Abstract
Purpose: :
Plus disease is defined as arterial tortuosity and venous dilation greater than that of a standard photograph selected by expert consensus in the 1980s. However the standard photograph has many potential limitations concerning image interpretation. This study analyzes the quantitative vascular characteristics of the standard photograph, and compares these values to expert interpretations of an independent set of wide-angle retinal images.
Methods: :
Vessels from the standard photograph were analyzed using a computer-based image analysis system to measure mean arterial tortuosity index (ATI) and venous diameter (VD). A set of 34 wide-angle retinal images was interpreted by 22 ROP experts for presence of plus disease, and was analyzed by the computer-based system to calculate ATI and VD. For each wide-angle image, a reference standard diagnosis ("plus" or "not plus") was defined using majority vote among all experts. Quantitative characteristics of the standard photograph were measured and compared to those of the wide-angle images.
Results: :
Mean ATI of the standard photograph was 1.15, which was significantly lower than both "plus" (1.26, p=0.003) and "not plus" (1.19, p=0.001) images from the wide-angle retinal image set. Mean VD of the standard published photograph was 66.88 µm, which was significantly lower than both "plus" (81.63 µm, p=0.002) and "not plus" (78.95 µm, p=<0.001) images. If quantitative characterstics of the standard photograph values were used as the cutoff for "plus disease," ATI would result in sensitivity of 85% and specificity of 38%, and VD would result in sensitivity of 85% and specificity of 14%.
Conclusions: :
Arterial tortuosity and venous diameter of the standard photograph may be lower than what is used by experts for diagnosis. Magnification and field of view of the standard photograph may cause difficulty for clinicians.
Keywords: retinopathy of prematurity • imaging/image analysis: clinical • clinical (human) or epidemiologic studies: systems/equipment/techniques