Glaucoma
Glaucoma is in fact a group of diseases characterized by raised intraocular pressure, optic nerve damage and gradual visual field loss.

Glaucoma is the leading cause of irreversible blindness in the world. It affects about 2% of people over 40 in the UK. Many people have the condition without knowing it, as it can have no symptoms either visual or pain and may go undetected until a routine eye examination or until the visual loss has become severe.



The different types of glaucoma can be differentiated by the age and speed of onset, and whether the raised pressure is a result of another eye condition. The disease can also be described as either open-angle (Chronic) or closed-angle (Acute) The Angle is between the Cornea and the Iris.

The space between the cornea and iris is filled with a clear fluid known as the aqueous humour. Usually, the aqueous humour is continually produced and circulates before draining away through the Trabecula Meshwork.

Open-angle glaucoma is the most common type of the disease. In open-angle glaucoma, the angle is wide and the entrance of the drainage canals is clear, just as they would be in the normal eye. However, the canals are blocked inside so the fluid cannot drain away as quickly as normal. If undiagnosed and untreated it can cause a gradual loss in vision. However it does usually respond well to treatment. Closed-angle glaucoma occurs when the angle narrows or closes suddenly and the pressure rises very quickly. This type of glaucoma does have symptoms: excessive pain around the eyes, headaches, nausea, halos around lights.

Secondary Glaucoma
Glaucoma can occur as a complication to another disease (Diabetes or advanced Cataracts) or can result from an eye injury or inflammation.

Testing for Glaucoma
There are three main tests that are used in the detection of Glaucoma it is important that the results of the three tests are looked as a whole rather than individually.The tests are:

Tonometry
Measurement of the pressure inside the eyeball. There are two main methods of measurement are either by using a Non Contact Method (Puff of Air) or by using a Contact method when a Probe is placed on the surface of the cornea (after it has been anaesthetised).

The "Normal" pressure inside the eye is usually between 10mm of mercury and 23 mm of mercury. It is possible for some patients to have raised intraocular pressure and no glaucoma while other patients may have normal intraocular pressure and have glaucoma.

Examination of the Optic Nerve
The Optic nerve is examined using OPHTHALMOSCOPY or Photography and abnormalities or changes in the Optic Nerve can be monitored.



Visual Fields
The function of the Optic Nerve can be determined by measuring the peripheral visual field. Glaucoma is a disease, which does not affect the central vision until it is very advanced. The earliest change experienced in glaucoma is a decrease in the sensitivity of the visual field (peripheral vision).

Modern Perimeters (Visual Field Tests) can show small changes in the sensitivity of the visual field. The Visual field loss is progressive and if left untreated Glaucoma can cause a complete reduction in peripheral vision leaving Tunnel Vision.

Treatment of Glaucoma
Glaucoma cannot be cured but once diagnosed it can be treated and controlled. The type of treatment needed will depend on the type of Glaucoma. For Open-angle Glaucoma the treatment usually involves taking medication either pills or eye drops. These cause the pressure inside the eye to reduce by making the eye produce less Aqueous Humor or by increasing the rate of drainage of the Aqueous Humour.

In advanced cases of Open-angle Glaucoma and in Acute Glaucoma medication as a treatment may not be suitable. The alternative is surgical; the treatment consists of opening up the drainage channels in the Trabecular Meshwork using either a laser or by conventional surgery.

Risk Factors
There are certain risk factors that need to be considered when checking a patient for Glaucoma. These include Race, Age, Family history of Glaucoma and the Presence of other eye conditions that may cause Glaucoma or raised Intra Ocular Pressures.

Monitoring Glaucoma
It is important that as there are no symptoms in the early stages of most types of Glaucoma that regular eye examinations by an Optometrist are carried out . As Glaucoma is a progressive condition, a negative result at one examination does not mean that it will never develop so continue to have regular check ups.

Astigmatism
Cataracts
Diabetes & Diabetic Retinopathy
Flashes & Floaters
Glaucoma
Hypermetropia (Long Sightedness)
Macula Degeneration
Myopia (Short Sightedness)
Presbyopia
Retinal Detachments & Retinal Tears