Visual Field Testing
A visual field test measures how much 'side' vision you have. It is a straightforward test, painless, and does not involve eye drops. Essentially lights are flashed on, and you have to press a button whenever you see the light. Your head is kept still; you have to rest your chin on a a chin rest. The lights are bright or dim at different stages of the test. Some of the flashes are purely to check you are concentrating.
Each eye is tested separately, and you should allow 15-45 minutes to have the whole test.
These are usually carried out by various optometrists seceted by the DVLA (Driving and Vehicle Licencing Centre in Swansea). The hospital department does not usually communicate with the DVLA.
A doctor may ask only for a driving licence visual field test if a oatient requests, which takes 5-10 minutes. The result will be recorded in your notes, and the notes can be requested by a court of law if need be.
You must notify the DVLA. if you have laser treatment of both eyes, or if you have laser to your one good eye.
The machine is the same butthe computer program combines the two eyes to create a result for both eyes combined.
Normally the test is carried out by a computerised machine, a Humphrey. Occasionally the manual test has to be used, a Goldman. Again, for each test you have to look at a central point, and have to press a buzzer each time you see the light. See videosGoldmann 1.6mb or computerised Humphrey 600kb (windows media) or Quicktime (550kb)
You need to bring your reading or bi-focal glasses you have. (But always bring your distance and reading glasses to every eye clinic visit.)
The glaucoma technician, an orthoptist, or optometrist will do the test.
The results are placed in your notes and the ophthalmologist will review the notes at your next consultation. (see Driving visual fields above).
Usually the test is advised at you previous consultation. It is one of the most important tests for glaucoma. If your side vision gets worse, you may need more drops to lower the eye pressure further. It is usually carried out before the NEXT appointment, to help the doctor advise you on the treatment that would be helpful.
The test determines whether or not you have lost sight from glaucoma and other conditions. Changes in the visual field help to determine if the sight is getting worse and the glaucoma is progressing (if it is progressing your eye needs a lower pressure).
Reduction in the mean deviation of Humphrey fields is significant, and is a very quick way to review the result.
It is vital that you let the eye clinic know (see appointments) so an alternative appointment can be arranged, and the appointment offered to someone else, so you have to wait less time for the next appointment.
There are reports that Gabapentin can affect visual field. If you use Gabapentin, have an eye examination at your optometrist and ask for a visual field test. If the visual fields are reduced, let your GP know.
This drug often causes serious visual field loss. Speak to your neurologist...many patients are transfering to different drugs. See