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Acute vision loss, distortion first component in wet AMD diagnosis
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Diagnosing wet age-related macular degeneration is straightforward. Administering appropriate treatment and providing social support are more gratifying.
When making the initial diagnosis of wet AMD from a symptomatic standpoint, “clinicians need to be aware of a subtle reduction in central vision, changes on the Amsler grid and/or metamorphopsia,” said Shaun K. Coombs, OD, in private group practice in Chehalis, Wash.
“Initially, we give the patient an Amsler grid to monitor the eye,” added Brett J. King, OD, in private group practice in Charleston, S.C. “Visual distortion is one indication of AMD. A drop in vision is a second indication.”
Dr. King said he also explores the inside of the eye stereoscopically. “You need to watch for subretinal fluid or hemorrhage,” he told Primary Care Optometry News. “Sometimes, this condition can be easily missed, unless the patient is dilated and you use a 78-D or 60-D lens. A 90-D lens does not provide quite the detail to look for subretinal fluid.”
Macular degeneration is always bilateral. “However, it can be very asymmetric between the two eyes,” Dr. King said. “So you are going to see deposits of drusen and pigment clumping in both eyes.”
According to Dr. Coombs, a staff optometrist at Pacific Cataract and Laser Institute, “Clinically, seeing any hemorrhages near the macula in patients with risk factors such as retinal pigment epithelium atrophy, drusen, pigment epithelial detachments and previous exudative involvement in the fellow eye should certainly raise your suspicion that there is a subretinal net.”
A second red flag is evidence of any retinal edema, with or without retinal hemorrhaging, he said in an interview. An older patient with a serous macular detachment is likely to have wet AMD.
“Many people with wet AMD come to our medical attention with advanced disease,” said Charles O. McCormick III, MD, a comprehensive ophthalmologist in private practice in Greenwood, Ind. “They have already experienced acute vision loss or distortion. There is usually a combination of dry and wet AMD findings. You will see slight elevation in the submacular region. A little crescent of hemorrhage may be adjacent. Typically, this is indicative of a chorioretinal net. The neovascular tissue is unique because these nets leak very easily and tend to hemorrhage.”
Dr. McCormick pointed out that wet AMD makes up only about 10% of all cases of AMD.
Diagnostic testing
Once a change in the patient’s macular degeneration has been determined, “a fluorescein angiogram is necessary,” Dr. King said. “In my previous practice, I was able to do that on the premises. However, in my current practice, I send the patient to a retinal subspecialist. A fluorescein angiogram tells me where the net is located and how active it is at the present time.”
Increasingly, optical coherence tomography or “some sort of retinal topography is scheduled,” Dr. King said. “These technologies can be helpful. He has used the OCT 3 (Carl Zeiss Meditec, Dublin, Calif.) and the HRT II (Heidelberg Retinal Tomograph, Heidelberg Engineering, Vista, Calif.).
Dr. McCormick told Primary Care Optometry News that a fluorescein angiogram or an OCT “is very helpful in confirming the diagnosis. In addition to a classic chorioretinal net, the subclassic or atypical net has some transitional features. There may also be pigment epithelial detachment in the macula that is actually not wet, but hyperfluorescent under a fluorescein angiogram.”
“Overall, it’s easy to make a tentative diagnosis of wet AMD,” Dr. Coombs said. “In our setting, we do fluorescein angiography to confirm the presence of the subretinal net. But most private optometrists will need to send the patient to a comanagement referral center or to a retinal specialist to have fluorescein angiography.”
Imaging, which is becoming more popular, “will tell you that the patient has retinal thickness, but will not necessarily confirm a subretinal net,” Dr. Coombs said. “The only way you can definitively diagnose a subretinal net is with fluorescein angiography.”
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Treatment options
Two currently available therapies for subfoveal neovascularization include photodynamic therapy (PDT) using Visudyne (QLT, Vancouver) and Macugen (Pfizer/Eyetech Pharmaceuticals), a pegaptanib sodium injection. “Some practitioners consider combining intravitreal steroid injection,” Dr. King said.
The current regimen for wet AMD therapy “is PDT, along with perhaps an intravitreal triamcinolone injection or intraocular Macugen,” Dr. McCormick said. “Stand-alone PDT leaves much to be desired in visually disabled outcomes and frequency of treatments.”
Dr. King said that 70% of patients with primarily classic nets still receive PDT. “But if a patient has an occult net or a mix net, he or she may get Macugen,” he said.
Macugen patients return monthly to the specialist because of the need for repeat injections. PDT patients are seen at 1 month and then 2 months later. For a focal destructive laser procedure, patients return in 1 to 2 weeks.
“The Macugen studies showed a benefit for both types of neovascularization — occult or classic,” Dr. King said. “However, it is such a new treatment that it is unknown at this time who is a better candidate for Macugen vs. PDT.”
PDT patients average four or five sessions over 1 to 2 years. “Specialists will start retreating after initial treatment,” he continued. “Usually, they retreat every 3 months, if the net is still leaking.” Macugen patients have multiple treatments every 6 weeks.
