Referable Retinopathy Research Articles

Cost-effectiveness of implementing automated grading within the national screening programme for diabetic retinopathy in Scotland

Aims:National screening programmes for diabetic retinopathy using digital photography and multi-level manual grading systems are currently being implemented in the UK. Here, we assess the cost-effectiveness of replacing first level...

Establishing ongoing quality assurance in a retinal screening programme

To establish a clinically efficient, cost-effective quality assurance programme as part of a routine retinopathy screening service. The operation of a quality assurance system as part of an ongoing retinal screening service is described. A random selection of 12% of images of all people reported to have retinopathy and of 2% reported to have no retinopathy are re-graded by a consultant ophthalmologist. Entry of the two sets of data into a purpose-designed excel spreadsheet allows automated calculation of sensitivity and specificity. The results of quality assurance from August 2001 to July 2003 are reported. Out of 8351 screening episodes, 498 were re-examined. Of the 62 cases identified by the ophthalmologist as having referable retinopathy, four false negatives for detection were identified. Three of these had been assigned to early re-screening by the retinal screener but were still regarded as false negative by the parameters of the quality assurance system. The sensitivity and specificity for detection of sight-threatening retinopathy were 93.5% (95% CI = 84.3-98.2%) and 97.8% (95% CI = 95.8-98.9%), respectively. A robust and cost-effective system has been developed to allow monitoring of performance of routine retinal screening which may be extended to meet current national recommendations.

Effective and accurate screening for diabetic retinopathy using a 60° mydriatic fundus camera

OBJECTIVES. To establish whether an experienced endocrinologist could screen accurately for diabetic retinopathy using mydriatic 60 degree fundus photographs compared with a reference standard, viz. the combined highest scores of two experienced ophthalmologists. Retrospective review of 60 degree colour transparency photographs taken over a 6-year period. Retinopathy was graded in a standardised way. Patients attending the diabetic clinic at Johannesburg Hospital, South Africa. Fifteen hundred and seventeen patients (2446 eyes) formed the basis for the study. Patients were included if there was more than 50% readability of the fundus photographs. Outcome measures were prevalence of any retinopathy and presence of referable (severe) retinopathy. Interobserver agreement was measured using the kappa statistic, and sensitivity and specificity of the screener were evaluated. The prevalence of retinopathy at the clinic was approximately 30%, but only about 12% was severe enough to warrant referral to the ophthalmology outpatient department. The endocrinologist was very accurate in determining cases requiring referral; there was 97% agreement with the reference standard, viz. the combined highest score of two experienced ophthalmologists (gold standard). Correlation on the determination of any retinopathy was less accurate (80% agreement), mostly owing to the endocrinologist reporting more isolated microaneurysms than the ophthalmologists. The screening method used gave a sensitivity of 83% and specificity of 99% which are within recommended standards. The screening strategy using a mydriatic fundus camera at the diabetic clinic was found to be effective and accurate and greatly reduced the number of possible referrals to the ophthalmology outpatient department.

The value of digital imaging in diabetic retinopathy

To assess the performance of digital imaging, compared with other modalities, in screening for and monitoring the development of diabetic retinopathy. All imaging was acquired at a hospital assessment clinic. Subsequently, study optometrists examined the patients in their own premises. A subset of patients also had fluorescein angiography performed every 6 months. Research clinic at the hospital eye clinic and optometrists' own premises. Study comprised 103 patients who had type 1 diabetes mellitus, 481 had type 2 diabetes mellitus and two had secondary diabetes mellitus; 157 (26.8%) had some form of retinopathy ('any') and 58 (9.9%) had referable retinopathy. A repeat assessment was carried out of all patients 1 year after their initial assessment. Patients who had more severe forms of retinopathy were monitored more frequently for evidence of progression. Detection of retinopathy, progression of retinopathy and determination of when treatment is required. Manual grading of 35-mm colour slides produced the highest sensitivity and specificity figures, with optometrist examination recording most false negatives. Manual and automated analysis of digital images had intermediate sensitivity. Both manual grading of 35-mm colour slides and digital images gave sensitivities of over 90% with few false positives. Digital imaging produced 50% fewer ungradable images than colour slides. This part of the study was limited as patients with the more severe levels of retinopathy opted for treatment. There was an increase in the number of microaneurysms in those patients who developed from mild to moderate. There was no difference between the turnover rate of either new or regressed microaneurysms for patients with mild or with sight-threatening retinopathy. It was not possible in this study to ascertain whether digital imaging systems determine when treatment is warranted. In the context of a national screening programme for referable retinopathy, digital imaging is an effective method. In addition, technical failure rates are lower with digital imaging than conventional photography. Digital imaging is also a more sensitive technique than slit-lamp examination by optometrists. Automated grading can improve efficiency by correctly identifying just under half the population as having no retinopathy. Recommendations for future research include: investigating whether the nasal field is required for grading; a large screening programme is required to ascertain if automated grading can safely perform as a first-level grader; if colour improves the performance of grading digital images; investigating methods to ensure effective uptake in a diabetic retinopathy screening programme.

The use of digital cameras in a mobile retinal screening environment.

To assess how successfully digital camera technology might be incorporated into a mobile screening environment. One hundred and ninety-seven people had their fundi photographed using a Topcon/Imagenet digital system and 534 using a Canon CR5/Ris-Lite system in addition to concurrent 45 degrees CR4NM Polaroid photography. One hundred and eighteen randomly selected patients were also sent for 7 field stereo photography as a gold standard. An acceptability questionnaire was answered by a random sample of those photographed. For the detection of any retinopathy, digital pictures had a sensitivity of 0.74 (95% confidence interval (CI) 0.68-0.80) whilst Polaroid was 0.72 (95% CI 0.66-0.78) and for referable retinopathy digital pictures had a sensitivity of 0.85 (95% CI 0.80-0.90) and Polaroid was 0.90 (95% CI 0.86-0.94). A concurrent ophthalmoscopic evaluation improved the sensitivity to 0.92 (95% CI 0.86-0.98) for detection of any retinopathy whilst the sensitivity at the referral level was improved to 0.95 (95% CI 0.91-0.99). Twenty-nine of 176 respondents experienced flash discomfort with the Polaroid system with only four of 154 describing 'some' discomfort from the digital systems which have a lower flash power (10 W vs. 300 W) and a faster recovery time. This study indicates that digital systems are a feasible and acceptable alternative to Polaroid-based cameras for use in a mobile environment.