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Aphakia is the absence of the lens of the eye, due to surgical removal, such as in cataract surgery, a perforating wound or ulcer, or congenital anomaly. It causes a loss of ability to maintain focus ( accommodation ), high degree of farsightedness ( hyperopia ), [ 1 ] and a deep anterior chamber .
Aphakia is the absence of the natural crystalline lens. The aphakic state is usually due to surgery to remove a cataractous lens, but post-surgical aphakia is rare nowadays because of the ubiquity of intraocular lenses. Rarely, aphakia can be post-traumatic or congenital in nature.
A phakic intraocular lens (PIOL) is an intraocular lens that is implanted surgically into the eye to correct refractive errors without removing the natural lens (also known as "phakos", hence the term).
Replacement of the lens as treatment for cataract can cause pseudophakic macular edema (‘pseudophakia’ means ‘replacement lens’). This could occur as the surgery involved sometimes irritates the retina (and other parts of the eye) causing the capillaries in the retina to dilate and leak fluid into the retina. This is less common today ...
Bullous keratopathy, also known as pseudophakic bullous keratopathy (PBK), is a pathological condition in which small vesicles, or bullae, are formed in the cornea due to endothelial dysfunction.
Aniseikonia due to uniocular aphakia is best corrected surgically by intraocular lens implantation. [4] Similarly retinal aniseikonia is corrected by treating causative retinal disease. [4] Note however that before the optics can be designed, first the aniseikonia should be measured.
The reading portion is an aspheric "progressive add". Also, in aphakia or extreme hyperopia, high plus power aspheric lenses can be prescribed, but this practice is becoming obsolete, replaced by surgical implants of intra-ocular lenses. Many convex types of lens have been approved by governing agencies regulating prescriptions.
The brightness of the Purkinje images can be determined using Fresnel's equation: = (′) / (′ +), where and ′ are the refractive indices before and after the reflecting surface.