Diabetic Eye Disease
What Is Diabetes?
Diabetes is a disease that affects the body’s ability to produce or use insulin effectively to control blood sugar (glucose) levels. Too much glucose in the blood for a long time can cause damage in many parts of the body. Diabetes can damage the heart, kidneys, and blood vessels. It damages small blood vessels in the eye as well. Even if diabetes is well controlled, it can affect your regular eye care.
The Centers for Disease Control and Prevention (CDC) says that having a yearly eye exam, or as recommended by an ophthalmologist, can prevent about 90% of diabetes-related vision loss. People with diabetes should get these critical, annual eye exams, even before they have signs of vision loss. Studies show that sixty percent of diabetics are not getting the exams their doctors recommend.
What Is Diabetic Eye Disease?
Diabetic eye disease is a term for several eye problems that can all result from diabetes. Diabetic eye disease includes: diabetic retinopathy, diabetic macular edema, cataract, and glaucoma.
Diabetic Retinopathy
Diabetic retinopathy is when blood vessels in the retina, the light-sensitive tissue at the back of the eye, swell, leak or close off completely. Abnormal new blood vessels can also grow on the surface of the retina. People who have diabetes or poor blood sugar control are at risk for diabetic retinopathy. Risk also increases the longer someone has diabetes.
There are two main stages of diabetic retinopathy, NPDR and PDR. NPDR (non-proliferative diabetic retinopathy) is the early stage of diabetic retinopathy. Many people with diabetes have it. With NPDR, tiny blood vessels leak, making the retina swell. NPDR can also cause blood vessels in the retina to close off. This is called macular ischemia. When that happens, blood cannot reach the centermost portion of the retina, called the macula. Sometimes tiny particles called exudates can form in the retina. These can affect your vision too.
PDR (proliferative diabetic retinopathy) is the more advanced stage of diabetic retinopathy. It happens when the retina starts growing new blood vessels. This is called neovascularization. These fragile new vessels often bleed into the vitreous, a clear gel that fills the space between the lens and the retina. If they only bleed a little, you might see a few dark floaters. If they bleed a lot, it might block all vision. These new blood vessels can also form scar tissue. Scar tissue can cause problems with the macula or lead to a detached retina. PDR is very serious and can steal both your central and peripheral (side) vision.
Diabetic Macular Edema
When diabetic retinopathy causes the macula to swell, it is called diabetic macular edema (DME). If you have DME, your vision will become blurry because the extra fluid in your macula keeps it from working properly. This is the most common reason why people with diabetes lose their vision.
Diabetes and cataracts
Diabetes can cause you to develop cataracts. You may need cataract surgery to remove lenses that are clouded by the effects of diabetes. Maintaining good control of your blood sugar helps prevent permanent clouding of the lens and surgery.
Diabetes and glaucoma
Glaucoma is a group of diseases that cause damage to your eye’s optic nerve, a nerve at the back of your eye that connects and sends light signals to your brain so you can see. This damage leads to irreversible loss of vision. Having diabetes doubles your chance of getting glaucoma.
What Are the Symptoms of Diabetic Eye Disease?
You can have diabetic retinopathy and not know it. This is because it often has no symptoms in the early stages. As diabetic retinopathy gets worse, you will notice symptoms such as: seeing an increasing number of floaters, blank or dark areas in your field of vision, having blurry or poor night vision, noticing colors appear faded or washed out, and losing vision. Diabetic retinopathy symptoms usually affect both eyes.
Diabetic macular edema can cause blurry vision, metamorphopsia (a visual distortion in which straight lines appear curved), changes in color vision, and difficulty reading. However, you can also have no symptoms with DME.
Glaucoma causes blind spots in the visual field. Cataracts cause things to look blurry, hazy or less colorful.
How Is Diabetic Eye Disease Diagnosed?
Drops will be put in your eye to dilate (widen) your pupil. This allows your ophthalmologist to look through a special lens to see the inside of your eye.
Your doctor may do optical coherence tomography (OCT) to look closely at the retina. A machine scans the retina and provides detailed images of its thickness. This helps your doctor find and measure swelling of your macula.
Fluorescein angiography or OCT angiography helps your doctor see what is happening with the blood vessels in your retina. Fluorescein angiography uses a yellow die called fluorescein, which is injected into a vein (usually in your arm). The dye travels through your blood vessels. A special camera takes photos of the retina as the dye travels throughout its blood vessels. This shows if any blood vessels are blocked or leaking fluid. It also shows if any abnormal blood vessels are growing. OCT angiography is a newer technique and does not need dye or injections to look at blood vessels.
How Is Diabetic Eye Disease Treated?
Your treatment is based on what your ophthalmologist sees in your eyes. Treatment options may include:
Medical control: Controlling your blood sugar and blood pressure can stop vision loss. Carefully follow the diet your nutritionist has recommended. Take the medicine your diabetes doctor prescribed for you – sometimes, good sugar control can even bring some of your vision back! Controlling your blood pressure keeps your eye’s blood vessels healthy.
Medicine: One type of medication is called anti-VEGF medication. These include Avastin, Eylea, and Lucentis. Anti-VEGF medication helps to reduce swelling of the macula, slowing vision loss and perhaps improving vision. This drug is given by injections (shots) in the eye. Steroid medicine is another option to reduce macular swelling. This is also given as injections in the eye. Your doctor will recommend how many medication injections you will need over time.
