The key to protecting your vision and eye health is to have regular and complete eye examinations with the appropriate level of diagnostic testing for Glaucoma as recommended by your eye doctor. There are a battery of tests that your doctor may use individually or together in order to make the most precise diagnosis of Glaucoma. These include the following Glaucoma testing procedures:
The Tonometry Test is a method of measuring your Intraocular Pressure (IOP). This test involves first placing some eye drops into your eyes to numb them and then lightly touching the surface of the Cornea with a specialized measuring instrument. There is no discomfort involved and the test is quick and gives your eye doctor the first piece of important information in determining whether you have Glaucoma.
Ophthalmoscopy is a method of carefully examining the inside of the eye-especially the optic nerve-in order to detect Glaucoma. Some eye drops will be placed in your eyes in order to dilate your pupils so that clear and direct observation of the optic nerve is possible. In a darkened room, your eye doctor may use several types of Ophthalmoscopes in order to examine the shape and color of your optic nerve.
If either your Intraocular Pressure (IOP) is elevated or your optic nerve appears unusual, additional tests will be necessary in order to complete the Glaucoma examination. As most types of Glaucoma are slowly progressive, it may take years for sufficient evidence to be found, so many of these test will need to be repeated periodically. These may include the following test procedures:
Optic Nerve Stereo Photography
A special camera may be used to obtain stereoscopic (often called “3D vision”) photographs of your optic nerves. These provide a useful objective record of your optic nerve appearance against which future comparisons may be made.
Visual Field Perimetry
Perimetry of Visual Field testing is an important part of the Glaucoma examination. During this test you will be asked to sit in front of a large “bowl like” instrument and look directly straight ahead. A computer program will present a number of lights in different positions of your “side” or peripheral vision to see how far your side vision extends in various directions. The computer will then plot an actual map of your field of vision so that your eye doctor can interpret this map in conjunction with other examination tests in order to understand how well your optic nerve is functioning.
Gonioscopy is a quick and painless test that allows the eye doctor to directly observe the health and condition of the angle where the Iris meets the Cornea. By directly observing the angle and its status your eye doctor can understand more about whether you are at risk for the angle to become closed or whether the Trabecular Meshwork appears to have a normal anatomical structure.
Optic Nerve Computer Imaging
Eye doctors should use the most advanced computer imaging technology in order to make the earliest and most accurate diagnosis of Glaucoma. These computerized imaging systems are often located right in the doctor’s office so that they are convenient for patients. Optic Nerve Computer Imaging systems include:
HRT II or Heidelberg Retinal Tomography
The HRT II uses an imaging method called “confocal laser ophthalmoscopy” to scan the retinal surface and optic nerve with a laser. It then constructs a topographic three dimensional (3-D) image of the optic nerve and measures the thickness of the retinal nerve fiber layer. These are very precise measurements that your eye doctor will interpret in conjunction with the other Glaucoma tests at your examination.
OCT or Ocular Coherence Tomography
The OCT uses a method called “optical coherence tomography” that is capable of creating digital images through the use of special beams of light in order to create a contour map of the optic nerve and measure the retinal nerve fiber thickness much in the same way that a CT Scan is able to digitize and analyze tissues throughout your body.
The goal of Optic Nerve Computer Imaging is to give your eye the ability to detect the slightest loss of optic nerve fibers, at the first possible moment, in order to diagnose Glaucoma at the earliest possible stage in order to stop the progression of the disease and preserve your vision.
Pachymetry Measurement of Corneal Thickness
The National Eye Institute of the National Institutes of Health released an important study in 2002, called the Ocular Hypertension Study (OHTS) (http://www.nei.nih.gov/glaucomaeyedrops/). In this study a key finding occurred regarding corneal thickness and its role in Intraocular Pressure and the development of Glaucoma.
The OHTS study found that corneal thickness is important because it can alter the accuracy of the measurement of Intraocular Pressure, potentially causing doctors to delay necessary treatment in some cases or causing doctors to treat normal people unnecessarily in other cases. Your actual Intraocular Pressure may be UNDERESTIMATED if you have thin corneas and it may be OVERESTIMATED if you have thicker corneas.
During your Glaucoma examination, your eye doctor may perform a Pachymetry Test to measure your corneal thickness as part of your examination and consider this finding in conjunction with the other Glaucoma testing in order to make the accurate diagnosis.
The Pachymetry Test is a simple, quick and painless way of accurately measuring your corneal thickness that our doctors do right in our office. The test is performed by first placing some drops in your eyes to make them numb and then lightly touching the cornea with a “pencil like” probe that uses sound waves to precisely measure your corneal thickness.