Diabetes and Your Vision: New Treatments Now Available
Millions of Canadians and Americans could face vision loss from the effects of diabetes each year. In the US and Canada, more than 30 million people, half of whom are of working age, have this disease, the leading cause of preventable blindness each year. Worse, about 30 percent of diabetic patients are undiagnosed.
Getting a yearly comprehensive vision examination is one of the best ways to catch diabetes early and prevent ocular damage, especially for those over 40 years of age.
What is Diabetes?
Diabetes is a condition that causes the levels of glucose (sugar) in the blood to be too high. After a meal, food is broken down in the digestive system and converted into glucose, which is then transported by the circulatory system to individual cells throughout the body. The pancreas then secretes insulin, which converts glucose into energy.
In type 1 Diabetes, also called juvenile- or early-onset diabetes, there is not enough insulin being produced. In type 2, known as late-onset or adult diabetes, the pancreas produces enough insulin, but the body does not use it properly.
Prolonged high blood sugar can lead to nerve and blood vessel damage, which causes damage to the circulatory system itself. This can lead to stroke, heart disease, damage to the extremities due to poor circulation, blood vessel abnormalities in the eyes, and even death.
Preserving Vision: Treating Ocular Diabetes
Patients with diabetes need a comprehensive eye examination at least once a year, and more often as their eyecare practitioner advises, because early changes from diabetes are not detectable without dilating the pupils; it is impossible to see the back of one’s own eye. The earliest changes to the back of the eye, called background retinopathy, have no symptoms and vision is usually unchanged. As the disease progresses, however, circulation becomes more compromised and the eyes enter a stage called pre-proliferative retinopathy. The third stage of ocular damage is called proliferative retinopathy (PR), and is almost always accompanied by significant vision loss.
As we have noted above, diabetes has profound adverse effects on the circulatory system of the body. In the eyes, proliferative retinopathy from the breakdown of circulation in the eyes leads to the growth of new blood vessels called neovascularization, and diabetic macular edema (DME), both of which can lead to permanent vision loss.
Because the circulation is compromised, oxygen is depleted in the retina causing a condition called hypoxia, and a build-up of fluids called edema.
Edema in and behind the macular area, where the eye gets its clear, sharp central vision, can cause visual distortion and blur, not correctible with any spectacle or contact lens. Hypoxia of the retinal tissues can cause the production of substances called vascular endothelial growth factors (VEGFs), which stimulate new blood vessels to begin to grow in an effort to increase circulation. While this may sound good in theory, these new blood vessels of proliferative retinopathy are bad news, because they are extremely fragile and subject to rupture. Blood and blood proteins leak into the eye, blocking vision.
Diabetic macular edema and diabetic retinopathy are the two factors causing most new cases of blindness in the US and Canada.
Enter Lasers and Anti-VEGFs
If retinopathy and macular edema become serious enough, treatment with a laser may be needed. There are two types of laser treatments, the use of which will depend on the type of retinopathy present and the extent of the damage.
The laser may be used in a process called focal photocoagulation, which can be thought of as a type of “spot-welding” in the back of the eye in order to seal off specific leaking blood vessels that have formed in response to VEGFs. In some instances, the second type of laser treatment may be needed, called pan-retinal photocoagulation, which is the intentional destruction of peripheral retinal tissue in order to preserve the more important central part. When peripheral areas of the retina are destroyed by photocoagulation, there is minimal effect on vision; it also improves the circulation to those central areas that are more critical. In addition, the areas of the retina that have been destroyed can no longer produce VEGFs, so the stimulus for further new blood vessel growth is reduced. With pan-retinal photocoagulation, 1200 to 1800 tiny laser spots are usually used, leaving the central part of the retina untouched.
Treatment with laser photocoagulation should be done as early as possible, to preserve remaining vision; early treatment is also indicated for diabetic macular edema.
Testing with fluorescent dye injected into a blood vessel in the arm may be performed to assess exactly where leakages are located and how severe the problem may be. The dye glows under certain types of light so is visible as it leaks from blood vessels into the back of the eye. This is called fluorescein angiography.
Another type of treatment for DR and DME is the use of medications called anti-VEGFs, which are usually injected directly into the back of the eye (this sounds much worse than it actually is) to decrease the production of the blood vessel growth factors. This type of treatment for DR and DME has been available since 2012, when the FDA in the US approved monthly injections of Lucentis™ (generic name: ranibizumab), a steroidal type of anti-VEGf.
While anti-VEGf therapy is aimed at preventing further vision loss, between one third and one half of patients in a two-year study were able to regain at least 15 letters on an eye chart with their best correction.
As of February, 2015, Lucentis™ has received approval for use in the treatment of age-related macular degeneration as well as diabetic macular edema.
Steroidal implants, which are held in place in the back of the eye by the vitreous, a thick gelatin-like substance that fills the eye, are another valuable and recent improvement in the ability to treat diabetic retinopathy and macular edema.
In some cases, if blood vessels have leaked fluid into the vitreous and obscured vision, the vitreous can be removed and replaced with saline, restoring vision, or at least allowing the doctor to see where to focus the laser.
As exciting as these advances in the treatment of diabetic vision loss, patients should be aware that there can be serious adverse events, such as increased pressure within the eye and cataracts.
What to Expect from Laser Treatment
Usually, laser photocoagulation will be done in a surgery center or the eye doctor’s office, and requires no overnight stay in a hospital.
Someone will need to drive you to and from the clinic where the laser procedure will be done, and you will need to protect your eyes from sunlight afterwards, because your pupils will be dilated, in a similar way to how they are done during a routine vision examination. This is to allow the doctor to see more of the back of the eye and properly aim the laser. (Figure 2: Pattern of laser photocoagulation)
The size of the beam and the “spot” it makes, the amount of energy for each burst and the pattern to be applied will all be decided before treatment begins. Usually a laser treatment will take several minutes, more or less depending on how extensive the treatment will be.
There may be some discomfort, but you should not feel pain, as there will usually be a numbing drop and/or a side injection of anesthetic used.
Your normal activities can resume right after the treatment, although you may have some discomfort and blurry vision for a day or two after the procedure.
The number of treatments you will need will be determined by the condition of your eye and the extent of leakage from the blood vessels. People with significant diabetic macular edema may need three or four laser sessions every few months to stop the swelling.
On the Horizon
Several of these treatments discussed for diabetic retinopathy and diabetic macular edema are also being investigated for the treatment of other eye conditions, including uveitis, an inflammation of the tissues forming the iris and focusing muscles, and central retinal vein occlusion, a type of eye stroke.
An anti-cholesterol medication called a statin (Lipitor™) has been investigated for use to prevent diabetic retinopathy by blocking free radicals and protecting retinal nerve cells.
A major study in 2010 sponsored by the US National Institutes of Health combined extensive control of blood sugar and cholesterol-lowering medications showed a reduction in the progression of diabetic retinopathy by about a third over four years.
There are several relatively new and exciting methods for treating diabetic retinopathy and macular edema, which are preserving vision that once would have been lost. The more we study this disease, the better the treatments become and the better we can prevent the loss of vision that was once considered to be just part of being diabetic.
Diet, exercise, medication, insulin and research are all part of what, someday, may lead to a cure and effective treatment for this widespread condition.