Biomedical subjects

B C Reeves

Publications and source records attributed to B C Reeves.

At least 19 recordsLinked to original sources

PubMed2006

Continuous monitoring of the performance of hip prostheses.

New brands of joint prosthesis are released for general implantation with limited evidence of their long-term performance in patients. The CUSUM continuous monitoring method is a statistical testing procedure which could be used to provide prospective evaluation of brands as soon as implantation in patients begins and give early warning of poor performance. We describe the CUSUM and illustrate the potential value of this monitoring tool by applying it retrospectively to the 3M Capital Hip experience. The results show that if the clinical data and methodology had been available, the CUSUM would have given an alert to the underperformance of this prosthesis almost four years before the issue of a Hazard Notice by the Medical Devices Agency. This indicates that the CUSUM can be a valuable tool in monitoring joint prostheses, subject to timely and complete collection of data. Regional or national joint registries provide an opportunity for future centralised, continuous monitoring of all hip and knee prostheses using these techniques.

Adult↗

PubMed2005

Systematic reviews incorporating evidence from nonrandomized study designs: reasons for caution when estimating health effects.

Systematic reviews that include nonrandomized studies (NRS) face a number of logistical challenges. However, the greatest threat to the validity of such reviews arises from the differing susceptibility of randomized controlled trials (RCTs) and NRS to selection bias. Groups compared in NRS are unlikely to be balanced because of the reasons leading study participants to adopt different health behaviours or to be treated differentially. Researchers can try to minimize the susceptibility of NRS to selection bias both at the design stage, for example, by matching participants on key prognostic factors, and during data analysis, for example, by regression modelling. However, because of logistical difficulties in matching, imperfect knowledge about the relationships between prognostic factors and between prognostic factors and outcome, and measurement limitations, it is inevitable that estimates of effect size derived from NRS will be confounded to some extent. Researchers, reviewers and users of evidence alike need to be aware of the consequences of residual confounding. In poor quality RCTs, selection bias tends to favour the new treatment being evaluated. Selection bias need not necessarily lead to systematic bias in favour of one treatment but, even if it acts in an unpredictable way, it will still give rise to additional, nonstatistical uncertainty bias around the estimate of effect size. Systematic reviews of NRS studies run the risk of compounding these biases. Nutritional choices and uptake of health education about nutrition are very likely to be associated with potential confounding factors. Therefore, pooled estimates of the effects of nutritional exposures and their confidence intervals are likely to be misleading; reviewers need to take into account both systematic and uncertainty bias.

Bias↗

PubMed2005

Evidence about evidence.

Explore the source record for details and available documents.

Diagnostic Techniques, Ophthalmological↗

PubMed2005

A population based survey of the prevalence and types of glaucoma in rural West Bengal: the West Bengal Glaucoma Study.

AIM: To determine (i) the prevalence of glaucoma in people aged > or =50 years, (ii) the proportions of different types of glaucoma, (iii) the distributions of intraocular pressure and vertical cup disc ratio. METHOD: Population based prevalence survey in rural West Bengal. People aged > or =50 years in randomly selected villages in 24 Parganas South district. The main outcome measures were diagnosis of glaucoma, based on criteria described by the International Society for Geographic and Epidemiological Ophthalmology. RESULTS: 1594 people aged > or =50 years were enumerated in nine villages; 1324 (83.1%) were surveyed and 1269 people adequately examined. 42 definite cases of glaucoma were identified, with prevalence increasing from 2.7% (95% CI 1.7 to 3.7) in people aged 50-59 years to 6.5% (95% CI 0.0 to 14.1) in those aged > or =80 years. The age standardised estimate for the prevalence of all glaucoma in people aged > or =50 years was 3.4%. Only three cases of primary angle closure glaucoma (PACG) were identified, giving a crude ratio of primary open angle glaucoma (POAG) to PACG of more than 10:1. Three people with glaucoma were blind in one eye but none was blind in both eyes. CONCLUSION: Compared to other surveys of glaucoma in India, the age standardised prevalence observed was less than in Hyderabad, but similar to Tamil Nadu and Dhaka. The ratio of POAG to PACG was much higher than found previously, suggesting that PACG may be less prevalent in Bengalis than in Indian populations living in south India. The authors conclude that ophthalmic services in West Bengal should focus on detecting POAG. Since there is still no satisfactory method of screening for POAG, there is no alternative to case detection (opportunistic screening) in eye clinics.

