Contact Lens Dictionary A-H
Astigmatism is the result of the cornea (the eye's outermost protective coating) becoming distorted, which causes light rays to be focused on a number of different points on the retina. This means that the eye is unable to focus properly and vision is impaired. Eye-care specialists often liken the sensation to that of walking round fairground Hall of Mirrors.
Bifocal Contact Lenses provide a comfortable alternative to glasses for anyone suffering from presbyopia. The onset of presbyopia is typically associated with people in their forties and is characterized by the eye having difficulty in shifting focus between near and distant objects. If someone in your family needs to hold a book at an arm's length to read it, they may well benefit from bi-focal contacts.
Color Blindness is something of a misnomer and actually refers to an inability to distinguish certain colors from one another, rather than any genuine blindness. Colour blindness affects a significantly greater percentage of men than women and is caused when the colour sensitive cone cells fail to function properly. Light filtering contact lenses (which ‘filter' the visual spectrum to help differentiate between confusing colours, such as red and green) are now available with a prescription.
Daily Disposable Contact Lenses are designed to be worn for a single day, thrown away, and replaced with a new pair the next morning. Their increasing popularity is largely owed to the time and hassle saved on lens care, and they are widely recognized as by far the healthiest way to wear contact lenses.
Extended Wear Contact Lenses can be worn for twenty four hours a day, including during sleep. The time period they may be used for depends on which brand you choose.
Farsightedness (also referred to clinically as hyperopia) is a result of the distance between the lens and the retina being too short for the eye to focus properly on near objects. The condition is usually congenital.
Glaucoma is characterized by a build up in eye pressure, which if left untreated can lead to impaired peripheral vision and damage to the optic nerve. It's one of the leading causes of blindness in the developed world, but responds well to treatment if caught early. In the UK eye tests are provide free of charge if there history of glaucoma in the family.
Hard Contact Lenses may take slightly longer to get used to than soft lenses, but for some people suffering from astigmatism and pesbyopia they are the most effective method of visual correction (their comparative rigidity helps to ‘reshape' the cornea and lens).
Contact Lens Dictionary I-R
Iris - The ring of pigmented tissue that surrounds the pupil which expands and contracts to control the size of the pupil and consequently the amount of light that reaches the retina. The iris gives the eye its colour, which can be altered with cosmetic contact lenses.
Johnson & Johnson are one of the world's leading contact lens suppliers mostly thanks to their constant innovation in developing such products as the world's first daily disposable contact lenses (1-Day Acuvue). Other market leaders include: CIBA Vision, Bausch & Lomb, Ocular Sciences and Wesley-Jessen Vision Care.
Keratitis refers to a generalized inflammation of the cornea which may be caused by a number of factors including exposure to intense bright light, vitamin A deficiency and contact lens usage.
Laser Vision Correction is an umbrella term given to variety of surgical procedures aimed at reshaping the cornea using a computer controlled laser. Designed to appeal to anyone who's fed up with both glasses and contact lenses, the jury's still out on the wisdom of undergoing nonessential optical surgery.
Macula is the highly sensitive central part of the retina which is responsible for detailed central vision. The macula may deteriorate with age leaving the individual with only peripheral vision.
Nearsightedness (also known as myopia) is caused by the lens focusing light in front of the retina. The result is that anyone suffering from myopia will have good reading vision, but will have difficulty seeing clearly at a distance.
Opticians grind and dispense glasses and supply contact lenses. They're not to be confused with Ophthalmologists, who specialize in medical and surgical treatment of eye disease as well as covering all other aspects of eye-care. Optometrists complete the trio and are qualified to treat all visual disorders and diseases (including prescribing lenses and medicines) with non-surgical intervention.
Pupil is the aperture through which light enters the eye. The surrounding muscles of the iris contract and dilate to control the size of the pupil and consequently the amount of light the retina receives.
Quarterly Replacement Lenses (also known as frequent replacement lenses) are designed to be worn for up to three months, before being replaced with a new pair. Fresh contacts reduce the chances of potentially damaging deposits building up on the lens and represent a healthier way to wear lenses.
Refractive Error is a broad term that refers to any optical weakness that affects the ability of the eye to focus light rays correctly on the retina. This includes farsightedness (where the focal point is effectively behind the retina), nearsightedness (where light converges in front of the retina), and astigmatism (where light is focused on several points on the retina). All of the above can be corrected with contact lenses.
Contact Lens Dictionary S-Z
Soft Contact Lenses are largely made of water, which makes them comfortable to wear and consequently a popular choice. They come in a wide variety models, designed to suit every lifestyle (from daily disposable lenses to extended wear), however some visual problems are best treated with hard contact lenses. The best advice is to consult your eye-care professional.
Toric Contact Lenses are great news for anyone suffering from astigmatism who thought they wouldn't be able to wear contact lenses. Often mild astigmatism is best corrected with Rigid Gas Permeable lenses (as they are ‘hard' they effectively ‘reshape' the lens and cornea) while soft toric lenses tend to be prescribed for more pronounced astigmatism.
UV Protection is an increasingly popular ‘built-in' feature of today's contact lenses, especially for people who enjoy an outdoors lifestyle. However, as they do not reduce glare they must be worn in conjunction with sunglasses.
Visual Acuity refers to the sharpness of vision based on reading a standardized Snellen eye chart at a distance of 20 feet. It's expressed as a fraction, with the ‘top' number referring to the distance from the chart (in the USA 20 feet, in the UK 6 meters) and the ‘bottom' number the distance at which someone with normal vision would be able to read the chart. Hence someone with 20/20 (or 6/6) vision is considered normal, whereas someone with 20/40 (or 6/12 in the UK ) would need to be 20 feet from a character to read it correctly when someone with normal vision could read it at 40 feet.
Wetting Solutions are applied to hard and rigid gas permeable lenses to increase comfort by acting as a ‘cushion' between the lens and the cornea. They may also be dropped directly into the eye while wearing lenses.
X-Coolers are one of a growing number of brands of novelty or cosmetic contact lenses. In the not too distant past special effects contact lenses were more or less restricted to the film industry, however recently their popularity with the general public has snowballed. Today there's wide variety on the market, including subtle shades that enhance natural eye colour at one end of the spectrum, and anything from cat's and alien's eyes at the other.
Young Contact Lens Wearers - parents often want to know at what age it's suitable for their children to start wearing contact lenses. Medically there are no reasons why children shouldn't start wearing lenses as soon as they can walk. However in reality it's going to be quite some time until they are responsible enough to look after their lenses properly. It's best to discuss all the issues thoroughly with your eye-care specialist.
Zinc is one of a handful of minerals that are essential for healthy eyes - along with copper, manganese and selenium. Vitamins are also known to play a fundamental role in optical health, notably vitamin A (for prevention of night blindness), vitamin C (to boost visual acuity), and vitamin E (for prevention of cataracts).