BIOMECHANICAL CONSIDERATIONS FOR OPTIMISING SUBRETINAL INJECTIONS.

Subretinal injection is the preferred delivery technique for various novel ocular therapies and is widely used because of its precision and efficient delivery of gene and cell therapies; however, choosing an injection point and defining delivery parameters to target a specified retinal location and area is an inexact science. We provide an overview of the key factors that play important roles during subretinal injections to refine the technique, enhance patient outcomes, and minimise risks. We describe the role of anatomical and physical variables that affect subretinal bleb propagation and shape and their impact on retinal integrity. We highlight the risks associated with subretinal injections and consider strategies to mitigate reflux and retinal trauma. Finally, we explore the emerging field of robotic assistance in improving intraocular manouvrability and precision to facilitate the injection procedure.

Referrals for proliferative diabetic retinopathy from two UK diabetic retinopathy screening services: a 10-year analysis of visual outcomes, requirement for vitrectomy, and mortality.

BACKGROUND/OBJECTIVES: To determine long-term outcomes of patients referred with proliferative diabetic retinopathy (PDR) from diabetic eye screening programmes (DESP) to tertiary care centres in the United Kingdom (UK). METHODS: Retrospective multicentre study of patients referred from two DESPs in the UK over a 36-month period (2007-9) and followed-up for 10 years. Critical outcomes included severe vision loss (SVL) and the need for vitrectomy. Other outcomes assessed included moderate vision loss (MVL), and patient survival time. Univariate and multiple variable Cox proportional hazards regressions were used to analyse survival outcomes. RESULTS: 212 eyes of 150 patients were referred with a diagnosis of PDR. 109 eyes of 72 patients were confirmed to have active PDR and included in the study. 61% of patients had low-risk PDR, while 39% exhibited high-risk features in at least one eye. Eight (7.3%) eyes developed SVL and 16 (14.7%) MVL during follow up. Vitrectomy was required in 24% (95% CI: 15 to 31%) of all PDR eyes and was most commonly performed for vitreous haemorrhage (65%). The 10-year survival in all PDR patients was 76% (95% CI: 63 to 85%) with the mean time to death for all deceased patients being 5.4 ± 3.6 years. On multivariable analysis, only age was found to have a significant association with the survival of patients with PDR. CONCLUSIONS: During the 10 year follow up SVL was uncommon, but MVL occurred in almost one-fifth of the eyes. Approximately 1 in 4 eyes required vitrectomy, highlighting its significance in patient management.

INTRAOCULAR EMULSION OF SILICONE OIL (ITEMS) GRADING SYSTEM: An Evidence-Based Expert-Led Consensus.

PURPOSE: To propose the InTraocular EMulsion of Silicone oil (ITEMS) grading system for the assessment of silicone oil (SiO) emulsion, applicable in a routine clinical setting and validated through an expert-led consensus procedure. METHODS: Seven experts on intraocular liquid tamponades, led by a facilitator, performed a literature review on the detection of SiO emulsion. Based on the proposed ideas, a questionnaire was developed and submitted to the experts on the methods to detect SiO emulsion and the items to grade. After 2 rounds of individual ranking using a 9-point scale and related discussion, the final grading system was developed including items that reached consensus (score ≥7 from ≥75% of members). RESULTS: The agreed ITEMS grading system includes the identification of SiO microbubbles and large SiO bubbles through slit-lamp biomicroscopy, gonioscopy, fundus examination under mydriasis, or ultra-wide-field fundus photography. Moreover, macular and disk optical coherence tomography are used to detect SiO-associated hyperreflective dots. CONCLUSION: An evidence-based expert-led consensus was conducted to develop grading system of SiO emulsion, allowing, for the first time, homogenous collection of data on SiO emulsion. This has the potential to improve the understanding of the role and clinical relevance of SiO emulsion, allowing comparisons between different studies.

The effect of sex and laterality on the phenotype of primary rhegmatogenous retinal detachment.