Age Distribution↗

PubMed2004

Surgical wound infection as a performance indicator: agreement of common definitions of wound infection in 4773 patients.

OBJECTIVE: To assess the level of agreement between common definitions of wound infection that might be used as performance indicators. DESIGN: Prospective observational study. SETTING: London teaching hospital group receiving emergency cases as well as tertiary referrals. PARTICIPANTS: 4773 surgical patients staying in hospital at least two nights. MAIN OUTCOME MEASURES: Numbers of wound infections based on purulent discharge alone, on the Centers for Disease Control (CDC) definition of wound infection, on the nosocomial infection national surveillance scheme (NINSS) version of the CDC definition, and on the ASEPSIS scoring method. RESULTS: 5804 surgical wounds were assessed during 5028 separate hospital admissions. The mean percentage of wounds classified as infected differed substantially with different definitions: 19.2% with the CDC definition (95% confidence interval 18.1% to 20.4%), 14.6% (13.6% to 15.6%) with the NINSS version, 12.3% (11.4% to 13.2%) with pus alone, and 6.8% (6.1% to 7.5%) with an ASEPSIS score > 20. The agreement between definitions with respect to individual wounds was poor. Wounds with pus were automatically defined as infected with the CDC, NINSS, and pus alone definitions, but only 39% (283/714) of these had ASEPSIS scores > 20. CONCLUSIONS: Small changes made to the CDC definition or even in its interpretation, as with the NINSS version, caused major variation in estimated percentage of wound infection. Substantial numbers of wounds were differently classified across the grades of infection. A single definition used consistently can show changes in percentage wound infection over time at a single centre, but differences in interpretation prevent comparison between different centres.

Adult↗

PubMed2004

Use of once-daily netilmicin to treat infants with suspected sepsis in a neonatal intensive care unit.

Once-daily administration of aminoglycoside antibiotics has become the most acceptable dosing schedule for the majority of patients. There are few published data on the impact of post-natal age on aminoglycoside concentrations in preterm infants receiving once-daily dosage regimens. Netilmicin was administered as a once-daily dose of 4 mg/kg. In 141 episodes of suspected sepsis in 123 babies, trough netilmicin concentrations ranged from undetectable to 4.0 mg/l. Netilmicin concentrations were above a level of 2 mg/l in 10.6% of episodes. Netilmicin concentrations decreased with increasing post-natal age and weight. Levels were higher in males compared to females. Increased creatinine concentrations were associated with higher netilmicin concentrations. This study emphasises the importance of post-natal age as a determinant of aminoglycoside concentrations with a once-daily dosing regimen in a neonatal intensive care population. Trough levels should be carefully monitored and consideration given to extending dosage intervals particularly when netilmicin is administered once daily to preterm infants in the first week of life.

Aging↗

PubMed2004

A comparison of Rasch with Likert scoring to discriminate between patients' evaluations of total hip replacement surgery.

The purpose of this study was to examine whether there are advantages in terms of outcome assessment of using Rasch methods of scoring the 12-item Oxford Hip Score (OHS) questionnaire over conventionally Likert scores. As part of a prospective cohort study of total hip replacements in five former regions of England the OHS was sent to patients pre-operatively, at 3 months and 1 year post-operatively. Post-operative data was collected on over 5000 cases. Based on the level of satisfaction with surgery, patients were divided into satisfied and dissatisfied. Analyses were performed to test the relative precision (RP) of Rasch scoring vs. conventionally Likert scores in discriminating the groups experiencing different level of satisfaction. Considerable gains in precision were achieved with Rasch scoring methods when groups were compared 3 and 12 months post-operatively. The results from the current study suggest that in some situations there may be substantial gains in measuring health related outcomes using Rasch-based scoring methods.

