Measured vessel length in retinal vessel diameter measurement

Retinal vessel diameters have been used to assess the vascular changes associated with possible systemic abnormality. The measured vessel lengths vary in different measurement protocols. This has impact on reliability of retinal vascular assessment but is lack of study. To study this impact, we developed a method to assess the diameter longitudinal change along the retinal vessel walls. Results demonstrate that the longer length of measured vessel has less variation and provides a more reliable result. It also suggests that the minimum measured vessel length should be over 400μm. This finding will be useful for the methodology and protocol development of retinal vessel diameter measurement.