Replenishing IRAK-M expression in retinal pigment epithelium attenuates outer retinal degeneration.

Chronic inflammation is a constitutive component of many age-related diseases, including age-related macular degeneration (AMD). Here, we identified interleukin-1 receptor-associated kinase M (IRAK-M) as a key immunoregulator in retinal pigment epithelium (RPE) that declines during the aging process. Rare genetic variants of IRAK3, which encodes IRAK-M, were associated with an increased likelihood of developing AMD. In human samples and mouse models, IRAK-M abundance in the RPE declined with advancing age or exposure to oxidative stress and was further reduced in AMD. Irak3-knockout mice exhibited an increased incidence of outer retinal degeneration at earlier ages, which was further exacerbated by oxidative stressors. The absence of IRAK-M led to a disruption in RPE cell homeostasis, characterized by compromised mitochondrial function, cellular senescence, and aberrant cytokine production. IRAK-M overexpression protected RPE cells against oxidative or immune stressors. Subretinal delivery of adeno-associated virus (AAV)-expressing human IRAK3 rescued light-induced outer retinal degeneration in wild-type mice and attenuated age-related spontaneous retinal degeneration in Irak3-knockout mice. Our data show that replenishment of IRAK-M in the RPE may redress dysregulated pro-inflammatory processes in AMD, suggesting a potential treatment for retinal degeneration.

Long-Term Visual Outcome of Patients with Blau Syndrome.

PURPOSE: To document the long-term visual outcomes in patients with Blau syndrome. METHODS: A retrospective institutional cohort study was conducted, and 13 patients with genetically confirmed Blau syndrome were included. Demographic and clinical data were collected from standardised medical charts. Baseline was defined as the first detected uveitis and data were recorded onwards at intervals of 1, 3, 5, 10, 15 and 20 years. RESULTS: Anterior uveitis was the most common classification at baseline (57.1%). Among patients with documented uveitis lasting 10 years or more, all of them developed panuveitis. Median logMAR visual acuity at baseline was 0 (range -0.5; 0.7), 0.19 (range 0; 1.5) at year 5, and 0.7 (range 0.1 - no perception of light) at year 20, as recorded in 13, 16, and 10 eyes, respectively. All patients received treatment with topical and oral steroids, and multiple systemic immunosuppressants including biologics. Disease control, defined as having cells <1+ in both eyes and using topical steroid eye drops less than twice daily, was achieved in 14.3% to 37.5% of patients at the different time points. Cataract surgery was performed in 12 eyes of 8 patients, 3 eyes of 3 patients necessitated glaucoma surgery, and 4 eyes of 4 patients required surgery for retinal detachment. CONCLUSION: Uveitis associated with Blau syndrome commonly leads to severe, chronic panuveitis, requiring long-term systemic immunosuppression. Early diagnosis and timely initiation of biologics may prevent significant visual impairment.

Establishing the Normative Data Set Necessary for Imaging-Based Childhood Uveitis Surveillance: A Cross-Sectional Study.

Purpose: Anterior segment optical coherence tomography (AS-OCT) is an emerging diagnostic and monitoring tool for anterior uveitis. We investigated AS-OCT findings in the eyes of a large, diverse population of children free of uveitis to establish its potential to "rule out" accurately those without disease. Methods: In this cross-sectional observational study, image acquisition was performed with swept source AS-OCT (Heidelberg Anterion), using a protocol of 13 B-scans per volume, from 217 children (434 eyes) aged 5 to 15 years, with analysis of acquired images (identification of apparent inflammatory cells, or "cell events") by multiple graders. Outcomes of interest were median and maximum cell event count (MEDCC, MAXCC) per B-scan from each eye and the total cell event count (TCC) per volume scan. Results: At least one cell event was detected in volume scans of 76% of eyes (329/434) and 87% of children (189/217). The maximum number (MAXCC) per scan ranged from 0 to 6 (median, 2). There was a strong positive association between increasing age (years) and the number of cell events detected within a volume scan following adjustment for gender and iris color (adjusted regression coefficient for TCC 0.5; P < 0.0001; 95% confidence interval, 0.4-0.7). Conclusions: Our findings demonstrate that apparent inflammatory cells are detectable on AS-OCT in the apparently healthy eyes of children and furthermore suggest early life developmental changes in blood-iris barrier stability that merit further exploration. We provide the foundation for the normative data set necessary for establishing the clinical utility of AS-OCT for surveillance of children with inflammatory eye diseases.

