These are the questions asked most frequently by my patients. If you have any others, consult your contact lens specialist.
A: No. Wearing contact lenses neither improves nor worsens vision. The only “dependence” is a psychological one. The excellent vision correction provided, the convenience, and the improvement of one’s appearance make many wearers contact lens “addicts.” Read the rest of this entry »
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.
Eventually everyone experiences presbyopia. This is the normal aging process of the eye, which begins around the age of forty for most people, and is caused by the gradual loss of elasticity in the natural crystalline lens of the eye. The lens loses its ability to change shape the way it used to, and fails to bring the light rays of near objects into sharp focus. Of course a nearsighted person over the age of forty can see near objects clearly with the naked eye, but will have difficulty doing so if he is wearing glasses or contact lenses that correct his myopia. Read the rest of this entry »
Conventional soft contact lenses cannot be used to correct moderate to large amounts of astigmatism. Their pliable nature causes them to conform to irregularities in the shape of the cornea and thus duplicate the astigmatic refractive error. Hard contact lenses are firm and hold their shape; they are able to correct high amounts of astigmatism because the spherical undersurface of the lenses and the tears beneath them create a new, smooth optical surface. Read the rest of this entry »
Though the eventual comfort level is somewhere between that of a hard lens and a soft lens, a few wearers may complain of an initial scratchy sensation. Because of the nature of the materials, the lenses are often made slightly larger than conventional hard lenses. There are also difficulties in modifying and adjusting the fit of some of the lenses, and these lenses cannot be fenestrated successfully to relieve any dry-eye problem.
Astigmatism is not corrected quite as well as it is with conventional hard lenses. However, vision is appreciably sharper than with soft lenses, even the toric soft contacts.
Gas-permeable lenses are more expensive than hard lenses; they cost even more than conventional soft lenses. But since they are nearly as durable as hard lenses, replacement is less frequent. The lenses can, however, be chipped and scratched. Warping may occur with time, though damage is minimized with proper handling. CAB lenses can be stained by eye makeup and hairspray. The surface deposits that form easily on the silicone lenses can’t always be removed completely with the usual cleaning and soaking solutions. This is less prevalent with the CAB lenses.
The lenses are difficult to make and delivery time may take a few weeks. The right lens cannot be dotted to avoid confusing the right and left lenses.
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 »
Contact Lenses Care .
