Short sighted? Long sighted? Astigmatism? Presbyopia?
Eye conditions explained. When the shape of your eye does not bend light correctly this results in a blurred image. The main types of refractive errors are myopia (nearsightedness), hyperopia (farsightedness), presbyopia (loss of near vision with age), and astigmatism. Refractive surgery corrects these errors with a laser or lens implant or lens exchange.
Normal Vision - Emmetropia
Vision when absolutely no refractive error or de-focus exists. Emmetropia refers to an eye that has no visual defects. Images formed on an emmetropic eye are perfectly focused, clear and precise.
Short Sight - Myopia
The focusing power of the eye is too strong and a negative (-) lens is required to correct vision. Glasses are required to provide good long distance vision.
Long Sight - Hyperopia
The focusing power of the eye is too weak and a positive (+) lens is required to correct vision.
If you are a LOW Hyperope your vision is clearer at distance than your close-up vision
If you are a HIGH Hyperope your vision is blurred at both distance and close-up vision
Astigmatism causes blurring at all distances. The eye is not perfectly round; it’s more like a rugby ball and its surface is not symmetrical. It focuses light from one direction better than from others.
A cataract is when the lens inside the eye becomes cloudy. As a result the lens interferes with vision which becomes blurry or darkened.
Another symptom of cataract is ‘glare’. If untreated, vision becomes progressively worse. This condition usually affects people after the age of 60 to 70 but could occur earlier.
- The need for reading glasses
Presbyopia is a gradual process starting at about 45 years of age when people find it increasingly difficult to see objects close up. This is caused when the lens inside the eye becomes less flexible. Presbyopia makes it hard to change focus from near to far and back again. If you have short-sight and are over 45, you may take off your glasses to read, or use bifocal glasses to see at both short and long distances.