There are 16 entries in the glossary.
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| 20/20 Vision | This is also known as perfect sight where no prescription is required in order to see things clearly and comfortably. The fraction 20/20 is understood as follows: the bottom half represents the distance in meters at which a perfect sighted person is able to see clearly a target seen by another at 20 feet. So if you are perfect sighted you will see at 20 feet exactly what another perfect sighted person will see at 20 feet. However, if you have trouble seeing things in the distance, you might see at 20 feet what a perfect sighted person sees at 40 feet. So this means your vision is measured as 20/40.
Assuming you have perfect sight then when you are looking at something in the distance, light from the object will focus on your retinas very precisely. When seeing something close-up the focusing is blurred very momentarily, but this is unnoticeable because your eye has an automatic refocusing ability that makes the target clear. This refocusing ability is called 'Accommodation' and it works by making the natural lens of the eye fatter, or more convex in shape. As we get older we lose more and more of this ability, which is why things close-up start to blur after about 45 years of plodding on the planet.
Short-sightedness means that the light focuses in front of your retinas or 'too short' and long-sightedness means it focuses 'behind' or 'too long' |
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| Astigmatic | Often the eye is shaped like an egg or football. This is what we call astigmatism. It is quite a normal condition and most of us have to some degree. Like an egg, two main areas of curvature are found: one is flatter and the other is steeper. This causes the light to focus in two different positions such that the steeper or more curved area focuses further forward and the less curved or flatter further back. The effect on vision is to distort shapes so similarly shaped characters become confused. The letter G may be confused with a C and the number 2 may be mistaken for the letter Z. |
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| Astigmatism | Often the eye is shaped like an egg or football. This is what we call astigmatism. It is quite a normal condition and most of us have to some degree. Like an egg, two main areas of curvature are found: one is flatter and the other is steeper. This causes the light to focus in two different positions such that the steeper or more curved area focuses further forward and the less curved or flatter further back. The effect on vision is to distort shapes so similarly shaped characters become confused. The letter G may be confused with a C and the number 2 may be mistaken for the letter Z. |
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| Bifocals | The gradual decrease in ability of the eye to focus is a natural part of the aging process. Bifocals contain two prescriptions for correcting vision at different distances. Bifocals aid both near and far vision, with a visible line dividing the two areas of power prescription. |
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| Blended multi-focals | These lenses have two focal corrections without the noticeable lines. The area that fuses the two powers together is unusable area. |
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| Cataract | A cataract refers to any cloudiness within the natural lens of the eye. Most often, this is age-related, but accelerated risk of cataract is now caused by over-exposure to ultra-violet light. This is worsened by the fact that the Ozone Layer is constantly thinning. Our advice is to take care when in the sun and always don a hat and a good pair of UV-blocking sunglasses. Ask your optometrist for more information. If you develop or are developing a cataract, don't worry unnecessarily. The sky does not fall down even though it might be slightly smeary to look at. A simple operation can be performed by an ophthalmologist whereby the cataractous lens of the eye is removed and replaced by a new implant. You will probably be sent home the same day! |
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| Glaucoma | There are two types of adult-onset glaucoma and both refer to an increased abnormal pressure within the eyeball. The rarer form is when an acute attack occurs. Symptoms include a painful, red eye and possible light sensitivity and nausea. The most common form of Glaucoma is the preventable chronic type. Sight is adversely affected if it is not picked up early, the long-term effect being progressively worsening tunnel vision. It is essential to have your eyes screened for glaucoma once you are over the age of 40 years as the relative risk increases from this point. Other factors increasing the risk of glaucoma are diabetes, high levels of short-sightedness, age and family history.
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| Long-sightedness | Also known as Far-sight or Hyperopia, long-sighted individuals have difficulty with anything close-up while their general distance vision is not as bad. Light from objects viewed will theoretically focus behind the retina and not on it. However because the eye is able to naturally fatten the lens and cause light to bend more, this error in focus is overcome, which explains why distance vision is generally pretty good. When the same individual tries to look at something up close, much more effort is required, as light from a near object will fall much further back behind the retina. Vision at near is therefore worse. |
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| Near-sighted | Also known as Near-sight or Myopia, short-sighted individuals have trouble seeing things in the distance while anything close-up is clearer. This occurs because light from the objects being viewed focuses in front of the retina and not on it. It is believed that this mostly happens as a result of the eyeball being slightly too long. The scientific term for this is Axial Myopia. |
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| Optometrist | also known as doctors of optometry, or ODs, provide most primary vision care. They examine people’s eyes to diagnose vision problems and eye diseases, and they test patients’ visual acuity, depth and color perception, and ability to focus and coordinate the eyes. Optometrists prescribe eyeglasses and contact lenses and provide vision therapy and low-vision rehabilitation. |
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| Presbyopia | As our eyes grow older the ability to focus clearly on anything close-up starts to diminish. This occurs because we lose our ability to accommodate or make the lens of the eye fatter in shape. One popular way of explaining how this happens likens the natural lens of the eye to a pillow with feathers inside. The lens contains many fibres (feathers) which grow throughout life in the same way that hair and skin continues to grow. This is not surprising considering that these tissues all come from the same founding cells. When the lens is younger and has fewer fibres it is more flexible and can change its shape more easily just as a pillow with fewer feathers can. When the lens is older and has many more fibres this flexibility is obviously lost which causes the near vision to blur. |
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| presbyopic | As our eyes grow older the ability to focus clearly on anything close-up starts to diminish. This occurs because we lose our ability to accommodate or make the lens of the eye fatter in shape. One popular way of explaining how this happens likens the natural lens of the eye to a pillow with feathers inside. The lens contains many fibres (feathers) which grow throughout life in the same way that hair and skin continues to grow. This is not surprising considering that these tissues all come from the same founding cells. When the lens is younger and has fewer fibres it is more flexible and can change its shape more easily just as a pillow with fewer feathers can. When the lens is older and has many more fibres this flexibility is obviously lost which causes the near vision to blur. |
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| Progressive flat-tops | These lenses change power gradually as the eye moves down through the near segment allowing a range of ten inches to ten feet. One visible line divides the distant power prescription to the intermediate and near prescription. |
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| Progressive no lines | Advanced technology allows these lenses to gradually change in power from the distance segment to the near vision segment Your specific prescription is ground from a series of custom lens designs and powers. |
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| Single vision | One focal distance is required for your eyes to make adjustments at differing focal distances. |
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| Trifocals | Trifocals are prescribed to aid near, far and middle distance seeing. The trifocal lens design has three distinct areas of power to be used, with visible lines dividing the three distinct areas of power prescription. |
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Glossary