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 are, in most cases, a far better solution once the aphake is convinced that the “newfangled” device is worth trying. Advantages are the normal appearance of the eye and crisp visual acuity. Since only 6 percent magnification of objects occurs, the images appear to be of normal size, fusion can take place, and excellent peripheral vision and depth perception will result. Therefore life can go back to normal, the cosmetic effect is far better, and most observers can’t tell that there’s ever been a cataract extraction. Read the rest of this entry »
Contact lenses that you can wear while you sleep—this earth- shattering concept arouses no less interest and excitement than the Pill did when it was first introduced. This is the glamour lens that everybody wants to know about and have, and is probably the lens of the future. Like the Pill, which forever altered our sexual standards, the extended-wear contact lens promises to usher in a new era and change our attitudes toward visual correction. But the similarity doesn’t end there: Though this lens seems to be the answer to every contact lens wearer’s prayers, it has not yet been perfected. It is definitely not for everyone, and some practitioners are reluctant to prescribe it at all.
Canada, Australia, and Europe enjoyed several types of extended-wear contact lenses several years before we did. However, there is no Food and Drug Administration in those parts of the world, and because of this lack of strict monitoring control and quality, these lenses have posed a health problem, especially as related to corneal complications. Read the rest of this entry »
These lenses offer a unique blend of the advantages of both hard and soft lenses. They provide excellent visual acuity, and correct most types of astigmatism better than soft lenses (but not quite as well as conventional hard lenses). The gas-permeable lenses correct astigmatism in the same manner as the hard lenses by forming a perfectly round, smooth inner surface filled with tears. Multifocal gas-permeable lenses are also available for the presbyope. They are almost as durable as hard lenses, and much more so than soft lenses. You can expect gas-permeable lenses to last up to five years. Since the lenses are firm in consistency, they are handled easily and with greater confidence than are soft lenses. They can be accurately reproduced, so there are none of the surprises that can occur when reordering a soft lens. Read the rest of this entry »
This type of contact lens fills the need for many people who— for one reason or another—are not suitable for conventional hard or soft lenses. This is the lens for you if you:
Have found hard lenses uncomfortable, but are unwilling to give up their sharp visual acuity.
Contact Lenses Care .
