David J Keegan

Risk factors and biomarkers of age-related macular degeneration

A biomarker can be a substance or structure measured in body parts, fluids or products that can affect or predict disease incidence. As age-related macular degeneration (AMD) is the leading cause of blindness in the developed world, much research and effort has been invested in the identification of different biomarkers to predict disease incidence, identify at risk individuals, elucidate causative pathophysiological etiologies, guide screening, monitoring and treatment parameters, and predict disease outcomes. To date, a host of genetic, environmental, proteomic, and cellular targets have been identified as both risk factors and potential biomarkers for AMD. Despite this, their use has been confined to research settings and has not yet crossed into the clinical arena. A greater understanding of these factors and their use as potential biomarkers for AMD can guide future research and clinical practice. This article will discuss known risk factors and novel, potential biomarkers of AMD in addition to their application in both academic and clinical settings.

Maintenance of perioperative antiplatelet and anticoagulant therapy for vitreoretinal surgery

The objective of this study was to prospectively assess the risk of bleeding from vitreoretinal surgery in a continuous unbiased cohort of patients taking unsuspended antiplatelet or anticoagulant therapy.Background The objective of this study was to prospectively assess the risk of bleeding from vitreoretinal surgery in a continuous unbiased cohort of patients taking unsuspended antiplatelet or anticoagulant therapy. Design Prospective hospital-based study. Participants Eighty-five patients taking unsuspended aspirin, clopidogrel and/or warfarin therapy undergoing all forms of vitreoretinal surgery at The Mater Misericordiae University and The Mater Private Hospital, Dublin, Ireland. Methods Consecutive patients undergoing vitreoretinal surgery taking unsuspended antiplatelet or anticoagulant therapy over a 1-year period were included in this prospective study to evaluate the intraoperative and postoperative bleeding complications. Main Outcome Measures The intraoperative and postoperative bleeding rates. Results One hundred and seven vitreoretinal procedures were performed on 85 patients taking unsuspended antiplatelet or anticoagulant therapy. The intraoperative bleeding rate was 23%, the majority of which consisted of mild bleeding into the vitreous cavity during vitrectomy. The postoperative bleeding rate was 22%, consisting of 3.7% anterior chamber haemorrhage, 11% dispersed vitreous cavity haemorrhage, 4.7% dense vitreous cavity haemorrhage, 0.9% subretinal haemorrhage and 1.9% localized choroidal haemorrhage. The single greatest significant independent predictor of intraoperative bleeding was proliferative diabetic retinopathy and of postoperative bleeding was the presence of diabetes mellitus. Conclusions There were no cases of uncontrolled intraoperative haemorrhage or serious postoperative choroidal haemorrhage. Mild haemorrhagic oozing during vitrectomy and dispersed vitreous cavity haemorrhage postoperatively were common. For the majority of patients taking antiplatelet or anticoagulant medication, these agents can be safely continued in the vitreoretinal surgical perioperative period.

Preparation of Pre-Confluent Retinal Cells Increases Graft Viability In Vitro and In Vivo: A Mouse Model

Purpose Graft failure remains an obstacle to experimental subretinal cell transplantation. A key step is preparing a viable graft, as high levels of necrosis and apoptosis increase the risk of graft failure. Retinal grafts are commonly harvested from cell cultures. We termed the graft preparation procedure “transplant conditions” (TC). We hypothesized that culture conditions influenced graft viability, and investigated whether viability decreased following TC using a mouse retinal pigment epithelial (RPE) cell line, DH01. Methods Cell viability was assessed by trypan blue exclusion. Levels of apoptosis and necrosis in vitro were determined by flow cytometry for annexin V and propidium iodide and Western blot analysis for the pro- and cleaved forms of caspases 3 and 7. Graft viability in vivo was established by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and cleaved caspase 3 immunolabeling of subretinal allografts. Results Pre-confluent cultures had significantly less nonviable cells than post-confluent cultures (6.6%±0.8% vs. 13.1%±0.9%, p<0.01). Cell viability in either group was not altered significantly following TC. Caspases 3 and 7 were not altered by levels of confluence or following TC. Pre-confluent cultures had low levels of apoptosis/necrosis (5.6%±1.1%) that did not increase following TC (4.8%±0.5%). However, culturing beyond confluence led to progressively increasing levels of apoptosis and necrosis (up to 16.5%±0.9%). Allografts prepared from post-confluent cultures had significantly more TUNEL-positive cells 3 hours post-operatively than grafts of pre-confluent cells (12.7%±3.1% vs. 4.5%±1.4%, p<0.001). Subretinal grafts of post-confluent cells also had significantly higher rates of cleaved caspase 3 than pre-confluent grafts (20.2%±4.3% vs. 7.8%±1.8%, p<0.001). Conclusion Pre-confluent cells should be used to maximize graft cell viability.