The Infectious Uveitis Treatment Algorithm Network (TITAN) Report 1-global current practice patterns for the management of Herpes Simplex Virus and Varicella Zoster Virus anterior uveitis.

AIMS: To present current expert practice patterns and to formulate a consensus for the management of HSV and VZV AU by uveitis specialists worldwide. METHODS: A two-round online modified Delphi survey with masking of the study team was conducted. Responses were collected from 76 international uveitis experts from 21 countries. Current practices in the diagnosis and treatment of HSV and VZV AU were identified. A working group (The Infectious Uveitis Treatment Algorithm Network [TITAN]) developed data into consensus guidelines. Consensus is defined as a particular response towards a specific question meeting ≥75% of agreement or IQR ≤ 1 when a Likert scale is used. RESULTS: Unilaterality, increased intraocular pressure (IOP), decreased corneal sensation and diffuse or sectoral iris atrophy are quite specific for HSV or VZV AU from consensus opinion. Sectoral iris atrophy is characteristic of HSV AU. Treatment initiation is highly variable, but most experts preferred valacyclovir owing to simpler dosing. Topical corticosteroids and beta-blockers should be used if necessary. Resolution of inflammation and normalisation of IOP are clinical endpoints. CONCLUSIONS: Consensus was reached on several aspects of diagnosis, choice of initial treatment, and treatment endpoints for HSV and VZV AU. Treatment duration and management of recurrences varied between experts.

The Infectious Uveitis Treatment Algorithm Network (TITAN) Report 2-global current practice patterns for the management of Cytomegalovirus anterior uveitis.

AIMS: To present current practice patterns in the diagnosis and management of Cytomegalovirus anterior uveitis (CMV AU) by uveitis experts worldwide. METHODS: A two-round modified Delphi survey with masking of the study team was performed. Based on experience and expertise, 100 international uveitis specialists from 21 countries were invited to participate in the survey. Variation in the diagnostic approaches and preferred management of CMV AU was captured using an online survey platform. RESULTS: Seventy-five experts completed both surveys. Fifty-five of the 75 experts (73.3%) would always perform diagnostic aqueous tap in suspected CMV AU cases. Consensus was achieved for starting topical antiviral treatment (85% of experts). About half of the experts (48%) would only commence systemic antiviral treatment for severe, prolonged, or atypical presentation. The preferred specific route was ganciclovir gel 0.15% for topical treatment (selected by 70% of experts) and oral valganciclovir for systemic treatment (78% of experts). The majority of experts (77%) would commence treatment with topical corticosteroid four times daily for one to two weeks along with antiviral coverage, with subsequent adjustment depending on the clinical response. Prednisolone acetate 1% was the drug of choice (opted by 70% of experts). Long-term maintenance treatment (up to 12 months) can be considered for chronic course of inflammation (88% of experts) and those with at least 2 episodes of CMV AU within a year (75-88% of experts). CONCLUSIONS: Preferred management practices for CMV AU vary widely. Further research is necessary to refine diagnosis and management and provide higher-level evidence.

Quality assessment of anterior segment OCT images: Development and validation of quality criteria.

BACKGROUND: The utility of medical imaging is dependant on image quality. We aimed to develop and validate quality criteria for ocular anterior segment optical coherence tomography (AS-OCT) images. METHODS: We undertook a cross-sectional study using AS-OCT images from patients aged 6-16. A novel three-level grading system (good, limited or poor) was developed based on the presence of image artefact (categorised as lid, eyelash, cropping, glare, or movement artefact). Three independent experts graded 2825 images, with agreement assessed using confusion matrices and intraclass correlation coefficients (ICC) for each parameter. RESULTS: There was very good inter-grader IQA agreement assessing image quality with ICC 0.85 (95 %CI: 0.84-0.87). The most commonly occurring artefact was eyelash artefact (1008/2825 images, 36 %). Graders labelled 621/2825 (22 %) images as good and 384 (14 %) as poor. There was complete agreement at either end of the confusion matrix with no 'good' images labelled as 'poor' by other graders, and vice versa. Similarly, there was very good agreement when assessing presence of lash (0.96,0.94-0.98), movement (0.97,0.96-0.99), glare (0.82,0.80-0.84) and cropping (0.90,0.88-0.92). CONCLUSIONS: The novel image quality assessment criteria (IQAC) described here have good interobserver agreement overall, and excellent agreement on the differentiation between 'good' and 'poor' quality images. The large proportion of images graded as 'limited' suggests the need for refine this classification, using the specific IQAC features, for which we also report high interobserver agreement. These findings support the future potential for wider clinical and community care implementation of AS-OCT for the diagnosis and monitoring of ocular disease.

