subject: Different Types Of Contact Lenses [print this page] People choose to wear contact lenses for many reasons. Aesthetics and cosmetics are often motivating factors for people who would like to avoid wearing glasses or would like to change the appearance of their eyes. Other people wear contacts for more visual reasons. When compared with spectacles, contact lenses typically provide better peripheral vision, and do not collect moisture such as rain, snow, condensation, or sweat. This makes them ideal for sports and other outdoor activities. Additionally, there are conditions such as keratoconus and aniseikonia that are typically corrected better by contacts than by glasses.
Contact lenses can be classified in many different manners. Contact lenses can be separated by their primary function, material, wear schedule (how long a lens can be worn before removing it), and replacement schedule (how long before a lens needs to be discarded).
Types of contact lenses:-
1:- Corrective contact lenses
2:- Cosmetic contact lenses
3:- Therapeutic contact lenses
Corrective contact lenses:
Corrective contact lenses are designed to improve vision by correcting refractive error which is done by directly focusing the light so that it enters the eye with the proper power for clear vision.
A spherical contact lens bends light horizontally as well as vertically evenly. They are typically used to correct myopia and hyperopia.
A toric contact lens has a different focusing power horizontally than it does vertically and as a result can correct for astigmatism.
Some spherical rigid lenses can also correct for astigmatism. (See below.) Because a toric lens must have the proper orientation to correct for a person's astigmatism, a toric contact lens must have additional design characteristics to prevent the lens from rotating out of the ideal alignment. This can be done by weighting the bottom of the lens or by using other physical characteristics to rotate the lens back into position. Some toric contact lenses have marks or etchings that can assist the eye doctor in fitting the lens.
The correction of presbyopia (a need for a reading prescription that is different from the prescription needed for distance) presents an additional challenge in the fitting of contact lenses.
Cosmetic contact lenses
A cosmetic contact lens is designed to change the appearance of the eye. These lenses may also correct refractive error. Although many brands of contact lenses are lightly tinted to make them easier to handle, cosmetic lenses worn to change the color of the eye are far less common, accounting for only 3% of contact lens fits.
Non-corrective cosmetic contact lenses also called decorative contact lenses. As with any contact lens, cosmetic lenses carry risks of mild and serious complications, including ocular redness, irritation, and infection. Cosmetic lenses can have more direct medical applications. For example, some lenses can restore the appearance and, to some extent the function, of a damaged or missing iris.
Therapeutic contact lenses
Soft lenses are often used in the treatment and management of non-refractive disorders of the eye. A bandage contact lens protects an injured or diseased cornea from the constant rubbing of blinking eyelids thereby allowing it to heal. They are used in the treatment of conditions including bullous keratopathy, dry eyes, corneal abrasions and erosion, keratitis, corneal edema, descemetocele, corneal ectasis, Mooren's ulcer, anterior corneal dystrophy, and neurotrophic keratoconjunctivitis. Contact lenses that deliver drugs to the eye have also been developed.
