the cell types that compose these tissues, we generated an anterior segment cell atlas of the human eye using high-throughput single-nucleus RNA sequencing (snRNAseq). We profiled 195,248 nuclei from nondiseased anterior segment tissues of six human donors, identifying >60 cell types. Many of these cell types were discrete, whereas others, especially in the lens and cornea, formed continua corresponding to known developmental transitions that persist in adulthood. Having profiled each tissue separately, we performed an integrated analysis of the entire anterior segment, revealing that some cell types are unique to a single structure, whereas others are shared across tissues. The integrated cell atlas was then used to investigate cell type-specific expression patterns of more than 900 human ocular disease genes identified through either Mendelian inheritance patterns or genome-wide association studies.

Corneal transplantation is the most frequent organ transplantation worldwide. Unfortunately, corneal graft failure is common and endothelial decompensation is considered the major cause. Corneal endothelial cells (CECs) lack the capacity to reproduce, and perioperative and postoperative endothelial cell loss remains a significant challenge associated with corneal graft viability. Therefore, strategies to preserve CEC density are critical to extend graft survival. Activated platelet rich plasma (aPRP), a product extracted from autologous blood, has both antioxidant and regenerative properties. aPRP eye drops have shown effectiveness in the treatment of corneal pathologies such as ulcers, dry eye, and burns. Our purpose is to determine the protective and regenerative effect of aPRP on corneal grafts by evaluating aPRP's effect on the survival and proliferation of human CECs. Human corneal grafts were incubated in aPRP for 15 min to assess the activation of the CEC pAkt survival pathway as measured by ELISA. Evaluation of the protective effect of aPRP was made using an apoptotic model, which simulated oxidative stress conditions. Expression of apoptotic markers was measured using ELISA and endothelial cell viability was determined by optical microscopy. The CEC proliferation rate was measured in vitro with Ki-67 staining. Corneal graft gross structure was evaluated by Hematoxylin & Eosin and Masson trichrome staining. Our results indicate that a short incubation of human corneal grafts in aPRP protects CECs from apoptosis by upregulating the pAkt survival pathway and promoting CEC proliferation. Additionally, aPRP incubation does not induce histological changes in the grafts. A brief pre-treatment of human corneal grafts in aPRP may be beneficial for transplant longevity, as it protects CECs from apoptosis by upregulating intracellular survival pathways and promoting proliferation. In addition, this approach appears to be safe and has the potential to improve surgical outcomes following corneal transplantation.

Specialized pro-resolving mediators (SPMs), including Maresins (MaR)-1 and 2, contribute to tear film homeostasis and resolve conjunctival inflammation. We investigated MaR2's signaling pathways in goblet cells (GC) from rat conjunctiva. Agonist-induced [Ca2+]i and high-molecular weight glycoconjugate secretion were measured. MaR2 increased [Ca2+]i and stimulated secretion. MaR2 and MaR1 stimulate conjunctival goblet cell function, especially secretion, by activating different but overlapping GPCR and signaling pathways, and furthermore counter-regulate histamine stimulated increase in [Ca2+]i. Thus, MaR2 and MaR1 play a role in maintaining the ocular surface and tear film homeostasis in health and disease. As MaR2 and MaR1 modulate conjunctival goblet cell function, they each may have potential as novel, but differing, options for the treatment of ocular surface inflammatory diseases including allergic conjunctivitis and dry eye disease. We conclude that in conjunctival GC MaR2 and MaR1, both increase the [Ca2+]i and stimulate secretion to maintain homeostasis by using one set of different, but overlapping, signaling pathways to increase [Ca2+]i and another set to stimulate secretion. MaR2 also resolves ocular allergy.