Replenishing Age-Related Decline of IRAK-M Expression in Retinal Pigment Epithelium Attenuates Outer Retinal Degeneration.

Unchecked, chronic inflammation is a constitutive component of age-related diseases, including age-related macular degeneration (AMD). Here we identified interleukin-1 receptor-associated kinase (IRAK)-M as a key immunoregulator in retinal pigment epithelium (RPE) that declines with age. Rare genetic variants of IRAK-M increased the likelihood of AMD. IRAK-M expression in RPE declined with age or oxidative stress and was further reduced in AMD. IRAK-M-deficient mice exhibited increased incidence of outer retinal degeneration at earlier ages, which was further exacerbated by oxidative stressors. The absence of IRAK-M disrupted RPE cell homeostasis, including compromised mitochondrial function, cellular senescence, and aberrant cytokine production. IRAK-M overexpression protected RPE cells against oxidative or immune stressors. Subretinal delivery of AAV-expressing IRAK-M rescued light-induced outer retinal degeneration in wild-type mice and attenuated age-related spontaneous retinal degeneration in IRAK-M-deficient mice. Our data support that replenishment of IRAK-M expression may redress dysregulated pro-inflammatory processes in AMD, thereby treating degeneration.

Limited Utility of Keratic Precipitate Morphology as an Indicator of Underlying Diagnosis in Ocular Inflammation.

OBJECTIVES: We aimed to establish the degree of consensus among clinicians on descriptors of KP morphology. METHODS: A web-based exercise in which respondents associated KP descriptors, as identified through a scoping review of the published literature, to images from different disorders. Inter-observer agreement was assessed using the Krippendorff kappa alpha metric. RESULTS: Of the 76 descriptive terms identified by the scoping review, the most used included "mutton-fat" (n = 93 articles, 36%), "fine/dust" (n = 76, 29%), "stellate" (n = 40, 15%), "large" (n = 33, 12%), and "medium" (n = 33, 12%). The survey of specialists (n = 26) identified inter-observer agreement for these descriptors to be poor ("stellate," kappa: 0.15, 95% confidence interval 0.13-0.17), limited ("medium": 0.27, 95% CI 0.25-0.29; "dust/fine": 0.36, 95% CI 0.34-0.37), or moderate ("mutton fat": 0.40, 95% CI 0.36-0.43; "large": 0.43, 95% CI 0.39-0.46). CONCLUSION: The clinical utility of KP morphology as an indicator of disease classification is limited by low inter-observer agreement.

Elastin Layer in Bruch's Membrane as a Target for Immunization or Tolerization to Modulate Pathology in the Mouse Model of Smoke-Induced Ocular Injury.

Age-related macular degeneration (AMD) is associated with an overactive complement system and an increase in circulating antibodies. Our search for potential neoantigens that can trigger complement activation in disease has led us to investigate elastin. A loss of the elastin layer (EL) of Bruch's membrane (BrM) has been reported in aging and AMD together with an increase of serum elastin-derived peptides and α-elastin antibodies. In the mouse model of cigarette smoke exposure (CSE), damage in BrM, loss of the EL, and vision loss are dependent on complement activation. We have examined the hypothesis that CSE generates immunogenic elastin neoepitopes that trigger an increase in α-elastin IgG and IgM antibodies, which can then bind to the neoepitopes in the target cells or membranes, triggering complement activation. Specifically, we showed that immunization with elastin peptide oxidatively modified by cigarette smoke (ox-elastin) exacerbated ocular pathology and vision loss in CSE mice. In contrast, mice receiving peptide immunotherapy (PIT) with ox-elastin did not lose vision over the smoking period and exhibited a more preserved BrM. Immunization and PIT correlated with humoral immunity and complement activation and IgG/IgM deposition in the RPE/BrM/choroid. Finally, PIT modulated immune markers IFNγ and IL-4. The data further support the hypothesis that complement activation, triggered by immune complex formation in target tissues, plays a role in ocular damage in the CSE model. As PIT with ox-elastin peptides reduces damage, we discuss the possibility that AMD progression might be preventable.

