|
|
Simultaneous lenses bring distant and near objects into focus at the same time. The ocular center of the lens corrects distance vision; the outer part corrects near vision. * Segmented lenses correct distance science vision in the top half and near vision in the bottom half.Monovision An alternative to bifocal contacts, monovision lenses correct distance vision in one eye and near vision contacts in the other. Modified monovision allows wearers to put a bifocal lens in one eye and a single-vision lens in the other.Implants Designed for mild nearsightedness, KeraVision Intacs are placed in the periphery of the cornea by an ophthalmic surgeon. Made of polymer, a type of hard plastic, ocular they require no maintenance and can be surgically removed. The outpatient procedure has a 97-percent success rate of 20/40 vision or better. Eye glasses and contact lenseses and contact are devices that correct refractive errors in vision. lenses lenses are mounted in frames worn on the face, sitting mostly on the ears and nose, so that the lenses are positioned in front of the science eyes. contact appear to be worn in direct contact with the cornea, but they actually float on a layer of tears that separates them from the contacts cornea.PurposeThe purpose of lenseses and contact is to correct or improve the vision ocular of people with nearsightedness (myopia), farsightedness science (hyperopia), contacts presbyopia, and astigmatism.Precautions People allergic ocular to certain plastics should not wear contact or lenses frames or lenses manufactured from that type of plastic. People allergic to nickel should not science wear Flexon frames. People at risk of being in accidents that might shatter glass lenses should wear plastic lenses, preferably polycarbonate. Plastic frames are durable, can accommodate contacts just about any lens prescription, and are available in a wide range of prices. They are also offered in a variety of plastics (including acrylic, epoxy, cellulose acetate, cellulose propionate, polyamide, and nylon) and in different colors, shapes, and ocular levels of resistance science to breakage. Epoxy frames are resilient and return to their original shape after being deformed, so they do not need to be adjusted as frequently as other types. Nylon frames are almost unbreakable. They revert to their original shape after extreme trauma and distortion; because of this property, though, they cannot be readjusted after they are contacts manufactured.Fit The patient should have the ocular distance between the eyes (PD) measured, so that the optical centers of the lenses will be in front of the patient''s science pupils. Bifocal heights also have contacts to be measured with the chosen frame in place and adjusted on the patient. Again, ocular this is so the lenses will be positioned science correctly. If not positioned correctly, the patient may experience eyestrain or other problems. This can occur with over-the-counter reading glasses contacts.
|