Eyes Are Not Always Perfect
Some eyes simply don't work as well as others. These problems are not always diseases, but are a part of the natural variation in people and how we are built.
Refractive errors are when the image of what you are looking at is not focussed properly onto the retina. The retina is like a film in a camera. There are four major refractive errors: myopia, hyperopia, presbyopia and astigmatism.
For perfectly clear vision, the image of a viewed object needs to be focused onto the back of the eye, just as a camera has to be focused properly in order to take a clear picture. If the image is not focused exactly on the retina, then the image will be blurred, just like an out-of-focus photograph. In this case, the person is said to have a refractive error.
If you think you may have an eye problem contact your optometrist immediately.
Short Sighted (Myopia)
Myopia, commonly called shortsightedness, is a condition in which the image that we see is focused in front of the retina, resulting in blurred vision.
Shortsighted people can often see reasonably clearly at short distances, but will not be able to see distant objects clearly. There is currently no cure for myopia, but spectacles, contact lenses and refractive surgery can all provide good distance vision for people with myopia.
Is My Child Short-sighted?
A complete eye test is the only sure way of determining whether your child's vision is normal. Some clues to myopia in a child are:
screwing up eyes to see distant objects;
difficulty reading the blackboard at school;
poor posture while reading; and
lack of interest in playing outdoor games.
Long Sighted (Hyperopia)
Long (or far)-sightedness, also known as hyperopia, is a condition of the eye in which light is focused behind the retina. This results in close objects appearing blurry, while far objects may appear normal.
As the condition worsens, objects at all distances may be blurry. Other symptoms may include headaches and eye strain (1). People may also experience accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus (2).
Hyperopia occurs when the eyeball is too short, or the lens or cornea is misshapen. There can be many reasons for this. Far-sightedness primarily affects young children, with rates of 8% at 6 years and 1% at 15 years. It then becomes more common again after the age of 40, affecting about half of people.The problem can be corrected with eyeglasses, contact lenses, or surgery. Glasses are easiest while contact lenses can provide other benefits.
Presbyopia (Age Related Long Sighted)
Presbyopia is the gradual reduction in the amount that the eye can change its focus. The changes are the result of the continued growth of the biological lens inside the eye, and are a normal part of ageing.
Presbyopia usually becomes noticeable between the ages of 40 and 50 as an inability to focus on near objects. People in this age group often find that they have to hold things further away to see them clearly.
Presbyopia can be corrected by glasses with an optical prescription specifically designed for close work. This can be provided in many forms, including reading glasses, bifocals, trifocals and progressive lenses (multifocals).
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Double Vision (Diplopia)
Diplopia, commonly known as double vision, is a problem in which the brain sees two images of a single object that may be displaced horizontally, vertically, diagonally (i.e., both vertically and horizontally), or rotationally in relation to each other.
It is usually the result of problems with the muscles that control the eye, where both eyes are still work but they cannot turn to see the desired object together. Problems with eye muscles may be due to mechanical problems, nerve issues, problems with stimulation of the muscles, and some very uncommon causes.
The appropriate treatment for binocular diplopia will depend upon the cause of the condition producing the symptoms. Our optometrist will undertake a careful and through eye examination to identify the underlying cause of the problem and recommend a way to move forward with the problem.
Astigmatism is a condition where the optical power of the eye varies depending on the angle of light passing through it.
Astigmatism produces blurred vision at all distances. It is usually due to the shape of the cornea (the front surface of the eye). If the curvature of the cornea is not the same in all directions (like the side of an Australian football) it will bend the light passing through it by different amounts depending on the direction of the light, producing astigmatism.
Astigmatism is a condition where the optical power of the eye varies depending on the angle of light passing through it. Astigmatism produces blurred vision at all distances. It is usually due to the shape of the cornea (the front surface of the eye). If the curvature of the cornea is not the same in all directions (like the side of an Australian football) it will bend the light passing through it by different amounts depending on the direction of the light, producing astigmatism.
Astigmatism is a focusing error which causes asymmetric blur. Some directions in an image are more out of focus than others. This can be contrasted with short-sightedness (myopia) where all directions are uniformly blurred.
Objects at all distances are indistinct or blurred and the eye cannot focus. Even slight degrees may encourage headaches, fatigue and reduce concentration. This is because the eyes may try, without success, to correct the blur, and because there is a tendency to screw up the eyes to try to see better, producing discomfort in the muscles of the eyelid and face.
Spectacles and contact lenses (hard and soft) can correct astigmatism. Sometimes correction of astigmatism can cause change in the apparent size and shape of objects and may affect judgement of distance. A patient may feel taller or shorter, or walls may appear to slope and floors curve.
In most cases, adjustment to these side effects takes only a week or so. Astigmatism correction may involve a compromise between optimal clarity and visual discomfort.
(2) Moore, Bruce D.; Augsburger, Arol R.; Ciner, Elise B.; Cockrell, David A.; Fern, Karen D.; Harb, Elise (2008). "Optometric Clinical Practice Guideline: Care of the Patient with Hyperopia" (PDF). American Optometric Association. pp. 2–3, 10–11. Archived (PDF) from the original on 2006-07-17
(3) Castagno, VD; Fassa, AG; Carret, ML; Vilela, MA; Meucci, RD (23 December 2014). "Hyperopia: a meta-analysis of prevalence and a review of associated factors among school-aged children". BMC Ophthalmology. 14: 163. doi:10.1186/1471-2415-14-163. PMC 4391667 . PMID 25539893.