AIM:To figure out the sequence of vessel density(VD)changes in the retina and deformation induced by mechanical force in the optic nerve head(ONH)tissue during intraocular pressure(IOP)elevation.

METHODS: This prospective study tested 34 eyes from 34 healthy volunteers. Group A had 23 subjects. Their testing protocol included a baseline phase, two elevated IOP phases(15 mmHg and 30 mmHg respectively for 2min), and a recovery phase. Group B had 11 subjects, and their protocol included an IOP elevation of 15 mmHg for 10min. In each phase the deformation in the ONH and macular region were scanned by optical coherence tomography(OCT), and Bruch's membrane opening(BMO)distance, the optic nerve head surface depth(ONHSD), the subfoveal choroidal thickness(SFCT)were measured, the VD was measured by OCTA.

RESULTS: After the first IOP elevation in group A, the VD in the ONH decreased(superficial capillary plexuses, from 67.39±7.65% to 43.78±5.89%, P<0.05), the BMO distance, the ONHSD, the VD in the macula and the SFCT did not change. After the second IOP elevation, the VD in the ONH and in the macular region both decreased, the BMO distance and ONHSD increased(all P<0.05). After the IOP elevation in group B, the VD in the ONH and in the macular region decreased significantly, the BMO distance increased, the SFCT did not change. ONH VD reduction is not associated with BMO distance increment(r=0.050, P>0.05).

CONCLUSION:The ONH tissue is more sensitive to hemodynamics than to morphological change. Hemodynamics during IOP elevation differs in the ONH and the macular tissue.