August 2010: Detecting and Treating Glaucoma
30 Jul 2010
Dr. Lawrence Stone serves as Chief of Ophthalmology at Weiss Memorial Hospital. He is a board-certified ophthalmologist who developed a paradigm for the early detection and treatment of glaucoma that was presented in 2009 at the American Academy of Ophthalmology Annual Meeting, in San Francisco. He has published and lectured extensively on this topic.
Lawrence Stone, M.D.
Chief of Ophthalmology
Weiss Memorial Hospital
What is Glaucoma?
Glaucoma is a serious, potentially disabling disorder of the optic nerve related to elevated intraocular pressure. It generally affects both eyes, although at the time of diagnosis, one eye may be more advanced than the other. It can effect all ages, races and ethnic groups, but one commonality is that most glaucoma sufferers are over age 40. Glaucoma is asymptomatic in its early stages—even someone with completely normal vision may have glaucoma.
The optic nerve travels from the eye to the brain and carries more than 1 million neurons of vision information. If it is damaged, the quality of vision suffers. The optic nerve is only 1.5 mm. It consists of two sections, an inner part called the cup and an outer part called the disk. The cup/disk ratio is used to assess risk for glaucoma. The cup/disk ratio (C/D) ranges from 0.0 to 0.99, with an average cup/disk ratio between 0.1 and 0.5. Cup disk ratios over 0.5 and a cup/disk ratio between two eyes that differs by .2 or more is a cause for concern. To further complicate the diagnosis of glaucoma, there are times when patients with high C/D ratios do not have glaucoma, and there are individuals with small C/D ratios that nonetheless do have glaucoma. Advanced imaging technology can be very helpful and is sometimes the only way to sort out these cases.
The optic nerve has a superficial layer called the retinal nerve fiber layer (NFL) and a deeper portion called the optic disk. In its initial stages, there is loss of either or both of the superficial (NFL) or deep portions of the nerve but no vision loss has yet occurred. Frequently, but not always, intraocular pressure is elevated during this stage. It is advantageous to detect the glaucoma during this pre-perimetric (no vision loss) phase.
And finally, having a normal intraocular pressure does not mean that you cannot have glaucoma. Twenty-five percent of patients with glaucoma have normal pressure (called normal pressure glaucoma).
Certain predictive factors can tell us a patient’s risk for glaucoma:
- Intraocular pressure
- Corneal thickness
- Vertical cup/disk ratio
- Visual field findings (pattern standard deviation)
Based upon these parameters, we can estimate a patient’s risk of developing glaucoma within the next five years.
Detecting glaucoma at an early stage is critical to future eye health and overall well-being. At Weiss we use ocular computer tomography testing, a cutting-edge device that ensures accurate diagnosis and resulting treatment options.
Although we focus a lot on the optic nerve (which is in the back of the eye) to see whether or not someone has glaucoma, it is the anatomy in the front of the eye, called the anterior chamber which determines if the pressure will be too high. At Weiss, to assess the anterior chamber, we offer a technology called anterior segment imaging. This can often be done instead of the older (and uncomfortable) gonioscopy procedure.
In glaucoma, side vision is lost. The central portion of the vision remains normal until the very late stages. Thus, the majority of glaucoma patients have normal central vision: 20/20 vision. Vision loss in glaucoma is therefore best determined by taking measurements of the side (peripheral) vision. The test that your doctor might order is called a visual field test.
There are different types of visual field tests. Some are used to detect early glaucoma; others are used for later stage glaucoma to follow visual field loss progression. Most centers only offer one type of visual field test, called standard automated perimetry (SAP). While this test is very valuable, many glaucoma specialists believe that by the time that SAP shows visual field damage from glaucoma, 20 or 30 percent of the optic nerve is already gone.
In addition to SAP, at Weiss we offer blue yellow visual field testing and double frequency testing. These modalities may offer earlier detection of visual field defects than SAP.
Finally, stereo disk photography is a test that requires dilation of your pupil. Two pictures of each optic nerve are taken, separated by 7 degrees. When these two images are projected side by side and viewed with a special device, a 3-dimensional or stereo-view of the optic nerve contour is possible.
Treatment consists of eye drops, laser treatments or eye surgery for more advanced cases in order to lower the pressure in the eye and to prevent further damage to the optic nerve. While there is no cure for glaucoma to date, early diagnosis and proper treatment and management of glaucoma can preserve eyesight.
Our main goal is to detect glaucoma early, before vision loss occurs. Glaucoma almost always starts without any symptoms. Often patients have silent glaucoma for up to eight years before they notice problems with vision. Because the vision loss is irreversible, it is critical that it be detected as early as possible.
Early detection not only prevents vision loss, but it also makes treatment easier. The more advanced the disease when it is first diagnosed the more difficult it is to prevent further vision loss.
For more information
If you would like more information about glaucoma, or would like an appointment, please call Dr. Stone at (773) 561-4545. Also visit www.midnortheyecenter.com for more detailed information about glaucoma and other eye diseases and conditions.