Contact lens

Contact Lens

Contact lenses are corrective, therapeutic, and cosmetic lenses which are normally placed over the eye, on the cornea.  Contact lenses have similar uses as those of eyeglasses and refractive surgery; they improve vision and correct astigmatism, nearsightedness, or farsightedness.  The main advantage of the contact lens over other vision correction methods is that it is lightweight and practically invisible when worn.

Characteristics of Contact Lenses, and Prerequisites prior to obtaining a Pair

The contact lens is gaining popularity as a vision correction implement for a number of reasons: some people find that wearing contact lenses, instead of glasses, enhance their physical appearance, as the latter can be tinted with any color, or made with any design which suits the user’s fancy; contact lenses do not steam up, are more reliable in wet weather, and provide a broader range of vision than normal glasses; they are the appropriate eye implement for most sporting activities which require constant mobility; and some eye conditions may not be acutely corrected by traditional eyeglasses. 

Contact lenses are usually worn with necessary prescriptions from an eye care practitioner.  They are considered as medical devices, and in the United States, Australia, and the United Kingdom, they are prescribed by optometrists; in Eastern Europe and France, contact lenses are given through prescriptions made by ophthalmologists.  In most other areas, opticians provide the prescriptions.  The corrective medical devices are best obtained with a prescription in order to avoid the potential of eye injury or disease, as a cause of wearing ill-fitting and improper lenses.

Usually, a contact lens fitter assesses a person’s suitability for wearing contact lenses during the course of an eye exam, where the health of the eye’s cornea is verified; the presence of optical allergies, or dryness which may significantly have an effect on the patient’s capability in wearing the contact lenses, are also determined.  The usual specifications included in a contact lens prescription include the material, cylinder axis, diameter, center thickness, the base curve radius, the power in diotropes, and the brand. 

Conversions of the prescription of glasses to that of contact lenses are possible, since the power of the two prescriptions are significantly different and are not interchangeable.  Similar to normal eyeglasses, contact lens prescriptions are particular to a specific patient, and may not apply to other patients who probably have totally different visual conditions.

Types of Contact Lenses

Contact lenses are available in many types; the classifications and varieties are dependent on a number of factors, such as the material used in making them, the maximum length of time in which they are worn without removal, their disposability, and their design.  There are three subtypes of contact lenses according to the material in which they are made.  Hard lenses, which are made from Plexiglass or Lucite, are presently seldom used and considered obsolete.  Soft contact lenses are the most common, and are made out of gel-like plastic, with water content; these are slightly bigger in size than the iris (the colored area of the eye’s surface). 

GP contact lenses, also called RGP, or lenses which are permeable by oxygen, are made out of rigid and waterless plastic, specifically prescribed for conditions like presbyopia or advanced astigmatism.  The lenses of this type are about 8mm in diameter, and are smaller than the iris.  Most lenses are, until recently, made out of hydrogel plastic material, but recent developments has seen the gain in acceptance of contact lenses made out of a silicone hydrogel (a hybrid version) by many eye care practitioners, as this new type affords more oxygen to permeate the eye, and also has a lower tendency for dehydration.  In terms of wearing duration, lenses come in either daily wear, or extended wear varieties. 

Previously, the prospect of wearing contact lenses to sleep was nonexistent; the relatively recent introduction of extended wear contact lenses, which can be worn overnight, and even for seven consecutive days without removal, has afforded the user more convenience in use.  A special variety of extended wear lenses even affords the user to wear them for thirty consecutive days without being removed, doing away with all the fuss and trouble of nightly removal and cleaning of the lenses. 

Disposable and Specifically-designed Contact Lenses

Contact lenses are classified according to disposability.  The usual problem with soft contact lenses involve the potential for discomfort and infection with wearing; proteins and lipids, substances which are common components of tears, have a tendency to stick on the surface of the contact lens, providing conducive breeding grounds for bacteria, and leading to irritation, discomfort, and infection.  This is why products used in lens cleaning are necessary.  But even with such a maintenance measure, the residue still manages to build up on the surface of the contact lens, thereby necessitating a replacement. 

