Autoregulation of Optic Nerve Head Blood Flow Induced by Elevated Intraocular Pressure during Vitreous Surgery.

PURPOSE: To investigate optic nerve head (ONH) blood flow changes resulting from intraocular pressure (IOP) elevation in subjects without systemic disorders.

MATERIALS AND

METHODS

Eighteen eyes of 18 patients who underwent vitrectomy to treat an epiretinal membrane or macular hole at Toho University Sakura Medical Center were included. Following standard 25-gauge microincision vitreous surgery, mean blur rate (MBR) in tissue (MT), an index of ONH blood flow, was measured using laser speckle flowgraphy. Measurements were taken before and 5 and 10 minutes after a 15 mmHg IOP elevation.

RESULTS

The ONH blood flow was initially lower than baseline (P = 0.001) after elevating IOP from 14.8 ± 2.8 mmHg to approximately 30 mmHg. Between 5 and 10 minutes after elevating IOP, ONH blood flow partially recovered (P = 0.004), even though ocular perfusion pressure was 20.2% lower than at baseline.

CONCLUSIONS

The ONH blood flow in subjects without systemic disorders was initially lower, but began to recover 5-10 minutes after a 15 mmHg elevation in IOP. These results indicate that autoregulatory mechanisms of ONH blood flow may help to minimize the effects of IOP elevations and fluctuations during vitreous surgery.