The Normal Eye

The cornea at the front of the eye is the most important structure for focusing light onto the back of the eye (the retina). The crystalline lens in the eye aids in this process by altering its shape to change the focus of the eye from distance to near.

In a normal or emmetropic eye, light rays from a distant source are sharply focused by the cornea and lens onto the retina, resulting in clear distance vision. Emmetropia is achieved when there is a balance between the optical power and the length of the eye, allowing images to be perfectly focused on the retina.

Refractive errors such as myopia (short-sightedness), hyperopia (long-sightedness) and astigmatism occur when the cornea’s optical power and length of the eye are not aligned, thereby preventing light rays from focusing accurately onto the retina.

Emmetropia of the Eye.png

Overview of Eye Conditions


In myopia or shortsightedness, light rays from distant objects are focused in front of the retina resulting in blurred distance vision.


In hyperopia or long-sightedness, light rays from distant objects are focused behind the retina because the focusing power of the eye is too weak relative to the length of the eye.


Astigmatism exists when the cornea is not uniformly curved, causing images to be blurred at all distances. Astigmatism can be present in both long and short-sighted eyes.


Presbyopia is a normal ageing process of the eye which makes reading and seeing objects up close more difficult, usually from your mid-40s onwards.


A cataract is the clouding of the natural crystalline lens of your eye. It is a natural part of the aging process and is a common cause of gradual deterioration in our eyesight as we get older.


In keratoconus, the cornea gradually thins and forms a cone-shaped bulge, resulting in progressive blurring of vision.


A pterygium is a pink, fleshy, wedged-shaped growth of tissue on the whites of the eye that encroaches onto the cornea.