EYE HEALTH A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Astigmatism This is an irregular curvature of the front surface of the eye. The best analogy is where the curves are shaped more like a rugby ball than a football. Cataracts: What is a cataract? A cataract is a clouding of part of your eye called the lens. Vision becomes blurred or dim because light cannot pass through the lens to the back of your eye. What causes cataract? Cataracts can form at any age, but most often develop as people get older. Some symptoms You may notice that some things seem blurred round the edges, of that your glasses seem dirty or scratched. Bright light or very sunny days make it more difficult to see. As the cataract develops its centre becomes more yellow, giving everything a yellowish tinge. What can be done to help? The most effective treatment for cataract is a small operation to remove the cloudy lens. The lens is usually replaced by a plastic implant which helps the eye focus properly. With modern surgery the operation can be carried out at any stage of the cataract's development when visual impairment interferes with your ability to read, work or your quality of life. Dispensing optician Dispensing opticians are qualified to examine optometrist's prescriptions to determine lens specifications. They recommend frames, lens types and coatings after considering the prescription and the customer's occupation, habits, and facial features. Glaucoma: What is glaucoma? Glaucoma is the name of an eye condition in which the optic nerve is damaged at the point where it leaves the eye. The eye needs a certain amount of pressure to keep its shape so that it can work properly. In some people, the damage is caused by raised eye pressure. Others may have an eye pressure within normal limits but damage occurs because of a weakness in the optic nerve. The most common form of glaucoma is chronic glaucoma where eye pressure rises very slowly but there is no pain to show there is a problem. If untreated, over a period of time, the field of vision gradually becomes impaired. Chronic glaucoma is more common with increasing age. It is uncommon below the age of 40, affecting 1% of people over this age and 5% over 65. If you have a close relative who has chronic glaucoma, then you should have regular eye tests. This is especially important if you are age over 40.Acute glaucoma is much less common. This happens when there is a sudden rise in eye pressure. It can be quite painful and will cause permanent damage to your sight if not treated properly. How is glaucoma detected? Tests for chronic glaucoma are carried out as part of a regular eye test. Viewing the optic nerve by shining a light from a special torch into your eye, measuring the eye pressure using one special instrument and testing your fields of vision with another, which shows a sequence of spots of light on a screen. A sudden increase in eye pressure can be very painful. The affected eye becomes red and sight deteriorates. Vision may seem misty with coloured rings around white lights. There may even be nausea and vomiting. How is glaucoma treated? The main treatment for chronic glaucoma aims to reduce the eye pressure. It is usually started with eye drops but can involve a small operation to reduce the pressure. Immediate hospital treatment may be required with acute glaucoma. Can glaucoma be cured? Although damage already done cannot be repaired, with early diagnosis and treatment, damage can usually be kept to a minimum. With thanks to the Royal College of Ophthalmologists and the IGA. Long sightedness (hypermetropia) Difficulty focusing on close objects eg. reading. Here the eyeball is too short to focus images on the back of the eye. Multifocal Lenses Around the age of 40, the eye increasingly loses its ability to "focus" the image during near vision (e.g. during reading). It becomes presbyopic. For this reason, lenses to compensate for presbyopia possess different powers for distant and near vision. In multifocal lenses, these different power zones are visibly separated from one another. Lenses with one zone for distance vision and one for near vision are known as bifocals; lenses with an additional intermediate zone for vision at medium distances as trifocals. Optometrist Previously known as Ophthalmic Optician, this term was adopted in the UK to conform to the international standard. Presbyopia ('ageing eye') This is part of growing older, and usually occurs in the late forties. Whilst distance vision can remain good there is an inability in the eye's optical system to focus on near objects, resulting in the need for reading glasses. Photochromics Lenses These are lenses that automatically react to varying degrees of light. Simply, the brighter your surroundings, the darker the lens becomes. These are available in Plastic or Glass. Short sightedness (myopia) The inability to see clearly at longer distances, for example when driving. This is usually caused by the eyeball being too long to focus images clearly on the back of the eye. Ultra Violet Light (UV) Ultraviolet light is a form of radiation which is not visible to the human eye. It's in an invisible part of the "electromagnetic spectrum". Your eyes are also sensitive to overexposure of UV radiation. UV-B is partly absorbed by the cornea. UV-A passes through the cornea and with time and overexposure may contribute to the formation of cataracts. Snow reflects up to 85% of the incident UV radiation. This additional amount of absorption of reflected UV-B radiation by the cornea can result in snow blindness -- a sun burning of the eye. Sunglasses screenout 99% of the UV-A and UV-B radiation reaching your eyes. UV light can be subdivided into:UVC - (wavelengths below 280nm) which are effectively filtered out before they reach us by the ozone layer.UVB - (wavelengths between 280nm and 315nm) these rays are responsible for sunburn and snow blindness. Reflective surfaces such as water or snow substantially increase the amount of UV entering our eyes. UVA - (wavelengths between 315nm and 380nm) potentially the most damaging area because they can cause chronic eye damage, especially low exposure over a long period of time. Back to Top A B C D E F G H I J K L M N O P Q R S T U V W X Y Z © 2004 i2i optometrists. Powered by Optisoft Ltd.