BACKGROUND: To assess the effect of sex and laterality on clinical features of primary rhegmatogenous retinal detachment (RRD). METHOD: This study is a retrospective analysis of data prospectively collected. We extracted data from two online datasets over a 7-year period of patients older than 16 years who had undergone surgery for primary RRD. Data on baseline characteristics were analyzed to compare males versus females, and right versus left eyes. RESULTS: Of 8133 eyes analyzed, 4342 (53.4%) were right. The overall male predominance (63.7%) was more marked in the age range 50-69 years. Men were more commonly pseudophakic and presented more frequently with baseline posterior vitreous detachment (PVD). Female sex was significantly associated with baseline myopia, retinal holes as causative retinal break, and isolated inferior RD. Men had more frequent foveal involvement, greater RRD extent, greater numbers and larger sized retinal tears including dialysis and giant retinal tears. Regarding laterality, foveal involvement, larger retinal breaks, isolated temporal RD and temporal retinal breaks were more common in right eyes, whereas left eyes were more myopic at baseline and presented more frequently with isolated nasal RD and nasal retinal breaks. CONCLUSIONS: This study confirmed the predominance of male sex and right laterality in RRD. Sex and laterality were associated with multiple presenting features of RRD including extent, break distribution, number, size and type, as well as RD distribution.

A randomised controlled trial evaluating internal limiting membrane peeling forceps in macular hole surgery.

PURPOSE: To assess study design and a range of anatomical and functional changes after internal limiting membrane (ILM) peeling using forceps developed for atraumatic ILM pick-up compared to standard forceps. METHODS: We conducted a masked proof-of concept randomised controlled trial (RCT) on 65 patients who underwent ILM peeling for idiopathic full-thickness macular hole (FTMH) using etched-tip forceps (etched-tip group, 33 eyes) compared to standard ILM forceps (smooth-tip group, 32 eyes). Patients were assessed preoperatively, 3 weeks, 3 and 6 months postoperatively. RESULTS: The primary closure rate was 95.4%. There was no statistically significant difference between the groups in terms of final visual acuity (66.9 vs 70.9 ETDRS letters, p = 0.13), difference of visual field mean deviation (1.32 vs 1.14 decibels), and number of eyes with pick-up-related retinal haemorrhages (16% vs 16%, p = 0.96), swelling of arcuate nerve fibre layer lesions (63% vs 55%, p = 0.54), number of dissociated optic nerve fibre layer lesions (31.4 vs 41.0, p = 0.16), nor inner retina defects (37% vs 22%, p = 0.17). Similar changes in inner retinal volumes were detected in all 9 sectors of an ETDRS grid except for a trend (p = 0.06) towards a lower reduction in the inferior inner sector in the etched-tip group. CONCLUSIONS: The study was successfully completed with masking maintained and a low risk of bias. Multiple endpoints relating to ILM peeling were assessed, and estimates were provided that can be used for future studies. Although the study was not powered to assess any specific endpoint, the anatomical and functional outcomes assessed did not significantly differ.

Artificial intelligence using deep learning to predict the anatomical outcome of rhegmatogenous retinal detachment surgery: a pilot study.

PURPOSE: To develop and evaluate an automated deep learning model to predict the anatomical outcome of rhegmatogenous retinal detachment (RRD) surgery. METHODS: Six thousand six hundred and sixty-one digital images of RRD treated by vitrectomy and internal tamponade were collected from the British and Eire Association of Vitreoretinal Surgeons database. Each image was classified as a primary surgical success or a primary surgical failure. The synthetic minority over-sampling technique was used to address class imbalance. We adopted the state-of-the-art deep convolutional neural network architecture Inception v3 to train, validate, and test deep learning models to predict the anatomical outcome of RRD surgery. The area under the curve (AUC), sensitivity, and specificity for predicting the outcome of RRD surgery was calculated for the best predictive deep learning model. RESULTS: The deep learning model was able to predict the anatomical outcome of RRD surgery with an AUC of 0.94, with a corresponding sensitivity of 73.3% and a specificity of 96%. CONCLUSION: A deep learning model is capable of accurately predicting the anatomical outcome of RRD surgery. This fully automated model has potential application in surgical care of patients with RRD.

Investigation of heterocellular features of the mouse retinal neurovascular unit by 3D electron microscopy.