Importance: Results of several small randomized clinical trials have suggested that supplements of marine ω-3 fatty acids may be beneficial in treating signs and symptoms of dry eye disease (DED). However, randomized clinical trial data to examine whether ω-3 fatty acid supplements can prevent DED are lacking. Objective: To evaluate whether long-term daily supplementation with marine ω-3 fatty acids prevents the development of DED. Design, Setting, and Participants: This was a prespecified ancillary study of the Vitamin D and Omega-3 Trial (VITAL), a nationwide randomized double-blind placebo-controlled 2 × 2 factorial trial of vitamin D and marine ω-3 fatty acids in the primary prevention of cancer and cardiovascular disease. Participants in this ancillary study were 23 523 US adults (men 50 years and older and women 55 years and older) who at study entry were free of a previous diagnosis of DED and were not experiencing severe dry eye symptoms. Participants were enrolled from November 2011 to March 2014, and treatment and follow-up ended on December 31, 2017. Data were analyzed from January 2020 to August 2021. Interventions: Marine ω-3 fatty acids, 1 g per day. Main Outcomes and Measures: The primary end point was incident clinically diagnosed DED confirmed by review of the medical records. The secondary end point was a composite of all confirmed incident clinically diagnosed DED cases plus all incident reports of severe DED symptoms. Results: The mean (SD) age of the 23 523 participants included in the analysis was 67.0 (7.0) years, and 11 349 participants (48.3%) were women. The cohort included 4610 participants (20.0%) who self-identified as Black, 16 481 (71.6%) who self-identified as non-Hispanic White, and 1927 (8.4%) of other racial or ethnic groups or who declined to respond, consolidated owing to small numbers, including American Indian or Alaska Native, Asian, Hispanic or Latino, and Native Hawaiian or Other Pacific Islander. During a median (range) 5.3 (3.8-6.1) years of treatment and follow-up, 472 of 23 523 participants (2.0%) experienced a medical record-confirmed diagnosis of DED. There was no difference in diagnosed DED by randomized ω-3 fatty acid assignment (232 of 11 757 participants [2.0%] with end points in the treated group vs 240 of 11 766 [2.0%] with end points in the placebo group; hazard ratio, 0.97; 95% CI, 0.81-1.16). Similarly, there was no difference between groups for the secondary end point of diagnosed DED plus incident severe DED symptoms (1044 participants [8.9%] with end points in the treated group vs 1074 [9.1%] with end points in the placebo group; hazard ratio, 0.97; 95% CI, 0.89-1.06). Conclusions and Relevance: In this randomized clinical trial, long-term supplementation with 1 g per day of marine ω-3 fatty acids for a median (range) of 5.3 (3.8-6.1) years did not reduce the incidence of diagnosed DED or a combined end point of diagnosed DED or incident severe DED symptoms. These results do not support recommending marine ω-3 fatty acid supplementation to reduce the incidence of DED. Trial Registration: ClinicalTrials.gov Identifier: NCT01880463.

Development of an artificial cornea can potentially fulfil the demand of donor corneas for transplantation as the number of donors is far less than needed to treat corneal blindness. Collagen-based artificial corneas stand out as a regenerative option, having promising clinical outcomes. Collagen crosslinked with chemical crosslinkers which modify the parent functional groups of collagen. However, crosslinkers are usually cytotoxic, so crosslinkers need to be removed from implants completely before application in humans. In addition, crosslinked products are mechanically weak and susceptible to enzymatic degradation. We developed a crosslinker free supramolecular gelation strategy using pyrene conjugated dipeptide amphiphile (PyKC) consisting of lysine and cysteine; in which collagen molecules are intertwined inside the PyKC network without any functional group modification of the collagen. The newly developed collagen implants (Coll-PyKC) are optically transparent and can effectively block UV light, are mechanically and enzymatically stable, and can be sutured. The Coll-PyKC implants support the growth and function of all corneal cells, trigger anti-inflammatory differentiation while suppressing the pro-inflammatory differentiation of human monocytes. Coll-PyKC implants can restrict human adenovirus propagation. Therefore, this crosslinker-free strategy can be used for the repair, healing, and regeneration of the cornea, and potentially other damaged organs of the body.

PURPOSE: Dry eye disease (DED) is a common age-related ocular surface disease. However, it is unknown how aging influences the ocular surface microenvironment. This systematic review aims to investigate how the aging process changes the ocular surface microenvironment and impacts the development of DED. METHODS: An article search was performed in PubMed, EMBASE, and Web of Science. 44 studies reporting on age-related ocular changes and 14 large epidemiological studies involving the prevalence of DED were identified. 8 out of 14 epidemiological studies were further analyzed with meta-analysis. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines were followed. Study-specific estimates (impact of aging on the prevalence of DED) were combined using one-group meta-analysis in a random-effects model. RESULTS: Meta-analysis revealed the prevalence of DED in the elderly aged 60 years old or older was 5519 of 60107 (9.2%) and the odds ratio of aging compared to younger age was 1.313 (95% confidence interval [CI]; 1.107, 1.557). With increasing age, the integrity of the ocular surface and tear film stability decreased. Various inflammatory cells, including senescent-associated T-cells, infiltrated the ocular surface epithelium, lacrimal gland, and meibomian gland, accompanied by senescence-related changes, including accumulation of 8-OHdG and lipofuscin-like inclusions, increased expression of p53 and apoptosis-related genes, and decreased Ki67 positive cells. CONCLUSIONS: The aging process greatly impacts the ocular surface microenvironment, consequently leading to DED.

