Alpha zone was defined as irregular hyperpigmentation and hypopigmentation and it was located in the periphery of the parapapillary atrophy. 

Beta zone was characterized by visible sclera and visible large choroidal vessels and a location between the peripapillary scleral ring and alpha zone. 

Correspondingly, histological studies in human eyes and monkey globes confirmed in clinical histological correlations that alpha zone corresponded histologically to irregularities in the retinal pigment epithelium (RPE), and that beta zone showed a complete loss of RPE cells and an almost complete loss of photoreceptors and a closure of the choriocapillaris.