Activities of Daily Living↗

PubMed2004

A comparison of anterior and posterior chamber lenses after cataract extraction in rural Africa: a within patient randomised trial.

BACKGROUND: Extracapsular cataract extraction (ECCE) with a posterior chamber intraocular lens (PC IOL) is the preferred method of cataract surgery in developed countries. However, intracapsular cataract extraction (ICCE) with an anterior chamber lens (AC IOL) may be appropriate in rural Africa. A randomised controlled trial was carried out to compare these surgical strategies. METHODS: Participants over 50 years requiring bilateral cataract surgery were recruited from outreach clinics in rural north and east Uganda. One eye was randomly allocated to AC IOL or PC IOL, the other eye being allocated to the second strategy. The main outcome measure was WHO distance visual acuity (VA) category after a minimum of 1 year. Secondary outcomes were numbers and causes of complications and refractive corrections. RESULTS: Of the 110 participants recruited, 98 (89%) were assessed at least 1 year after the operation (median follow up 17.5 months). Nine eyes randomised to PC IOL were converted to AC IOL; one eye randomised to AC IOL inadvertently received PC IOL. There was no difference in VA between 95 pairs of eyes for which data for both eyes were available (uncorrected VA, p = 0.26; corrected VA, p = 0.59). 80 (82%, 95% CI 73 to 89) and 82 (84%, 95% CI 75 to 90) eyes randomised to AC IOL and PC IOL respectively had corrected VA of 6/18 or better. 16 (16%, 95% CI 10 to 25) and eight (8%, 95% CI 4 to 15) eyes respectively had secondary procedures or other complications. CONCLUSIONS: Where both strategies are available, ECCE with PC IOL should be first choice because of fewer complications. Where ECCE with PC IOL is not immediately feasible, ICCE with AC IOL is an acceptable interim technique.

Aged↗

PubMed2004

Enhanced low vision rehabilitation for people with age related macular degeneration: a randomised controlled trial.

AIM: To compare the effectiveness of three models of low vision rehabilitation for people with age related macular degeneration (AMD) referred for low vision rehabilitation (LVR): (a) an enhanced low vision rehabilitation model (ELVR) including supplementary home based low vision rehabilitation; (b) conventional low vision rehabilitation (CLVR) based in a hospital clinic; (c) CLVR with home visits that did not include rehabilitation (CELVR), intended to act as a control for the additional contact time with ELVR. METHOD: A single centre parallel group randomised controlled trial in participants' homes and the low vision clinic, Manchester Royal Eye Hospital. People referred for LVR with a primary diagnosis of AMD and visual acuity worse than 6/18 in both eyes and equal to or better than 1/60 in the better eye. The main outcome measures were vision specific quality of life (QoL) (primary outcome, VCM1) and generic health related QoL (SF-36); psychological adjustment to vision loss; measured task performance; restriction in everyday activities; use of low vision aids (LVAs). RESULTS: 226 participants were recruited (median age 82 years); 194 completed the trial (86%). Except for SF-36 physical and mental component summary scores, arms did not differ significantly for any of the outcomes. Differences for the VCM1 were ELVR v CLVR, 0.06 (95% CI to 0.17 to 0.30, p = 0.60); ELVR v CELVR, 0.12 (95% CI to 0.11 to 0.34, p = 0.31); CELVR v CLVR, -0.05 (95% CI -0.29 to 0.18, p = 0.64). Differences for the SF-36 favoured CLVR compared to ELVR (ELVR v CLVR: physical = -6.05, 95% CI -10.2 to -1.91, p = 0.004; mental = -4.04, 95% CI -7.44 to -0.65, p = 0.02). At 12 months, 94% of participants reported using at least one LVA. CONCLUSION: ELVR was no more effective than CLVR. Researchers should be wary of proposing new LVR interventions without preliminary evidence of effectiveness, given the manifest lack of effectiveness of the model of enhanced LVR evaluated in the trial.