The retina has a complex structure with a diverse collection of component cells that work together to facilitate vision. The retinal capillaries supplying the nutritional requirements to the inner retina have an intricate system of neural, glial and vascular elements that interconnect to form the neurovascular unit (NVU). The retina has no autonomic nervous system and so relies on the NVU as an interdependent, physical and functional unit to alter blood flow appropriately to changes in the physiological environment. The importance of this is demonstrated by alterations in NVU function being apparent in the blinding disease diabetic retinopathy and other diseases of the retina. It is, therefore, imperative to understand the anatomy of the components of the NVU that underlie its functioning and in particular the nanoscale arrangements of its heterocellular components. However, information on this in three spatial dimensions is limited. In the present study, we utilised the technique of serial block-face scanning electron microscopy (SBF-SEM), and computational image reconstruction, to enable the first three-dimensional ultrastructural analysis of the NVU in mouse retinal capillaries. Mouse isolated retina was prepared for SBF-SEM and up to 150 serial scanning electron microscopy images (covering z-axes distances of 12-8 mm) of individual capillaries in the superficial plexus and NVU cellular components digitally aligned. Examination of the data in the x-, y- and z-planes was performed with the use of semi-automated computational image analysis tools including segmentation, 3D image reconstruction and quantitation of cell proximities. A prominent feature of the capillary arrangements in 3D was the extensive sheath-like coverage by singular pericytes. They appeared in close register to the basement membrane with which they interwove in a complex mesh-like appearance. Breaks in the basement membrane appeared to facilitate pericyte interactions with other NVU cell types. There were frequent, close (<10 nm) pericyte-endothelial interactions with direct contact points and peg-and-socket-like morphology. Macroglia typically intervened between neurons and capillary structures; however, regions were identified where neurons came into closer contact with the basement membrane. A software-generated analysis to assess the morphology of the different cellular components of the NVU, including quantifications of convexity, sphericity and cell-to-cell closeness, has enabled preliminary semi-quantitative characterisation of cell arrangements with neighbouring structures. This study presents new data on the nanoscale spatial characteristics of components of the murine retinal NVU in 3D that has implications for our understanding of structural integrity (e.g. pericyte-endothelial cell anchoring) and function (e.g. possible paracrine communication between macroglia and pericytes). It also serves as a platform to inform future studies examining changes in NVU characteristics with different biological and disease circumstances. All raw and processed image data have been deposited for public viewing.

Epimacular brachytherapy for previously treated neovascular age-related macular degeneration: month 36 results of the MERLOT randomised controlled trial.

BACKGROUND/AIM: To assess the long-term safety and efficacy of epimacular brachytherapy (EMB) for chronic, active, neovascular age-related macular degeneration (nAMD). METHODS: This pivotal, randomised, controlled surgical device trial recruited patients with chronic nAMD receiving intravitreal ranibizumab from 24 UK hospitals. Participants were randomised to either pars plana vitrectomy with 24 Gray EMB and pro re nata (PRN) ranibizumab (n=224) or PRN ranibizumab monotherapy (n=119). Although masking was not possible, masked clinicians assessed best-corrected visual acuity (BCVA) and imaging. After month 24, participants reverted to standard care, with either ranibizumab or aflibercept, returning for a month 36 study visit. RESULTS: Of 363 participants, 309 (85.1%) completed month 36. The number of injections was 12.1±8.1 in the EMB group versus 11.4±6.1 in the ranibizumab group (difference 0.7, 95% CI of difference -0.9 to 2.3, p=0.41) between months 1 and 36, and 3.6±3.3 (n=200) versus 3.9±2.7 (n=102) (difference -0.3, 95% CI of difference -1.0 to 0.4, p=0.43) between months 25 and 36 (standard care). Over 36 months, BCVA change was -19.7±18.5 letters in the EMB group and -4.8±12.5 in the ranibizumab group (difference -14.9, 95% CI of difference -18.5 to -11.2, p<0.0001). The month 36 BCVA of 20 EMB-treated participants with microvascular abnormalities (MVAs) at month 24 was similar to EMB-treated participants without MVAs (-21.8 vs -19.4 letters, p=0.65). CONCLUSION: EMB does not reduce the number of anti-vascular endothelial growth factor (VEGF) injections, either within or outside of a trial setting, and is associated with worse BCVA than anti-VEGF monotherapy. TRIAL REGISTRATION NUMBER: NCT01006538.

The effect of age on phenotype of primary rhegmatogenous retinal detachment.

