How we see?
Light enters the eye through the cornea (transparent layer in front of iris and pupil) and focuses on the retina at the back of the eye. The retina is the layer of the eye which is very sensitive to light and is where the clear image we see is created.
Myopia (Short-Sightedness) = when we are myopic or short-sighted things in the distance are hard to see or appear blurry, but we can focus on things up close easily. This is usually because our eye is longer than normal, so instead of the light focusing exactly on the retina it focuses in front of it. That is why we need glasses, the prescription to correct myopia helps the light focus exactly on the retina, to give us clear vision.
Hyperopia (Long-sightedness) = when we are hyperopic or long-sighted, we will be able to see things far away clearly, but things up close may be blurry or appear out of focus. This is usually because our eye is shorter than normal, so the light focuses behind the retina instead of sharply on it. That is why we need glasses, the prescription to correct hyperopia helps the light focus exactly on the retina, to give us clear vision.
Astigmatism = You may have already heard of the common phrase “astigmatism is when your eye is shaped like a rugby ball”. Most people have a small amount of astigmatism, with some people having a larger amount than others. It means that the cornea at the front of the eye is slightly more curved rather than perfectly round and this causes the light to focus on multiple points in the retina rather than one, giving us a blurry or distorted image rather than a clear and sharp one. Again, the prescription to help this helps the light focus in one place giving us clear vision.
Presbyopia = The lens in our eye changes shape to allow us to change our focus from seeing clearly in the distance to seeing clearly up close. As time goes on the lens becomes a bit stiffer and doesn’t change shape as quickly meaning we struggle to focus up close or to read and must hold things further away or hold them at arm’s length to read clearly. This is called Presbyopia. It can be easily corrected with a pair of reading glasses to help us see clearly up close with no discomfort.