Activities of Daily Living↗

PubMed2004

A framework for classifying study designs to evaluate health care interventions.

Researchers who are trained in epidemiology recognise and use the standard range of designs, i. e. retrospective and prospective cohort studies and case control studies, for studying aetiological questions. The application of study designs to health care interventions is more complex. Researchers may modify familiar designs, in response to specific problems posed by the interventions being evaluated, and an unambiguous nomenclature has not been established. Also, researchers who set out to evaluate interventions are not always trained in epidemiology and often use familiar study design labels in an ambiguous or inappropriate manner. The susceptibility to bias of different study designs is a critical consideration for users of research evidence. Sources of bias are the same for all studies, i. e. selection, performance, detection and attrition bias, but the susceptibility of studies is likely to vary depending on their design. Evidence of associations between features of study designs, specific biases and their consistent influence on effect estimates is lacking. A framework for classifying study design will be proposed, based on key features of study designs, i. e. what researchers actually did. This framework may (a) help to reduce the ambiguity about study design labels, and uncertainty about how a study was actually carried out, and (b) help methodological researchers to gather evidence about associations between different study design features and susceptibility to bias.

Bias↗

PubMed2004

Reasons for caution when evaluating health care interventions using non-randomised study designs.

The key difference between randomised (RCTs) and non-randomised studies (NRS) is their susceptibility to selection bias. Unlike RCTs, groups in non-randomised cohort studies are unlikely to be balanced because of the reasons leading patients to receive one or another treatment, giving rise to "confounding by clinical indication" (CCI). Researchers can try to minimise the susceptibility of NRS to selection bias both at the design stage, e. g. by matching participants on key prognostic factors, and during data analysis, e. g. by regression modeling. Nevertheless, because of i) logistical difficulties in matching, ii) imperfect knowledge about the relationships between prognostic factors and between prognostic factors and outcome, and iii) because of measurement limitations, it is inevitable that estimates of effect size derived from NRS will be confounded to some extent. Researchers and users of evidence alike need to be aware of the consequences of residual confounding. CCI need not necessarily lead to systematic bias in favour of one treatment but, if CCI acts in an unpredictable way, it will still give rise to additional, non-statistical "uncertainty bias" around the estimate of effect size.

Bias↗

PubMed2004

Guidelines for reporting non-randomised studies.

Non-randomised studies (NRSs) are useful because they allow interventions to be evaluated that are difficult to investigate by randomised controlled trials (RCTs). However, NRSs are more susceptible to bias. The Consolidated Standards of Reporting Trials (CONSORT) statement was established to ensure that researchers report features of RCTs that must be considered when appraising their quality. CONSORT has improved the reporting of key information, highlighting missing key information for users. Researchers have a responsibility to report essential information that allows users to assess the susceptibility of NRS to selection, performance, detection and attrition bias. This paper considers criteria for reporting cohort studies: the rationale behind the CONSORT criteria for reporting of RCTs will be applied to cohort studies. Many of the criteria need no modification but application of others raise difficult issues for cohort studies, e.g.: description and standardisation of control and intervention treatments; description of the method of allocation; choice of prognostic factors to be collected; distinguishing between intended and provided treatments; collection of data on adverse and longterm outcomes; establishing a priori plans for analysis.

Bias↗

PubMed2004

A multi-centre randomised controlled trial of minimally invasive direct coronary bypass grafting versus percutaneous transluminal coronary angioplasty with stenting for proximal stenosis of the left anterior descending coronary artery.