BACKGROUND: To evaluate the influence of age on the clinical characteristics of primary rhegmatogenous retinal detachments (RRD). METHODS: We conducted a retrospective review of a prospectively collected dataset. Data regarding adult patients (aged 16-100 years) who had undergone primary RRD repair, were extracted from two online databases. Baseline demographics, preoperative clinical characteristics and surgical management details were collected. Age-based groups (16-30, 30-39, 40-49, 50-59, 60-69, 70-79, ≥80) were compared using univariate analysis, with multivariate testing for interaction of age with sex, laterality and pseudophakia. RESULTS: In total, 8,133 eyes were analysed, of which the majority (59%) were in the 50-69 age-range peaking at 60, with a male predominance (64%). Myopia was significantly more frequent in patients aged <50 years. The presence of posterior vitreous detachment increased up to 50 years, then remained >95%. Foveal involvement, grade C proliferative vitreoretinopathy, total RD and greater RD extent were more common and progressively increased after 60 years, with worsening visual acuity. Isolated superior RRDs became more prevalent with age reaching a plateau in the age-range 50-69, before reducing again; conversely, isolated inferior RRDs were commoner in those <30, with a minimum in the 70-79 age-range. The incidence of fellow-eye RRD decreased linearly with age. CONCLUSIONS: Age appeared a key variable in RRD phenotype influencing a wide range of RRD characteristics. The higher incidence of myopia, PVD absent and bilateral RRD in patients <40 years and the significant phenotypical differences in the under 40 and over 50 age-groups highlight that there are several discrete forms of RRD.

Late-Onset Autosomal Dominant Macular Degeneration Caused by Deletion of the CRX Gene.

PURPOSE: To characterize the phenotype observed in a case series with macular disease and determine the cause. DESIGN: Multicenter case series. PARTICIPANTS: Six families (7 patients) with sporadic or multiplex macular disease with onset at 20 to 78 years, and 1 patient with age-related macular degeneration. METHODS: Patients underwent ophthalmic examination; exome, genome, or targeted sequencing; and/or polymerase chain reaction (PCR) amplification of the breakpoint, followed by cloning and Sanger sequencing or direct Sanger sequencing. MAIN OUTCOME MEASURES: Clinical phenotypes, genomic findings, and a hypothesis explaining the mechanism underlying disease in these patients. RESULTS: All 8 cases carried the same deletion encompassing the genes TPRX1, CRX, and SULT2A1, which was absent from 382 control individuals screened by breakpoint PCR and 13 096 Clinical Genetics patients with a range of other inherited conditions screened by array comparative genomic hybridization. Microsatellite genotypes showed that these 7 families are not closely related, but genotypes immediately adjacent to the deletion breakpoints suggest they may share a distant common ancestor. CONCLUSIONS: Previous studies had found that carriers for a single defective CRX allele that was predicted to produce no functional CRX protein had a normal ocular phenotype. Here, we show that CRX whole-gene deletion in fact does cause a dominant late-onset macular disease.

Vitreous protein networks around ANG2 and VEGF in proliferative diabetic retinopathy and the differential effects of aflibercept versus bevacizumab pre-treatment.

Extracellular signalling proteins interact in networks rather than in isolation. In this context we investigated vitreous protein levels, including placental growth factor (PlGF), angiopoietin-2 (ANG2) and vascular endothelial growth factor (VEGF), in patients with proliferative diabetic retinopathy (PDR) with variable disease severities, and after anti-VEGF pre-treatment. Vitreous samples of 112 consecutive patients undergoing vitrectomy for PDR and of 52 non-diabetic patients with macular holes as controls were studied. A subset of the PDR patients were treated with either aflibercept (AFB, n = 25) or bevacizumab (BVZ)/ranibizumab (RZB) (n = 13), before surgery. Antibody-based analysis of 35 proteins (growth factors and cytokines) showed a significant increase in expression levels of 27 proteins in PDR patients as compared to controls. In network analysis of co-regulated proteins, a strong correlation in expression levels between VEGF, PlGF, MCP1 and ANG2 was found, mostly clustered around ANG2. In the AFB treatment group, concentrations of several proteins were decreased, including VEGFR1, whereas interleukin 6 and 8 were increased as compared to untreated PDR patients. The observed differences in vitreous protein levels between the different treatments and untreated PDR patients may underlie differences in clinical outcomes in patients with PDR.

Retinal and Corneal Changes Associated with Intraocular Silicone Oil Tamponade.

Silicone oils (SO) are used as long-term intraocular tamponades and have an irreplaceable role in vitreoretinal surgery. They can, however, be associated with multiple and potentially severe complications, involving different ocular tissues, in particular retina and cornea. Recent advances in ophthalmic imaging have allowed the precise characterization of retinal and corneal microstructural changes, at a subclinical level. This detailed analysis of SO-related retinal and corneal changes has improved our understanding of their pathogenesis and offer the potential for optimized monitoring and management of patients with SO-filled eyes. This review aims to provide clinicians and ophthalmic scientists with an updated and comprehensive overview of the corneal and retinal changes associated with SO tamponade.

