Glaucoma is a very common condition and the risk increases with age. There are many different types of glaucoma, however they have one thing in common, they all cause damage to the optic nerve. This can then start to affect your field of vision (side vision). The treatment involves reducing the pressure within the eye which we refer to as the intra ocular pressure.
The most common type of glaucoma is known as chronic open angle glaucoma. This tends to be a slow insidious disease with no symptoms until it is very advanced. There is also another type of glaucoma known as angle closure glaucoma. This is not as common, but has definite symptoms and it is more sudden onset. Glaucoma can occur due to other eye conditions and we would refer to this as secondary glaucoma. Rarely a baby can be born with glaucoma and this is known as congenital glaucoma.
The front part of the eye is known as the anterior chamber. We produce a fluid known as aqueous humour in a part of the eye known as the ciliary body. This flows through the pupil and then drains into a network of tiny vessels in the angle between the cornea and the iris. This provides nutrients to the eye and maintains a normal intra ocular pressure. In open angle glaucoma ,the drainage becomes impaired and slowly the eye pressure increases, this causes damage to the optic nerve. Not all open angle glaucoma has elevated pressures and these people are known to have normal tension glaucoma. It is uncertain why they develop glaucoma but the mainstay of treatment is to still reduce the intra ocular pressure. Also many people have elevated pressures and maintain normal optic nerves and visual fields – this is known as ocular hypertension (OHT). These people have to be monitored regularly as they are at greater risk of developing glaucoma. In acute closed angle glaucoma this occurs when the iris comes into close contact with the drainage pathways resulting in near complete or complete obstruction of the drainage system. This causes a dramatic rise in intra ocular pressure and as such causes pronounced symptoms which can include redness, pain, loss of vision and haloes around lights. This type of glaucoma is an emergency and needs urgent referral to reduce the high pressure. This type of glaucoma is less common.
As primary open angle glaucoma is the most common type of glaucoma particularly in the over 40 age group, it is important to have regular examinations with your optometrist as there are no symptoms in the early stages. In glaucoma it can start to affect your field of vision, due to damage to the nerve fibres within the optic nerve. However you may be unaware of this. The earlier we can detect and treat glaucoma the sooner we can protect any further irreversible damage to the optic nerve.
During an assessment for glaucoma the optometrist will examine and assess the health of the optic nerve at the back of the eye, check your intra- ocular pressures, assess the front chamber of the eye known as the anterior chamber angle (where fluid drains into this angle), and where appropriate perform a field of vision test. We may do further tests such as checking the thickness of your cornea as this affects the pressure readings. Also now with additional technology with OCT (Optical Coherence Tomography) we are able to assess the structure of the optic nerve in great detail. This allows us to analyse the thickness of the nerve fibre layer within the optic nerve and to analyse a cell layer in the retina known as the ganglion cell layer, which can help us to detect any early change which may suggest glaucoma. OCT is part of an enhanced examination and is highly recommended.
Risk Factors for glaucoma
- Increasing age
- Family history
- Ethnicity Afro- Caribbean (open angle glaucoma) Asian (closed angle glaucoma)
- High myopia
- Migraine sufferers / Reynauds
The mainstay of treatment for glaucoma is to reduce the intra ocular pressure to avoid damage to the optic nerve. This is usually in the form of eye drops, however other treatments are available with a form of laser, and also drainage surgery. Newer treatments are becoming available at the moment known as minimally invasive glaucoma surgery.