Introduction
Emmetropia (Optically Normal Eye)
Emmetropia is the state of refraction wherein the parallel rays of light coming from infinity focuses at the sensitive layer of retina with the accommodation at rest.
At birth, eye is hypermetropic by +2 to +3D and usually becomes emmetropic by the age of 5 to 7 years.
Ammetropia (a condition of refractive error)
Ammetropia is the state of refraction wherein the parallel rays of light coming from infinity focuses either in front or behind the sensitive layer of retina,in one or both the meridia with accommodation at rest.
Types of Ammetropia
Myopia
Technically, it is a type of refractive error in which parallel rays of light coming from infinity focuses in front of the retina when accommodation is at rest.
Another term for this is nearsightedness. Usually, it is occurs when the eyeball becomes big, causing blurred vision. Some people can develop it from the genetics and eyestrain. Someone who is nearsighted can see things up close but have trouble with objects that are at a distance. The correction for this condition is through the prescribed glasses, contacts or vision correction surgery. Usually, surgery is the best suggestion when the power is quite high. There are natural vision improvement methods which including better diet and vitamin – A.
Hypermetropia or hyperopia – Follow this link for more details
Technically, is a type of refractive error in which parallel rays of light coming from infinity focuses behind the retina when accommodation is at rest.
Another term for this is farsightedness. Usually, it is occurs when the eyeball becomes small, causing blurred vision again, eyestrain. Some people can develop it from the genetics and eyestrain. Someone who is farsighted cannot see things up close but have no problem with objects that are at a distance. The correction for this condition is through the prescribed glasses, contacts or vision correction surgery. Again in this case, surgery is the best suggestion when the power is quite high. But, just like myopia, there are natural methods to prevent and treat farsightedness. They include changing your diet and incorporating eye exercises into your daily routine.
Astigmatism
Technically and generally speaking, Astigmatism is the type of error where in the refraction varies. It occurs when the cornea or lens have irregular shape. This results the lights to focus on the different focal points causing blurred vision. Symptoms for this is as similar to that of refractive error like blurred vision, headaches, and eyestrain. It can get better or worse over time as per conditions. Again in this case, correction is by prescribing the glass not for correcting vision but to relieve the strain, fatigue and headaches.
Source Reference : Rebuild your vision
