<unk>  <unk>  is a lens implanted in the eye as part of a treatment for cataracts or myopia. If the natural lens is left in the eye, the<unk>  is known as phakic, otherwise it is a pseudophakic, or false lens. Such a lens is typically implanted during cataract surgery, after the eye's cloudy natural lens (cataract) has been removed. The pseudophakic<unk>  provides the same light-focusing function as the natural crystalline lens. The phakic type of<unk>  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). This is an alternative to LASIK.<unk> s 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.<unk> s were conventionally made of an inflexible material (PMMA), although this has largely been superseded by the use of flexible materials, such as silicone. Most<unk> s fitted today are fixed monofocal lenses matched to distance vision. However, other types are available, such as a multifocal<unk>  that provide multiple-focused vision at far and reading distance, and adaptive<unk> s that provide limited visual accommodation. Multifocal<unk> s can further be, Trifocal<unk> s or extended depth of focus (EDOF) lenses. More than six million lenses are implanted annually. The procedure can be done under local or topical anesthesia with the patient awake throughout the operation. The use of a flexible<unk>  enables the lens to be rolled for insertion into the capsular bag through a very small incision, thus avoiding the need for stitches. This procedure usually takes less than 30 minutes in the hands of an experienced ophthalmologist, and the recovery period is about 2–3 weeks. After surgery, patients should avoid strenuous exercise or anything else that significantly increases blood pressure. They should visit their ophthalmologists regularly for 3 weeks to monitor the implants.<unk>  implantation carries several risks associated with eye surgeries, such as infection, loosening of the lens, lens rotation, inflammation and nighttime halos, but a systematic review of studies has determined that the procedure is safer than conventional laser eye treatment. Though<unk> s enable many patients to have reduced dependence on glasses, most patients still rely on glasses for certain activities, such as reading. These reading glasses may be avoided if Multifocal<unk> s, Trifocal<unk> s or EDOF lenses are used.
Intraocular lens
Scleral lens
Corneal button
Eye dropper
Optic cup 
Intrastromal corneal ring segment
Lacrimal sac
Fundus