According to Dr. Coombs, PDT is especially effective for near or subfoveal lesions. “But for a lesion that is away from the fovea, generally it is much more common to treat with traditional argon laser,” he said. “The end goal for most macular degeneration is stabilization, not necessarily improvement. It is rare that patients improve with these treatments. I believe that PDT offers stabilization in most patients.”
“Clinicians need to recognize that wet AMD is a high-risk, vision-loss scenario,” Dr. McCormick said. “Usually, I attempt to place the patient in the hands of a capable retina specialist willing to offer PDT, if PDT is suitable. PDT is optimal for lesions adjacent to the macula, not subfoveal, in patients who have some degree of vision — 20/80 or better. Although PDT can be performed for subfoveal lesions, it is probably too late. You basically end up with a significant deprivation of the subfoveal architecture. Even with good care, patients with subfoveal lesions tend to become profoundly impaired.”
Early PDT literature “could not find an improvement at 1-year post-treatment compared to those patients who did not have PDT,” Dr. McCormick said. “But there was improvement at 2 years. Treated eyes had better functional vision and less disability. I think the reason it takes 2 years is because the macula is only about 2 mm in diameter. This is fragile tissue. A small amount of injury can cause a fairly impressive vision deficit.”
According to Dr. McCormick, Macugen is a vascular endothelial growth factor (VEGF) inhibitor. “VEGF is the protein that stimulates new vessel growth within the eye,” he said. “We know that VEGF is capable of being secreted by a variety of tissues in the body, not just ocular tissues. This includes kidney tissue and lung tissue. VEGF appears to be a very significant piece of the architecture for any new vascular proliferation of a wound or, in this case, macular degeneration.”
Dr. McCormick added that smoking cessation, vitamins, fresh fruits and vegetables and UV protection are all important adjunctive aspects of care.
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| Progression from dry to wet: The photo on the left shows dry AMD. The photo on the right shows wet transformation with disciform scarring 7 years later. | |
Comanagement issues
Dr. Coombs said once a patient has established a relationship with a vitreoretinal specialist, he encourages the patient to directly contact that specialist if an acute change in vision occurs. “If it’s not convenient, I tell the patient he or she needs to be seen promptly by their primary eye care provider,” he said.
“Once the diagnosis of wet AMD has been established and treatment has been initiated, I usually do not see the patient until they return for a cataract evaluation,” Dr. Coombs continued. “However, it is important for the primary care optometrist to be available for those patients who develop an acute loss of vision, even after AMD treatment.”
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Dr. King estimates that more than 90% of his wet AMD patients are seen by a vitreoretinal specialist. “Frequency depends on how active the choroidal neovascular membrane is,” he said. “Initially, the surgeon will probably see the patient monthly or quarterly. But if the membrane it not very active, the specialist may refer the patient back to the optometrist after only one visit.
“It is critical to have a good relationship with your retinal subspecialist,” Dr. King continued. “The two of you should have a good understanding of what treatment regimen you are both comfortable with and monitoring the patient. Spend some time in each other’s offices. You should also watch the specialist do surgery, especially a vitrectomy or a membrane peeling. In addition, try to find out what type of treatment parameters the specialist recommends.”
Dr. King typically schedules the wet AMD patient once every 6 months, once stabilized, after therapy begins. “I want to make sure that there is no drastic change in vision,” he said. “I also want to ensure that the patient is comfortable using the home Amsler grid.”
The patient should call the optometrist immediately if he or she notices any change.
Social support
Once the patient’s vision has stabilized, the specialist should refer him or her back to the optometrist for low vision aids. “In today’s society, these aids are not used as often as they should be,” Dr. King said.
“The optometrist can provide many social support functions that are part of the doctor-patient relationship,” said Dr. McCormick. “Low vision tools are important. Often, when the smoke clears, the retina surgeon has done his or her duty and the macula is quiet and dry, the patient is left with a low vision challenge. The patient needs to be interfaced with a competent clinician who can offer magnification aids and other tools of the trade.”
Optometrists are also frequently the direct link to the drivers’ license branch, securing a disabled parking sticker or qualifying a legally blind person for a federal tax exemption, he added.
For Your Information:
- Shaun K. Coombs, OD, can be reached at 2517 Kresky Ave., Chehalis, WA 98532; (800) 888-9903; fax: (360) 748-3869; e-mail: shaun.coombs@pcli.com.
- Brett J. King, OD, can be reached at 1470 Tobias Gadson Blvd., Charleston, SC 29416; (843) 556-2020; fax: (843) 763-3937; e-mail: bking@draisinvision.com.
- Charles O. McCormick III, MD, can be reached at 30 N. Emerson, Greenwood, IN 46143; (317) 881-3937; fax: (317) 887-4008; e-mail: comiii@msn.com. Drs. Coombs, King and McCormick have no direct financial interest in the products mentioned in this article, nor are they paid consultants for any companies mentioned.