View clinical trials related to Ocular Physiology.
Filter by:This will be a prospective, randomized, bilateral eye, crossover, non-masked single site pilot study to compare the severity of symptoms of itching between test and control lens after two weeks of wear.
Adequate perfusion and oxygenation is essential for the function of the inner retina. Although this is a well known fact, measurement of oxygen saturation in the eye is still a delicate and not fully explored task. However, recently a new instrument for the non-invasive measurement of retinal vessel oxygen saturation has been introduced. Unfortunately, no data about reproducibility in humans is yet available for this instrument. Consequently, the current study seeks to evaluate the short term and day to day reproducibility of retinal vessel oxygenation in healthy volunteers. 20 healthy volunteers will be included and oxygen saturation of retinal vessels will be determined. The reproducibility of the results will be tested by repeated measurements and the collected data will be independently analyzed by two observers.
Topical brimonidine is a recently introduced alpha 2 receptor agonist which is used in the therapy of intraocular pressure (IOP) reduction in patients with open angle glaucoma. Although adequate IOP reduction is achieved in many patients there is a considerable degree of variability in IOP reduction among subjects. The reason for this interindividual variability is not entirely clear. Obviously differences in pharmacokinetic properties due to variable penetration of the drug through the cornea may be responsible. Alternatively, polymorphisms of the alpha-2 receptor may account for the differences in IOP-lowering efficacy of topical brimonidine. This hypothesis is tested in the present study. Polymorphisms of the alpha-2 receptor have been described in a number of previous studies. In addition, polymorphisms in the alpha-2 receptor gene have been shown to be functionally important, particularly a polymorphism of the alpha-2B receptor, which has a high allele frequency in caucasians.
Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. The existence of an effective autoregulation in the optic nerve circulation has been shown in animals and humans. The exact mechanism behind this autoregulation is still unknown. The motive for the investigation of optic nerve head (ONH) blood flow autoregulation is to enhance the understanding of pathologic eye conditions associated with ocular vascular disorders. To clarify the regulatory mechanisms of ONH microcirculation is of critical importance to understand the pathophysiology of glaucoma because there is evidence that glaucoma is associated with optic nerve head ischemia. Several studies indicate that a disturbed autoregulation might contribute to glaucomatous optic neuropathy. Previous findings suggest endothelial dysfunction in glaucomatous optic neuropathy, in particular alterations in endothelin- and nitric oxide- system, which both play an important role in local regulation of vascular tone. In the present study, changes in ocular perfusion pressure will be performed during administration of drugs, which may potentially alter the pressure-flow relationship. These drugs include endothelin-1 and the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA).