Contact Lenses - What are they?
Contact lenes are thin lens designed to be worn on the surface of the eye, usually to correct defects of vision. It is made of plastic polymer and lies in contact with the eyeball or the cornea. The contact lens is an FDA regulated optical correction device and is only available on prescription.
Contact lenses - History
Contact lenses were first conceptualized by Leonardo da Vinci, but it was Rene Descartes and Sir John Herschel who refined his idea. In 1888, the Swiss physician Adolf Eugene Fick became the first person to develop and prescribe glass contact lenses to his patients. Dr William Feinbloom of New York introduced the hard plastic contact lens in 1936, but it was not until Otto Wichterles development in the 1960s of an entirely new class of water absorbing soft plastic polymers that contact lenses became comfortable enough to find widespread acceptance. The common types of visual defects like myopia (near or short sight) and hypermetropia (far or long sight) were now amenable to correction by the use of the contact lens. A major advance was the development of the toric contact lens for correcting the visual defect known as astigmatism. Improvement in contact lens technology has spawned thinner and lighter lenses made of newer materials resulting in the availability of tinted lens, extended wear lens, disposable lens, and bifocal contact lens.
Who can use contact lenses?
The vast majority of people with visual defects qualify for wearing the contact lens. Users should be highly motivated, have scrupulous personal hygiene, and good manual dexterity. Contact lenses are suitable for all age groups; even infants may be prescribed contact lenses for specific ophthalmic indications.
Contact lenses - Who should NOT use them?
People with allergic conditions like asthma and hay fever may not be able to tolerate contact lenses. Infections of the eyelid, conjunctiva or the cornea preclude the use of contact lens till the eye completely recovers. Pregnancy sometimes causes edema or swelling of the cornea, and may require the woman to discontinue the use of contact lenses. People living in hot dusty climates or high altitudes too may face difficulties with the use of contact lenses.
Contact lenses - benefits
Compared to spectacles, the contact lens has two major advantages. Firstly, it gives a better cosmetic result; indeed this is the reason why most users prefer contact lenses. Secondly it gives a superior optical result, with a larger field of vision, no peripheral distortion, and no misting up in humid conditions.
Types of contact lenses
Earlier lenses were made of a hard plastic called Perspex or PMMA (Poly Methyl MethAcrylate), and were called rigid or hard contact lens. These are now virtually obsolete, although an improved version called Gas Permeable Rigid Lens is sometimes prescribed for specific eye diseases like high astigmatism and keratoconus.
The non-rigid or soft contact lens is made of newer plastic polymers and is more comfortable, although it requires meticulous care and cleaning.
The contact lens is typically worn during the daytime and removed at night for disinfection. Extended wear soft lens may be used continuously for longer periods, but are not universally recommended presently. Disposable soft lens are used like the regular ones for a week or a fortnight and then discarded. Single use disposable lenses are also available, but cost remains a constraint. Colored lens may be used to change eye color for cosmetic or therapeutic purposes; or for camouflaging eye defects.
Patient comfort is determined by three technical factors. First, the lens should be able to efficiently transmit oxygen. Secondly it should have high water content. Thirdly it should have an easily wettable surface. Soft contact lenses score over hard lenses in most of these parameters.
Caring for contact lenses
The contact lens patient needs to be counseled and educated about the correct way to insert and remove the contact lens. Hand washing and nail clipping are simple measures that help avoid infection. Attention to hygiene and regular disinfection of the lens is essential. Hydrogen peroxide is often used for disinfection, but the lens requires neutralization before reuse. Polyquat is a new disinfecting solution that has superior properties. After disinfection, the lens should be soaked overnight in preservative-free, sterile saline solution. Enzymatic cleaning is recommended weekly in order to remove protein and debris.
Contact Lenses - Complications
Contact lenses are sued by millions of users all over the world wear, and these are generally well tolerated and safe. Incorrect handling, improper disinfection or storage, continuous use for long periods, or infection may sometimes result in complications. The over wearing syndrome causes discomfort, redness, and blurring of vision due to swelling of the cornea.
Discharge, itchiness, dryness or watering of eyes should alert the user about possible adverse effects. Infections with pseudomonas or acanthemoeba are dreaded complications and require immediate therapy. Remove contact lenses promptly, wash eyes with clean water, and consult a qualified ophthalmologist.
Important Note: This information should NOT be taken in any way a medical advice, which can only be offered by your qualified ophthalmologist.