Background: To examine the psychophysical correlate of alpha zone and beta zone of parapapillary atrophy.
Methods: The study included 20 eyes of 10 patients affected by primary open-angle glaucoma and 12 normal eyes of 6 subjects. The parapapillary region was psychophysically examined by direct fundus microperimetry. The parapapillary atrophy was ophthalmoscopically differentiated into a peripheral alpha zone with pigmentary irregularities and a central beta zone characterized by a good visibility of the large choroidal vessels and the sclera.
Results: The mean stimulus attenuation values in the beta zone of parapapillary atrophy measured 1.00 ± 2.54 dB corresponding to an absolute scotoma. In the alpha zone, the mean stimulus attenuation values was 6.29 ± 4.82 dB corresponding to a relative scotoma. The difference in the stimulus attenuation between alpha zone and beta zone was statistically significant (P=0.028).
Conclusions: The psychophysical correlate of beta zone of parapapillary atrophy is an absolute scotoma, the correlate of alpha is a relative scotoma. It agrees with the histological correlate of beta zone with a complete loss of retinal pigment epithelium cells and photoreceptors, and with the histological correlate of alpha zone with structural irregularities of the retinal pigment epithelium.