Towards molecular-pathology informed clinical trials in childhood arthritis to achieve precision medicine in juvenile idiopathic arthritis.

In childhood arthritis, collectively known as Juvenile idiopathic arthritis (JIA), the rapid rise of available licensed biological and targeted small molecule treatments in recent years has led to improved outcomes. However, real-world data from multiple countries and registries show that despite a large number of available drugs, many children and young people continue to suffer flares and experience significant periods of time with active disease for many years. More than 50% of young people with JIA require ongoing immune suppression well into adult life, and they may have to try multiple different treatments in that time. There are currently no validated tools with which to select specific treatments, nor biomarkers of response to assist in such choices, therefore, current management uses essentially a trial-and-error approach. A further consequence of recent progress is a reducing pool of available children or young people who are eligible for new trials. In this review we consider how progress towards a molecular based approach to defining treatment targets and informing trial design in JIA, combined with novel approaches to clinical trials, could provide strategies to maximise discovery and progress, in order to move towards precision medicine for children with arthritis.

Quantitative and qualitative assessment of anterior segment optical coherence tomography capture of disease state in childhood anterior uveitis.

BACKGROUND/AIMS: Anterior segment optical coherence tomography (AS-OCT) assessment of anterior chamber inflammation is an emerging tool. We describe the performance of AS-OCT in a paediatric population. METHODS: A mixed-methods prospective study, using routine clinical assessment as reference standard, and AS-OCT, with Tomey CASIA2 or Heidelberg Spectralis HS1, as index test, with data collected on patient perceptions of imaging. Repeatability, diagnostic indices, responsiveness to clinical change and clinical correlations of imaging-based metrics (image cell count, size, density and brightness) were assessed, with construction of receiver operated characteristic curves. Exploratory thematic analysis of responses from families was undertaken. RESULTS: A total of 90 children (180 eyes) underwent imaging. Bland Altman limits of agreement for CASIA2 repeatability ranged from +17 cells (95% CI 13.6 to 21.1) to -19 cells (95% CI -15.6 to -23.2) and HS1 from +1 (95% CI 0.9 to 1.2) to -1.0 (-1.2 to -0.8) cells. CASIA2 imaging had higher sensitivity of 0.92 (95% CI 0.78 to 0.97) vs HS1 imaging 0.17 (95% CI 0.07 to 0.34), with positive correlation between clinical grade and CASIA2 cell count (coefficient 12.8, p=0.02, 95% CI 2.2 to 23.4). Change in clinical grade at follow-up examinations correlated with change in image based 'cell' count (r2=0.79, p<0.001). Patients reported a potential positive impact of seeing their disease activity. CONCLUSION: Our findings suggest that OCT-based imaging holds the promise of deeper understanding of disease, improved patient experience and more granular monitoring of activity with resultant improved outcomes, but further work is needed to refine acquisition and analysis protocols.

Similarities in the histological mouse model of early herpes simplex retinopathy with punctate inner choroidopathy and Ebola virus disease retinopathy.

ABSTRACT PURPOSE: To highlight similarities between the cross-sectional retinal lesion appearance in a patient with punctate inner choroidopathy (PIC), Ebola virus disease (EVD) retinopathy and the von Szily mouse model of herpes simplex virus type 1 (HSV) retinopathy. METHODS: Case report and cross-sectional retinal lesion comparison. RESULTS: Whilst phenotypically different on colour imaging, a near-identical lesion appearance on optical coherence tomography, characterised by a focal photoreceptor loss and distinctive V-shaped collapse of the overlying retinal layers, was observed in both PIC and EVD retinopathy. This mirrored the early histological appearance of the neuronally transmitted HSV retinopathy in a mouse model. CONCLUSIONS: Given the occurrence of this phenotypic appearance has been demonstrated in an animal model where the viral pathophysiological mechanism is known, together with its observation in EVD retinopathy with a shared, hypothesised neurotropic retinal pathogenesis, the potential of a common pathophysiology accounting for the appearance in PIC lesions is a possibility which may provide a potential avenue for future research.

Epigenetic drug screen identified IOX1 as an inhibitor of Th17-mediated inflammation through targeting TET2.

