Pattern Electroretinography (PERG) Gives up to 8 Years of Advanced Warning
Incorporating the most advanced technology available in caring for our patients is important to the way we practice at Total Eye Care. The Diopsys® Pattern Electroretinograph is the newest addition to our suite of technology. The Pattern ERG (PERG) measures the signal strength of the retinal information being sent to the optic nerve. Studies show that a 10% decrease in this signal can be detected up to 8 years earlier than a 10% loss of nerve fibers detected by the scanning laser ophthalmoscope or optical coherence tomographer, thus allowing for a much earlier diagnosis and treatment.
Early detection and treatment of glaucoma is important due to the fact that nerve tissue cannot be regenerated. Twenty years ago, in the absence of a very high intra-ocular pressure, it was a common practice to wait until a visual field defect was present before initiating treatment. There is a significant amount of redundancy in the retinal nerve fibers, thus studies have shown that a patient must lose approximately 50% of the nerve fibers serving a given section before the loss of nerve fibers result in a detectable visual field defect. The scanning laser ophthalmoscopes changed all of that allowing us to detect earlier, more subtle changes in the retinal nerve fiber layer. Now patients are treated before visual field defects become apparent.
The Diopsys® Pattern Electroretinograph is the next step in early detection. The PERG will not replace the scanning laser ophthalmoscopes such as the Zeiss Cirrus Optical Coherence Tomographer (OCT) in the diagnosis of glaucoma; however, it gives us another valuable tool in the diagnosis and treatment of glaucoma.
New technology now available at Total Eye Care allows us to scan a patient’s retina for glaucoma and macular degeneration, and the best part ….. it does it WITHOUT DILATION! This new instrument is called the Zeiss Cirrus OCT and it is truly state of the art.
The Zeiss OCT uses infra-red light from a scanning laser to make a very high resolution, 3D image of the inside of your eye, much like that of an MRI. We can now identify retinal objects as small as 4 microns. So how small is 4 microns? A single sheet of 20 lb copy paper is 100 microns thick. This new technology allows us to detect glaucoma and macular degeneration much earlier as well as allowing us to detect and track subtle retinal changes.
Who is a candidate for this new technology? Anyone with a family or personal history of glaucoma, glaucoma suspect or macular degeneration should take advantage of this technology.
Call the Colleyville office at 817.416.0333 and let Rona or Kelsey know that you would like to take advantage of the new scanning laser technology right away.
David Calkins, Ph.D., Director of Research at the Vanderbilt Eye Institute published a study indicating that the brain may hold the key to the early signs of glaucoma. Published in the Proceedings of the National Academy of Sciences, the study indicates that glaucoma may be like other central nervous system disorders with its origins being in the brain.
Traditional thinking regarding glaucoma is that the either the high pressure slowly crushes the nerve fibers or the pressure decreases blood flow to the optic nerve. Should Dr. Calkins’ findings be confirmed in human studies it would cause a paradigm shift in the treatment and diagnosis of glaucoma. Dr. Calkin’s study demonstrates that glaucoma starts in the brain and then as the disease progresses the optic nerve starts to show evidence of the disease. Currently Dr. Calkins’ research is directed toward looking for medical therapies that can restore the connection of the nerve fibers between the brain and the retina.
I have to applaud Dr. Calkins and his team for thinking outside the box in their pursuit of answers to the second leading cause of blindness. The study was funded by the National Eye Institute, the Glaucoma Research foundation and Research to Prevent Blindness. More details on the study results are available on The Reporter, Vanderbilt Medical Center’s Weekly Newspaper.
FOR IMMEDIATE RELEASE
COLLEYVILLE, TEXAS – March 6, 2010 – In honor of World Glaucoma Awareness Week (March 7 to March 13, 2010), Total Eye Care will be offering free Glaucoma Screenings on World Glaucoma Day, March 12, 2010 at the Colleyville office located at 6114 Colleyville Blvd. from Noon to 2pm.
“Early detection and awareness are crucial to limiting vision loss from glaucoma. The purpose of Glaucoma Awareness Week is to get the word out and prompt patients to seek an evaluation from their eye doctor. At Total Eye Care we would like to make it easier for patients to learn about glaucoma by offering a free screening ” says Dr. Richard Driscoll, clinical director at Total Eye Care. Glaucoma is the second leading cause of blindness worldwide, not because of lack of effective methods for diagnosis and treatment, but due to insufficient information available to the public and low awareness of the implications of the disease. Glaucoma is asymptomatic in its early stages, while the patient’s vision suffers irreversible and cumulative damage. Visual disturbances are noted by the patient during the later stages on the way to blindness, whereas timely diagnosis and therapy could have prevented this degradation.
“We have so many advanced medications and diagnostic instruments available to us that the detection and treatment of glaucoma has been greatly advanced in the last 10 to 15 years” says Dr. Alycia Green. A glaucoma awareness questionnaire is available on the Total Eye Care website along with detailed handouts for patients on glaucoma and many other eye diseases such as macular degeneration and keratoconus.
Total Eye Care participates in Glaucoma Awareness Week, the complete press release.
About Total Eye Care
Therapeutic Optometrist and Optometric Glaucoma Specialist Dr. Richard Driscoll has been serving the eye care needs of Colleyville, Texas since 1995. Dr. Alycia Green brings over 10 years of experience to Total Eye Care, specializing in pediatrics. The Colleyville office is located at 6114 Colleyville Blvd. Total Eye Care’s Keller office is located at 1834 Keller Parkway. More information can be found on The Eye Doc Blog or the Total Eye Care website at www.TotalEyeCare.com
Dr. Richard Driscoll
Total Eye Care
6114 Colleyville Blvd.
Colleyville, TX 76034
We are frequently asked to explain how glaucoma causes blindness. Glaucomatous damage to the eye is caused when the pressure within the eye is greater than the optic nerve can tolerate. How does the pressure cause blindess? The simple answer is we don’t know exactly, however there are two main theories as to why the damage occurs. Neither theory fully explains how the optic nerve damage occurs in the different types of glaucoma.
The Vascular Theory of Glaucoma
The premise of the vascular theory is that high pressure inside the eye restricts blood flow to the optic nerve causing the optic nerve to slowly die from lack of oxygen and nutrients.
The Mechanical Theory of Glaucoma
Physical damage is the underlying hypothesis of the mechanical theory of glaucoma. It is thought that the high pressure damages the optic nerve fibers.
So Which One Is It?
That’s a good question the leading researchers can make a convincing case for both theories and neither theory, by itself can completely explain how glaucoma damages the eye. In reality both probably play a role in how an eye is damaged by glaucoma.
A: This is a great question that gets asked a lot. The pressure inside your eye is completely unrelated to your blood pressure. The intra-ocular pressure system and the blood pressure are completely separate systems and fluid is not exchanged between them. Therefore, if you have high blood pressure you won’t necessarily have glaucoma.