Diabetic Eye Care
Diabetes Mellitus
When the body does not use and store sugar properly, a condition called diabetes develops. If unmanaged, the disease can result in significant damage to the lining of blood vessels, which affects the major organs – the eyes, heart, and kidneys.
Who is at risk for diabetic eye disease?
Anyone with type 1 or type 2 diabetes is at risk for eye disease. Patients who fall into either category should have a comprehensive dilated eye exam at least every year. The longer someone has the disease, the greater the potential for developing diabetic retinopathy becomes. Patients with diabetic retinopathy may need to be seen more frequently to reduce the risk of blindness.
Diabetic Eye Disease
How is diabetic eye disease diagnosed?
- Visual acuity test – measures how well the patient sees at various distances.
- Dilated eye exam – allows the eye doctor to better see inside the eye to observe the blood vessels in their actual functional state. The eye is the only structure where blood vessels can be seen in their smallest size. These vessels supply oxygen to the tissues.
- Tonometry – measures the pressure inside the eye.
Complications from diabetes can reveal themselves in several forms of eye disease. Patients with diabetes tend to form cataracts (a clouding of the normally clear lens of the eye) at an earlier age. Similarly, an adult patient with diabetes is twice as likely to develop glaucoma. This is significant because the increased intraocular pressure from glaucoma can damage the optic nerve, resulting in permanent loss of vision.
If untreated, high blood sugar levels can damage the delicate vessels in the retina, the nerve layer at the back of the eye that senses light and helps to send visual messages to the brain. The damage to retinal vessels is called diabetic retinopathy. It is the most common diabetic eye disease.
There are two types of diabetic retinopathy.
- Nonproliferative Diabetic Retinopathy (NPDR)
- Proliferative Diabetic Retinopathy (PDR)
There are four stages of the disease process.
Mild Nonproliferative Retinopathy – Phase I of the disease. Normal blood vessels do not leak. In patients with NPDR, the retinal vessels become damaged and develop tiny leaks. Blood and fluid seep from the damaged vessels. Occasionally, a fatty material called exudate can deposit on the retina. This causes swelling of the retina.
- If fluid leaks into the center of the macula (the part of the eye where sharp, straight-ahead vision occurs) the macula will swell, causing blurred vision. This condition is called macular edema. Vision loss may be mild to severe and may include blurring, distortion, or darkening – but even in the worst cases, the peripheral vision of the patient continues to function. Typically, the problem occurs in both eyes – but one eye may be more acutely involved than the other. If the maculae of both eyes have been severely affected, the central vision may be lost. Macular edema can happen at any phase of diabetic retinopathy, although it tends to be more common in the advanced stages. Approximately half of the patients with proliferative retinopathy have macular edema.
Moderate Nonproliferative Retinopathy – Phase II of the disease; some of the blood vessels that nourish the retina become blocked.
- Macular ischemia occurs when small capillaries close. Vision blurs because the macula is no longer able to receive adequate blood supply to function normally.
Severe Nonproliferative Retinopathy – Phase III of the disease; many vessels become blocked depriving the blood supply to many areas of the retina. The areas of the retina that lack adequate blood supply send signals (vascular endothelial growth hormones) to the body to grow new vessels for nourishment.
Proliferative Retinopathy – Phase IV – the advanced phase of the disease. Signals sent by the retina trigger the growth of numerous new vessels. Unfortunately, these vessels do not resupply the retina with adequate blood flow. They are often accompanied by scar tissue that can lead to wrinkling or detachment of the retina. The new vessels are fragile and abnormal – growing along the retina and the surface of the clear vitreous gel that fills the inside of the eye. Alone, these vessels do not cause symptoms or vision loss. If their thin, fragile walls begin to leak blood, the result can be severe vision loss or even blindness.
- Vitreous hemorrhage occurs when the fragile, new vessels bleed into the vitreous (the clear, gel-like substance that fills the center of the eye). If the bleed is small, the patient may see only a few, new dark floaters. However, a very large bleed could block all vision. Depending on the amount of blood present, it could be reabsorbed or a vitrectomy could be recommended. A vitreous hemorrhage alone will not cause permanent vision loss unless the macula is damaged.
- Traction retinal detachment occurs when scar tissue associated with new vessel growth begins to shrink, wrinkling and pulling the retina from its normal position. This process can result in visual distortion. More severe vision loss can occur if the macula or large areas of the retina become detached.
- Neovasular glaucoma can develop following the growth of abnormal vessels on the iris of the eye. The growth blocks the normal flow of fluid out of the eye and the pressure within the eye builds, resulting in damage to the optic nerve.
How is diabetic retinopathy diagnosed?
As mentioned earlier, diabetic patients should have regular, dilated medical eye exams. The eye doctor will look through the dilated pupil with an ophthalmoscope.
Typically, no (ocular) treatment is required other than the systemic treatment necessary to keep your blood sugar under control during the first three stages of the disease. If evidence of diabetic retinopathy is detected, a special test called a fluorescein angiogram may be ordered to determine what type of treatment is required.
Fluorescein Angiogram
During the angiogram, a special dye is injected into a vein in the arm. The dye travels through the circulatory system, including the vessels of the eyes. Using a special camera and flashes of light, pictures of the retina are taken to determine if there are areas of hemorrhage or other changes. The photographs serve as a map, guiding the eye doctor if laser surgery is necessary.