BACKGROUND: Targeting helper T cells, especially Th17 cells, has become a plausible therapy for many autoimmune diseases. METHODS: Using an in vitro culture system, we screened an epigenetics compound library for inhibitors of IFN-γ and IL-17 expression in murine Th1 and Th17 cultures. FINDINGS: This identified IOX1 as an effective suppressor of IL-17 expression in both murine and human CD4+ T cells. Furthermore, we found that IOX1 suppresses Il17a expression directly by targeting TET2 activity on its promoter in Th17 cells. Using established pre-clinical models of intraocular inflammation, treatment with IOX1 in vivo reduced the migration/infiltration of Th17 cells into the site of inflammation and tissue damage. INTERPRETATION: These results provide evidence of the strong potential for IOX1 as a viable therapy for inflammatory diseases, in particular of the eye. FUNDING: This study was supported by the National Key Research and Development Program of China 2021YFA1101200 (2021YFA1101204) to LW and XW; the National Natural Science Foundation of China 81900844 to XH and 82171041 to LW; the China Postdoctoral Science Foundation 2021M700776 and the Scientific Research Project of Guangdong Provincial Bureau of Traditional Chinese Medicine 20221373 to YZ; and the National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS (National Health Service) Foundation Trust and University College London Institute of Ophthalmology, UK (DAC, LPS, PJPL, MS, ADD and RWJL). The views expressed are those of the authors and not necessarily those of the NIHR or the UK's Department of Health and Social Care.

Triazole-derivatized near-infrared cyanine dyes enable local functional fluorescent imaging of ocular inflammation.

Near-infrared (NIR) chemical fluorophores are promising tools for in-vivo imaging in real time but often succumb to rapid photodegradation. Indocyanine green (ICG) is the only NIR dye with regulatory approval for ocular imaging in humans; however, ICG, when employed for applications such as labelling immune cells, has limited sensitivity and does not allow precise detection of specific inflammatory events, for example leukocyte recruitment during uveitic flare-ups. We investigated the potential use of photostable novel triazole NIR cyanine (TNC) dyes for detecting and characterising activated T-cell activity within the eye. Three TNC dyes were evaluated for ocular cytotoxicity in-vitro using a MTT assay and optimised concentrations for intraocular detection within ex-vivo porcine eyes after topical application or intracameral injections of the dyes. TNC labelled T-cell tracking experiments and mechanistic studies were also performed in-vitro. TNC-1 and TNC-2 dyes exhibited greater fluorescence intensity than ICG at 10 µM, whereas TNC-3 was only detectable at 100 µM within the porcine eye. TNC dyes did not demonstrate any ocular cell toxicity at working concentrations of 10 µM. CD4+T-cells labelled with TNC-1 or TNC-2 were detected within the porcine eye, with TNC-1 being brighter than TNC-2. Detection of TNC-1 and TNC-2 into CD4+T-cells was prevented by prior incubation with dynole 34-2 (50 µM), suggesting active uptake of these dyes via dynamin-dependent processes. The present study provides evidence that TNC dyes are suitable to detect activated CD4+T-cells within the eye with potential as a diagnostic marker for ocular inflammatory diseases.

Development of a Nationally Agreed Core Clinical Dataset for Childhood Onset Uveitis.

Background: Childhood onset uveitis comprises a group of rare inflammatory disorders characterized by clinical heterogeneity, chronicity, and uncertainties around long term outcomes. Standardized, detailed datasets with harmonized clinical definitions and terminology are needed to enable the clinical research necessary to stratify disease phenotype and interrogate the putative determinants of health outcomes. We aimed to develop a core routine clinical collection dataset for clinicians managing children with uveitis, suitable for multicenter and national clinical and experimental research initiatives. Methods: Development of the dataset was undertaken in three phases: phase 1, a rapid review of published datasets used in clinical research studies; phase 2, a scoping review of disease or drug registries, national cohort studies and core outcome sets; and phase 3, a survey of members of a multicenter clinical network of specialists. Phases 1 and 2 provided candidates for a long list of variables for the dataset. In Phase 3, members of the UK's national network of stakeholder clinicians who manage childhood uveitis (the Pediatric Ocular Inflammation Group) were invited to select from this long-list their essential items for the core clinical dataset, to identify any omissions, and to support or revise the clinical definitions. Variables which met a threshold of at least 95% agreement were selected for inclusion in the core clinical dataset. Results: The reviews identified 42 relevant studies, and 9 disease or drug registries. In total, 138 discrete items were identified as candidates for the long-list. Of the 41 specialists invited to take part in the survey, 31 responded (response rate 78%). The survey resulted in inclusion of 89 data items within the final core dataset: 81 items to be collected at the first visit, and 64 items at follow up visits. Discussion: We report development of a novel consensus core clinical dataset for the routine collection of clinical data for children diagnosed with non-infectious uveitis. The development of the dataset will provide a standardized approach to data capture able to support observational clinical studies embedded within routine clinical care and electronic patient record capture. It will be validated through a national prospective cohort study, the Uveitis in childhood prospective national cohort study (UNICORNS).