OBJECTIVES: To compare the clinical- and cost-effectiveness of minimally invasive direct coronary artery bypass grafting (MIDCAB) and percutaneous transluminal coronary angioplasty (PTCA) with or without stenting in patients with single-vessel disease of the left anterior descending coronary artery (LAD). DESIGN: Multi-centre randomised trial without blinding. The computer-generated sequence of randomised assignments was stratified by centre, allocated participants in blocks and was concealed using a centralised telephone facility. SETTING: Four tertiary cardiothoracic surgery centres in England. PARTICIPANTS: Patients with ischaemic heart disease with at least 50% proximal stenosis of the LAD, suitable for either PTCA or MIDCAB, and with no significant disease in another vessel. INTERVENTIONS: Patients randomised to PTCA had local anaesthetic and underwent PTCA according to the method preferred by the operator carrying out the procedure. Patients randomised to MIDCAB had general anaesthetic. The chest was opened through an 8-10-cm left anterior thoracotomy. The ribs were retracted and the left internal thoracic artery (LITA) harvested. The pericardium was opened in the line of the LAD to confirm the feasibility of operation. The distal LITA was anastomosed end-to-side to an arteriotomy in the LAD. All operators were experienced in carrying out MIDCAB. MAIN OUTCOME MEASURES: The primary outcome measure was survival free from cardiac-related events. Relevant events were death, myocardial infarction, repeat coronary revascularisation and recurrence of symptomatic angina or clinical signs of ischaemia during an exercise tolerance test at annual follow-up. Secondary outcome measures were complications, functional outcome, disease-specific and generic quality of life, health and social services resource use and their costs. RESULTS: A total of 12,828 consecutive patients undergoing an angiogram were logged at participating centres from November 1999 to December 2001. Of the 1091 patients with proximal stenosis of the LAD, 127 were eligible and consented to take part; 100 were randomised and the remaining 27 consented to follow-up. All randomised participants were included in an intention-to-treat analysis of survival free from cardiac-related events, which found a non-significant benefit from MIDCAB. Cumulative hazard rates at 12 months were estimated to be 7.1 and 9.2% for MIDCAB and PTCA, respectively. There were no important differences between MIDCAB and PTCA with respect to angina symptoms or disease-specific or generic quality of life. The total NHS procedure costs were 1648 British pounds and 946 British pounds for MIDCAB and PTCA, respectively. The costs of resources used during 1 year of follow-up were 1033 British pounds and 843 British pounds, respectively. CONCLUSIONS: The study found no evidence that MIDCAB was more effective than PTCA. The procedure costs of MIDCAB were observed to be considerably higher than those of PTCA. Given these findings, it is unlikely that MIDCAB represents a cost-effective use of resources in the reference population. Recent advances in cardiac surgery mean that surgeons now tend to carry out off-pump bypass grafting via a sternotomy instead of MIDCAB. At the same time, cardiologists are treating more patients with multi-vessel disease by PTCA. Future primary research should focus on this comparison. Other small trials of PTCA versus MIDCAB have now finished and a more conclusive answer to the original objective could be provided by a systematic review.

Aged↗

PubMed2003

Incidence of visual loss in rural southwest Uganda.

