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Diabetic Retinopathy

Diabetes is the most common cause of irreversible blindness in people under the age of 65. The tragedy is that this can usually be avoided if detected and treated early enough. One of the crucial components of treatment is blood sugar control. Decades ago many doctors advised their patients to run blood sugars on the high side to avoid the occasional, frightening episodes of hypoglycemia (low blood sugar). Since that time numerous medical trials have shown that fairly tight control of blood sugar can dramatically reduce the risk of organ damage, including damage to the retina, and can reduced the rate at which it progresses and the severity of the disease. Control of hypertension and kidney failure are also important elements in the treatment of diabetic retinopathy.

We recommend that patients work with their primary care physician or endocrinologist to control their blood glucose. Many patients that present to our office for the evaluation of diabetic retinopathy either don’t check their blood sugar at home or don’t check it regularly. The question “How is your blood sugar” often elicits an answer like “Well, it was 130 yesterday”, but this isn’t really helpful. If the average blood sugar is higher than this, it can still have significant damaging effects on the small blood vessels in the body. Many patients also think that if their early morning blood sugar before they eat is good, that it doesn’t matter what the blood sugar is after a meal. But recurrent high blood sugars after meals can also be damaging. For this reason, the hemoglobin A1C (Hgb A1C) test often tells us more about the risk of damaging the blood vessels in the eye. A Hgb A1C in the range of 7% or lower reduces the risk of progression of diabetic retinopathy. Each increase of 1% over 7 significantly increases the risk of vision loss and progression of retinopathy.

The highest blood sugar recorded within the past 6 weeks can also be valuable information. Even if the blood sugar is generally well controlled, a short burst of blood sugar of 300 or greater can change the shape of the natural lens in the eye and cause a decrease in vision. It can also cause the glasses prescription, or refractive error, to change making it difficult to get an accurate prescription for glasses until the blood sugar is under control for at least 6 weeks. Patients with uncontrolled blood sugar often get frustrated because they get a prescription for glasses from their optometrist which changes within a few days or weeks. This is usually reversible and can be stabilized if the blood sugar can be controlled

The highest blood sugar recorded within the past 6 weeks can also be valuable information. Even if the blood sugar is generally well controlled, a short burst of blood sugar of 300 or greater can change the shape of the natural lens in the eye and cause a decrease in vision. It can also cause the glasses prescription, or refractive error, to change making it difficult to get an accurate prescription for glasses until the blood sugar is under control for at least 6 weeks. Patients with uncontrolled blood sugar often get frustrated because they get a prescription for glasses from their optometrist which changes within a few days or weeks. This is usually reversible and can be stabilized if the blood sugar can be controlled

Type 1 & Type 2 Diabetes

Diabetic retinopathy can progress differently in Type 1 and Type 2 diabetes. Type 1 diabetes is usually detected early in the course of the disease and often in young people. Since it usually takes at least 5 years for diabetes to begin damaging the retina, the American Academy of Ophthalmology recommends that annual screening examinations of the retina with dilation should begin 5 years after diagnosis. The exception is during pregnancy. Diabetic retinopathy can progress very rapidly during pregnancy, so it is recommended that the first eye exam should take place as soon as possible after conception. Depending on the findings, the patient may have to be followed every 1 to 3 months during pregnancy. Patients that develop diabetes during pregnancy (gestational diabetes) are at low risk of developing diabetic retinopathy and do not require eye examinations during pregnancy.

Patients with Type 2 diabetes can have diabetes for years without any symptoms, so it is difficult to know how long a patient with Type 2 diabetes has been diabetic. For this reason it is recommended that a patient with Type 2 diabetes have a dilated eye examination at the time of diagnosis.

All diabetics should have an annual dilated eye examination to detect the onset of diabetic retinopathy. There has been concern in the past as to whether the use of aspirin increases the risk of worsening diabetic retinopathy, and this has not been shown to be the case, so aspirin can be used without concern.

Stages of Diabetic Retinopathy

Diabetic retinopathy is generally divided into to two categories, proliferative and non-proliferative diabetic retinopathy. “Proliferation” refers to the development of abnormal blood vessels and scar tissue that grow off of the surface of the retina into the interior cavity (vitreous cavity) of the eye.  Proliferative diabetic retinopathy is the more advanced stage of retinopathy.   Non-proliferative diabetic retinopathy refers to the stage when there is damage to the blood vessels of the retina, but proliferation has not yet developed.

