Patients most commonly have their clouded lenses replaced with artificial monofocal lenses that enable them to see things far away.
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Typically, Medicare covers regular cataract surgery and implantation of standard monofocal lenses but does not pay for multifocal lenses, so insurance reimbursements may be limited.
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Monofocal lenses are standard lenses used in cataract surgery. People who have a multifocal intraocular lens after their cataract is removed may be less likely to need additional glasses compared with people who have standard monofocal lenses. People receiving multifocal lenses may experience more visual problems, such as glare or haloes (rings around lights), than with monofocal lenses. People receiving accommodative intraocular lenses had improvements in near vision but these improvements were small and reduced over time.
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People who have a multifocal IOL after their cataract is removed may be less likely to need additional glasses compared with people who have standard monofocal lenses. However, people receiving multifocal lenses may experience more visual problems than with monofocal lenses. The most common adverse visual effects from multifocal IOLs include glare, halos (rings around lights), and a loss of contrast sensitivity, in low light conditions.
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In all types of surgery, the cataractous lens is removed and replaced with an artificial lens, known as an intraocular lens, which stays in the eye permanently. Intraocular lenses are usually monofocal, correcting for either distance or near vision. Multifocal lenses may be implanted to improve near and distance vision simultaneously, but these lenses may increase the chance of unsatisfactory vision.
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They should also visit their ophthalmologists regularly for several months so as to monitor the implants. Most intraocular lenses fitted today are fixed monofocal lenses matched to distance vision. However, other types are available, such as multifocal IOLs which provide the patient with multiple-focused vision at far and reading distance, and adaptive IOLs which provide the patient with limited visual accommodation.
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Multifocal IOLs allow good vision at a range of distances. Monofocal intraocular lenses which are commonly available give clear point of focus in the distance or closer, but you can choose only one focal point. Multifocal intraocular lenses are designed to avoid the need for glasses by providing two or more points of focus. These intraocular lenses are intended to be placed in the capsular bag.
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By utilizing the iris sphincter muscle, some species move the lens back and forth, some stretch the lens flatter. Another mechanism regulates focusing chemically and independently of these two, by controlling growth of the eye and maintaining focal length. In addition, the pupil shape can be used to predict the focal system being utilized. A slit pupil can indicate the common multifocal system, while a circular pupil usually specifies a monofocal system.
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A clinically isolated syndrome (CIS) is a clinical situation of an individual's first neurological episode, caused by inflammation or demyelination of nerve tissue. An episode may be monofocal, in which symptoms present at a single site in the central nervous system, or multifocal, in which multiple sites exhibit symptoms. CIS with enough paraclinical evidence can be considered as a clinical stage of multiple sclerosis (MS). It can also be retrospectively diagnosed as a kind of MS when more evidence is available.
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Monofocal IOLs are standard lenses used in cataract surgery. One of the major disadvantages of these conventional IOLs is that they can only be focussed for one particular distance - either optical infinity (rendering the eye emmetropic) or a fixed finite distance (rendering the eye myopic). Patients that undergo a standard IOL implantation no longer experience clouding from cataracts, but they are unable to accommodate (change focus from near to far, far to near, and to distances in between). This is not a concern for most cataract surgeries, as they are primarily performed on elderly people that are already completely presbyopic.
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The second type of IOL, more commonly known as a phakic intraocular lens (PIOL), is a lens which is placed over the existing natural lens and is used in refractive surgery to change the eye's optical power as a treatment for myopia (nearsightedness). IOLs usually consist of a small plastic lens with plastic side struts, called haptics, to hold the lens in place in the capsular bag inside the eye. IOLs were conventionally made of an inflexible material (PMMA), although this has largely been superseded by the use of flexible materials, such as silicone and acrylic glass. Most IOLs fitted today are fixed monofocal lenses matched to distance vision.
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PML is diagnosed in a patient with a progressive course of the disease, finding JC virus DNA in spinal fluid together with consistent white-matter lesions on brain magnetic resonance imaging (MRI); alternatively, a brain biopsy is diagnostic when the typical histopathology of demyelination, bizarre astrocytes, and enlarged oligodendroglial nuclei are present, coupled with techniques showing the presence of JC virus. Characteristic evidence of PML on brain CT scan images are multifocal, noncontrast enhancing hypodense lesions without mass effect, but MRI is far more sensitive than CT. The most common area of involvement is the cortical white matter of frontal and parieto occipital lobes, but lesions may occur anywhere in the brain, such as the basal ganglia, external capsule, and posterior cranial fossa structures such as the brain stem and cerebellum. Although typically multifocal, natalizumab-associated PML is often monofocal, predominantly in the frontal lobe.
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