The accuracy of digital-video retinal imaging to screen for diabetic retinopathy: an analysis of two digital-video retinal imaging systems using standard stereoscopic seven-field photography and dilated clinical examination as reference standards

Abstract

Purpose: To evaluate the accuracy of two digital-video retinal imaging (DVRI) systems to detect diabetic retinopathy.

Methods: A prospective, masked, technology assessment was conducted for two DVRI systems at a tertiary care Veterans Affairs Medical Center. Group A (n = 151 patients) was imaged with a 640x480 resolution system and group B (n = 103 patients) with an 800x600 resolution system. Four retinal evaluations were performed on each patient: DVRI with undilated pupils using one imaging field (U-DVRI), DVRI with dilated pupils using three imaging fields (D-DVRI), dilated clinical examination, and Early Treatment Diabetic Retinopathy Study stereoscopic seven-field photography (ETDRS-P). Two analyses of accuracy were conducted, one using ETDRS-P as a "gold standard" (ETDRS-GS) and one using dilated clinical examination as a "gold standard" (C-GS).

Results: For group A, using the ETDRS-GS, sensitivities of U-DVRI and D-DVRI were 0.66 and 0.66; specificities of U-DVRI and D-DVRI were 0.66 and 0.86. Using the C-GS, sensitivities of U-DVRI and D-DVRI were 0.79 and 0.80; specificities of U-DVRI and D-DVRI were 0.68 and 0.85. For group B, using the ETDRS-GS, sensitivities of U-DVRI and D-DVRI were 0.76 and 0.85; specificities of U-DVRI and D-DVRI were 0.45 and 0.80. Using the C-GS, sensitivities of U-DVRI and D-DVRI were 0.81 and 0.87; specificities of U-DVRI and D-DVRI were 0.45 and 0.69. For both groups, dilation significantly improved specificities.

Conclusions: The 800x600 resolution DVRI system offers an accurate method of detecting diabetic retinopathy, provided there is adequate pupillary dilation and three retinal images are taken. DVRI technology may help facilitate retinal screenings of growing diabetic populations.

Figure 1

Comparison of 45-degree imaging fields to standard Early Treatment Diabetic Retinopathy Study (ETDRS) fields. Designations of the fields taken for the digital-video retinal imaging (DVRI) in relation to the ETDRS seven standard 30-degree fields. One 45-degree field (field B) was imaged through undilated pupils. Three fields (A, B, and C) were imaged through dilated pupils. ETDRS seven standard 30-degree fields: field 1 (F1) - optic disk centered in the field; field 2 (F2) - macula centered in the field; field 3 (F3) - temporal to the macula; field 4 (F4) - superior temporal; field 5 (F5) - inferior temporal; field 6 (F6) - superior nasal; field 7 (F7), inferior nasal. DVRI 45-degree fields: field A -nasal to optic disk: optic disk is placed at temporal edge of the field; field B - macula centered in the field; field C - temporal to macula: macula is placed at nasal edge of the field.

Figure 2

Single 45-degree field in an undilated pupil. Field B of the right eye of a 52-year-old man with a 3-mm pupil (undilated) from group B (high-resolution digital-video retinal imaging). Note the superior shadow artifact that obscures a portion of the retina.

Figure 3

Three 45-degree fields in the same eye as in Figure 2 after pupillary dilation. Neovascularization is seen superotemporal to the fovea, which was obscured by shadow artifact in Figure 2.

Figure 3

Three 45-degree fields in the same eye as in Figure 2 after pupillary dilation. Neovascularization is seen superotemporal to the fovea, which was obscured by shadow artifact in Figure 2.

Figure 3

Three 45-degree fields in the same eye as in Figure 2 after pupillary dilation. Neovascularization is seen superotemporal to the fovea, which was obscured by shadow artifact in Figure 2.

Figure 4

Sensitivity of digital-video retinal imaging (DVRI) methods and dilated clinical examination (DCE) using two “gold standards”: Early Treatment Diabetic Retinopathy Study (ETDRS) photography and DCE. For every group, the sensitivity of DVRI to accurately detect diabetic retinopathy is higher using the dilated clinical examination as the “gold standard” than using standard ETDRS photography as the “gold standard.”

Figure 5

Sensitivity of digital-video retinal imaging (DVRI) methods and dilated clinical examination plotted by increasing Early Treatment Diabetic Retinopathy Study (ETDRS) retinopathy severity levels. As the severity levels of diabetic retinopathy increase, the sensitivity of DVRI increases, showing that the rate of false-negatives diminishes with more severe disease.