The introduction of disposable contact lenses in 1987 has afforded a solution to this problem.  Disposable lenses are available in different optional varieties.  Daily disposable lenses are replaced daily, doing away with the necessity of nightly cleaning; Disposable lenses which are used only for daytime wear may be replaced after two weeks; Disposable lenses which may be used for overnight wear are replaceable after a week; and planned replacement lenses are usually replaceable after a month of use. 

Contact lenses are also classified according to their design; these vary depending on the vision problem which requires correction.  Spherical lenses involve the normal round design, effective in correcting nearsightedness and farsightedness.  Bifocal lenses have different focal areas for correcting presbyopia, an age-related visual disability which gradually prevents a person from having a full and broad range of visual acuity.  Orthokeratology contact lenses are specifically designed for reshaping the cornea while the user is asleep, consequently providing the possibility of not wearing lenses during the daytime. 

Toric lenses are used as corrective aids for astigmatism, and also for nearsightedness and farsightedness.  All of the lens designs mentioned can be possibly made for custom fit, especially for patients with hard-to-fit eyes.  Other lens designs are also available; however, these are particularly made for special visual conditions, such as in correction of keratoconus, and are consequently less common.

Secondary Features of the Contact Lens

Aside from the purpose of an improved visual acuity, contact lenses may also be made in order to afford the user other secondary benefits.  The more popular varieties involve the design, the color, or the tint of the surface of the lens itself.  Colored contact lenses are popularly considered during lens fittings, since numerous types of the contact lens are also available in colors or tints which can provide an enhanced or striking color to the eyes. 

Users can choose to give their eyes a deeper shade of blue if they wish, or go for an entirely different color, other than the natural color of their eye’s iris; the possibilities are numerous and are dependent on the user’s preference.  Colored lenses can also be used for prosthetic purposes; some people may incur disfigured or blemished eyes, as caused by an accident or illness, and may need custom-made, opaque-tinted lenses in order to cover up the disfiguration, and be of a closer match to the look of their normal eye. 

Contact lenses for special effect, also known as novelty and costume lenses, provide even more variety by offering the user the option of design in addition to color; the lens may give the eyes the same appearance as that of any animal, or any other object, for that matter, which the user takes a fancy to.  Ultraviolet-inhibiting contact lenses are used for the purpose of blocking UV light which can cause cataracts or other vision problems.  The blocking layer is invisible upon looking at the lens itself. 

However, since contact lenses do not cover the entire eye, this UV blocking layer is not meant as an effective substitute for ordinary sun protection for the eyes, such as a pair of sunglasses can provide.  Hybrid contact lenses are made with a GP center and a softer outer skirt, thereby affording users with the benefit of crisp visual acuity as provided by a rigid lens, and the relative comfort of a larger and softer lens.

How to Obtain a Pair: Sources, and Purchasing Advice

With the various types of contact lenses which are available to any user who needs them, it can be difficult to choose which combination bests suits their need and their current visual condition.  This problem is addressed by following a few rudimentary tips.  The lenses must serve the first and foremost purpose of providing visual acuity.  It must be accurate in correcting the visual disorder which the user experiences, such astigmatism, myopia or nearsightedness, hyperopia or farsightedness, or any combination of these. 

They must then comfortably fit the eye.  Contact lenses are available in very numerous combinations and variations of diameter or curvature, and not all lens brands offer lenses of all sizes.  The lens should also consider other medical needs which your eye should be corrected for, such as an inherent tendency for dryness.  Finally, the user can choose a lens which fits a specific preference, such as color or disposability.  These factors are best considered with the help of a qualified eye specialist.  Contact lenses are acquirable in different brands, and varied sources, and the basic factors which must be considered before purchasing a pair include availability, customer support, convenience, product offerings and services, and finally, the price. 

The usual sources of contact lenses for purchase include the patient’s eye doctor; the price of a pair may be more expensive than usual, but some doctors offer bulk quantities, in addition to consultation services, at a competitive price package.  Optical chain outlets have in-house services like eye examinations or contact lens fittings, and can also offer a wide variety of lenses to fit most prescriptions at a competitive cost, and without the long wait. 

Mass retailers like warehouse stores usually have optical departments, and offer products and services similar to optical chains.  Contact lenses are also recently available online, affording the buyer easy access to price lists and comparisons, in addition to being able to place an order at anytime; however, this advantage is balanced out by shipping periods, and extra charges, especially for rush deliveries.