Normal vision occurs when incoming light rays focus precisely on the eye's retina The retina acts as a camera to the brain.
Vision problems occur due to the shape, health or age of your eyes.
Myopia, more commonly known as nearsightedness, occurs when an eye has too much focusing power.
This means that the eyeball is either too long or the cornea is too steep, and the projected image falls short of the retina.
The result is an improperly transmitted message to the brain or simply a blurred image.
Hyperopia or farsightedness occurs when an eyeball is too short or the cornea’s curvature is too flat.
The image that is being focused upon falls past the retina in this case resulting in blurred or distorted vision.
Many people who wear glasses due to either myopia or hyperopia will often have some astigmatism as well. But astigmatism can also occur on its own and cause the need to wear glasses.
An astigmatic eye has an uneven surface - the cornea can be more curved or steeper at one axis than at all others. This results in having more than one focal point and, of course, blurred vision.
An astigmatic eye is shaped more like a football (toric) whereas a normal shaped eye is more spherical, like a basketball.
Astigmatism can make wearing contact lens difficult or impossible.
Presbyopia is a natural aging process that usually occurs between the ages of 40 and 50. The lens of the eye hardens and the muscles weaken. When people who have perfect vision all their lives become presbyopic, they need to wear reading glasses. People who already wear glasses for distance vision need to wear bifocals. Monovision compensates for presbyobia.
With monovision, patients choose to slightly under-correct one eye. This would leave a targeted amount of residual myopia or nearsightedness which in turn would allow you to read comfortably without the need for magnification (reading glasses). This way, the under corrected eye will provide near vision, while the fully corrected eye will provide distance vision.
The next natural question is: “Will I not be unbalanced if my two eyes are not the same prescription?” In the vast majority of cases, the answer is “No”. The amount of difference between the two eyes is minimal. The brain typically adapts to monovision within the first few weeks or months.