British Ophthalmological Surveillance Unit Research Articles

Incidence, mechanism and outcomes of schisis retinal detachments revealed through a prospective population-based study

AimTo determine the incidence, presentation and outcomes of progressive sight-threatening retinal detachment (RD) complicating degenerative retinoschisis.MethodsWe conducted the first prospective population-based epidemiological study of progressive schisis detachment over a 1-year...

Severe adverse events associated with local anaesthesia in cataract surgery: 1 year national survey of practice and complications in the UK

BackgroundRecent years have seen a major change in practice of local anaesthesia (LA) for cataract surgery.Aims(1) To estimate current usage of LA techniques for cataract surgery, (2) to estimate the...

Active surveillance of visual impairment due to adverse drug reactions: findings from a national study in the United Kingdom.

As visual impairment (VI) due to adverse drug reactions (ADR) is rare in adults and children, there is an incomplete evidence base to inform guidance for screening and for counseling patients on the potential risks of medications. We report on suspected drugs and the eye conditions found in a national study of incidence of diagnosis of visual impairment due to suspected ADR. Case ascertainment was via the British Ophthalmological Surveillance Unit (BOSU), between March 2010 and February 2012, with follow-up after 6 months. Case definition: any child or adult with bilateral or unilateral visual impairment due to a suspected ADR, using distance acuity worse than Snellen 6/18 (logMAR 0.48) in the better eye (bilateral) or affected eye (unilateral). Anonymized patient information on potential cases was provided by managing ophthalmologists, comprising visual status before and after suspected ADR, ophthalmic condition attributable to the ADR, preexisting eye disease and prescribed medications at the time of the ADR. Permanency and causality of the visual impairment were confirmed by the managing clinician, after 6 months, using the WHO Uppsala Monitoring Committee criteria. Over 2 years, 36 eligible cases were reported of whom 23 had permanent VI. While most cases were due to drugs known to have adverse side-effects, some were unanticipated sporadic cases. Visual impairment due to ADRs is rare. However, with for example, increasing polypharmacy in the elderly, monitoring of ocular ADRs, although challenging, is necessary.

Incidence of periorbital necrotising fasciitis in the UK population: a BOSU study

BackgroundPeriorbital necrotising fasciitis (PNF) is a devastating infection of subcutaneous soft tissue and underlying fascia causing severe morbidity and even loss of life. Few case reports of PNF exist and...

A prospective and nationwide study investigating endophthalmitis following pars plana vitrectomy: clinical presentation, microbiology, management and outcome

Background/AimsThis is the first prospective and nationwide study aiming to provide epidemiological data relating to presentation, microbiology, management and outcome of endophthalmitis following vitrectomy.MethodsTwo years of prospective and nationwide surveillance...

Visual Impairment Owing to Adverse Drug Reaction: Incidence and Routine Monitoring in the United Kingdom

Visual Impairment Owing to Adverse Drug Reaction: Incidence and Routine Monitoring in the United Kingdom

A prospective and nationwide study investigating endophthalmitis following pars plana vitrectomy: incidence and risk factors

Background/aimsThis is the first nationwide prospective study to investigate the incidence and risk factors of endophthalmitis following pars plana vitrectomy (PPV).MethodsThis was a prospective, nationwide case–control study. Cases of presumed...

Reply to Bhavsar et al

Sir, We would like to thank Bhavsar et al1 for their critical reading of our manuscript.2 They correctly highlight the need for a proper method of developing and validating questionnaires. In the reference they cite, the authors advocate that a questionnaire should be designed as part of a systematic, prospective case ascertainment system.3 We did exactly this as part of the British Ophthalmological Surveillance Unit (BOSU) framework. Both authors of the citation3 were also on the BOSU committee that reviewed our study before it commenced and personally critically appraised our questionnaire and overall methodology. The committee was also composed of a statistician and independent specialists in the field. We also piloted our questionnaire on one local case of endophthalmitis and several control cases to ensure its robustness. This method of data collection and reporting has been used in multiple BOSU studies in the literature (PubMed search term: ‘British Ophthalmological Surveillance Unit'), with all questions in our questionnaire framed in a similar manner. We appreciate the work done by Bhavsar and others to advocate not using topical antibiotics during intravitreal injections.4 Our study, which presents data on 47 cases of post-intravitreal anti-VEGF endophthalmitis (PIAE), is still one of the largest data sets in the literature with the primary aim of studying PIAE.2 Other studies, with the primary aim of studying the efficacy of anti-VEGF therapy, draw conclusions on the use of topical antibiotics based on statistical analysis of fewer overall injections and incident PIAE cases.4 We disagree with the comments regarding our case–control selection. As we performed a prospective, national surveillance study, we selected 10 control centres from across the country to avoid any regional or single centre bias. Individual control cases were selected randomly, again to avoid any bias. This was done in order to obtain control data that was as representative as possible of the national population receiving anti-VEGF therapy at that time. This method has been reported in the literature.5 As acknowledged, we discussed the reasoning for not including data on the use of povidone-iodine in our manuscript.2 It was in fact the BOSU committee who recommended that we did not include this in our questionnaire as part of the strict, independent, peer review process. We agree that povidone-iodine reduces the bacterial flora on the ocular surface, as does modification of many of the other risk factors that we identified in our study. The use of povidone-iodine is regularly used as part of standard practice throughout the United Kingdom. Therefore, to attempt to discredit the valuable risk factor data we report by suggesting that failure to administer povidone-iodine ‘may be' the underling risk factor in many of the cases is unlikely and not a fair comment on the BOSU process.

