AIM: To examine the retinal nerve fiber layer(RNFL)changes in early primary open angle glaucoma(POAG)by comparing the superior half of the optic disc with the inferior disc half.

METHODS: It was a clinical observational study. The study included 30 patients(39 eyes)with POAG and 20 normal subjects(40 eyes). Visual field was tested by Zeiss Humphrey750 and the optic disc topographic parameters and RNFL thickness were measured by Zeiss Cirru HD-OCT. Collecting information included visual field mean defect(MD), glaucoma hemifield test(GHT), intraocular pressure(IOP), C/D ratio and RNFL thickness. Data were analyzed by statistic software SPSS18.0. The differences between two groups were assessed using t test.

RESULTS: The differences of superior RNFL minus inferior RNFL thichness on the corresponding clock-hour locations were caculated in two groups. There was a significant difference in superonasal-inferonasal RNFL thickness between two groups(t=2.526, P=0.014), and there were no significant differences in the others(all P>0.05).

CONCLUSION: The asymmetry of optic disc hemifield RNFL is found in early primary open angle glaucoma patients. The superonasal RNFL(1 o'clock for right eye, and 11 o'clock for left eye)is more fragile to loss than inferonasal RNFL(5 o'clock for right eye, and 7 o'clock for left eye).