November 7, 2019 By Dr Chang
By Peter Y. Chang, MD
Diabetes affects 415 million adults worldwide, and it is becoming more prevalent in children and adolescent thanks to the unhealthy diets and physical inactivity that have become the hallmarks of our modern society. Excessive hunger and thirst, frequent urination, weight loss, fatigue, and blurry vision are the classic early symptoms. However, it is estimated that in the U.S. 1 out of 3 patients remains undiagnosed, because these symptoms can be quite mild (that is especially true for type 2 diabetes). In addition to keeping up with routine physicals and blood work with your primary care doctor, getting a dilated fundus exam is critical in detecting early vascular changes of the eye. In fact, an astute observer can learn a lot about your overall health just by an eye exam!
What is diabetic retinopathy? Simply put, chronically elevated blood sugar leads to pathological alterations in the small blood vessels supplying the retina, in turn causing potentially irreversible vision loss. It usually takes several years for the high sugar to cause noticeable changes on the retina, but it is recommended that every newly diagnosed diabetic patient gets a yearly eye exam to catch any early changes (in fact, that is a good practice for anyone). The retinopathy progresses in stages and can be broadly categorized into:
- Nonproliferative diabetic retinopathy (NPDR): this can be mild, moderate, or severe, based on the amount of bleeding and vascular changes noted on the fundus exam. Patients do not usually have vision change unless there is associated macular edema (more details below), or if there is early cataract formation as a result of the elevated sugar. Some of the common findings your doctor might use to describe this stage of retinopathy include: microaneurysm, dot-blot hemorrhages, cotton wool spots, vascular attenuation, venous beading, and intraretinal microvascular abnormality (IRMA). Venous beading and IRMA are two of the defining features of severe NPDR. If present, the risk for progression to the proliferative stage of diabetic retinopathy is quite high. Regardless of the stage of NPDR, the standard of care is glucose, blood pressure, and cholesterol control. Laser or intraocular injection are typically not indicated during NPDR, unless there is concomitant diabetic macular edema. NPDR staging can regress nicely if diabetes is under good control and the patient’s overall health is good.
- Proliferative diabetic retinopathy (PDR): the retinopathy enters this stage when the retina is so deprived of oxygen that numerous chemical mediators are up-regulated inside the eye, ultimately leading to abnormal proliferation of blood vessels. This so-called neovascularization can grow anywhere on the retina, but most often on the surface of the optic nerve and along the retinal veins. These abnormal vessels are fragile, and thus can bleed into the vitreous gel. This vitreous hemorrhage can cause sudden loss of vision and can be quite frightening (and this is usually when a diabetic patient stops taking his vision for granted!). To prevent such an occurrence, your doctor will likely recommend in-office panretinal photocoagulation (“peripheral laser”) in order to help the neovascularization regress. If hemorrhage is significant and does not clear spontaneously, then the doctor will refer you to a vitreoretinal surgeon for vitrectomy, so that the blood can be physically removed (and laser can be done at the same time to help prevent future hemorrhage).
- Tractional retinal detachment (TRD): If laser is not done to suppress the neovascularization, with time, the abnormal proliferation of vessels, together with numerous other complex biochemical alterations that happen at the junction of vitreous gel and the retina, will lead to opacification and thickening of the vitreous. The abnormally strong vitreous can then begin to contract and, in the process, pull the retina away from the eye wall. This is referred to as TRD, to distinguish it from the types of retinal detachment caused by a retinal tear or other systemic conditions (I will write a separate blog on retinal detachment later). If TRD is close to the center of the eye and threatening central vision loss, then a vitreoretinal surgeon will perform a vitrectomy to remove the abnormal vitreous. In the ideal world, no diabetic patient should ever develop TRD because they would be so closely monitored that their retinopathy not allowed to get to this point. In reality, unfortunately, far too many patients suffer irreversible blindness because of it.
- Diabetic macular edema (DME): this refers to the swelling of the macula, which is the center of the retina that governs our central vision. The swelling is due to leaky, fragile vessels that form as a result of diabetes. DME can accompany either NPDR or PDR, so it should always be watched for. If you have NPDR and your central vision is gradually worsening, chance is that you have DME. In addition to the aforementioned control of glucose, blood pressure, and cholesterol, the treatment for DME includes intraocular injections of anti-VEGF and steroids, focal laser, and even vitrectomy for very difficult cases.
The bottom line: maintaining a good control of your diabetes, hypertension, and hyperlipidemia are of paramount importance when it comes to diabetic retinopathy prevention. However, if you already have retinopathy, it is never too late to seek out a vitreoretinal specialist in your area for a thorough dilated eye exam.
Dr. Chang is a vitreoretinal and uveitis specialist at MERSI. He is accepting new patients and has a strong interest in diabetic retinopathy among other retinal diseases.