This guide is one of two describing common eye conditions, both explain what these conditions are and how optometrists can help. This one covers refractive error – the reason that people need corrective lenses (glasses or contact lenses). The Common eye conditions – eye disease guide covers eye disease, both minor eye conditions and sight threatening diseases.
For refractive error, an optometrist will assess the correction needed and prescribe corrective lenses if necessary.
Refraction is the bending of light as it passes from one medium to another. The eye has several optical elements that, if correctly powered, focus light onto the retina at the back of the eye. However, there are four common types of refractive eye conditions where the eye is unable to correctly focus light onto the retina. These ‘refractive errors’ can cause vision to be blurred, and may lead to headaches and eye strain.
Myopia – short sightedness
Myopia is a refractive condition of the eye where light focuses in front of the retina. This makes distant objects appear blurry, but objects that are close are clearer. If the amount of myopia is large enough and is left uncorrected, distance vision is poor and may lead to headaches and eye strain.
Hyperopia – long sightedness
Hyperopia is a refractive condition of the eye where light focuses behind the retina. This makes close objects blurry, and while distant objects may appear clearer sometimes they are blurry too.
If the amount of hyperopia is large enough and is left uncorrected, close vision may be poor and may lead to headaches and eye strain, particularly in adults.
Astigmatism is where the optical surfaces are shaped more like a rugby ball than a football. This means that there is not a clear single point of focus. If left uncorrected, it can also lead to headaches and eye strain.
Presbyopia is caused by a loss of flexibility of the lens inside the eye. It affects all people as they age, generally becoming problematic after 40 years of age. Presbyopia results in the inability to focus on close objects.
Presbyopia makes it difficult to read small print, and focus on closer objects, particularly in poor light.
Optometrists can recommend wearing an appropriate correction, such as reading glasses, or multifocal glasses.
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