Know more about your eye
Anatomy of the eye
Ocular structures contribute to the refractive apparatus of the human eye are cornea, aqueous (the clear fluid filling the space between the cornea and the lens), crystalline lens, and vitreous (the transparent jelly-like liquid filling the eyeball behind the lens and in front of the retina).
A relaxed eye or an eye looking at distant object (6m and beyond) has an approximate optical power of 60D (diopters). Cornea has a power of 40D, about the two thirds of the total power of the eye and the lens has a power of 20D.
An eye that has too much or too little refractive power to focus light onto the retina has a refractive error.
There are different types of refractive errors: short-sightedness (myopia), long-sightedness (hyperopia), astigmatism and presbyopia.