A basic eye examination

There are many tools that eye doctors use for diagnosing glaucoma, including the most basic - the eye chart - which tests the sharpness of your central vision. Your pupils will also be tested to see if your pupils react normally and equally to light stimulation. This is done by shining a bright light in your eyes.

The front structures of your eye will be examined using a slit lamp, which is a microscope with a special light source that allows your eye doctor to examine with magnification. Your doctor will be looking specifically at your cornea, anterior chamber, iris, and lens for any abnormalities.

Measuring intraocular pressures

Measuring your intraocular pressures involves placing a drop of anesthetic in your eye, which instantly numbs the surface of the eye and lasts for about 15 minutes. Your doctor or a technician will then use a tool called a tonometer to measure the eye pressure: this involves either extremely gentle contact with the surface of the eye or a warm puff of air and this is why anesthetic is used.

Determining open- and closed-angle glaucoma

The outflow angle of your eye will be examined, with an instrument called a goniolens. This procedure allows the eye doctor to detect any abnormal visible obstruction in the drainage area. A drop of anesthetic is placed on your eye and the ophthalmologist then places the goniolens (similar to a contact lens) gently on the eye surface. This is an important part of your assessment because it is the only way to determine if your glaucoma is open- or closed-angle.

Optic nerves and retina examinations

Your doctor will examine the health of your optic nerve and retina by dilating your pupils with eye drops. This allows a clear view of the back part of your eye. An ophthalmoscope is used to assess the optic nerve for changes and the retina for any defects in the nerve fibre layer. In order to measure each eye's individual ability to see lights of varying brightness in the peripheral fields of vision, your doctor may arrange for you to have a visual field examination.

Your doctor may also arrange for an imaging examination of your optic disc (the part at the back of the eye where the optic nerve appears). This could involve either a photographic assessment or a computerized laser image of the three dimensional structure of your optic disc. If photographs are taken using a fundus camera, your pupils must first be dilated with some eye drops. If a computerized image is taken, it is not necessary to dilate your pupils. With a computer, the images are immediately visible on the attached video monitor, so you may want to ask your doctor to let you have a look.

When the examination is over

After the examination your vision will be blurred significantly from the bright lights, eye drops, and lubricants. The effect of the lights, lubricants, and freezing drops will wear off in about 15 minutes but the dilating drops will take at least 2 hours and often, significantly longer to wear off. It is therefore advisable for you not to drive to your examination appointment.

Frederick S. Mikelberg, MD 
in association with the MediResource Clinical Team