Glaucoma (Part One)
Definition
Glaucoma is a term that describes a group of eye disorders with the common characteristic of increased pressure of the eye fluid (aqueous humour), which is called intraocular pressure.
Anatomy of the Eye
The eye is an asymmetric globe.
The front part of the eye consists of:
- iris – the pigmented part
- cornea – the layer above the iris
- pupil – the circular black opening that allows light to enter
- sclera – the white part
- conjunctiva – the thin layer that covers the front part of the eye except for the cornea
Just below the iris and pupil, the lens (eye lens) is located.
The eye is filled with a gel called vitreous.
The eye is enveloped by three layers:
- Sclera (the outer layer)
- Choroid (the middle layer)
- Retina (the inner layer)
Normal Intraocular Pressure
The intraocular pressure of the eye is measured in millimeters of mercury. The normal values of intraocular pressure are 12-22 mmHg.
Physiology of the Normal Circulation of Eye Fluid.
The eye fluid (aqueous humour) is produced by the ciliary processes of the eye, then this fluid passes into the posterior chamber of the eye, further through the pupil into the anterior chamber of the eye, from here the trabecular meshwork drains this fluid through Schlemm's canal into the scleral plexus and into the blood circulation.
Optic Nerve
An increase in intraocular pressure can damage the vision in the affected eye and can lead to complete blindness if not treated. Loss of vision occurs due to damage to the optic nerve which transmits visual signals from the eye to the brain.
Classification
Glaucoma is classified into two categories:
- Open-angle glaucoma
- Closed-angle glaucoma
*The angle refers to the space between the cornea and the iris – the iridocorneal angle, through which the eye fluid must flow to be drained through the trabecular meshwork into the blood circulation.