People experience many defects of vision. Although it seems as wearing glasses is the solution to any defect, not all defects can be overcome by using the same type of glasses. The causes should be properly observed and addressed accordingly. Among all eye defects, hyperopia (or Long sightedness) and myopia (or short sightedness) are two very common problems. Their differences are highly distinguishable as their names imply.
Hyperopia (Long Sighted)
Long sightedness also known by the names far-sightedness or hyperopia is the condition where objects at a close distance cannot be focused properly. People with long sightedness have problems adjusting the optical power to focus on closer objects hence experience blurred vision. Other symptoms associated with long sightedness are eyes aches, eyes aching while reading and headache etc.
Long sightedness can be resulted by injuries, aging or genetics. The physiological characteristics of this defect are having short eyes (light travel distance to the retina) or flat cornea focusing images behind the retina. The solution is to shift the reflection in front and on to the retina. To do this long sighted people should wear convex lenses. Refractive surgery can also help to overcome the problem. There are many sub variations of the long sightedness such as simple hyperopia, functional hyperopia, or pathological hyperopia. Long sightedness is not common among children because they have flexible lenses. The impact increases with age; a common sign is holding the newspaper faraway when reading.
Myopia (Short Sighted)
Short sightedness is known as myopia or near sightedness. This is the defect where vision is weak when observing objects at a distance. People with myopia also experience blurred vision when looking at a distant object. This also occurs due to various genetic effects. Many sub variations are found in short sightedness. These are classified by cause, clinical appearance and degree of severity. Some of them are axial myopia, refractive myopia, simple myopia, nocturnal myopia, induced myopia, low myopia, high myopia etc.
The physiological characteristics of the defect are having long eyes (axial length) or high curvature of the cornea. These make the reflection to fall, not on the retina, but get focused before reaching the retina. The solution is to shift the reflection behind and on to the retina. To do this short sighted people should wear concave lenses or do refractive surgery.
Hyperopia vs Myopia
• Hyperopia or Long sightedness is when the short distance vision is weak and myopia or short sightedness is when the long distance vision is weak.
• In long sightedness, the reflections of objects are focused behind the retina and in short sightedness the reflections of objects are focused in front of the retina.
• To overcome long sightedness the reflections should be moved front to be focused on to the retina; therefore, convex glasses are used and to overcome short sightedness the reflections should be moved behind to be focused on to the retina; therefore, concave glasses are used.
• A long sighted person reads Snellen eye chart for long distance well but find difficult to read Jaeger eye chart for short distance, but a short sighted person reads Jaeger chart well but not the Snellen eye chart.