The dye used during fluorescein angiography is bright yellow. Some patients notice a temporary yellowing or discoloration of the skin following the procedure. Urine will also appear a more intense yellow for a brief period of time. Both side effects are short term.
What is laser surgery and how does it work?
The purpose of laser surgery is to prevent further vision loss in patients with diabetic retinopathy. Laser surgery is not always required and, occasionally, may not be an option due to the advanced progression of the disease. The decision to use the laser for treatment is often determined by the type of diabetic retinopathy, the severity of the disease, and how well the eye doctor feels the patient will respond.
The laser beam is a high-energy light that converts to heat when focused on the areas of the retina requiring treatment. This process is called photocoagulation. For patients with nonproliferative diabetic retinopathy (NPDR) and macular edema, the laser may seal the leaking vessels of the macula or reduce the leakage, allowing the macula itself to dry. The main goal is to prevent further vision loss. Patients with blurred vision from macular edema do not typically recover normal vision, but for many there is some improvement.
In patients with proliferative diabetic retinopathy (PDR), the laser beam destroys the diseased portions of the retina (other than the macula). The treatment is called panretinal photocoagulation (PRP) and is done to stop the progress of abnormal vessel growth. Occasionally, the abnormal vessel growth will disappear entirely following laser surgery. The laser treatment also reduces the potential for further neovascularization, hemorrhage (bleeding) into the vitreous, and retinal distortion. Multiple laser treatments over time may be necessary to achieve the best results. PRP does not improve vision; but it is the best means of stabilizing vision to prevent further vision loss.
At present, there is no cure for diabetes. The disease can continue to cause damage to the retina despite the best efforts to control the process. When laser surgery is the right treatment, the chances of it making a positive impact are good. However, it is important to remember that the laser will not cure diabetic retinopathy and cannot always prevent further loss of vision.
Vitreous Hemorrhage – Diagnosis and Treatment
Vitreous hemorrhage is the result of bleeding from abnormal vessel growth into the vitreous cavity (center) of the eye. Mild bleeding may cause the patient to see many small spots in front of the eye. As the bleeding progresses, the patient may see numerous hair-like strands, large floaters, or a curtain or veil covering the vision of the affected eye. If a patient suddenly develops spider webs, floaters, spots, a curtain or veil over the eye, or blurred vision, they should contact their eye doctor immediately.
Panretinal photocoagulation (PRP) can be performed using the laser to shrink the hemorrhaging vessels. This process can reduce the chance of further bleeding into the vitreous. The blood in the vitreous usually disappears over time, but it can take months for that process to occur.
If the vitreous hemorrhage is severe or if the blood does not disappear on its own, it may be necessary for a retinal surgeon to perform a vitrectomy. This procedure can be performed in the hospital or surgery center under general or local anesthesia. After making a tiny incision in the eye, a small instrument is used to remove the vitreous gel that is clouded with blood. Typically, the gel is then replaced with saline solution. The eye will be sensitive and red and may be uncomfortable for several days. Antibiotic and steroid drops are prescribed to reduce the potential for infection and inflammation.
Traction Retinal Detachment – Diagnosis and Treatment
In proliferative diabetic retinopathy (PDR), abnormal vessel growth causes scar tissue. This abnormal vessel growth, along with scar tissue attaches itself to the back surface of the vitreous gel. The vitreous and the scar tissue may contract; pulling on the retina and lifting it up, separating it from the back of the eye. This is known as traction retinal detachment.
Patients with retinal detachment may notice a large, dark area in their field of vision. If the macula is included in the retinal detachment, the patient will see a dark shadow straight ahead and their vision will typically be very poor.
If the abnormal vessel growth and scar tissue cause the retina to wrinkle, the patient may notice blurring and distortion of the vision.
For the patient to regain their vision, the retinal surgeon must perform a vitrectomy – removing the abnormal blood vessels and scar tissue from the surface of the retina. Once this is accomplished, the traction on the retina will be released and the retina itself can be smoothed out. A laser may be used inside the eye to seal any tears in the retina. Occasionally, it may be necessary for the surgeon to place a large gas bubble in the eye to force the retina against the back wall of the eye. Patients requiring this technique may be asked to lie face down for up to a week following surgery.
Neovascular Glaucoma or Rubeosis – Diagnosis and Treatment
Rubeosis is the result of growth of abnormal vessels on the iris of the eye. Unfortunately, the development and growth of neovascularization on the iris is not always apparent to the patient. When the growth by new, abnormal vessels begins to block the normal flow of fluid out of the eye, the pressure within the eye builds to dangerously high levels. The result is neovascular glaucoma and may result in permanent damage to the optic nerve. Treatment often includes medication to control the intraocular pressure and panretinal photocoagulation (PRP) with the laser to treat the underlying ischemic disease.
Diabetic Retinopathy Research
Studies are ongoing to find better ways to detect, treat, and prevent vision loss for patients with diabetes. Current laboratory investigations are underway to develop medications that will stop the retina from sending signals to the body to grow new blood vessels. The hope is that in the future, it will be far easier for people to control diabetic retinopathy and reduce the need for surgical intervention.
For patients with severe macular edema, new treatments are currently available including the injection of steroid and antivascular epithelial growth hormone medications into the vitreous cavity or vitrectomy – or both.
We can’t stress strongly enough the importance of routine dilated examinations for patients with diabetes. It is the first line of defense against this insidious disease.