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Treating diabetic retinopathy requires attention to overall health
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Diabetic retinopathy is the leading cause of new blindness in the United States in people 20 to 74 years old and is responsible for an estimated 24,000 people losing their sight each year, according to the National Eye Institute. Many of these cases could be prevented with better management of diabetes and its ocular impact. Careful monitoring of the progression of diabetes and a thorough understanding of the mechanism of the disease will allow optometrists to maintain as much of their patients' vision as possible.
"The optometrist's key role is getting new patients who may not even know they have diabetes examined, handling the patient appropriately, referring appropriately and, above all, educating the patient," said Richard M. Calderon, OD, FAAO, associate chief of the Beetham Eye Institute at the Joslin Diabetes Center in Boston.
Health care team
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Because diabetes has such a significant impact on a patient's overall health, optometrists should develop a good working relationship with the patient's internist and other health care providers, Dr. Calderon said.
"Be aware of other health problems, especially those involving the kidneys, because it seems the eyes and the kidneys go hand-in-hand," he said. "When doctors see problems developing with the eye, they should also find out about the patient's kidney function tests, because that could change the timing of the patient's treatment. When the kidneys start to develop complications due to diabetes, there are changes in the eye that can make it more difficult to perform laser treatment. When we see the kidneys are in trouble, the ophthalmologist may do laser surgery a little sooner."
Doctors should be aware of the patient's overall health, paying special attention to factors that would put them at higher risk for developing diabetic retinopathy. These factors include duration of the diabetes, poor control of blood sugar, hypertension, lack of exercise, smoking and a family history of diabetes.
Understanding the overall mechanism of the disease is critical in treating patients with diabetic retinopathy, said Jerry D. Cavallerano, OD, PhD, staff optometrist and assistant to the director at the Beetham Eye Institute, and an associate professor at New England College of Optometry.
"Any optometrist who is working with patients with diabetes should be familiar with the findings of the Diabetic Retinopathy Study, the Early Treatment of Diabetic Retinopathy Study and the Diabetes Complications and Control Study. Any optometrist or ophthalmologist should have a firm grasp of how those studies apply to clinical management," he said.
Close monitoring
The optometrist's primary responsibility is to track the progression of the disease. For patients with type 1 diabetes, or insulin-dependent diabetes mellitus, which is more commonly found in patients younger than 30, dilated fundus exam and photographs should begin about 5 years after the diabetes is diagnosed and should be repeated at least once a year thereafter, Dr. Calderon said. A close follow-up also should be performed on young adults in or near puberty. Puberty and changing hormone levels seem to affect the rate of progression of retinopathy.
Also, women planning pregnancy should have a dilated eye exam prior to conception and then during their first trimester, Dr. Calderon said. Women who are already pregnant should have a dilated eye evaluation during their first trimester. All pregnant women should have frequent follow-up evaluations based on the level of retinopathy, control of blood sugar and other diabetic complications.
In type 2 diabetes, or non-insulin-dependent diabetes mellitus, fundus exams should begin when the disease is diagnosed and should be repeated annually.
After retinopathy is detected, exams should be repeated more frequently based on the level of retinopathy. When significant dot-and-blot hemorrhages, exudates and cotton-wool spots appear, the patient should be seen every 4 to 6 months, depending on the severity of the symptoms or lesions, said William L. Jones, OD, FAAO, a charter member of the Editorial Board of Primary Care Optometry News.
When more severe signs develop, such as venous beading and intraretinal microvascular abnormalities (IRMAs), exam frequency should be increased to every 3 to 4 months, Dr. Jones said.
In each exam, the optometrist should determine the level of the diabetic retinopathy by evaluating the presence and degree of hemorrhages, microaneurysms, IRMAs, venous beading, neovascularizations and macular edema, Dr. Cavallerano said.
When patients have progressed into proliferative diabetic retinopathy, the optometrist should refer the patient promptly to a retina specialist. An important indicator is the presence of new proliferative vessels. Doctors also should note the location of the vessels, in particular if they are on or within a disk diameter of the optic nerve, and how much of the disk area they cover, he said.
Macular edema
In addition to the retinopathy, doctors should take note of presence or absence of diabetic macular edema, Dr. Cavallerano added.
"Diabetic macular edema can be present at any level of retinopathy, regardless of the patient's vision. A patient may be able to see 20/20 or better, have normal color vision, have normal Amsler grid findings and still have clinically significant macular edema," he said.
Close monitoring of the progression of the diabetic retinopathy and appropriate referrals can substantially reduce the patient's risk of vision loss. Patients with proliferative diabetic retinopathy may have a 60% risk of severe vision loss - defined as best-corrected visual acuity of 5/200 or worse - over 3 years if the disease goes unchecked, Dr. Cavallerano said. With proper treatment, either laser photocoagulation and/or vitrectomy, that risk can be reduced to less than 4%.