Sterilization of biodegradable, collagen-based implants is challenging as irradiation sterilization methods can alter their mechanical properties. Electron beam (EB) irradiation is a terminal sterilization method that has been used for biologically-derived implants. Here, recombinant human collagen type III-phosphorylcholine (RHCIII-MPC) hydrogels were irradiated with EB doses of 17, 19, or 21 kGy and their subsequent biocompatibility and ability to promote regeneration in rabbit corneas was evaluated. Unirradiated hydrogels stored in 1% chloroform in phosphate-buffered saline (C-PBS) were the controls. There were no significant differences between irradiated and non-irradiated samples in optical or physical properties (tensile strength, modulus, elasticity), or the ability to support cell growth. However, irradiated implants were more sensitive to high levels of collagenase than unirradiated controls and the C-PBS implants had increased cell growth compared to EB and controls at 72 h. Corneal implants e-beamed at 17 kGy or e-beamed and subsequently frozen (EB-F) to increase shelf-life showed no adverse biological effects of the irradiation. EB, EB-F, and C-PBS implanted corneas all rapidly re-epithelialized but showed mild neovascularization that resolved over 6 months. The regenerated neo-corneas were transparent at 6 months post-operation. In vivo confocal microscopy confirmed normal morphology for the epithelium, stroma, sub-basal nerves and unoperated endothelium. Histology showed that all the regenerated corneas were morphologically similar to the normal. Immunohistochemistry indicated the presence of a differentiated corneal epithelium and functional tear film. In conclusion, the e-beamed corneal implants performed as well as non-irradiated control implants, resulting in fully regenerated neo-corneas with new nerves and without blood vessels or inflammation that may impede vision or corneal function. Therefore, a complete validation study to establish EB irradiation as an effective means for corneal implant sterilization prior to clinical application is necessary as a next step.

PURPOSE: To describe the characteristics of neurotrophic keratopathy (NK) in the United States. DESIGN: Retrospective database study. PARTICIPANTS: Thirty-one thousand nine hundred fifteen eyes of 27 483 patients with a diagnosis of NK. METHODS: Retrospective analysis of visits associated with a diagnosis of NK between 2013 and 2018 using the American Academy of Ophthalmology Intelligent Research in Sight (IRIS®) Registry. MAIN OUTCOME MEASURES: Demographic information, prevalence, visual acuity (VA), concomitant diagnosis and procedure codes, and risk factors impacting VA most closely after NK onset date. RESULTS: Mean ± standard deviation (SD) age at initial diagnosis of NK was 68.0 ± 16.0 years, and 58.91% of patients were women (P &lt; 0.0001). Presentation was unilateral in 58.14%, bilateral in 16.13%, and unspecified in 25.73%. Average 6-year prevalence of NK in the IRIS Registry was 21.34 cases per 100 000 patients. Mean ± SD VA was 0.60 ± 0.79 logMAR before diagnosis and 0.88 ± 0.94 logMAR after diagnosis (P &lt; 0.0001). Most common concomitant diagnoses included herpetic keratitis (33.70%), diabetes (31.59%), and corneal dystrophy (14.28%). Common procedures for NK management included the use of amniotic membrane (29.90%), punctal plugs (29.65%), and bandage contact lenses (22.67%). Age, male sex, Black race, Hispanic or Latino ethnicity, unilateral involvement, concomitant diagnoses of diabetes, corneal transplantation, and herpetic keratitis were associated significantly with worse VA. CONCLUSIONS: Based on the IRIS Registry, the prevalence of NK is 21.34 cases per 100 000 patients. Visual acuity was significantly worse after NK diagnosis compared with other time points. Neurotrophic keratopathy was associated most commonly with herpetic keratitis and diabetes. Worse VA in patients with NK was associated with several demographic characteristics, history of diabetes, corneal transplantation, and herpetic keratitis.