PDGF as an Important Initiator for Neurite Outgrowth Associated with Fibrovascular Membranes in Proliferative Diabetic Retinopathy.

PURPOSE: The formation of fibrovascular membranes (FVMs) is a serious sight-threatening complication of proliferative diabetic retinopathy (PDR) that may result in retinal detachment and eventual blindness. During the formation of these membranes, neurite/process outgrowth occurs in retinal neurons and glial cells, which may both serve as a scaffold and have guiding or regulatory roles. To further understand this process, we investigated whether previously identified candidate proteins, from vitreous of PDR patients with FVMs, could induce neurite outgrowth in an experimental setting. MATERIALS AND METHODS: Retinal explants of C57BL6/N mouse pups on postnatal day 3 (P3) were cultured in poly-L-lysine- and laminin-coated dishes. Outgrowth stimulation experiments were performed with the addition of potential inducers of neurite outgrowth. Automated analysis of neurite outgrowth was performed by measuring ß-tubulin-immunopositive neurites using Image J. Expression of PDGF receptors was quantified by RT-PCR in FVMs of PDR patients. RESULTS: Platelet-derived growth factor (PDGF) induced neurite outgrowth in a concentration-dependent manner, whilst neuregulin 1 (NRG1) and connective tissue growth factor (CTGF) did not. When comparing three different PDGF dimers, treatment with PDGF-AB resulted in the highest neurite induction, followed by PDGF-AA and -BB. In addition, incubation of retinal explants with vitreous from PDR patients resulted in a significant induction of neurite outgrowth as compared to non-diabetic control vitreous from patients with macular holes, which could be prevented by addition of CP673451, a potent PDGF receptor (PDGFR) inhibitor. Abundant expression of PDGF receptors was detected in FVMs. CONCLUSION: Our findings suggest that PDGF may be involved in the retinal neurite outgrowth, which is associated with the formation of FVMs in PDR.

Biomechanical properties of retina and choroid: a comprehensive review of techniques and translational relevance.

Studying the biomechanical properties of biological tissue is crucial to improve our understanding of disease pathogenesis. The biomechanical characteristics of the cornea, sclera and the optic nerve head have been well addressed with an extensive literature and an in-depth understanding of their significance whilst, in comparison, knowledge of the retina and choroid is relatively limited. Knowledge of these tissues is important not only to clarify the underlying pathogenesis of a wide variety of retinal and vitreoretinal diseases, including age-related macular degeneration, hereditary retinal dystrophies and vitreoretinal interface diseases but also to optimise the surgical handling of retinal tissues and, potentially, the design and properties of implantable retinal prostheses and subretinal therapies. Our aim with this article is to comprehensively review existing knowledge of the biomechanical properties of retina, internal limiting membrane (ILM) and the Bruch's membrane-choroidal complex (BMCC), highlighting the potential implications for clinical and surgical practice. Prior to this we review the testing methodologies that have been used both in vitro, and those starting to be used in vivo to aid understanding of their results and significance.

The Association between Foveal Floor Measurements and Macular Hole Size.

PURPOSE: Determining which factors influence idiopathic macular hole (MH) size is important because it is a major prognostic indicator of treatment success. Foveal pit morphologic features are highly symmetrical within individuals and may influence idiopathic MH size. Using a series of patients with unilateral idiopathic MHs, we examined the foveal floor size of the fellow eye to evaluate its relationship with idiopathic MH size and postoperative outcomes. DESIGN: Retrospective observational study. PARTICIPANTS: Two hundred forty-one participants with a unilateral idiopathic MH treated with surgery and a fellow eye with no ocular pathologic features. METHODS: Both eyes underwent spectral-domain (SD) OCT imaging at the time of surgery. Minimum linear diameter (MLD) and base diameter (BD) defined idiopathic MH size. Foveal floor width (FFW) and minimal foveal thickness defined foveal pit morphologic features of the fellow eye. MAIN OUTCOME MEASURES: Baseline characteristics, SD OCT measurements, and preoperative variables were compared to determine their relationship with idiopathic MH size and postoperative visual acuity (VA) in logarithm of the minimum angle of resolution units. RESULTS: Foveal floor width was correlated with MLD (r = 0.36; P ≤ 0.001) and BD (r = 0.30; P ≤ 0.001), but not postoperative VA. Minimum linear diameter correlated with preoperative VA (r = 0.49; P ≤ 0.0001) and postoperative VA (r = 0.54; P ≤ 0.0001). A 2-stage regression model was developed to predict postoperative VA (r2 = 0.28): preoperative VA (ß = 0.36; P = 0.002) explained 13% of variability and MLD (ß = 0.29; P = 0.002), and idiopathic MH duration (ß = 0.23; P = 0.004) explained a further 16%. CONCLUSIONS: Foveal floor width of the fellow eye in patients with a unilateral idiopathic MH was correlated significantly with idiopathic MH size and may explain some of the variability in idiopathic MH size observed between individuals. However, FFW could not predict postoperative vision.