In the early stages of non-proliferative diabetic retinopathy the smallest branches of the arterial network in the retina, the capillaries, become structurally weakened and dilate up forming small bubbles in the blood vessels, known as micro-aneurysms. These will frequently rupture causing small spots of blood, called dot and blot hemorrhages, in the retina. Early in the course of the disease these are few and outside the central area of the retina, called the macula, and may not cause any visual symptoms or threaten the vision.  However, as the disease progresses more microaneurysms develop and frequently are closer to the central area of the retina.  These damaged blood vessels leak fluid from the damaged capillaries.  This causes fluid to collect within the tissue of the retina.  The retina absorbs the fluid like a dry sponge absorbing water and thickens.  This swelling is known as edema.  Diabetic macular edema is diagnosed when there is swelling that affects the central area of the retina.  As this progresses closer into the central area, known as the fovea, the vision usually becomes progressively more blurred and distorted.

Swelling & Edema


The treatment of diabetic retinopathy depends on the stage and the type of damage that has occurred to the retina.  There are generally 3 aspects of diabetic retinopathy that can cause a decrease in vision.  One is bleeding within the retinal tissue or within the cavity of the eye.  The second is swelling within the tissue of the retina, diabetic macular edema.  And the third is loss of capillaries within the retina which cause a decrease in the penetration of oxygen and nutrients, known as ischemia.

Diabetic Macular Edema

When swelling within the retina damages or threatens the vision, there are 3 modes of treatment which can be considered.

Medical therapy

This consists of injecting one of several medications that are currently available into the eye.  These injections are known as “intravitreal injections”.  Intravitreal injections are performed in the office using topical or injectable anesthetics.  Although this sounds terrifying to most patients, the injections can be made very tolerable and even painless with anesthetics.  There are 2 classes of medication that are currently available and FDA approved.


Anti-VEGF medication

This is a class of medication which blocks the hormone VEGF,  (Vascular Endothelial Growth Hormone) which is produced by the eye when the tissues become oxygen starved or “ischemic”.  His hormone has a number of different effects in the eye, but one of the effects is to promote vascular leakage of fluid from the blood stream through damaged capillaries.  This results in diabetic macular edema.  Decreased vision from diabetic macular edema is the most common cause of vision loss in diabetics.  The 3 currently available anti-VEGF drugs are:

  • Avastin (generic bevacizumab)

  • Lucentis (generic ranibizumab)

  • Eylea (generic aflibercept)


Although all of these medications have been found to be roughly equivalent in terms of their long-term effect on diabetic macular edema, Lucentis and Eylea have been found to work more rapidly in some patients.

A frequently ask question by patients is “how many of these injections am I going to have to have”.This depends on the response.Some patients can respond very rapidly and require fewer injections, and some patients respond more slowly and require more.Patients tend to respond more slowly and require more injections if they have more severe swelling and if their blood sugar is poorly controlled.It is common for patients to require injections for 6 months or longer, and he even up to several years in some cases, depending on the response.If one medication is not having a successful effect after several injections, another medication is frequently tried.

Steroid therapy

The other class of medication that can be used to treat diabetic macular edema are anti-inflammatory steroid medications.  These are also injected into the eye using local anesthetic.  These are frequently reserved for patients who do not respond to anti-VEGF medications because they can have potential side effects that are less common than with the previously discussed drugs.  The 2 side effects that are of most concern are progression of cataracts in patients that have not previously had cataract surgery, and elevation of the pressure in the eye (intraocular pressure or IOP) either temporarily or permanently.  In some cases this can lead to or worsen glaucoma. 

However the medications can have a very beneficial effect in patients that have not responded optimally to anti-VEGF medications.  The 2 currently available medications are:​

  • Ozurdex.  This is a long-acting, slow release dexamethasone pellet, which is smaller than a grain of rice.  It is injected into the eye and slowly dissolves releasing the medication over a period of 3 months or longer.  When it has a beneficial effect it can last for months.

  • Iluvien. This is also a small pellet containing the steroid fluocinolone acetonide.  In patients with a good response the effect can last for up to 2 years.


All intravitreal injections, which penetrate the eye, carry with them the very small risk of a severe complication. These include the possibility of a bacteria entering the eye causing endophthalmitis, a severe infection within the eye which requires rapid and aggressive treatment. This can cause permanent vision loss in some cases.A retinal detachment is also possible, which can usually be repaired with surgery.IT is important to understand that the incidence of these complications is extremely low, somewhere between 1 in 3000 and 1 in 5000 injections.These risks have to be weighed against the significant risk of severe vision loss without treatment.

