Regular glaucoma check-ups include two routine eye tests: tonometry and slit-lamp examination with optic disc assessment.
Tonometry
A normal eye pressure varies between 12 and 21 mmHg. The tonometry test measures the pressure inside the eye. Drops are used to numb the eye. Then the doctor or technician uses a special instrument that indirectly measures the eye’s pressure.
(For those interested, the physics of this technique are as follows: 2 prisms are used to split the reflection of a circle from the cornea. The reflection appears as a ring, outlining the amount of cornea touched by the tonometer. The area touched can be measured exactly, when the split prism images overlap. The force applied to 'applanate' the cornea for this given area is measured in mmHg).
Goldmann Tonometer Tip (disposable)
Slit-lamp examination with optic disc assessment
Slit-lamp examination is used to examine the inside of the eye, particularly the optic nerve. A 3 dimensional view of the optic nerve is a useful way to clinically identify changes in the appearance of the optic nerve.
If the pressure in the eye is not within the normal range, or if the optic nerve looks unusual, then one or two special glaucoma tests will be done. These two tests are called perimetry and gonioscopy.
Perimetry
The perimetry test is also called a visual field test. During this test, you will be asked to look straight ahead and then indicate when a moving light passes your peripheral (or side) vision. This helps draw a “map” of your vision. These tests are subjective and rely critically on your absolute concentration during the test. There are many types of visual field test. In the UK, the Humphrey Visual field test is the standard type for assessing visual field loss.
Gonioscopy
Gonioscopy is a painless eye test that checks if the angle where the iris meets the cornea is open or closed, showing if either open angle or closed angle glaucoma is present.
Other tests for glaucoma
Anterior segment OCT ("Visante"). The image below shows a cross section of a trabeculectomy "bleb" illustrating a fluid lake within the outer coats of the eye (conjunctival / tenons region). This test is useful for demonstrating bleb morphology after glaucoma surgery.
The information on our website is for educational purposes only and is not to replace a consultation with an eye care professional. The condition of each patient is unique and needs to be evaluated properly before any decision can be taken. For appointments with Mr P Galloway contact: BUPA Hospital Leeds, Jackson Avenue, Roundhay, Leeds, West Yorkshire, LS8 1NT, UK. T:0113 269 3939; for Mr Burnett please click here.
