1. A method of analyzing the degree of abnormality in a patient's eye comprising: collecting a set of measurements of the patient's eye; calculating the thickness of one or more layers of retinal tissue using the measurements over an annular region surrounding the fovea, said layers including at least the ganglion cell layer (GCL) and excluding the retinal nerve fiber layer (RNFL); determining a representative value of the calculated thickness in each of a set of sub-regions, said sub-regions being located around the fovea; identifying, the minimum representative value determined; comparing the minimum value to a distribution of minimum values from a collection of thickness measurements from the eyes of a plurality of subjects; and storing or displaying information quantifying the comparison.