The incidence of serious eye injury in Scotland: a prospective study

Ocular trauma remains an important cause of visual morbidity worldwide. A previous population-based study in Scotland reported a 1-year cumulative incidence of 8.14 per 100 000 population. The purpose of this study was to identify any change in the incidence and pattern of serious ocular trauma in Scotland. This study was a 1-year prospective observational study using the British Ophthalmological Surveillance Unit reporting scheme among Scottish ophthalmologists. Serious ocular trauma was defined as requiring hospital admission. Data were collected using two questionnaires for each patient 1 year apart. The response rate from ophthalmologists was 77.1%. There were 102 patients reported with complete data giving an incidence of 1.96 per 100 000 population, four times less than in 1992. In patients younger than 65 years, the age-adjusted incidence ratio (males/females) indicated a ninefold higher risk of trauma in males. In 25 patients (27.2%), the injured eye was blind (final visual acuities (FVA) <6/60), 24 being attributable to the eye injury. Standardised morbidity ratios suggested a threefold decrease in risk of poor visual outcome in 2009 compared with 1992. The incidence of serious ocular trauma has fallen; this study has shown hospital admission for serious eye injury in Scotland has decreased fourfold in 17 years. Young adult males continue to be at highest risk, which needs to be specifically addressed in future health-prevention strategies. This study also observed a reduction in visual loss from serious ocular injuries, although the reasons for this require further exploration.

The Incidence of Blindness Due to Idiopathic Intracranial Hypertension in the UK

Purpose:To determine the incidence of blindness secondary to idiopathic intracranial hypertension (IIH) in the United Kingdom.Methods:New cases of blindness occurring secondary to IIH were identified prospectively through the British Ophthalmological Surveillance Unit (BOSU) from October 2005 to November 2006. Only idiopathic cases of intracranial hypertension and those meeting the World Health Organisation`s definition of blindness were included. Cases that were already blind or had already been blind registered before the study period were excluded.Results:There were 24 new cases of registerable blindness secondary to IIH reported during the 12 month period. Questionnaires were completed for 19 cases. Of these 19 cases, 3 were not truly idiopathic and 3 cases did not fulfil the strict criteria for blindness. One case was a duplicate report. There were 12 definite cases of blindness secondary to IIH giving a UK incidence of blindness secondary to IIH of 0.6-2% (assuming a UK population of 63.2 million and an incidence of IIH of 1-3/100,000). If the 5 cases reported as blind but without a completed questionnaire are assumed to be true cases then the incidence of blindness would be 1-3%.Conclusions:The results of this study suggest that approximately 1-2% of new cases of IIH are likely to become blind in a given year. This contrasts with rates of between 4-10% reported previously in hospital-based studies, but may be a more accurate figure for the population as a whole. Under-ascertainment and improving standards of care may also have contributed to the lower figure than previously reported.

Reply to Alexander et al (Subconjunctival anaesthesia for intravitreal injections)

