Glaucoma

Home     Introduction     Map & Opening times     Eye Examination

   Contact lenses     Specialist Services     Spectacle Frames     Spectacle Lenses       

  Charity Projects     Sports Vision     Specs Favourites     Fact Sheets

< Back to Eye Examination


        What is glaucoma? - Glaucoma is the name for a group
        of eye conditions in which the optic nerve is damaged at the
        point where it leaves the eye. The circle in the photograph is
        the pale damaged nerve, compare it to the one on the previous
        page. This causes a loss of peripheral vision which is why it
        can go undetected until the later stages. If it remains undetected
        for a long period of time then it may result in "tunnel
        vision" and blindness. The optic nerve carries information
        from the light sensitive layer in your eye, the retina, to the
        brain where it is perceived as a picture.

        Your eye needs a certain
        amount of pressure to keep the eyeball in shape so that it can
        work properly. In some people, the damage is caused by raised
        pressure. Others may have an eye pressure within normal limits
        but damage occurs because there is a weakness in the optic nerve.
        In most cases both factors are involved but to a varying extent.

How common is glaucoma? - In the UK some form of glaucoma affects about 2 in 100 people over the age of 40. Some people are particularly at risk of chronic glaucoma. There are several factors which increase the risk:

Age: Chronic glaucoma becomes much more common with increasing age. It is uncommon below the age of 40 but affects one percent of people over this age and five percent over 65.
Race: If you are of African origin you are more at risk of chronic glaucoma.
Family: If you have a close relative who has chronic glaucoma then you should have regular eye examinations. You should advise other members of your family to do the same. This is especially true if you are over 40. Those with a family history of glaucoma are 10 times more likely to develop it.
Short sight: People with a high degree of short sight are more prone to chronic glaucoma.
Diabetes: It is believed that diabetics have an increased risk of developing chronic glaucoma.

Testing for Glaucoma - Raised ocular pressure is NOT the same as high blood pressure and detection of the early stages of glaucoma is often difficult because it is so gradual. We measure the pressure using the slit-lamp microscope. The pressure can vary at different times of day so it is sometimes necessary to repeat measurements.

. Henson Visual Field Screener

This is the Henson Visual Field Screener which is used to check the peripheral nerves of the eye. The computer shows small flashes of light at different levels of brightness over 25 degrees around the central point to check how sensitive the nerves are.

Pachymetry - Recent discoveries about the cornea, the clear part of the eye's protective covering, are showing that corneal thickness is an important factor in accurately diagnosing eye pressure. When we measure the IOP we don't always get a truly accurate reading. The IOP reading depends on the thickness of the cornea, thicker corneas cause falsely higher eye pressure readings and thinner corneas cause falsely lower eye pressure readings

Your corneal thickness therefore affects your risk for glaucoma, and knowing what your corneal thickness is can make your diagnosis more accurate. With an ultrasonic device called a Pachymeter we can measure your corneal thickness. It is also know that people with a thin central corneal less than 0.555mm are significantly more at risk of developing Primary Open Angle Glaucoma.

Are there different types of glaucoma?

Yes there are four main types:

Chronic Glaucoma: This is the most common type of glaucoma. The eye pressure rises very slowly and there is no pain to show there is a problem, but the field of vision gradually become impaired.
Acute Glaucoma: This is less common in western countries. This type of glaucoma occurs when there is a sudden blockage to the flow of aqueous fluid to the eye. This can be quite painful and will cause permanent damage to your sight if not treated properly.
Secondary Glaucoma: This type of glaucoma occurs as a result of a rise in eye pressure caused by another eye condition.
Developmental Glaucoma: This is a rare but sometimes serious condition which occurs in babies and is caused by a malformation in the eye.



        Can glaucoma be treated?
        - If detected early
        enough, glaucoma can usually be treated. In most cases, eyedrops
        to reduce the pressure will be prescribed, although in some cases
        a minor operation is needed. Treatment is unable to restore vision
        that has been lost but aims to preserve the remaining sight so
        it is very important to detect glaucoma as early as possible.

        Regular eye examinations
        where the ocular health, eye pressure and field of vision are
        checked are essential. If you are worried about glaucoma, or
        would like any more information then just contact the practise
        and we will be happy to talk to you.  
        

        This picture shows a normal
        visual field. The dark patch is the natural blind spot that occurs
        where the optic nerve enters the eye, this corresponds to the
        white area on the photograph at the top of the page.

        This second picture has
        a large black area which is caused by damaged nerves. Damage
        to the peripheral nerves occurs without any pain, and it is often
        not until someone gets tunnel vision and starts bumping in to
        things that they notice they have a problem.  
< Back to Eye Examination