The eye is spherical. Most of the eye's interior consists of a gelatinous mass called the vitreous body. Behind the vitreous body sits the retina with its light-sensitive cells, impulses from which are lead to the optical nerve. In front of the vitreous body the lens of the eyes is suspended and in front of the lens is the iris, with its round opening known as the pupil. The cornea is the outermost layer. Between the cornea and the iris, is a cavity known as the anterior camera and there is also a cavity between the iris and the lens, called the posterior camera. These two cavities are filled with a clear liquid called the chamber fluid. This liquid is produced by structures in the posterior camera, it passes through small canals to the anterior camera, from which it leaves the eye through veins in the surrounding sclera. Normally the amount of liquid drained from the eye equals the amount produced, this ensures that the eyeball is kept distended at a constant pressure.
If the drainage of the chamber fluid is completely or partially blocked for various reasons, an overpressure is created which damages the optical nerve and leads to decreased vision, visual disturbances, possibly pain in and surrounding the eye and in the worst case blindness.
In glaucoma the pupil turns various shades of green. Usually only one eye is affected initially but eventually both eyes will be affected.
Glaucoma is divided into two types: Angle Closure Glaucoma (acute glaucoma) and Primary Open-angle Glaucoma. The angle that is referred to is the skewed angle where the iris and cornea meets, and where the chamber fluid leaves the cameras.
Angle Closure Glaucoma
Arises when the chamber fluids ability to flow freely through the eye suddenly is compromised. Elderly, far-sighted persons are at the biggest risk to develop this type of glaucoma, and the symptoms arise in waves associated with the attacks. The symptoms are caused by the closure of the angle between the cornea and the iris, but may also be caused by the iris pressing against the cornea thus inhibiting the flow of chamber fluid. Dim light, which dilates the pupil may trigger such an attack. In cases where the pressure in the eye does not decrease, but continues to rise, acute surgery is required to avoid loss of the optical nerve.
Primary Open-Angle Glaucoma
In these cases the pressure gradually rises over several years as the pores which drain the chamber fluid from the eye are congested. The reason this happens is unknown. Inheritance may be a factor.
The symptoms are usually felt after the fortieth birthday. Initially vision becomes unfocused. With the passage of time the optical nerve is damages in such a way that the field of vision is narrowed. Rainbow vision may develop, in which circles of rainbow-coloured light surround sources of light.
Normal Tension Glaucoma
A more rare type of glaucoma is normal tension glaucoma. In these cases the pressure in the eye is not increased but often the cornea is thin.
Factors which Increase the Risk of Developing Glaucoma
- Intolerance towards certain foods is thought to be able to increase the liquid pressure in the eye.
- Working in front of a monitor. Research indicates that near-sighted persons who work a lot in front of computer monitors have increased risk of developing glaucoma.
- A tie, tied too tightly. Research indicates that the increased pressure on the veins of the neck can increase the intraocular pressure of the eye, through which the symptoms may worsen.
Factors which Decrease the Risk of Developing Glaucoma
- Working in front of a computer monitor. Persons with normal vision are actually thought to be able to lessen their risk of developing glaucoma through working a lot in front of a computer monitor.