Patient Information

Cornea

The cornea is the transparent front covering part of the eye.

Medical terms of the cornea often start with the prefix "kerat."

Because transparency is of prime importance, the cornea has no blood supply; it gets oxygen directly through the air. It receives nutrients via diffusion from the tear fluid through the outside surface and the aqueous humour through the inside surface.

Function of the cornea: The cornea is the primary (most powerful) structure focusing light entering the eye (along with the secondary focusing structure, the crystalline lens).

Cataracts

What are cataracts?

A cataract is a clouding of the normally clear lens of the eye. When the lens becomes cloudy, light cannot pass to the retina properly, and vision is blurred and decreased.

Retina

Light-sensitive layer of tissue, lining the inner surface (back) of the eye

Contains millions of photoreceptors that capture light rays and convert them into electrical impulses.

These impulses travel along the optic nerve to the brain where they are turned into images.

The retinal blood vessels nourish the inner layers of the retina.

Glaucoma

What is the normal intraocular pressure?

Intraocular Pressure (IOP) is the pressure of the contents of the eyeball. Normal intraocular pressure varies between 12 and 20 mm Hg. However, some eyes can tolerate higher pressures than others. That is why it may be normal for one person to have a higher pressure than 20 mm Hg and yet remain symptomless.

What is glaucoma?

Glaucoma is a disease caused by increased intraocular pressure resulting either from a malformation or malfunction of the eye's drainage structures. Left untreated, an elevated IOP causes irreversible damage to the optic nerve and retinal fibers resulting in a progressive permanent loss of vision. However, early detection and treatment can slow, or even halt the progression of the disease.

How is the IOP balanced?

The ciliary body constantly produces aqueous humor - a clear fluid that fills the anterior chamber (the space between the cornea and iris). The aqueous drains out of the anterior chamber through a complex drainage system. The delicate balance between the production and drainage of aqueous determines the eye's intraocular pressure (IOP).