Aniseikonia is an ocular condition where there is a significant difference in the perceived size of images. It can occur as an overall difference between the two eyes, or as a difference in a particular meridian. If the ocular image size in both eyes are equal, the condition is known as iseikonia. Symptoms and signs
Up to 7% difference in image size is well tolerated. If magnification difference becomes excessive the effect can cause diplopia, suppression, disorientation, eyestrain, headache, and dizziness and balance disorders. Asthenopic symptoms alone may occur even if image size difference is less than 7%. Causes
Retinal image size is determined by many factors. The size and position of the object being viewed affects the characteristics of the light entering the system. Corrective lenses affect these characteristics and are used commonly to correct refractive error. The optics of the eye including its refractive power and axial length also play a major role in retinal image size.Aniseikonia can occur naturally or be induced by the correction of a refractive error, usually anisometropia (having significantly different refractive errors between each eye) or antimetropia (being myopic (nearsighted) in one eye and hyperopic (farsighted) in the other.) Meridional aniseikonia occurs when these refractive differences only occur in one meridian (see astigmatism). One cause of significant anisometropia and subsequent aniseikonia has been aphakia. Aphakic patients do not have a crystalline lens. The crystalline lens is often removed because of opacities called cataracts. The absence of this lens left the patient highly hyperopic (farsighted) in that eye.
Trospium chloride is used to treat overactive bladder.It has side effects typical of drugs like it, namely dry mouth, stomach upset, and constipation; these side effects cause problems with people taking their medicine as directed. However it doesnt cause central nervous system side effects like other drugs of its class. It is pregnancy category C and is excreted somewhat in breast milk.Chemically it is a quaternary ammonium cation which causes it to stay in periphery rather than crossing the blood-brain barrier. It works by causing the smooth muscle in the bladder to relax.It was patented in 1966 and approved for medical use in 1974. It was first approved in the US in 2004, and an extended release version with once-daily dosing was brought to market in 2007. It became generic in Europe in 2009 and in the US the first extended-release generic was approved in 2012.