A circadian rhythm of aqueous flow underlies the circadian rhythm of IOP in NZW rabbits.

There is a daily rhythm of aqueous flow in New Zealand White rabbits entrained to 12 hr light:12 hr dark. The phase of the rhythm of flow is determined by the phase of the light:dark cycle, and the rhythm persists in constant dark. Therefore, in New Zealand White rabbits the rhythm of aqueous flow, like the rhythm of intraocular pressure, is circadian. The range of the circadian rhythm of flow suggests it plays a major role in producing the circadian rhythm of intraocular pressure. This animal model provides a powerful tool for studying endogenous mechanisms which regulate aqueous humor formation and intraocular pressure.