BACKGROUND: Surveys have been conducted to measure prevalence of eye disease in Africa, but not of incidence, which is needed to forecast trends. The incidence of visual loss is reported in southwest Uganda. METHODS: A rural population residing in 15 neighbouring villages was followed between 1994-5 (R1) and 1997-8 (R2). Survey staff screened adult residents (13 years or older) for visual acuity using laminated Snellen's E optotype cards at each survey. Those who failed (VA >6/18) were evaluated by an ophthalmic clinical officer and an ophthalmologist. Incidence of visual loss (per 1000 person years (PY)) was calculated among those who had normal vision at R1. RESULTS: 2124 people were studied at both survey rounds (60.9% of those screened at R1); 48% were male. Participants in R1 were older (34.7 versus 31.5 years at R2, p<0.001). Visual loss in R2 occurred in 56 (2.8%) of 1997, yielding a crude incidence rate of 9.9, and an age standardised incidence rate of 13.2, per 1000 PY. Incidence of visual loss increased with age from 1.21 per 1000 PY among people aged 13-34 to 64.2 per 1000 PY in those aged 65 years or older (p for trend >0.001). The six commonest causes of visual loss were: cataract, refractive error, macular degeneration, chorioretinitis, glaucoma, and corneal opacity. If similar rates are assumed for the whole of Uganda, it is estimated that 30 348 people would develop bilateral blindness or bilateral visual impairment, per year. CONCLUSIONS: Cataract and refractive error were the major causes of incident visual loss in south west Uganda. These data are valuable for forecasting and planning eye services.

Adolescent↗

PubMed2003

Diagnostic accuracy of flow rate testing in urology.

OBJECTIVE: To highlight the importance of methodological standards in diagnostic testing in urology, by reviewing the extent of compliance with these standards in reports of published evaluations. METHODS: Sixteen papers evaluating the diagnostic accuracy of urinary flow-rate testing were independently assessed by two reviewers for compliance with the following methodological standards: specification of study population, analysis of pertinent subgroups, avoidance of evaluation (verification) bias, avoidance of review bias, reporting of precision of estimates of test accuracy, indeterminate test results, and test reproducibility. Compliance with each standard was expressed as a percentage with a 95% confidence interval. RESULTS: Compliance ranged from just 12.5 (1.5-38)% for reporting of test reproducibility to 87.5 (62-98)% for specification of the study population. Only nine of the 16 evaluations complied with four or more of the methodological standards; one paper did not comply with any. CONCLUSIONS: This evaluation of urological flow-rate testing show poor compliance with accepted methodological standards. The study design, reporting and evaluation of new diagnostic tests can be improved by adhering to these standards. Policy-makers, purchasers and providers would be less likely to adopt new diagnostic tests inappropriately if they were to appraise published evaluations against the standards. A reduction in the inappropriate use of tests would in turn lead to more cost-effective use of healthcare resources.

Diagnostic Techniques and Procedures↗

PubMed2002

Evaluation of E-optotypes as a screening test and the prevalence and causes of visual loss in a rural population in SW Uganda.

BACKGROUND: Few population-based eye surveys have been conducted in sub-Saharan Africa, limiting the quality of epidemiological information on visual loss from Africa. In the present paper, we describe the prevalence of visual loss in rural Uganda and the screening accuracy of E-optotypes when used by non-medical staff. METHODS: Residents of 15 neighbouring villages were screened for visual loss (<6/18 in either eye) using Snellen's E-optotypes. Individuals who failed were initially referred to an ophthalmic clinical officer (OCO), who retested visual acuity and subsequently referred to an ophthalmologist to determine the cause of visual loss. Subjects from two villages (248 individuals) who passed visual acuity screening were re-examined by the OCO to estimate the accuracy of the screening procedure. RESULTS: Of the 4076 adults (aged 13 years and over, 69.3% of the censused population) who participated, 191 (4.7%) failed the vision screening criteria and 648 (15.9%) had non-vision impairing conditions. The prevalence of visual loss was at least 3.9%: 0.4% had bilateral blindness, 1.6% had bilateral visual impairment, 0.7% had unilateral blindness and 1.2% unilateral visual impairment. Cataract was the leading cause for all categories of visual loss except bilateral blindness, for which suspected glaucoma was most frequent. Refractive errors were the second leading cause of bilateral and unilateral visual impairment. Based on one subject (0.4%) in the validation sample who was found to have low vision, we estimated the sensitivity and specificity of E-optotypes for detecting visual loss to be 93% and 99%, respectively. CONCLUSIONS: Cataract and refractive errors were responsible for most of the visual loss in rural Uganda. Snellen's E-optotypes provide a suitable cost-saving tool for conducting population-based eye surveys in sub-Saharan Africa.

