The second phase of this study was performed with the same procedures as the first phase, and the study population was limited to young recruits in the Army. After examination of 1028 norriial eyegrounds, it became apparent that there are several definite and easily recognizable variations in the distribution of the vessels as they emerge from the optic nerve head.
The classification is made by dividing the surface of the nerve head into four quadrants, i.e., the upper and lower nasal and the upper and lower temporal. Since there are four main branches of the retinal artery, namely, the superior and inferior temporal and the superior and inferior nasal, there are nine possible variation in the distribution of these vessels over the surface of the optic nerve head.
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