Diurnal change of anterior chamber depth in rabbits

It has been shown that there is a circadian rhythm of intraocular pressure and aqueous humor flow in rabbits. It has also been shown that there is a fluctuation in the volume of the aqueous that can be aspirated from the anterior chamber at different times of day. This finding would suggest that the depth and volume of the anterior chamber of this species also undergoes a circadian rhythm. To confirm this hypothesis, we measured by pachometry the anterior chamber depth in 11 adult New Zealand albino rabbits that had been conditioned to light from 6 a.m. to 6 p.m. and to dark from 6 p.m. to 6 a.m. The measurements were performed at noon and at midnight. The anterior chamber was found to be 4% deeper at midnight than at noon (p < 0.001). This finding suggests that the volume of the anterior chamber would be slightly larger at night than during the day in the rabbit eye. We have no explanation for this finding. However, the difference is too small to have an appreciable effect on the measurement of aqueous dynamics or pharmaceutical effects.