In patients with clinically significant macular edema, the risk of moderate vision loss, defined as the doubling of the visual angle, or best-corrected visual acuity being reduced from 20/20 to 20/40, for example, is almost 30% over a 3-year period, according to Dr. Cavallerano. With focal laser photocoagulation, that risk can be reduced to 12% to 13%.
Time to refer
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Most optometrists are more than capable of monitoring a patient through the early stages of progression, but when the disease reaches moderately severe nonproliferative diabetic retinopathy, the patient should be referred to a retina specialist, Dr. Calderon said. "Misdiagnosing the level of diabetic retinopathy can drastically affect the goal of maintaining good vision, making the prognosis guarded," he said.
Here, the optometrist's training and ability to compare the patient's fundus photos with established benchmarks showing each stage of the disease become important, he said. Recognizing such signs as soft exudates, IRMAs in more than one field and more pronounced venous beading is important in determining when to refer the patient.
With diabetic retinopathy, and any disease of the macula, in most cases, a consultation with a retina specialist is indicated, even if the optometrist continues to follow the patient, Dr. Cavallerano said.
Optometrists also should recognize signs that require immediate referral, such as neovascularization of the disc (NVD) greater than one-fourth of the area of the disc, Dr. Jones said. Neovascularization that covers less than one-fourth does not require immediate treatment unless there are other findings such as an area of neovascularization elsewhere (NVE) greater than one-third disc diameter in size or preretinal or vitreous hemorrhage. However, even without such associated findings the optometrist should seek a consultation because the disease is approaching a critical stage, he said. Also, NVE that is greater than one-third the disc diameter that produces a vitreous or preretinal bleed requires immediate referral and treatment. These guidelines are from the Diabetic Retinopathy Study.
"If there is clinically significant macular edema - edema within 500 m of the fovea, hard exudates within 500 m of the fovea with associated retinal edema in the area, or an area of edema one disk diameter that is within 1,500 m of the fovea - referral is definitely needed to see if laser application will help prevent further macular deterioration," Dr. Jones said. These guidelines come from the Early Treatment of Diabetic Retinopathy Study.
Nationwide network
A telemedicine project developed by the Beetham Eye Institute of the Joslin Diabetes Center will offer a new approach to evaluating patients with diabetic retinopathy and will provide a national comanagement service to assist optometrists in determining when referral to a retina specialist is appropriate. Also, this will offer a second opinion for the patient, optometrist and retinal specialist, Dr. Calderon said.
The Beetham Eye Institute is in the process of developing the Joslin Vision Network to review fundus photography from satellite offices across the country via telemedicine, Dr. Calderon said. This is also being tested within the U.S. Department of Defense at Veterans Administration hospitals between Boston and Hawaii.
Through the Joslin Vision Network, optometrists would take digital stereo photographs of three fields of the eye with a non-mydriatic, low-light level camera. Experts at a central location, likely to be located in Boston, would read the photographs. If the readers detect a problem, they would determine the level of retinopathy and return a report while the patient was still in the examining chair, Dr. Calderon said.
In addition to the digital fundus photos, an electronic ophthalmic record will be created and carried within the network. The telemedicine project is in validation phase where it is being compared with the current approach of taking seven standard fields, he said.
Preparing the patient for surgery
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When laser surgery is indicated, the patient should be told there might be a slight decrease in vision, as the laser is destroying a small part of the healthy retina, but hopefully the decrease will be followed by a stabilization or slowing of loss, Dr. Jones added.
Doctors should be specific when discussing the procedure. Many patients hear they are having surgery and expect to be out of work for a week, Dr. Cavallerano said. The accompanying chart offers more tips for preparing patients for the procedure.
For Your Information:
- Richard M. Calderon, OD, FAAO, associate chief, and Jerry D. Cavallerano, OD, PhD, staff optometrist and assistant to the director, can be contacted at the Beetham Eye Institute of the Joslin Diabetes Center, 1 Joslin Place, Boston, MA 02215; (617) 732-2554; fax: (617) 732-2545; e-mail rcalderon@joslin.harvard.edu.
- William L. Jones, OD, FAAO,is a member of the Primary Care Optometry NewsEditorial Board. He can be contacted at 1828 Conestoga SE, Albuquerque, NM 87123; (505) 293-7347; e-mail: wm_jones@email.msn.com. Neither Dr. Calderon, Dr. Cavallerano nor Dr. Jones has a direct financial interest in the products mentioned in this article, nor is any a paid consultant for any companies mentioned.