PURPOSE: The aim of this study was to evaluate the clinical and topographic features of posterior polymorphous corneal dystrophy (PPCD) in children aged 15 years or younger with a long-term follow-up. Retrospective case series. METHODS: A retrospective chart review of patients who were diagnosed with PPCD at Boston Children's Hospital from 1999 to 2020 was performed. Data collected included age at the time of diagnosis, slit lamp findings, cycloplegic refraction, best-corrected visual acuity, central corneal thickness, specular microscopy, and corneal topography findings whenever available. RESULTS: Twenty-seven eyes of 19 patients were included (11 unilateral and 8 bilateral cases). Ten patients were girls (52.6%). Left eye was affected in 14 eyes. The mean age at the time of diagnosis was 8.5 ± 3.3 years, with a mean follow-up of 5.3 years. In unilateral cases, there was a statistically significant difference in the endothelial cell density (P = 0.01), coefficient variation (P = 0.03), and hexagonality (P = 0.01) between the affected and the contralateral unaffected eyes. The mean best-corrected visual acuity at initial presentation was 0.8 ± 0.2 compared with 0.9 ± 0.08 in unaffected eyes (P = 0.04). The mean astigmatism was higher in the affected eye (+1.7 diopters) compared with (+1.00) the unaffected eye (P = 0.07). At initial presentation, 7 of 27 eyes had amblyopia, which resolved, either partially or completely, in 5 eyes after treatment. CONCLUSIONS: PPCD can present early in children with astigmatism and anisometropic amblyopia. A careful slit lamp examination for children presenting with anisoastigmatism is necessary to diagnose PPCD. Contrary to adults, presentation is often unilateral. Such patients should be followed up regularly with cycloplegic retinoscopy to prevent and treat refractive amblyopia if present.

Dry eye disease (DED), a multifactorial ocular surface disease, is estimated to affect up to 34% of individuals over 50 years old. Although numerous animal models, including rodents and rabbits, have been developed to mimic the pathophysiologic mechanisms involved in dry eye, there is a lack of non-human primate (NHP) models, critical for translational drug studies. Here, we developed a novel desiccating stress-induced dry eye disease model using Rhesus macaque monkeys. The monkeys were housed in a controlled environment room for 21 to 36 days under humidity, temperature, and airflow regulation. Following desiccating stress, NHPs demonstrated clinical symptoms similar to those of humans, as shown by increased corneal fluorescein staining (CFS) and decreased tear-film breakup time (TFBUT). Moreover, corticosteroid treatment significantly reduced CFS scoring, restored TFBUT, and prevented upregulation of tear proinflammatory cytokines as observed in dry eye patients following steroid treatment. The close resemblance of clinical symptoms and treatment responses to those of human DED patients provides great translational value to the NHP model, which could serve as a clinically relevant animal model to study the efficacy of new potential treatments for DED.

Dry eye disease (DED) is a highly prevalent and debilitating condition affecting several hundred million people worldwide. Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan commonly used in the treatment of DED. This review aims to critically evaluate the literature on the safety and efficacy of artificial tears containing HA used in DED treatment. Literature searches were conducted in PubMed, including MEDLINE, and in Embase via Ovid with the search term: "(hyaluronic acid OR hyaluronan OR hyaluronate) AND (dry eye OR sicca)". A total of 53 clinical trials are included in this review, including eight placebo-controlled trials. Hyaluronic acid concentrations ranged from 0.1% to 0.4%. Studies lasted up to 3 months. A broad spectrum of DED types and severities was represented in the reviewed literature. No major complications or adverse events were reported. Artificial tears containing 0.1% to 0.4% HA were effective at improving both signs and symptoms of DED. Two major gaps in the literature have been identified: 1. no study investigated the ideal drop frequency for HA-containing eyedrops, and 2. insufficient evidence was presented to recommend any specific HA formulation over another. Future investigations assessing the optimal drop frequency for different concentrations and molecular weights of HA, different drop formulations, including tonicity, and accounting for DED severity and aetiology are essential for an evidence-based, individualized approach to DED treatment.

BACKGROUND: Visual display terminal (VDT) use is a key risk factor for dry eye disease (DED). Visual display terminal (VDT) use reduces the blink rate and increases the number of incomplete blinks. However, the exact mechanisms causing DED development from VDT use have yet to be clearly described. PURPOSE: The purpose of the study was to conduct a review on pathophysiological mechanisms promoting VDT-associated DED. METHODS: A PubMed search of the literature investigating the relationship between dry eye and VDT was performed, and relevance to pathophysiology of DED was evaluated. FINDINGS: Fifty-five articles met the inclusion criteria. Several pathophysiological mechanisms were examined, and multiple hypotheses were extracted from the articles. Visual display terminal (VDT) use causes DED mainly through impaired blinking patterns. Changes in parasympathetic signalling and increased exposure to blue light, which could disrupt ocular homeostasis, were proposed in some studies but lack sufficient scientific support. Together, these changes may lead to a reduced function of the tear film, lacrimal gland, goblet cells and meibomian glands, all contributing to DED development. CONCLUSION: Visual display terminal (VDT) use appears to induce DED through both direct and indirect routes. Decreased blink rates and increased incomplete blinks increase the exposed ocular evaporative area and inhibit lipid distribution from meibomian glands. Although not adequately investigated, changes in parasympathetic signalling may impair lacrimal gland and goblet cell function, promoting tear film instability. More studies are needed to better target and improve the treatment and prevention of VDT-associated DED.