Effect of image compression and resolution on retinal vascular caliber.

Purpose: Changes in retinal vascular caliber measured from digital color fundus photographs have been independently associated with systemic outcomes in epidemiologic studies, but the effect of image resolution and compression on vascular measurements has not been previously evaluated.

Methods: To explore image compression, 40 natively digital fundus images were selected with good photo quality, high spatial resolution, and no previous image compression. Using Adobe Photoshop, these images were compressed at progressively higher levels up to 147:1, and then retinal vascular caliber was measured at each level using semiautomated software.

Suboptimal image focus broadens retinal vessel caliber measurement.

Purpose: Studies have used central retinal arteriolar (CRAE) and central retinal venular (CRVE) calibers, measured from images produced with computerized image analysis, to detect risk factors for systemic diseases. The authors explored suboptimal image focus as a possible contributing factor to artificially larger vascular caliber measurements.

Methods: From the reading center image collections, 30 digital retinal images were selected for optimum quality.