Rhythm Of Intraocular Pressure Research Articles

Circadian rhythm in intraocular pressure: a rabbit model.

An animal model for study of the circadian rhythm in intraocular pressure (IOP) was developed using carefully maintained environmental lighting conditions. Highly predictable, precipitous increases and decreases in IOP of somewhat more than 10 mm Hg were found to be closely correlated with the onset of darkness and light, respectively. The daily spontaneous variations in IOP, once entrained, were maintained in constant darkness, but were eliminated by constant light, as is similarly seen in many mammalian systems. This model provides a novel means of investigating circadian IOP oscillation, which has been shown to be especially amplified in primary open angle glaucoma (POAG). This new rabbit model may also warrant consideration for use in screening ocular antihypertensive drugs since it could obviate the gross physiological manipulations and concomitant side effects inherent in the popular methods of inducing ocular hypertension in animal models.

Development of eye enlargement of domestic fowl subjected to low intensity light.

Week-old White Leghorn chicks were randomly divided into two light control chambers. One chamber was equipped with clear incandescent light with a maximum intensity of 0.66µW cm−2 mµ−1 and the remaining chamber was equipped with blue light with a maximum intensity of 0.015µW cm−2 mµ−1. Both groups received a daily photoperiod of 14 hours' light and 10 hours' dark. Low intensity blue light caused a definite eye enlargement after 7 weeks of exposure.The eye enlargement was not related to an increase release rate of thyroidal131I or oxygen consumption. Intraocular pressure was no greater in the enlarged eyes than in control eyes.Length of exposure to light and dark cycles caused a daily rhythm in intraocular pressure which was not different in the two light treatments. Associated with the eye enlargement was an exophthalmic condition during the developmental stages, a slight flattening of the cornea, and definite alterations in visual parameters resulting in an axial length myopia. Some lenticular contribution to the myopia was inferred by reason of an increase in size of the lens.