1. A method for assigning to a retinal image a confidence metric for automated determination of optic disc location, comprising: accessing a retinal image of a patient using an image analysis system; determining at least two sets of coordinates locating an optic disc in the retinal image using said image analysis system, wherein a first set of coordinates is determined using a first image analysis technique, and a second set of coordinates is determined using a second image analysis technique that is different from said first image analysis technique; calculating an accuracy parameter of the at least two sets of coordinates; comparing the accuracy parameter to a primary risk cut-off value; and assigning a high confidence level to the retinal image if the accuracy parameter is less than the primary risk cut-off value, and assigning a low confidence level to retinal image if the accuracy parameter is greater than the primary risk cut-off value, wherein the primary risk cut-off value is selected to represent a value where the risk of a misdiagnosis using an automated disease diagnosis process meets a predetermined limit.