Sir, We would like to thank Alexander et al1 for their interest in our study. We reported the incidence, features and outcomes of post-intravitreal anti-VEGF endophthalmitis (PIAE) in a prospective, population-based study to provide ophthalmologists with important clinical information. We also performed a case–control study to identify risk factors, as this is recognised as a valid methodology to identify possible risk factors for rare conditions.2 Our conclusions regarding the use of subconjunctival anaesthesia are based on the analysis of 3 out of 47 PIAE cases compared with 1 out of 200 control cases receiving this anaesthesia.3 Although this study reports one of the largest known series of PIAE, due to the relatively small number of patients with individual risk factors, it was not possible to fit our results to a multivariate model (as acknowledged in our paper). However, of these four patients, other than all four not receiving pre-procedural antibiotics, none were reported to have any of the other potential risk factors. After excluding these four patients, the other risk factors (failure to administer topical antibiotics immediately post-injection, blepharitis, patient squeezing, and failure to administer pre-procedural topical antibiotics) had no significant change in respective odds ratios (ORs). Therefore, it would be difficult to attribute the large OR of 13.669 for subconjunctival anaesthesia to confounding risk factors alone. We hypothesised that a possible explanation for subconjunctival anaesthesia as a risk factor was that it compromised the conjunctival surface before intravitreal injection, allowing the introduction of pathogens into the subconjunctival space. We read with interest your experience in Southampton. The incidence rate of 0.07% that you report is comparable to our reported rate of 0.025%. However, by only reporting the incidence rate at a single centre, it is unclear whether any of the other risk factors that we analysed in our paper have been controlled for. Therefore, it is not possible to make any further conclusions on whether the use of subconjunctival anaesthesia is a risk factor for PIAE based on the data you supply. One cannot ascertain the effect that individual risk factors will have on the incidence rate of PIAE based on the odds ratio calculated as part of the case control study that we performed. Owing to the anonymous way the information is collected through the British Ophthalmological Surveillance Unit, we were unable to ascertain whether subconjunctival anaesthesia was the standard of care at the reporting institutions. Further evidence of risk factors for PIAE is always welcome. Comparing the figures from your centre to others, where subconjunctival anaesthesia is not used, in a matched, case–control study may provide firmer evidence as to whether subconjunctival anaesthesia is a significant risk factor.

Observational prospective cohort study of patients with newly-diagnosed ocular sebaceous carcinoma

PurposeTo investigate the epidemiology and clinicopathological management for ocular sebaceous carcinoma (OSC) in the UK.MethodsObservational prospective cohort study of patients with newly-diagnosed OSC. The British Ophthalmological Surveillance Unit captured incident...

Post-intravitreal anti-VEGF endophthalmitis in the United Kingdom: incidence, features, risk factors, and outcomes

To describe the incidence, features, management, and risk factors of post-intravitreal anti-VEGF endophthalmitis (PIAE) in patients undergoing treatment for exudative age-related macular degeneration in the United Kingdom. Prospective observational case control study. Forty-seven cases of PIAE were identified through the British Ophthalmological Surveillance Unit from January 2009 to March 2010. Data collected at diagnosis and at 6 months follow-up included patient demographics, intravitreal injection details, pre- and post-injection management, visual acuity, clinical features and management of PIAE, causative organisms, and clinical outcomes. Details were compared with 200 control cases from 10 control centres to identify potential risk factors. Estimated PIAE was 0.025%. Culture-positive PIAE incidence was 0.015%. Mean age of presentation was 78 years. Mean number of intravitreal injections before PIAE was 5. Mean days to presentation was 5 (range 1-39). Positive microbiology culture was found in 59.6%. The majority of causative organisms were Gram positive (92.8%). Significant risk factors were failure to administer topical antibiotics immediately after the injection (P=0.001), blepharitis (P=0.006), subconjunctival anaesthesia (P=0.021), patient squeezing during the injection (P=0.021), and failure to administer topical antibiotics before anti-VEGF injection (P=0.05). The incidence of PIAE in the United Kingdom is comparable to other studies at a rate of 0.025%. The most common causative organisms were Gram positive. Measures to minimise the risk of PIAE include treatment of blepharitis before injection, avoidance of subconjunctival anaesthesia, topical antibiotic administration immediately after injection with consideration to administering topical antibiotics before injection.

Incidence, presenting features, and diagnosis of cicatrising conjunctivitis in the United Kingdom.

PurposeCicatrising conjunctival disorders are uncommon, and are difficult to diagnose and manage. This study was designed to assess the annual incidence and underlying diagnosis of patients with cicatrising conjunctivitis (CC) within the United Kingdom.MethodsClinical data of newly diagnosed cases of CC were reported via the British Ophthalmological Surveillance Unit at diagnosis and at 12 months follow-up.ResultsA total of 50 (61%) ocular mucous membrane pemphigoid (OcMMP), 16 (20%) Stevens–Johnson syndrome/toxic epidermal necrolysis (SJS-TEN) and 16 (20%) other causes of CC, equating to an incidence of 0.8, 0.2, and 0.2 per million, respectively, were reported. Although diagnosis of SJS-TEN was usually within a median of 7 days of symptom-onset, that for OcMMP and other CC was a median 225 days for both. At diagnosis, 64/163 (39%) eyes had moderate/severe conjunctival inflammation, and 102/164 (62%) had symblepharon formation. Although 43/82 (52%) patients were commenced on immunosuppression or had this therapy modified, at follow-up there was an increase in the number of symblepharon, despite control of inflammation (P<0.001). Mortality only occurred in the SJS-TEN group (4/16 (25%)).ConclusionCC has a substantial morbidity and for non-SJS-TEN causes, diagnosis is frequently delayed. The proportion of patients given immunosuppressive therapy to prevent disease progression may be less than optimal. These data highlight the need for developing patient access to specialist-designated centres with expertise in CC.

