Glaucoma Diagnosis

Since for the most common type of Glaucoma there are no early glaucoma symptoms, people do not realize they have this eye disease. Symptoms are subjective to the patient. Before glaucoma is eventually diagnosed, you can lose significant peripheral vision.

However, there are detectable early signs of glaucoma that your eye doctor can find through various tests. Signs of a disease are objective and not necessarily noticed by the patient, but are visible to the doctor. This is one reason why anyone in mid-life or older should go for regular eye exams. When glaucoma is diagnosed early, its progress can be slowed or halted and your vision saved.

Recent Change in Diagnostic Technique

The presence of glaucoma used to be confirmed by measuring intraocular pressure (IOP). High pressure inside the eye was thought to define glaucoma. Now the diagnostic emphasis is on optic nerve damage rather than IOP levels and the existence of normal tension glaucoma is recognized.

• Elevated IOP damages the optic nerve where it leaves the retina. That nerve is made up of over a million individual nerve fibers running from retinal cells and carrying electrical data for the brain to interpret as images.


• When any of those tiny fibers are damaged or destroyed by the increased IOP, their data never arrives at the brain’s vision center. That means some loss of vision and when no treatment is done, nerve fibers continue to die until blindness occurs. Glaucoma is a worldwide leading cause of blindness.

Eye doctors have found that some people have normal IOP but have glaucomatous damage on the optic nerves; and conversely, others have high IOP but no optic nerve damage. High IOP in itself is no longer thought to define glaucoma. Please see Glaucoma Signs and Symptoms for more information.

This is welcome news to many who were previously diagnosed with glaucoma because of their high IOP levels. Now they need no longer use the daily eyedrops or worry about the silent vision loss of open angle glaucoma. However, there are others with normal IOP levels who were previously thought not to have glaucoma, but who are now diagnosed with glaucoma because optic nerve damage has been detected. In a sense, that is good news too, in that diagnosis leads to glaucoma treatment which will save their vision.

Tonometry

A tonometer is used to measure intraocular pressure.  Elevated intraocular pressure is associated with most types of glaucoma.  One type of tonometer blows a puff of air onto your eye's surface.  Another type of tonometer rests a small probe against the surface of your eye.  The average intraocular pressure is about 21 millimeters of mercury (0.4 pounds per square inch) or less.

Ophthalmoscopy

Opthalmoscopy is a normal part of most regular eye exams.  An ophthalmoscope is the hand-held, lighted magnification device that your ophthalmologist or optometrist uses to get a better view inside your eye and potentially identify visible problems.  Sometimes, the doctor can see damage to the optic nerve by looking at its shape and color.

Perimetry

Perimetry is also known as a visual field test.  While you are looking straight ahead, a light is moved through your peripheral vision.  By telling when you can see the light and when you cannot, you help the doctor draw a map of your peripheral vision.

Gonioscopy

A gonioscope or goniolens is a device used for measuring the angle between your cornea and iris to see whether it is narrow, putting you at risk for angle closure glaucoma.  It is also often possible for your doctor to identify if your angle has closed, is swollen, or clogged.

Imaging the Optic Nerve

Imaging the optic nerve allows your ophthalmologist to track damage to the optic nerve.  Three commonly used methods for imaging the optic nerve are:  scanning laser polarimetry, confocal laser ophthalmoscopy (also known as Heidelberg Retinal Tomography (HRT)), and optical coherence tomography (OCT).  All three of these techniques are used to map the optic nerve and/or related structures to identify changes over time.  This allows ophthalmologists to determine whether glaucoma treatment is effective or must be increased.

Ultrasound Biomicroscopy

Ultrasound biomicroscopy (UBM) is being investigated and used by many ophthalmologists to identify the structural causes of glaucoma, including pupillary block, iris plateau, and pigmentary glaucoma, a form of secondary glaucoma.

Exams Necessary

The only way to detect glaucoma before it damages your vision is with regular vision exams. Find a local ophthalmologist who utilizes the latest and best detection methods for glaucoma diagnosis and schedule an eye exam today.