Glaucoma

During a regular NHS eye exam we check for any signs of glaucoma. Eye pressure is measured, visual fields assessed as required and the optic nerve head is checked. These tests are covered under the free NHS eye examination, which all patients over 60 and those aged over 40 with a family history of glaucoma, are entitled to.

At risk groups include:

• Older age groups.
• Those with a family history (close relative) with glaucoma.
• Diabetics.
• Extremely short-sighted or long-sighted people.
• People of African and East Asian descent.
• Those who have suffered eye trauma.

Glaucoma community clinic: 
Clamp Optometrists run a glaucoma community clinic for Addenbrooke’s Eye Department. Optometrists and doctors refer patients, who are thought to be showing signs of glaucoma, into our glaucoma clinic via Addenbrooke's. We carry out extensive tests to determine if glaucoma is present. The patient is then either given a clean bill of health or referred to Addenbrooke’s for immediate or long-term treatment. Once glaucoma is detected, treatment depends upon which type of glaucoma is present. Many patients are managed simply with eye drops, although some require laser or surgical intervention.

This glaucoma work-up includes:

Measurements of the intraocular pressure with Goldmann tonometry.
Detailed examination of the anterior segment of the eye.
Retinal photography.
Visual field test using Humphrey visual field analyzer.
Gonioscopy which enables us to examine the angle of the anterior chamber to determine whether effective drainage of aqueous fluid can take place.

Corneal pachymetry, which measures the thickness of the cornea. This can effect the true intraocular pressure reading. A thicker-than-average cornea can result in an artificially high pressure reading, whereas a thinner-than-average cornea can produce a pressure reading lower than the 'true' pressure.

Extended glaucoma assessment
Private glaucoma screening is also available at Clamp optometrists for those people who want to take advantage of our optometrists’ expertise in the field of early detection of glaucoma and our state-of-the-art technology.
This is particularly useful for people who are in higher risk groups due to their family history or other ocular factors. In each standard eye exam our optometrists will only recommend further tests if it is considered appropriate.

We use optical coherence tomography (OCT) and Heidelberg Retinal Tomography (HRT3) to assess the retinal nerve fibre layer with imaging techniques. This enables us to measure the thickness of the nerve fibre layer around the optic disc. Any optic nerve head damage can be accurately detected using a light echo technique rather like an optical ultrasound, to obtain detailed cross sectional images of the optic nerve.

Background to glaucoma
Glaucoma is a generic name for a group of eye conditions where the optic nerve is damaged at the point where it leaves the eye. This nerve carries information from the retina to the brain where it is perceived as a picture. Damage to the optic nerve as a result of glaucoma results in patchy loss of the peripheral visual field which varies in severity from one individual to the next. 

 A properly functioning eye needs the right amount of pressure to keep it eyeball-shaped, so that it can work properly. Some people develop raised eye pressure and this causes glaucomatous damage. Others have a normal eye pressure but damage occurs because of a weakness in the optic nerve. However in most cases of glaucoma, both factors of high pressure and weakness in the optic nerve are involved to varying extents.

There are two main types of glaucoma. The most common is chronic or open angle glaucoma in which the aqueous fluid in the eyeball can get to the drainage channels but over many years these channels become blocked causing a build up of pressure in the eye. This happens slowly over a long time and doesn’t cause any pain, but there is eventually a loss in the peripheral field of vision.

Acute glaucoma is much less common and occurs when there is a sudden and complete block to the flow of aqueous fluid. This is caused by narrow angles in the anterior chamber of the eye, which prevent the aqueous fluid getting to the drainage channels. This type of glaucoma occurs rapidly and the affected eye becomes red and very painful. Acute glaucoma requires emergency medical intervention.

As early open angle glaucoma does not have any symptoms, it is important that people with a family history of glaucoma are screened regularly. This will enable us to detect the condition at the earliest opportunity, allowing quick preventative treatment to manage and slow down or stop the progression of glaucoma. Loss of visual field is irreversible and does not affect the eye's ability to focus, so regular eye examinations are particularly important for those who may be at risk.

Table of tests available to detect glaucoma, at Clamp Optometrists: