Retina co-morbidity for the anterior segment surgeon
Cataract surgery and diabetic retinopathy

Experts weigh in on timing and treatment

A pre-op view of extensive, proliferative diabetic retinopathy with tractional macular detachment and somewhat hazy view secondary to associated cataract
Dr. Mahmoud said these patients need bimanual vitrectomy to segment, delaminate, and remove all the traction. A crisp view is needed for that procedure, and that may necessitate simultaneous or staged procedure with cataract beforehand
A post-op image 1 year after the combined procedure Source: Tamer H. Mahmoud, M.D.

Diabetic patients can be tough cases for cataract surgeons to work with, and managing diabetic retinopathy in prospective and current cataract patients is just one challenge in an already long line. As new data shows, the problem won't be going away anytime soon. According to the 2011 National Diabetes Fact Sheet, which was released January 2011, 25.8 million children and adults in the U.S.—8.3% of the population—have diabetes. In adults 65 and order, 10.9 million, or 26.9% of all people in this age group, have diabetes. Furthermore, in 2010 alone, 1.9 million new cases of diabetes were diagnosed in people aged 20 years and older. How can cataract surgeons manage diabetic macular edema (DME) before, during, and after cataract surgery? And does the timing of the surgery matter for the short- and long-term prognosis?

Timing and treatment

In deciding when to have patients with baseline DME undergo cataract surgery, David G. Telander, M.D., assistant professor of ophthalmology, Eye Center, University of California Davis, urged surgeons to wait until the edema is resolved. "You can't argue that's not the best way to do it," he said. "If there's some reason you have to proceed, like the patient can't function normally or he's had chronic edema that rebounds every time you stop treatment, then you have to actively treat him during cataract removal. But those are exceptions. You want to get the edema resolved as much as possible." There are a number of modern-day strategies for treating DME including anti-VEGF injections, intraocular steroid injections, and laser treatment. "If patients have chronic DME, nowadays they are most likely going to be treated along the way with anti-VEGF agents," said John Loewenstein, M.D., Massachusetts Eye and Ear Infirmary, Boston. "If that's the case, it's probably unlikely that cataract surgery is going to significantly exasperate their edema, although it can happen. The information we have to date suggests that coverage with anti-VEGF agents prevents the worst of what we used to see.
"In the anti-VEGF era," he continued, "we're generally not as concerned with patients having cataract surgery as we used to be."
Tamer H. Mahmoud, M.D., associate professor of vitreoretinal surgery, Duke University Eye Center, Durham, N.C., called attention to a study published in the Journal of Cataract and Refractive Surgery (2008; 34:1001-1006). The authors specifically looked at outcomes in patients with diabetic retinopathy and cataract who had panretinal photocoagulation (PRP) first and cataract surgery second in one eye, and cataract surgery followed by PRP in the fellow eye. "You'd expect that patients who had PRP initially would have a better outcome," said Dr. Mahmoud. "But interestingly the study showed the other way around. In patients that had cataract surgery initially followed by PRP, the rate of progression of macular edema was less. And their visual outcome was significantly better at 1 year." Dr. Mahmoud speculated that the reason for this is because surgeons aren't accurately detecting the severity of the DME before cataract surgery. "Maybe the density of the cataract does not allow a good enough treatment by laser before the procedure because there are those lens opacities in the way," he said. If a patient does have a dense cataract and you suspect he may have DME, Dr. Mahmoud suggested doing a potential acuity meter test, even though it's not always the most reliable. You can also try an optical coherence tomography (OCT), but if it's really bad the OCT might not measure it, Dr. Telander said. "The studies are conflicting, but if there is an effect on DME on contemporary, uncomplicated phaco, the effect is probably pretty small," said Dr. Loewenstein. "The effect is more likely to be on OCT measurement of central macular thickness rather than visual acuity. Also it may be transient. There are some studies that show that the thickening is more likely to occur within 6 weeks after surgery, and then there's no difference between patients with DME and without DME at 6 months." Another study Dr. Mahmoud pointed to was in a 2009 Ophthalmology publication (2009 Jun;116(6):1151-7), which specifically looked at patients with DME at baseline, randomized into two groups. One group had phaco in conjunction with an Avastin (bevacizumab, Genentech, South San Francisco) injection, and the second group had only phaco. "They found that at 3 months both groups improved significantly," he said. "However, the group that had the Avastin injection had significantly better visual acuity at 3 months and a much decreased retinal thickness by OCT. How do we explain this? We can explain this by saying that having one of those injections at the time of cataract surgery or before cataract surgery can improve the short- and long-term outcomes of patients with DME." In addition, after cataract surgery, prognosis often depends on how inflammatory the surgery was, said Dr. Telander. "The more inflammatory it is, the more increased macular edema there is," he said. "So if patients already had some DME, it will be worse, and if they didn't have any they can still have it. If they already have DME you should anticipate that it's going to get worse with any inflammation."

The trick with multifocal IOLs


Dr. Mahmoud can't say for certain that surgeons should not put a multifocal IOL in a diabetic patient after cataract surgery, but he does advise retina surgeons to be aware of the issues that could arise. "You need good visualization with a contact lens to be able to deliver a good focal laser for DME," he explained. "This view will not be the same for the multifocal lenses. One of the options we have for focal lasers nowadays is the PASCAL laser. I think we have to be very careful and do specific studies that look at safety using those types of lasers with diabetic patients with macular edema if a patient has a multifocal lens in the eye because the refractions of the multifocal lenses may be different."
Dr. Mahmoud advised surgeons to use "regular, single-spot lasers" until adequate safety data on other lasers become available. "At each spot you're trying to look through the center of the multifocal lens or any of the segments," he explained. "Make sure that spot is very focused on the retina, and deliver that spot safely."
One tip that could help with visualization is to position the patient's head so that his nasal bridge is not in the way during subsequent laser treatments, allowing you to easily access the nasal side with a vitrectomy probe and any other instruments used. "Usually, if we're doing a procedure that involves peeling, we would like the head to be as straight as possible so it would be easy to focus on the macula and safely peel the membrane and not tilt the head beforehand," he explained. "This step is even more important if the patient has a multifocal lens. The head has to be straight up because in this case, you have to focus through the center of the multifocal IOL to be able to safely peel."

Editors' note: The doctors interviewed have no financial interests related to this article.

Contact information

Loewenstein: john_loewenstein@meei.harvard.edu
Mahmoud: thmahmoud@yahoo.com
Telander: david.telander@yahoo.com