This type of lens has been put to artistic use in the movies by actors creating bizarre special effects, such as the eyes of monsters. Ironically prosthetic lenses can also be of real help to those who need something special in order to appear normal. They can dramatically improve the appearance (and sometimes the vision as well) of eyes that have been disfigured or in some way appear abnormal. This includes those who suffer from albinism or unsightly, deformed eyes whose defect is congenital in origin or due to accidental injury or a result of eye surgery. The ultimate type of prosthetic contact lens is the one that forms the “false eye“—or shell over the entire socket when an eye is enucleated (surgically removed).
Prosthetic contact lenses, which may cover the entire sclera or only the cornea, are predominantly manufactured in rigid form, though soft prosthetic lenses are available. The lenses simulate a normal iris and pupil by incorporating an opaque area that is colored artistically to achieve the final appearance of the eye. The desired image may be placed on any portion of the lens, and may be of any color. It is stable and nontoxic because in one type the image is “painted” on the surface of one lens and then covered with another lens, forming a “sandwich.” Another method employs a special tinting process of a soft lens.
CosmeticContact Lenses
For those who wish to change the color of their eyes, especially actors or models, the cosmetic contact lens is a real boon. Some of these lenses cover only the cornea, are made of rigid PMMA material, and are opaque, except in the transparent central area. This clear zone covers the pupil and may have a prescription incorporated. Obviously the lens has to center perfectly. Fitting is difficult and may require many sessions. Care and handling is similar to the standard hard lens. Soft lenses may also be tinted to provide similar cosmetic results.
Keratoconus is a relatively common hereditary disorder that manifests itself in adolescence. It affects both eyes, but one eye usually progresses faster than the other. During the course of this disease the cornea changes from its round shape to that of a cone, hence the name: kera meaning “cornea” and conus meaning “cone.” The apex of the cone is thin and may become scarred. In severe cases the apex may actually perforate.
The poor vision brought on by keratoconus is due to a highly exaggerated form of astigmatism that is poorly corrected by glasses. Until contact lenses became available, keratoconus patients often had to be satisfied with partially corrected vision and led less-than-normal lives. But contact lenses can provide almost perfect vision in most cases and are the best means of vision correction for this disorder.
Hard contact lenses are usually used because the smooth, dome-shaped shell plus the tears beneath it provide a new smooth, round refracting surface for the eye. Because the cornea is diseased, the eye may not tolerate conventional hard lenses. In that case gas-permeable contact lenses may be prescribed instead. Soft contact lenses, in general, do not work well with keratoconic eyes. As is the case with astigmatism, the pliable material from which they are made conforms to the misshapen cornea, duplicating the refractive error. Soft contact lenses may, however, correct a portion of the faulty vision. And in some cases the patient is fitted with hard lenses on top of the soft lenses, piggyback fashion, to take advantage of the comfort of the soft lens plus the sharp visual acuity provided by the hard lens. In all cases the lenses are difficult to manufacture, and the fitting process must be extremely exact to achieve acceptable results.
It is estimated that there are 8.5 million people in the United States who have some degree of color blindness. This is the common name given to the inability to distinguish colors and shades; some people have trouble with only a few colors, others see no colors at all. This inherited disorder affects mostly males: 8 percent of the male population is red-green color deficient, as compared with only one half of 1 percent of the female population. Read the rest of this entry »
Contact Lenses Care .
