Improving the economic value of photographic screening for optical coherence tomography-detectable macular oedema: a prospective, multicentre, UK study.

OBJECTIVES: To determine the best photographic surrogate markers for detecting sight-threatening macular oedema (MO) in people with diabetes attending UK national screening programmes. DESIGN: A multicentre, prospective, observational cohort study of 3170 patients with photographic signs of diabetic retinopathy visible within the macular region [exudates within two disc diameters, microaneurysms/dot haemorrhages (M/DHs) and blot haemorrhages (BHs)] who were recruited from seven study centres. SETTING: All patients were recruited and imaged at one of seven study centres in Aberdeen, Birmingham, Dundee, Dunfermline, Edinburgh, Liverpool and Oxford. PARTICIPANTS: Subjects with features of diabetic retinopathy visible within the macular region attending one of seven diabetic retinal screening programmes. INTERVENTIONS: Alternative referral criteria for suspected MO based on photographic surrogate markers; an optical coherence tomographic examination in addition to the standard digital retinal photograph. MAIN OUTCOME MEASURES: (1) To determine the best method to detect sight-threatening MO in people with diabetes using photographic surrogate markers. (2) Sensitivity and specificity estimates to assess the costs and consequences of using alternative strategies. (3) Modelled long-term costs and quality-adjusted life-years (QALYs). RESULTS: Prevalence of MO was strongly related to the presence of lesions and was roughly five times higher in subjects with exudates or BHs or more than two M/DHs within one disc diameter. Having worse visual acuity was associated with about a fivefold higher prevalence of MO. Current manual screening grading schemes that ignore visual acuity or the presence of M/DHs could be improved by taking these into account. Health service costs increase substantially with more sensitive/less specific strategies. A fully automated strategy, using the automated detection of patterns of photographic surrogate markers, is superior to all current manual grading schemes for detecting MO in people with diabetes. The addition of optical coherence tomography (OCT) to each strategy, prior to referral, results in a reduction in costs to the health service with no decrement in the number of MO cases detected. CONCLUSIONS: Compared with all current manual grading schemes, for the same sensitivity, a fully automated strategy, using the automated detection of patterns of photographic surrogate markers, achieves a higher specificity for detecting MO in people with diabetes, especially if visual acuity is included in the automated strategy. Overall, costs to the health service are likely to increase if more sensitive referral strategies are adopted over more specific screening strategies for MO, for only very small gains in QALYs. The addition of OCT to each screening strategy, prior to referral, results in a reduction in costs to the health service with no decrement in the number of MO cases detected. STUDY REGISTRATION: This study has been registered as REC/IRAS 07/S0801/107, UKCRN ID 9063 and NIHR HTA 06/402/49. SOURCE OF FUNDING: This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 17, No. 51. See the HTA programme website for further project information.

External quality assurance for image grading in the Scottish Diabetic Retinopathy Screening Programme.

AIMS: To develop and evaluate an image grading external quality assurance system for the Scottish Diabetic Retinopathy Screening Programme. METHOD: A web-based image grading system was developed which closely matches the current Scottish national screening software. Two rounds of external quality assurance were run in autumn 2008 and spring 2010, each time using the same 100 images. Graders were compared with a consensus standard derived from the top-level graders' results. After the first round, the centre lead clinicians and top-level graders reviewed the results and drew up guidance notes for the second round. RESULTS: Grader sensitivities ranged from 60.0 to 100% (median 92.5%) in 2008, and from 62.5 to 100% (median 92.5%) in 2010. Specificities ranged from 34.0 to 98.0% (median 86%) in 2008, and 54.0 to 100% (median 88%) in 2010. There was no difference in sensitivity between grader levels, but first-level graders had a significantly lower specificity than level-two and level-three graders. In 2008, one centre had a lower sensitivity but higher specificity than the majority of centres. Following the feedback from the first round, overall agreement improved in 2010 and there were no longer any significant differences between centres. CONCLUSIONS: A useful educational tool has been developed for image grading external quality assurance.

Colour Doppler imaging of the ocular circulation in diabetic retinopathy.

PURPOSE: To measure blood flow velocity in the ophthalmic artery (OA) and central retinal artery (CRA) in patients with diabetic retinopathy. SUBJECTS AND METHODS: 62 age-matched subjects divided into 3 groups: nondiabetic controls (n=17); diabetics with no clinical retinopathy or background changes (n=24); diabetics with either pre-proliferative or proliferative retinopathy (n=21). Colour Doppler imaging was performed on supine patients by one masked observer using the Acuson 128 machine. RESULTS: There was a statistically significant (p<0.05) decrease in both the peak systolic velocity (PSV 0.073 m/s) and end diastolic velocity (EDV 0.014 m/s) of the central retinal artery in the pre-proliferative/proliferative group compared to the no retinopathy/background retinopathy group (PSV 0.096 m/s, EDV 0.024 m/s) and the control group (PSV 0.142 m/s, EDV 0.029 m/s). The resistance index of the ophthalmic artery was significantly increased in both the preproliferative/proliferative (0.81) and the no retinopathy/background group (0.81) compared to controls (0.72). CONCLUSION: Reduced blood flow velocity was found in the CRA of diabetic patients and appeared to become further reduced with the progression of retinopathy. This suggests that monitoring with Colour Doppler imaging may have predictive power in identifying those at greatest risk of developing sight threatening proliferative disease. The resistance index of the OA was increased in diabetics compared to controls.

Pulsatile ocular blood flow in untreated diabetic retinopathy.

PURPOSE: To measure the pulsatile component of total ocular blood flow in patients with untreated diabetic retinopathy. SUBJECTS AND METHODS: An adapted pneumotonometer attached to a slit-lamp biomicroscope. 82 age-matched subjects divided into 4 groups: non-diabetic controls (n = 22); diabetics with no clinical retinopathy (n = 20); background diabetic retinopathy (n = 20); pre-proliferative/proliferative diabetic retinopathy (n = 20). RESULTS: The mean pulsatile ocular blood flow values were found to be increased in all grades of diabetic retinopathy (no retinopathy 818 microl/min, background 1015 microl/min, pre-proliferative/proliferative 1097 microl/min) compared to the control group (644 microl/min). These pulsatile ocular blood flow values were significantly higher (p<0.05) in the background and pre-proliferative/proliferative retinopathy groups compared to controls. Pulse volume and pulse amplitude were also higher in the diabetic subjects. Mean arterial blood pressure did not differ across the groups studied. CONCLUSION: Pulsatile ocular blood flow was found to be higher in diabetics compared to controls and appears to increase as the severity of retinopathy progresses. Such a hyperdynamic circulation may contribute to the pathogenesis of diabetic eye disease.