Specially ground lenses placed over the cornea of the eye to correct various vision defects.
Small, thin, plastic disks shaped to correct visual defects and designed to be worn on the surface of the cornea (the clear outer covering on the front of the eye) over the iris and pupil. Contact lenses float on the thin layer of liquid that lubricates the cornea. They are particularly useful for people who suffer from pronounced refraction errors, such as severe nearsightedness, farsightedness, or astigmatism (a l ack of symmetry in the cornea); possess a cone-shaped cornea (keratoconus); or have undergone cataract surgery. Since contact lenses require manual dexterity to insert and remove, they are not suitable for small children or for people with diseases that limit mobility of the hands, such as arthritis or Parkinson disease. They are also unsuitable for people with frequent eye infections, dry eyes, or severe allergies or for people who work in dusty or dirty environments.
Glass or plastic lenses worn directly against the eye, separated from it only by a film of tear fluid. Corneal microlenses cover only the cornea, while haptic lenses cover some of the surrounding sclera as well. Contact lenses are used mainly in place of glasses to correct far and near-sightedness and other errors of refraction, but they may be used in a protective capacity in some types of corneal disease.
Contact lenses are lenses worn in contact with the eye, behind the eyelids and in front of the cornea. They may be worn for cosmetic, optical or therapeutic reasons. The commonest reason for wear is cosmetic, many shortsighted people preferring to wear contact lenses instead of glasses. Optical reasons for contact lens wear include cataract surgery (usually unilateral extraction) and the considerable improvement in overall standard of vision experienced by very short-sighted people when wearing contact lenses instead of glasses. Therapeutic lenses are those used in the treatment of eye disease: ‘bandage lenses’ are used in certain corneal diseases; contact lenses can be soaked in a particular drug and then put on the eye so that the drug slowly leaks out on to the eye. Contact lenses may be hard, soft or gas permeable. Hard lenses are more optically accurate (because they are rigid), cheaper and more durable than soft. The main advantage of soft lenses is that they are more comfortable to wear. Gas-permeable lenses are so-called because they are more permeable to oxygen than other lenses, thus allowing more oxygen to reach the cornea.
Contact lenses are thin, shell-like, transparent discs that are placed over the cornea of the eye to correct vision problems. They are primarily used to address conditions such as myopia (shortsightedness) and hypermetropia (long-sightedness). Additionally, non-corrective lenses are available for cosmetic purposes, allowing individuals to alter their eye color, for instance.
Contact lenses come in various types. Hard plastic lenses offer excellent vision correction and have the advantages of being long-lasting, durable, inexpensive, and easy to maintain. However, some wearers may find them uncomfortable or prone to falling out. Hard gas-permeable lenses, on the other hand, provide improved comfort by allowing oxygen to reach the eye, although they are slightly less durable. Soft lenses are renowned for their exceptional comfort due to their high water content. There are disposable soft lenses designed for single-use only, while extended-wear lenses can be worn continuously for up to a month.
Additional variations of contact lenses include rigid scleral lenses, which envelop the entire front surface of the eye and serve to conceal disfigurement. Bifocal contact lenses offer multiple focal points for individuals with presbyopia. Toric contact lenses, featuring an uneven surface curvature, are designed to correct astigmatism.
Extended wear of hard plastic lenses can potentially lead to corneal abrasion. Some individuals wearing soft lenses may experience sensitivity in the eyes and eyelids. Redness of the eye can occur with any type of contact lens. Infection poses the most severe complication associated with lens usage, as it can result in permanent corneal damage and vision impairment. Maintaining meticulous hygiene significantly reduces the risk of infection.