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Most people should have their eyes tested at least every two years. It is even more important to have a regular eye test if you are in one of the groups at greater risk, diagnosed with Glaucoma or Ocular Hypertension.
Monitoring glaucoma and hospital visits
If you are diagnosed with glaucoma you may need to visit the hospital frequently to start with. This is because your ophthalmologist will want to make sure you are responding to treatment and that your eye pressure is in the right range for you and it is stable.
If your eye pressure continues to be stable and you are not having any problems with treatment then you will be able to go for check-ups less often. With time, you may only need to be seen every six or 12 months. However, it is very important that you attend these appointments to make sure your eye pressure continues to be stable as you will not be aware of any changes to the pressure, and you could permanently lose more sight if your current treatment becomes ineffective. On each visit, you will have the pressure measured in your eye, your visual field tested and the back of your eye examined using drops to dilate your pupil. The effects of the dilating drops usually wear off in about six hours, although sometimes it will happen overnight. It is not safe to drive until the effects of these drops have worn off.
The three tests are very straightforward – they do not hurt and can be done by most high street optometrists (opticians) – and they:
- Examine the retina, especially the area where the optic nerve leaves your eye (optic disc). This is done by shining a bright light into your eye from either a slit lamp, into which you place your chin, or a hand-held ophthalmoscope
- Measure the pressure in your eye, using a special instrument called a tonometer. This involves a machine which uses a few puffs of air in each eye to record the pressure. Eye pressure can also be tested using eye drops and another instrument which touches the front of the eye. This method is most often used by the hospital clinic
- Test your visual field. This involves being shown a sequence of spots of light on a screen and you say which ones you can see.
The visual field test used in monitoring glaucoma is much more detailed than the screening tests used by your optometrist. Some of the tests can take 10 minutes per eye and this can get boring. It is important to be prepared for this as accurate testing allows the specialist to make the right decisions about your treatment.
There are 5 Glaucoma Tests
1 Corneal thickness
Why is this important?
- Thin cornea gives a lower pressure reading
- Thick cornea gives a higher pressure reading
How is it measured?
No anaesthetic drops required
- OCT imaging can be used to give a rough measure of corneal thickness
Anaesthetic Drops Required
- Pachymetry - A lens is placed on your eye and the optometrist will examine your angles to get an curate diagnosis
2 Drainage Angles
Why is it important?
- Narrow angles can increase eye pressure
- Short sighted eyes = Wider angles
- Long sighted eyes = Narrower angles
How is it measured?
No anaesthetic drops required
- OCT imaging can be used to give a rough idea of whether your angles are open or closed
Anaesthetic Drops Required
- Gonioscope - A contact lens is placed on your eye and angles measured
3 Eye Pressure
Why is it important?
- High pressure is the main symptom of glaucoma and ocular hypertension
How is it measured?
Anaesthetic Drops Required
- Tonometry - a small puff of air measures the pressure of your eye
- Touching probe: Touches the cornea for a split second
- Goldmann - This is currently the most accurate way to measure intra-ocular pressure. The Goldmann devise is pressed against the front of the eye and the amount of pressure it takes to flatten the surface is measured
4 Optic Nerve Assessment
Why is this important?
- Optic Nerve = Bundle of nerve fibres that carry visual messages from the eye to the brain
- The optic nerve is stretched with high eye pressure
How is measured?
No anaesthetic drops required
- 3D OCT imaging is used to look at your optic nerve to assess its shape
5 Field of Vision
Why is it important?
- Glaucoma affects your peripheral vision
- Eventually leading to tunnel vision
- Nerve fibres are accurately arranged, so damage to these give peripheral defects
How is measured?
No drops required
- Measures your field of view
- Subjective measure of central and peripheral vision
- Light spot appears in different positions of your field of view, you will be asked to push a button when you can see it
- Full attention & corporation is required
- Can detect and monitor any changes to your field of view