Adolescent↗

PubMed2001

Multicentre randomised controlled trial of nasal diamorphine for analgesia in children and teenagers with clinical fractures.

OBJECTIVE: To compare the effectiveness of nasal diamorphine spray with intramuscular morphine for analgesia in children and teenagers with acute pain due to a clinical fracture, and to describe the safety profile of the spray. DESIGN: Multicentre randomised controlled trial. SETTING: Emergency departments in eight UK hospitals. PARTICIPANTS: Patients aged between 3 and 16 years presenting with a clinical fracture of an upper or lower limb. MAIN OUTCOME MEASURES: Patients' reported pain using the Wong Baker face pain scale, ratings of reaction to treatment of the patients and acceptability of treatment by staff and parents, and adverse events. RESULTS: 404 eligible patients completed the trial (204 patients given nasal diamorphine spray and 200 given intramuscular morphine). Onset of pain relief was faster in the spray group than in the intramuscular group, with lower pain scores in the spray group at 5, 10, and 20 minutes after treatment but no difference between the groups after 30 minutes. 80% of patients given the spray showed no obvious discomfort compared with 9% given intramuscular morphine (difference 71%, 95% confidence interval 65% to 78%). Treatment administration was judged acceptable by staff and parents, respectively, for 98% (199 of 203) and 97% (186 of 192) of patients in the spray group compared with 32% (64 of 199) and 72% (142 of 197) in the intramuscular group. No serious adverse events occurred in the spray group, and the frequencies of all adverse events were similar in both groups (spray 24.1% v intramuscular morphine 18.5%; difference 5.6%, -2.3% to 13.6%). CONCLUSION: Nasal diamorphine spray should be the preferred method of pain relief in children and teenagers presenting to emergency departments in acute pain with clinical fractures. The diamorphine spray should be used in place of intramuscular morphine.

Administration, Intranasal↗

PubMed2001

Agreement between ophthalmologists and optometrists in optic disc assessment: training implications for glaucoma co-management.

BACKGROUND: Many studies have estimated observer variability for optic disc assessment among experts, but there are few data on agreement between optometrists and ophthalmologists. The aim of this study is to report inter- and intraobserver agreement among optometrists and ophthalmologists in optic disc assessment and discuss the implications for glaucoma co-management. METHODS: Twelve observers (six optometrists and six ophthalmologists) graded 48 stereo-pairs of optic disc photographs from 48 patients on two separate occasions. Observers graded the vertical C/D ratio, the narrowest rim width and the presence/absence of disc haemorrhage. Agreement was assessed by calculating the standard deviation (SD) of differences and the kappa statistic, within and between observers. Systematic differences in grading between and within individuals were described by calculating mean differences. RESULTS: Intra-observer agreement is "substantial" and significantly better than inter-observer agreement for all disc features (P<0.0001). Intra-observer agreement is comparable for optometrists and ophthalmologists with regard to C/D ratio estimates. Although some optometrists show close agreement with ophthalmologists, overall agreement between optometrists and ophthalmologists is significantly worse than agreement among ophthalmologists alone for vertical C/D ratio (P=0.002) and disc haemorrhage (P=0.02). There are fewer inter-observer mean differences that differ significantly from zero among ophthalmologists (7%) than among optometrists (67%; chi2=11.63, P<0.001) or between optometrists and ophthalmologists (69%; chi2=16.7, P<0.001). There is evidence of systematic under-reading of C/D ratios by less experienced optometrists. CONCLUSION: Although individual optometrists can show good agreement with ophthalmologists on disc grading, the variation in individual performance indicates that training and accreditation in disc assessment is an essential prerequisite for participation by optometrists in glaucoma co-management.

Clinical Competence↗