Laser treatment

Laser treatment is less commonly used than it was 10 or more years ago.  The purpose of laser treatment is to reduce leakage from damaged blood vessels.  This can be successful in some cases, but it tends to be less effective than medical treatment and carries the risk of damaging the retina.  Most types of laser treatment require that a burn is created within the retina in an attempt to either close damaged, leaking blood vessels or stimulate the tissue to reabsorb the excess fluid from the retina.  This frequently leaves behind scars which can cause permanent blind spots in the central vision.  Under some circumstances the judicial use of laser treatment, when it poses a low risk to the vision, can be helpful as treatment or as an adjunct to medical therapy.  Laser treatment is performed in the office with topical anesthetic.


Surgical procedures are much less commonly used for the treatment of diabetic macular edema, but they may occasionally be appropriate.  If other methods are not successful at improving or resolving macular edema, sometimes a surgical procedure known as a vitrectomy will be recommended to remove scar tissue or adherent vitreous from the surface of the retina.  This is generally done under local anesthetic in an outpatient operating room.

Proliferative Diabetic Retinopathy

When abnormal blood vessels begin to grow off of the surface of the retina there is a risk of bleeding into the cavity of the eye (vitreous hemorrhage) and eventually the development of fibrosis, or scar tissue, that can contract and cause a retinal detachment, known as a traction retinal detachment. In the late stages this can become inoperable with complete, irreversible loss of vision. The goal of treatment is to prevent bleeding and detachment of the retina by causing the abnormal blood vessels to regress. If the condition is detected too late for this, the blood and scar tissue may have to be removed from the eye surgically.

Medical therapy

As with diabetic macular edema, the same medications mentioned earlier can be injected into the eye to cause regression of the abnormal blood vessels. This can be very effective, and often works faster than laser, but it can sometimes result in bleeding inside the eye as the blood vessels regress, especially if the treatment is started after there is extensive growth of blood vessels (neovascularization) into the eye. This may be a risk worth taking since avoiding treatment will usually result in progression of the disease, making it much more difficult to treat.

Laser treatment

Panretinal photocoagulation is laser treatment performed for proliferative diabetic retinopathy to cause regression of the abnormal blood vessels.  This is frequently used in conjunction with medical therapy or surgery.  This treatment can be performed in the office in one or multiple sessions sometimes with local anesthetic.  Studies have shown that laser treatment is very effective at controlling the growth of abnormal blood vessels in the eye and can result in stabilization of the condition indefinitely if the blood sugar can be controlled.


Surgery is sometimes necessary if the above treatments fail, or if the patient is severely visually handicapped in both eyes, in order to restore functional vision to at least one eye as soon as possible.  The surgical procedure performed is called a vitrectomy, in which the blood and vitreous gel are removed from the internal cavity of the eye.  Scar tissue and abnormal blood vessels are also removed and cauterized to prevent further growth and bleeding.  Laser treatment is also performed during surgery in many cases.  If the retina is detached it may also require the injection of gas or clear silicone oil into the eye to hold the retina in position while it heals.

     Vitreous Hemorrhage

A vitreous hemorrhage is bleeding into the vitreous cavity of the eye.  This is the result of proliferative diabetic retinopathy.  This is a sudden and often frightening occurrence with a relatively rapid loss of vision.  The important thing to understand with vitreous hemorrhages is that the blood inside the cavity of the eye will not permanently damage to the vision.  The bleeding can frequently be stopped and the blood can be successfully removed with surgery if necessary.  If the bleeding is not severe, the body will often reabsorb the blood without surgery.  Your ophthalmologist will determine the best option for treatment.  It is usually advisable to avoid strenuous activity such as lifting, coughing, and constipation.  Also, sleeping with the head elevated can help to promote gravitational settling of the hemorrhage and more rapid clearing.  Patients that are on anticoagulants (blood thinners) are encouraged to ask their primary care physician or cardiologist if these can be temporarily discontinued.

     Retinal ischemia

Loss of circulation to the retina due to damage to the small blood vessels in the retina, retinal ischemia, can continue to damage the vision even after all the other previously discussed conditions have been successfully treated.  Patients with uncontrolled blood sugar can still experience progressive vision loss due to loss of capillaries in the retina even after they have had adequate medical, laser, or surgical treatment.  This is the reason why control of the blood sugar, blood pressure, and kidney function are important factors in stabilizing diabetic retinopathy.

Vitreous Hemorrhage
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