Diagnostic Tests
OCT (optical coherence tomography)
OCT stands for optical coherence tomography and is based on the imaging of reflected light. Unlike a camera, it can resolve depth, at a very fine level. The resolution can be down to 0.01mm and provides us with a very nice cross-sectional view of the retina.
OCT reveals structural or anatomical changes in the retina. It does not assess the function of the retina although conclusions can be made based on the OCT. Learn more...
Digital Photography
It is possible to takes photos of various parts of the eye including the cornea, lens and retina. A special camera is needed to photograph the retina inside the eye. The photos are taken using a bright flash and processed digitally by computer. You can often view the images on the computer screen.
These images allow the doctor to assess macular degeneration, diabetes, glaucoma, vein blockages and other conditions. The photos also make a good record against which future changes can be calibrated.
FFA (Fluorescein Angiography)
Fluorescein is a yellow dye injected into a vein in the arm or hand. The dye travels in the blood stream to the eye and photographs are taken during its passage through the eye’s circulation. The test demonstrates abnormalities in retinal blood vessels and aids in diagnosis and treatment of many eye conditions, especially macular degeneration, diabetic retinopathy, retinal vein blockages. Learn more...
Visual Fields
Visual field analysis is a very sensitive way of assessing your side vision. This procedure is commonly used to monitor glaucoma but is also useful in a wide variety of eye disorders, particularly those affecting the optic nerve or retina. The procedure takes about 7 minutes per eye, is painless, and merely requires the patient to press a button when they see a flash of light. You do not require eyedrops for this test. Glaucoma sufferers are typically tested in this way every 6-12 months.
Eye Measurements
If you are having cataract surgery you will need to have the eyes measured. The reason is that when the cataract is removed, a new acrylic lens will be placed inside your eye. The lens is customised for each eye so the doctor needs to know all about your eye.
Measurements of the outside shape of the eye are taken at first. This determines how much astigmatism (eye out of round) is present. Next the diameter of the eyeball is assessed using ultrasound. This requires the use of a small eye bath and some water. It’s a bit wet! With these numbers a computer will estimate what lens is suitable for your eyes. In the majority of cases the doctor is able to implant a lens to very accurately correct for long distance. Equally, corrections to give reading vision can be done in some cases. Astigmatism can also be corrected.
ERG (Electroretinogram)
Electroretinography is a highly sophisticated method of objectively assessing the function of the retina. Using standardised light stimuli, tiny electrical currents generated by your retina can be measured using powerful computers. These currents are amplified and recorded onto the screen, giving a waveform which is then analysed. There are two types of ERG, the full field and the multifocal. Full field ERG gives a measure of the combined response of rod and cone cells. Multifocal ERG examines only the cone cells. ERG testing can take up to 1-2 hours and often requires a period of dark adaptation in which the patient must remain in a darkened room for 20 minutes. Eyedrops are required. The procedure is painless.
VER (Visual-evoked response)
Visual evoked response testing is a method of assessing objectively the function of the optic nerve. Small electrical currents produced by the brain in response to standardised stimuli are recorded. The time taken for these responses to form is measured and can be analysed. This procedure is painless, does not require drops, but can take up to 30 minutes. The test is useful in patients with suspected optic nerve dysfunction for whatever reason. It is applicable to sufferers of optic neuritis.