Phenotype and Outcomes of Phakic Versus Pseudophakic Primary Rhegmatogenous Retinal Detachments: Cataract or Cataract Surgery Related?

PURPOSE: To compare phakic and pseudophakic primary rhegmatogenous retinal detachments (RD) and, within phakic RD, eyes with and without cataract. DESIGN: Retrospective comparative clinical study. METHODS: Setting: Online database of prospectively collected data. StudyPopulation: Patients aged ≥50 years who had undergone RD repair. PROCEDURE: Data included baseline demographic and clinical features, surgical details, and anatomical and functional outcomes. Univariate analysis was performed to compare pseudophakic with phakic RD, and phakic RD with and without cataract. Age and sex dependency of variables was analyzed and the association of preoperative variables with final visual acuity was assessed using multivariate analysis. MainOutcomeMeasures: Preoperative features, intraoperative management, postoperative outcomes, association of preoperative features with postoperative outcomes. RESULTS: Of 4,231 eyes, 1,212 were pseudophakic and 3,019 phakic, among which 310 had cataract. Pseudophakic RD showed significant differences compared with phakic RD, including older age, higher prevalence of male sex, foveal detachment, grade C proliferative vitreoretinopathy (PVR), inferior retinal breaks, inferior retinal involvement, and greater RD extent. Despite the more advanced features of pseudophakic RD, pseudophakia was a positive factor for visual outcome. Contralateral RD was more frequent in pseudophakic than phakic RD eyes (P < .0001). Within phakic RD, phakic RD with cataract exhibited several similarities with pseudophakic RD, including greater age, more frequent foveal detachment, PVR, and greater RD extent. CONCLUSIONS: The presenting features differed significantly between pseudophakic and phakic RD, with greater occurrence of inferior retinal breaks and inferior retinal involvement in particular. Phakic RD with cataract shared several features in common with pseudophakic RD.

Incidence, characteristics, outcomes and confidence in managing posterior capsular rupture during cataract surgery in the UK: an ophthalmology trainees' perspective.

PURPOSE: To examine the incidence, characteristics and outcomes of posterior capsular rupture (PCR) cases amongst the ophthalmology trainees and to evaluate the trainees' confidence in managing PCR. METHODS: A two-staged cross-sectional study was carried out between September 2017 and April 2018 in the North East of England, UK. All ophthalmology trainees were surveyed on their confidence level in managing PCR and the characteristics and outcomes of their PCR cases. RESULTS: Fifteen (71.4%) out of 21 trainees completed the study. The mean number of phacoemulsification was 268.9 ± 250.9 cases (range, 0-705) per trainee. There were 82 (1.9%) cases of PCR reported among 4303 phacoemulsification. PCR occurred most commonly during quadrant removal (44.0%) and cortex removal (21.3%). The best-corrected visual acuity (in logMAR) improved significantly from 0.47 ± 0.32 preoperatively to 0.20 ± 0.19 postoperatively (p < 0.001). The supervising consultant took over 80.5% of the PCR cases. The PCR rate decreased significantly from 3.1% at 0-100 cases to 0.6% at 301-400 cases (p = 0.004) and to 0.4% at >500 cases (p = 0.005). Confidence in managing PCR (without supervision) improved from 0% (9/9) at junior level to 50% (3/6) at senior level, and the average number of anterior vitrectomies performed was 0.6 ± 0.9 (range: 0.0-2.0). CONCLUSIONS: We observed a low PCR rate among the trainees in our region, with the majority of cases achieving good visual outcome. A significant reduction in PCR rate was observed at the threshold of >500 cases. There is however a lack of confidence among trainees in managing PCR, highlighting the need for devising new training strategies in this area.