Light exposure decreases IOP in rabbits during the night

Abstract

Elevated IOP observed in rabbits during the dark phase of the circadian cycle decreased rapidly and reversibly when rabbits were exposed to light during the dark phase. The decrease of IOP does not result from decreased aqueous flow and only part of the decrease requires intact ocular sympathetic innervation.

The Circadian Rhythm in Intraocular Pressure and its Relation to Diurnal Ocular Growth Changes in Chicks

“…cycles, whereas in both rat and rabbit the amplitude was unchanged by constant dark (Lee et al, 1995 ;Moore et al, 1996). This difference implies that in chickens, the normal IOP rhythm is partly circadian and partly driven by light, whereas in the rabbit the daytime IOP is lower than is achieved by light during the night and apparently cannot be lowered further by light during the day (Lee et al, 1995).…”

“…We find that IOP in chickens shows diurnal changes similar to those in humans, being high during the day, and thus opposite to those of rats and rabbits, a difference perhaps associated with diurnal v. nocturnal activity. Possibly also related to this behavioural difference, we find that light causes IOP to rise, whereas in rabbits light in the middle of the dark period causes a decrease in IOP (Lee et al, 1995).…”

“…This difference implies that in chickens, the normal IOP rhythm is partly circadian and partly driven by light, whereas in the rabbit the daytime IOP is lower than is achieved by light during the night and apparently cannot be lowered further by light during the day (Lee et al, 1995). Also, the wave form of the IOP rhythm in normal chickens is approximately sinusoidal [Fig.…”

“…Also, the wave form of the IOP rhythm in normal chickens is approximately sinusoidal [Fig. 5(C)], whereas in the rat and rabbit the wave form of the rhythm was more like a square wave (Lee et al, 1995 ;McLaren, Brubaker and FitzSimon, 1996 ;Moore et al, 1996).…”

“…In humans, intraocular pressure undergoes diurnal fluctuations of about 5 mm Hg, being lowest during the night and highest during the early morning (Drance, 1960 ;Henkind et al, 1973 ;Frampton et al, 1987). In both rats and rabbits, the amplitude of the IOP rhythm is approximately 10 mm Hg, being low during the day and higher at night (rabbits : Rowland et al, 1981 ;Gregory, Aviado and Sears, 1985 ;Lee, Kiuchi and Gregory, 1995 ;McLaren, Brubaker and FitzSimon, 1996 ;Schnell, Debon and Pericot, 1996 ;rats : Moore, Johnson and Morrison, 1996 ;Krishna et al, 1995). We find that IOP in chickens shows diurnal changes similar to those in humans, being high during the day, and thus opposite to those of rats and rabbits, a difference perhaps associated with diurnal v. nocturnal activity.…”