Recent developments of neuroprotective agents for degenerative retinal disorders.

Retinal degeneration is a debilitating ocular complication characterized by the progressive loss of photoreceptors and other retinal neurons, which are caused by a group of retinal diseases affecting various age groups, and increasingly prevalent in the elderly. Age-related macular degeneration, diabetic retinopathy and glaucoma are among the most common complex degenerative retinal disorders, posing significant public health problems worldwide largely due to the aging society and the lack of effective therapeutics. Whilst pathoetiologies vary, if left untreated, loss of retinal neurons can result in an acquired degeneration and ultimately severe visual impairment. Irrespective of underlined etiology, loss of neurons and supporting cells including retinal pigment epithelium, microvascular endothelium, and glia, converges as the common endpoint of retinal degeneration and therefore discovery or repurposing of therapies to protect retinal neurons directly or indirectly are under intensive investigation. This review overviews recent developments of potential neuroprotectants including neuropeptides, exosomes, mitochondrial-derived peptides, complement inhibitors, senolytics, autophagy enhancers and antioxidants either still experimentally or in clinical trials. Effective treatments that possess direct or indirect neuroprotective properties would significantly lift the burden of visual handicap.

Applications of three-dimensional printing in ophthalmology.

Three-dimensional (3D) printing is increasingly used to produce customized objects and is a promising alternative to traditional manufacturing methods in diverse fields, such as dentistry and orthopedics. Already in use in other medical specialties, adoption in ophthalmology has been limited to date. This review aims to provide an overview of 3D printing technology with respect to current and potential applications in ophthalmic practice. Medline, Embase, and Internet searches were performed with "3D printing," "ophthalmology," "dentistry," "orthopaedics" and their synonyms used as main search terms. In addition, search terms related to clinical applications such as "surgery" and "implant" were employed. 3D printing has multiple applications in ophthalmology, including in diagnosis, surgery, prosthetics, medications, and medical education. Within the past decade, researchers have produced 3D printed models of objects such as implants, prostheses, anatomical models and surgical simulators. Further development is necessary to generate optimal biomaterials for various applications, and the quality and long-term performance of 3D models needs to be validated.

Corneal Transplant Follow-up Study II: a randomised trial to determine whether HLA class II matching reduces the risk of allograft rejection in penetrating keratoplasty.

PURPOSE: A randomised trial to test the hypothesis that human leucocyte antigen (HLA) class II matching reduces the risk of allograft rejection in high-risk penetrating keratoplasty (PK). METHODS: All transplants were matched for HLA class I antigens (≤2 mismatches at the A and B loci) and corneas were allocated to patients by cohort minimisation to achieve 0, 1 or 2 HLA class II antigen mismatches. The corneal transplants (n=1133) were followed for 5 years. The primary outcome measure was time to first rejection episode. RESULTS: Cox regression analysis found no influence of HLA class II mismatching on risk of immunological rejection (HR 1.13; 95% CI 0.79 to 1.63; p=0.51). The risk of rejection in recipients older than 60 years was halved compared with recipients ≤40 years (HR 0.51; 95% CI 0.36 to 0.73; p=0.0003). Rejection was also more likely where cataract surgery had been performed after PK (HR 3.68; 95% CI 1.95 to 6.93; p<0.0001). In univariate analyses, preoperative factors including chronic glaucoma (p=0.02), vascularisation (p=0.01), inflammation (p=0.03), ocular surface disease (p=0.0007) and regrafts (p<0.001) all increased the risk of rejection. In the Cox model, however, none of these factors was individually significant but rejection was more likely where≥2 preoperative risk factors were present (HR 2.11; 95% CI 1.26 to 3.47; p<0.003). CONCLUSIONS: HLA class II matching, against a background of HLA class I matching, did not reduce the risk of allograft rejection. Younger recipient age, the presence of ≥2 preoperative risk factors and cataract surgery after PK all markedly increased the risk of allograft rejection. TRIAL REGISTRATION NUMBER: ISRCTN25094892.