Management of ganciclovir-resistant cytomegalovirus retinitis in HIV infection in the era of antiretroviral therapy.

The incidence of cytomegalovirus retinitis has decreased significantly since the advent of antiretroviral therapy. However, it remains an important problem in both the developed and developing worlds. Furthermore, long-term antiviral suppression is associated with a significant increase in viral resistance. We present the case of a 46-year-old man who developed cytomegalovirus retinitis one year after being diagnosed with HIV. While he initially demonstrated an excellent clinical response to ganciclovir, his cytomegalovirus viral load remained persistently elevated. Over the subsequent years, his virus developed ganciclovir resistance with a concomitant deterioration in his visual acuity. He responded poorly to salvage therapy with foscarnet and cidofovir. This case highlights the ongoing difficulty of managing cytomegalovirus disease nearly two decades into the era of antiretroviral therapy and underlines the need to develop new treatment strategies.

Early Subretinal Allograft Rejection is Characterized by Innate Immune Activity

Successful subretinal transplantation is limited by considerable early graft loss despite pharmacological suppression of adaptive immunity. We postulated that early innate immune activity is a dominant factor in determining graft survival and chose a nonimmunosuppressed mouse model of retinal pigment epithelial (RPE) cell transplantation to explore this. Expression of almost all measured cytokines by DH01 RPE cells increased significantly following graft preparation, and the neutrophil chemoattractant KC/GRO/CINC was most significantly increased. Subretinal allografts of DH01 cells (C57BL/10 origin) into healthy, non immunosuppressed C57BL/6 murine eyes were harvested and fixed at 1, 3, 7, and 28 days postoperatively and subsequently cryosectioned and stained. Graft cells were detected using SV40 large T antigen (SV40T) immunolabeling and apoptosis/necrosis by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL). Sections were also immunolabeled for macrophage (CD11b and F4/80), neutrophil (Gr1 Ly-6G), and T-lymphocyte (CD3-∊) infiltration. Images captured with an Olympus FV1000 confocal microscope were analyzed using the Imaris software. The proportion of the subretinal bolus comprising graft cells (SV40T+) was significantly (p < 0.001) reduced between postoperative day (POD) 3 (90 ± 4%) and POD 7 (20 ± 7%). CD11b+, F4/80+, and Gr1 Ly-6G+ cells increased significantly (p < 0.05) from POD 1 and predominated over SV40T+ cells by POD 7. Colabeling confocal microscopic analysis demonstrated graft engulfment by neutrophils and macrophages at POD 7, and reconstruction of z-stacked confocal images confirmed SV40T inside Gr1 Ly-6G+ cells. Expression of CD3-∊ was low and did not differ significantly between time points. By POD 28, no graft cells were detectable and few inflammatory cells remained. These studies reveal, for the first time, a critical role for innate immune mechanisms early in subretinal graft rejection. The future success of subretinal transplantation will require more emphasis on techniques to limit innate immune-mediated graft loss, rather than focusing exclusively on suppression of the adaptive immune response.

Ocular presentation of natural killer/T-cell lymphoma in a Caucasian man.

Natural killer/T-cell (NK/T-cell) lymphoma—nasal subtype, is a rare form of non-Hodgkins lymphoma, most common in South East Asia, and can have an ophthalmological presentation. This report describes a 51-year-old Caucasian man with uveitis, recurrent retinal detachment and paraneoplastic features subsequently diagnosed as NK/T-cell lymphoma.