Acute retinal necrosis in the United Kingdom: results of a prospective surveillance study

To determine the incidence of acute retinal necrosis (ARN) in the United Kingdom and to describe the demographics, management, and visual outcome in these patients. This was a prospective study carried out by the British Ophthalmological Surveillance Unit (BOSU) between September 2007 and October 2008. Initial and 6-month questionnaires were sent to UK ophthalmologists who reported cases of ARN via the monthly BOSU report card system. In all, 45 confirmed cases (52 eyes) of ARN were reported in the 14-month study period, giving a minimum incidence of 0.63 cases per million population per year. There were 20 females and 25 males. Age ranged from 10 to 94 years. Eight patients had a history of herpetic CNS disease. Aqueous sampling was carried out in 13 patients, vitreous in 27, and cerebrospinal fluid (CSF) in 4. Varicella-zoster virus followed by herpes simplex were the most common causative agents. Treatment in 76% of the cases was with intravenous antivirals; however, 24% received only oral antivirals. In all, 47% of patients had intravitreal antiviral therapy. Visual outcome at 6 months was <6/60 in 48% of the affected eyes. The minimum incidence of ARN in the UK is 0.63 cases per million. Patients with a history of herpetic CNS disease should be warned to immediately report any visual symptoms. There is increased use of oral and intravitreal antivirals in initial treatment.

A population-based study of Coats disease in the United Kingdom I: epidemiology and clinical features at diagnosis

coats disease is an uncommon form of retinal telangiectasis. Published case series mostly originate from tertiary referrals centres and may provide a skewed view of disease severity. We conducted a prospective population-based study of Coats disease in the United Kingdom to ascertain the incidence and provide a more representative picture. the study was conducted through the British Ophthalmological Surveillance Unit. This first paper reports the features at presentation; gender, mode of presentation, visual acuity, anterior and posterior segment findings, amount of retinal exudation, and disease staging. a total of 55 eligible cases of Coats disease were identified giving an estimated population incidence of 0.09 per 100.000 of the population. All cases were unilateral and 85% were male. Mean age at presentation was 146 months (median 96 months). The mean age of diagnosis was markedly different with differing mechanisms of presentation. Cases presenting with leucocoria or strabismus presented early whereas subjective visual loss presented much later. A large proportion of eyes (44%) were blind at diagnosis. The great majority of eyes (71%) had 6 or fewer clock hours of retinal exudation. More severe forms/stages of Coats disease were more common in the youngest patients. compared with published studies of Coats disease, we have found milder disease severity at presentation. This is most likely because of the population-based nature of our study reflecting the full disease spectrum. A large proportion of eyes with Coats have poor visual acuity and disease severity is worse in younger patients.

Surveillance of severe chemical corneal injuries in the UK

Aim:To estimate the incidence of severe chemical corneal injuries in the UK and describe presenting clinical features and initial management.Methods:All patients with severe chemical corneal injury in the UK from...

Displacement of nuclear fragments into the vitreous complicating phacoemulsification surgery in the UK: incidence and risk factors

Aims:To study the epidemiology and risk factors contributing to displacement of nuclear fragments into the vitreous (DNFV) complicating phacoemulsification in the UK.Methods:Cases were collected prospectively between March 2003 and March...

Displacement of nuclear fragments into the vitreous complicating phacoemulsification surgery in the UK: clinical features, outcomes and management

Aims:To study the clinical features, management and outcomes of displacement of nuclear fragments into the vitreous (DNFV) complicating phacoemulsification in the UK.Methods:Cases were collected prospectively between March 2003 and March...

Purtscher’s retinopathy: epidemiology, clinical features and outcome

Aims:To study the incidence, systemic associations, presenting features and natural history of Purtscher’s retinopathy in the UK and Ireland.Methods:Cases were collected prospectively by active surveillance through the British Ophthalmological Surveillance...