Laser surgery: Laser surgery might be used to help seal off leaking blood vessels. This can reduce swelling of the retina. Laser surgery can also help shrink blood vessels and prevent them from growing again. Sometimes more than one treatment is needed.
Vitrectomy: If you have advanced PDR, your ophthalmologist may recommend surgery called vitrectomy. Your ophthalmologist removes vitreous gel and blood from leaking vessels in the back of your eye. This allows light rays to focus properly on the retina again. Scar tissue also might be removed from the retina.
What Other Eye Problems Are Related to Diabetes?
Diabetes can cause vision problems even if you do not have a form of diabetic eye disease. If your blood sugar levels change quickly, it can affect the shape of your eye’s lens, causing blurry vision. Your vision goes back to normal after your blood sugar stabilizes. Have your blood sugar controlled before getting your eyeglasses prescription checked, to ensure you receive the correct prescription.
Diabetes can also damage the nerves that move the eyes and help them work together. This nerve damage can lead to double vision.
Diabetes is a risk factor for several other eye diseases. They include branch retinal vein occlusion (BRVO) and central retinal vein occlusion (CRVO), where vein(s) from the retina become blocked.
How Can You Protect Your Vision?
To prevent eye damage from diabetes, maintain good control of your blood sugar. Follow your primary care physician’s diet and exercise plan. If you have high blood pressure or kidney problems, ask your doctor about ways to manage and treat these conditions. If you have not had an eye exam with an ophthalmologist, it is crucial to get one now. Be sure to never skip the follow-up exams that your ophthalmologist recommends and get a comprehensive dilated eye examination from your ophthalmologist at least once a year. If you notice vision changes in one or both eyes, call your ophthalmologist right away. Get treatment for diabetic retinopathy as soon as possible. Early treatment is the best way to prevent vision loss.
What Is the Latest Research on Diabetic Eye Disease?
1. DME is commonly treated with anti-VEGF drugs, which block the development of new blood vessels and limit the leakage from the abnormal blood vessels in the eye. However, anti-VEGF drugs must be repeatedly injected into the eye for them to be effective.
A phase 2 study of the injected medication UBX1325 helped patients with DME achieve improved visual acuity with only one injection, according to a press release from Unity Biotechnology. In addition, more than 50% of patients in the treatment arm of the phase 2 BEHOLD study did not require rescue treatment. UBX1325 also demonstrated a favorable safety and tolerability profile “Achieving sustained improvements in visual acuity and stabilization of retinal structure for almost 1 year after a single injection of UBX1325 is a remarkable result,” Anirvan Ghosh, PhD, CEO of Unity, said in the release.
2. As an alternative to injections of anti-VEGF medications such as ranibizumab, Roche and Genentech have developed the Port Delivery System (PDS). “The Port Delivery System is designed for continuous delivery of ranibizumab,” Arshad M. Khanani, MD, MA, FASRS, said at the Angiogenesis, Exudation, and Degeneration 2023 meeting. “For diabetic macular edema, it offers a strategy to maintain clinical benefits of monthly … anti-VEGF therapy while reducing overall treatment burden.”
A phase 3 trial showed that the PDS was as effective as monthly ranibizumab injections for the treatment of DME and was well tolerated by patients. The PDS, now known as Susvimo, was previously approved for the treatment of wet age-related macular degeneration in 2021.
3. Cataracts—the clouding of the lens of the eye—are the number one cause of blindness worldwide and are a common complication of type 2 diabetes. The current hypothesis behind diabetic cataract development is coined “the sugar hypothesis” and suggests that high blood sugar—a hallmark of diabetes—precedes cataract development.
New findings from investigators at Brigham and Women’s Hospital published in the Journal of Biomedical Science contradict this theory. The investigators used an animal model that more closely recapitulates type 2 diabetes in humans; they first develop insulin resistance and high blood insulin levels before their blood sugar rises above normal. The research team found early signs of damage in the eye before blood sugar started to rise, suggesting that high blood sugar itself does not lead to cataract development. The study may bring the medical community a step closer to understanding the cellular mechanisms underlying the origins of diabetic complications during the pre-diabetic stage of the disease. The authors hope that they can now start to search for how to prevent people with diabetes from developing cataracts, potentially preventing the need for cataract surgery.
For more information on diabetic eye disease, you can subscribe to the free monthly e-mail diabetes research update. Contact thl@vistacenter.org.
Sources
Turbert, David. “Diabetic eye disease” American Academy of Ophthalmology, 14 Oct. 2021
Boyd, Kierstan. “Diabetic Retinopathy: Causes, Symptoms, Treatment” American Academy of Ophthalmology, 27 Oct. 2022
Jacoba, Cris Martin P., MD, et al. “Diabetic Macular Edema” American Academy of Ophthalmology EyeWiki, 6 Jun. 2022
“Phase 2 study shows benefit of UBX1325 in diabetic macular edema” Healio Ocular Surgery News, 2 May 2023
DeFino, Anthony. “Phase 3 Pagoda trial meets primary endpoint goal for DME” Healio Ocular Surgery News, 13 Mar 2023
Brigham and Women’s Hospital. “Research challenges ‘sugar hypothesis’ of diabetic cataract development” Medical Xpress, 25 Jan. 2023
Compiled/edited by M. Kaplan, PhD, 5/2023