Myopia (Short-sightedness)
Hyperopia (Long-sightedness)
Astigmatism
Presbyopia
Glaucoma
Keratoconous
Cataract
Dry Eye
Pterygium
Age Related Maculopathy
Diabetic Retinopathy
Myopia
Someone who is myopic, or short-sighted, will have difficulty seeing distant objects clearly. Myopia is very common and often begins to develop in teenage years, though many individuals become affected earlier than this. The exact causes for myopia are unknown, but the condition can easily be corrected with spectacles, or contact lenses.
Hyperopia
Hyperopia, or “long-sightedness” is a condition which makes it difficult for people to work comfortably at a close range. For some people close range is blurred and glasses are required. For others, objects at close range may be clear, but more effort is required to focus. These people may tire more quickly and experience difficulty concentrating when conducting tasks such as reading.
Astigmatism
Like short sightedness or long sightedness, astigmatism is an optical condition of the eye. It is basically an irregularity in the shape of the cornea, where the surface of the eye is more curved in one direction than the other. The ideal shape of the cornea is like a soccer ball with the same curve throughout. Any difference in the curve means that each meridian of the eye focuses light differently on to the retina and vision is not clear. Astigmatism is most often combined with myopia or hyperopia. The condition can be corrected with spectacles or contact lenses.
Presbyopia
Presbyopia is an age related progressive condition that makes it difficult to focus objects at near. The first signs of this condition are often difficulty in focusing on phone directories, reading maps or threading needles, even though distance vision is still good. Almost all people notice this problem creeping up on them after their 40th birthday, though some will be affected earlier than this. Presbyopia is caused by a progressive loss of elasticity of the crystalline lens inside the eye. This loss starts early in life but only creates practical difficulties at around 42-45 years of age. Currently only spectacles or contact lenses solve the problems that presbyopia creates.
Glaucoma
Glaucoma is a condition in which nerve cells in the retina become damaged. These nerve cells are important in transmitting information about what we see to the brain. One of the risk factors for this condition is elevated pressure in the eye. Patients with advanced stages of the condition suffer from loss in peripheral vision, or “tunnel vision” and may ultimately lose all vision. Unfortunately, damage to the nerve cells is not reversible. There are not usually any symptoms associated with the condition initially, so this makes it important for everyone, particularly for those aged over 40, or with a family history of glaucoma to have regular eye examinations.
Keratoconous
Keratoconus is a condition affecting the cornea that causes thinning of the tissue and a resulting protrusion of the front surface into a cone-like shape. Vision is severely distorted and the use of specially designed rigid gas permeable (RGP) lenses is required. In very advanced cases a corneal graft may be necessary to improve visual capability.
Cataract
Cataract is a loss of transparency of the clear crystalline lens inside the eye. This can make it difficult to see clearly or to distinguish colours. Cataracts may be uniform throughout the lens or particular areas of the lens may be affected. Once present, changes in transparency are irreversible. Causes can be age, UV damage, other eye conditions, trauma, certain medications or unknown. Treatment is usually the removal of the lens and replacement by a plastic substitute (intra-ocular lens). This operation has had a very high success rate for a number of years.
Dry Eye
A dry eye condition can occur due to an error in the quantity or quality of the components of the tear film covering the eye. The tear film is a complex secretion of oils, mucous and water that is produced by numerous glands and its role is to lubricate the conjunctival and corneal cells. A lack of an oily superficial layer on the tear film results in faster evaporation of the underlying water (aqueous layer). A deficiency of mucin on the surface of the eye leads to poor lubrication. An inadequate aqueous layer occurs when the lacrimal gland produces insufficient fluid and this condition is often referred to as kerato-conjunctivitis sicca (KCS). Age and gender can be factors affecting the prevalence of dry eye as it is more common amongst older people, particularly post-menopausal women.
The vast majority of dry eye cases do not involve contact lens wear. However, some contact lens wearers, particularly soft contact lens wearers, do report that their eyes feel dry, particularly towards the end of their normal wearing period, i.e. after 8 hours or more of continued lens wear. This sensation may be reported as a regular occurrence or as an intermittent/random event. Contact lens wear in an air-conditioned environment is usually found to make the situation worse. This is because most air-conditioning technologies remove significant amounts of water vapour from the air. Therefore, the relative humidity of the wearer’s environment is lower and this increases the rate of evaporation of water from the eye.
The most common treatment for dry eye is the use of artificial tear supplements.
Pterygium
A pterygium is a degenerative condition of the conjunctiva that progresses across the conjunctiva and onto the cornea. It typically forms on the surface of the eye near to the nose and has a triangular shape with the base on the conjunctiva. The tissue contains many blood vessels and as it grows in size it destroys the superficial tissue of the cornea. Pterygia are usually harmless, though ultimately they can affect vision by changing the shape of the cornea or, if large enough, by blocking the light entering the pupil. In these cases surgical removal is necessary.
Age Related Maculopathy
About 250,000 older Australians have Age Related Maculopathy (ARM). Some of these people have severely impaired vision and some are legally blind. ARM affects the macula, which is the most sensitive part of the retina responsible for central vision. When the integrity of the macula is impaired, as in ARM, vision can be dramatically affected.
People do not become blind with ARM as they can still see clearly at the sides, above and below. In the centre however, they develop a black or grey patch that prevents them from seeing clearly. Often the first sign for people with ARM is that they see a bend in straight lines or that there is distortion in their central area of vision.
There is no hard evidence as to why ARM develops. Generally ARM is not considered to be an inherited disorder. However, there is some evidence that ensuring that adequate amounts of antioxidants are included in the diet slows, and in some instances halts, progress of the disease. Green leafy vegetables are rich in the appropriate antioxidants, and it is recommended that at least three servings per week are included in the diet.
Although there is no cure for ARM, patients who have ARM may consult their optometrist to prescribe appropriate optical aids to assist in reading, and to provide advice on how to make best use of remaining vision.
Diabetic Retinopathy
Almost 1,000,000 Australians have diabetes. About half of these people are unaware that they have diabetes and many don’t discover the disorder until it affects them badly. For example, about 15% of diabetics already have evidence of diabetic eye disease at the time diabetes is diagnosed. Generally diabetic eye disease would indicate that the disease had been present for a number of years.
Diabetes affects the small blood vessels in the retina of the eye. The “walls” of the blood vessels weaken, and unless action is taken the blood vessel may rupture. The effects of the resulting hemorrhage may be catastrophic for vision.
Usually these changes to the eye are irreversible and as a result, vision is lost. The tragedy of this is that in very many instances these vision problems could have been avoided. Research has shown that tight control of blood sugar level prevents or delays the onset of these retinal changes and subsequent hemorrhages. “Tight control” simply means checking blood sugar levels regularly and ensuring that it falls within the normal range.
With or without tight control, it is essential that those people with diagnosed diabetes have their retinas examined by an optometrist regularly. This is done in a simple in-office procedure, by dilating the pupils. When viewing the retina, the optometrist can look for and detect the presence of early retinal changes before damage occurs, and can arrange appropriate treatment if needed.
