Ocular blood flow alters with age

There is a large variation in the blood flow to the macula across a 24-hour period in old, but not young, eyes, according to results published in the August issue of the Journal of Glaucoma.

Teruyo Kida, MD, PhD of the Hamilton Glaucoma Center and Department of Ophthalmology, University of California, San Diego, US and colleagues monitored the blood flow to the optical nerve head and the macula in one group of subjects aged 50–80 years (n=15), and in a second group of subjects aged 20–25 years (n=15). The subjects spent 24 hours under observation, and blood pressure and intraocular pressure (IOP) were measured - after five minutes sitting upright - every two hours, to calculate ocular perfusion pressure. Blood volume, flow and velocity in the optic nerve head and macula were also monitored.

The team found that nocturnal IOP was significantly lower than diurnal IOP among the older subjects, although ocular perfusion pressure remained stable. Ocular blood flow increased from 6.8% during the day to 16.8% at night in this group. The second group (younger subjects) were found to have higher IOP and lower ocular perfusion pressure at night compared with during the day, although ocular blood flow did not vary during the study period. Nocturnal ocular perfusion pressure was higher in older subjects compared with younger subjects.

The team concluded that the changes in the blood flow to the optic nerve head and the macula, which were confined to the older subjects, were independent of changes in ocular perfusion pressure.