Identification of diabetic retinopathy by stereoscopic digital imaging via teleophthalmology: a comparison to slide film

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Abstract

Background: Diabetic retinopathy is a leading cause of vision loss in North America. We compared mydriatic seven-field stereoscopic digital imaging to 100 ASA slide film photography for the identification of diabetic retinopathy via teleophthalmology.

Methods: Patients from a northern Alberta community with diabetes mellitus diagnosed by a physician were asked to participate in a teleophthalmology pilot project. Patients were enrolled at four different times between October 1999 and June 2000. Seven 30° fields of the retina were photographed with both slide film and digital imaging (resolution 2008 × 3040 pixels) through a dilated pupil. Slide film was developed and reviewed in a masked fashion by a retinal specialist. Digital images for each patient were transmitted by satellite to Edmonton and analysed a minimum of 2 months after the original slide film. Retinal abnormalities were graded with' the use of the Early Treatment Diabetic Retinopathy Study extension of the modified Airlie House classification. We calculated the sensitivity and specificity of digital imaging for the identification of features of diabetic retinopathy as seen on slide film. Pearson's correlation coefficient was also calculated.

Results: A total of 121 patients (241 eyes), of whom 114 (94.2%) had non-insulindependent diabetes, participated in the study. The average duration of diabetes was 8.5 years. Of the 121 patients 57 (47. I %) had diabetic retinopathy, 12 (9.9%) had clinically significant macular edema and 2 (1.6%) had neovascularization. Pearson's correlation coefficient for the presence of retinopathy between slide film and stereoscopic digital imaging was 0.92 for microaneurysms, 0.80 for hemorrhages, 0.45 for intraretinal microvascular abnormalities, 0.32 for venous beading, 1.00 for neovascularization of the disc, 1.00 for neovascularization elsewhere in the retina and 0.97 for clinically significant macular edema (p < 0.001). The correlation between the two techniques for severe nonproliferative diabetic retinopathy (NPDR) was 0.86 and for high-risk proliferative diabetic retinopathy 1.00 (p < 0.001).

Interpretation: Stereoscopic digital imaging has a high level of correlation with slide film for the identification of most features of diabetic retinopathy, including microaneurysms, hemorrhage, severe NPDR, highrisk proliferative diabetic retinopathy and clinically significant macular edema.

Resumé

Contexte : La rétinopathie diabétique est une des principales causes de la perte de la vue en Amérque du Nord. Nous avons compare l'imagerie numérique stéréoscopique mydriatique à sept champs avec l'image d'une diapositive 100 ASA pour l'identification de la rétinopathie diabétique par le biais de la téléophtalmologie.

Méthodes: Un groupe de personnes du nord de l'Alberta chez qui les médecins avaient diagnostiqué le diabète sucré ont été invitees à participer à un projet pilote de téléophtalmologie. Ces patients ont été inscrits à quatre dates entre octobre 1999 et juin 2000. On a recueilli des photographies à sept champs de 30° de la rétine à travers la pupille dilateé pour obtenir des diapositives d'une part et, d'autre part, des images numériques (résolution 2008 × 3040 pixels). Les diapositives furent développées et examinées à I'insu par un spécialiste de la rétine. Les images numériques de chaque patient furent transmises par satellite à Edmonton et analysées au moins deux mois aprés les diapositives originales. Les anomalies de la rétine furent classées en utilisant l'extension de la classification Airlie House utilisée dans la Early Treatment Diabetic Retinopathy Study. Nous avons calculé la sensibilité et la spécificité de l'imagerie numérique pour identifier les particularités de la reéinopathie diabétique apparaissant sur les diapositives. On a aussi calculé le coefficient de corrélation de Pearson.

Résultats : En tout, 121 patients (241 yeux), parmi lesquels 114 (94,2 %) avaient un diabète non insulinodépendant, ont participé à l'étude. Its avaient le diabète depuis 8,5 ans en moyenne. Parmi les 121 patients, 57 (47,1 %) avaient une rétinopathie diabétique, 12 (9,9 %) avaient un œdème maculaire cliniquement important et 2 (1,6%) avaient une néovascularisation. Le coefficient de corrélation de Pearson concernant la présence de la rétinopathie entre les diapositives et l'image numérique stéréoscopique était : 0,92 pour les microanévrismes, 0,80 pour les hémorragies, 0,45 pour les anomalies microvasculaires intrarétiniennes, 0,32 pour les veines en collier de perles, 1,00 pour la néovascularisation de la papille, 1,00 pour les autres néovascularisations de la rétine et 0,97 pour l'œdème maculaire cliniquement important (p < 0,001). La corrélation entre les deux techniques était de 0,86 pour la rétinopathie diabétique non proliférative (NPDR) grave et de 1,00 pour la rétinopathie diabétique proliférative è risque élevé (p < 0,00 1).

Interprétation: L'imagerie numérique stéréoscopique a un haut degré de corrélation avec les diapositives quant à l'identification de la plupart des caractéristiques de la rétinopathie diabétique, notamment, le microanévrisme, l'hémorragie, le NPDR grave, la rétinopathie diabétique proliférative è risque élevé et l'œdeme maculaire cliniquement important.

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    Preliminary results of this study were presented as a poster paper at the Canadian Ophthalmological Society meeting held in Whistler, BC, June 17–20, 2000.

    b

    From the Department of Ophthalmology, University of Alberta, Edmonton, Alta.

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