Anterior segment surgeons can take steps to manage diabetic patients who need cataract surgery
Diabetes and cataract are both age-related diseases. The median age that a patient undergoes cataract surgery in the United States is now approximately 69 years, having just recently dipped under 70 years. According to the most recent National Health and Nutrition Examination Survey, 20% of Americans older than age 65 years have diabetes, 90% being type 2, and 40% have impaired glucose tolerance or so-called pre-diabetes. Thus, diabetes rivals age-related macular degeneration as the most common comorbidity that the cataract surgeon must manage every day. Many diabetic patients also suffer from hypertension and obesity, and many smoke. Each of these puts the cataract patient at increased risk for sight-threatening postoperative complications, especially diabetic macular edema.
After 10 or more years of diabetes, there is damage to the pericytes lining the blood vessels, resulting in microvascular abnormalities that can lead to retinal edema and ischemia. These manifest in the eye as nonproliferative or proliferative diabetic retinopathy and/or DME. In severe cases, rubeosis iridis with the potential for secondary glaucoma can also develop.
The following are a few thoughts on how I, a cataract surgeon who practices in a large metropolitan area with easy access to quality retina specialist consultation, manage the cataract patient with diabetes. As a preamble to these comments, I do not personally utilize intravitreal injections or photocoagulation for retinal or macular disease, nor does anyone in our group at Minnesota Eye Consultants. Ideally, I would like the patient to have good diabetic control and hypertension management before surgery. I delegate this responsibility to the primary care physician, but occasionally find myself canceling a case on the day of surgery if a patient has very poor blood sugar control, especially if associated with a significantly elevated blood pressure. It is not reasonable to manage obesity in the weeks before cataract surgery, but patients can be counseled and encouraged to stop smoking.
In the preoperative examination, I examine the iris carefully for subtle neovascularization. If the patient has no signs of proliferative or nonproliferative diabetic retinopathy, I do not require him or her to see a retina specialist before surgery. If there is evidence of significant nonproliferative diabetic retinopathy, including venous dilation, significant microaneurysms, and dot and blot hemorrhages, and the retina either appears “wet” or has areas of capillary nonperfusion, I personally want these patients to be seen by a retina specialist before cataract surgery. Any evidence of iris neovascularization, neovascularization elsewhere, neovascularization of the disc or DME also generates a retina consult before surgery. I do an OCT of the macula on all my patients before cataract surgery because it is especially helpful in the diabetic patient to rule out subtle DME.
Many of my patients who present for cataract surgery are already under the care of a retina specialist, and they may have already undergone extensive treatment with panretinal photocoagulation or be under treatment with intravitreal anti-VEGF or steroid therapy. I rely on the retina specialist to help me time the cataract surgery, and in some patients with DME, an intravitreal injection of an anti-VEGF is performed within a month of cataract surgery. I pretreat all my diabetic patients with a topical NSAID because the trauma of the cataract surgery with the release of prostaglandins and leukotrienes is additive to the cytokines, such as VEGF and PDGF, that are present in the diabetic patient and can accelerate disease. The most common complication resulting in a visual acuity less than 20/40 in any cataract patient is macular edema, and the incidence in the diabetic patient is at least twice that in the patient without diabetes. If I am using a topical steroid, I start it 1 week before surgery.
I use topical NSAID and steroid drops for a longer period of time after surgery in the diabetic patient — at least 1 month and in many cases 6 to 8 weeks. At 1 month, I will look carefully for DME and perform an OCT if there is any question it might be present. If present, I will continue treatment with a topical NSAID and steroid until it resolves or is stabilized. I am quick to refer to a retina specialist for consultation because the longer DME persists, the less likely the patient is to recover his or her best potential visual acuity. Usually these patients are best treated with intravitreal anti-VEGF agents, which are more effective than steroids.
Recent results of the DRCR.net, RISE and RIDE studies suggest that Eylea (aflibercept, Regeneron) may be more effective than the alternative agents when visual acuity is less than 20/40 from DME. It is estimated that the VEGF level in the diabetic patient is 5 to 10,000 times higher than in the patient with exudative AMD. Some surgeons routinely inject subconjunctival or intravitreal steroids or even anti-VEGF agents on the table at the time of cataract surgery. I have been using Tri-Moxi (triamcinolone and moxifloxacin, Imprimis Pharmaceuticals) intravitreally over the past year in my cataract patients as an alternative to topical antibiotics and steroids for the prophylaxis of infection and inflammation. I have used this in my diabetic patients along with a topical NSAID and am impressed that it is a reasonable option. I am quick to add a topical steroid if there is any breakthrough inflammation or evidence of DME. I prefer hydrophobic acrylic IOLs in diabetic patients. I am comfortable using toric IOLs when indicated and requested. I am cautious with multifocal IOLs but have implanted them in select diabetic patients with no evidence of diabetic retinopathy and normal maculae after careful informed consent. After surgery with an uncomplicated outcome, the diabetic patient requires at least an annual dilated fundus examination and long-term monitoring for the development of diabetic retinopathy or maculopathy.
I have not been impressed that a YAG laser capsulotomy exacerbates diabetic retinopathy, but I screen the diabetic patient who presents with capsular opacity for DME with a careful fundus examination and OCT because macular edema can masquerade as capsular opacity and be exacerbated by opening the capsule.
The diabetic patient with cataract is a common challenge for the anterior segment surgeon, and the incidence and prevalence of both diabetes and cataract are increasing as the population ages. Fortunately, working in collaboration with our retina specialist colleagues and patients’ primary care physicians, we are able to help most of these patients achieve significant improved vision after cataract surgery and retain it for a lifetime.