Quantitative comparison of vascular characteristics of plus disease images published over time: International Classification of Retinopathy of Prematurity.

Plus disease was first defined in the original International Classification of retinopathy of prematurity (ICROP) publication in 1984. Over time, the definition of plus disease has evolved, and each ensuing ICROP publication has included example plus disease images. Because plus disease is often present when treatment is indicated, it is important to evaluate whether the retinal vascular characteristics (ie, dilation and tortuosity) depicted in these example images have remained the same or changed over time. Using a semiautomated computer program to trace and quantitatively analyze the retinal vessels in all example plus disease images published in three iterations of ICROP over time, the most recent ICROP publication (ICROP3) consistently exhibited the lowest amount of vascular dilation and tortuosity. This suggests a potential shift towards less tortuous and dilated retinal vessels in example plus disease images published in ICROP3, possibly indicating a lowering of the threshold for diagnosing plus disease and treatment of retinopathy of prematurity.