Diabetic retinopathy Macular Degeneration

Neovascularization Causes Blindness

Both macular degeneration and diabetic retinopathy can cause “blindness” from neovascularization.  Both are diseases of the retina, both can lead to “blindness,” both increase with age/time and both can be associated with abnormal blood vessel formation known as neovascularization.”

The two diseases differ in the location of the neovascularization.

Diabetic Retinopathy – In cases of diabetic retinopathy, the presence of neovascularization defines a particular stage of eye disease; proliferative diabetic retinopathy.  The neovascularization may “proliferate” along the surface of the retina and other structures inside the eye.  As long as the VEGF is circulating, the vessels will continue to grow.

Diabetic retinal detachments may occur if the the neovascular tissue proliferates out of control.  Neovascular glaucoma may develop if the abnormal blood vessels “clog” the internal drain of the eye.  In this case, intraocular fluid that normally filters out of the eye can no longer escape as the drain is closed.  The pressure escalates out of control and severe pain (and redness) develop.

In short, proliferative diabetic retinopathy, as defined by the presence of neovascularization, can causes retinal detachments and neovascular glaucoma (not the usual form of glaucoma).  Both are mechanisms by which diabetes can cause blindness.

Macular Degeneration – “Wet” macular degeneration, by definition, exists when neovascularization develops underneath the retina.  This neovascular tissue causes physical separation of the layers of the retina and destruction of the normal tissue.  Almost all neovascularization leaks, and, at times, bleeds.  Loss of central vision occurs due to this rather rapid growth of abnormal blood vessels.

VEGF – In either case, neovascular tissue is a complex of “abnormal blood vessels.”  As best we can tell, neovascular tissue develops in response to Vascular Endothelial Growth Factor, or VEGF.  This growth factor causes both proliferation of the neovascular tissue and sustains existing neovascularization.  Without circulating VEGF, the neovascular tissue shrinks up and goes away.

Anti-VEGF treatments are simply directed at blocking the effects of VEGF.

Anti-VEGF medications (e.g. Avastin, Lucentis and Macugen) are antibody like molecules that find circulating VEGF and prevent VEGF from “doing its duty.”   The treatment of choice for proliferative diabetic retinopathy remains pan-retinal photocoagulation (PRP).  The end result of PRP is decreased … VEGF.

With timely diagnosis, both diseases can usually be controlled.  Neovascularization in diabetes can be reversed before a retinal detachment is formed, neovascular glaucoma may be reversed and “wet” macular degeneration can be halted.

What Does This Mean? A few years ago, I would not have been able to write this article.  We have learned a lot about the mechanisms by which both diabetic retinopathy and macular degeneration cause blindness.  It amazes me how the pathogenesis (i.e. the disease process) of both diseases are so similar.  Both diseases can cause blindness via VEGF.

This is why it is so confusing.  Two separate diseases that respond to the same treatment.

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Macular Degeneration Retina

Here's Blood in Your Eye!

Blood in your eye can mean many things to different people.  The most common “blood” is the sudden appearance of fire engine red blood on the outside of the.  It is called a subconjunctival hemorrhage.  It is usually scary, painless, ugly and benign.  As a black and blue bruise, it will clear in about 1-2 weeks.

I am talking about blood inside your eye.

Vitreous Hemorrhage – In patients with diabetic retinopathy, the sudden appearance of “floaters” can be signs of a vitreous hemorrhage.  Patients with proliferative diabetic retinopathy, by definition, have developed neovascularization, or abnormal blood vessels, somewhere inside the eye.  Most commonly, the neovascularization, is found on the surface of the retina, but can also be present on the optic nerve and iris. These blood vessels are very fragile and may break open and bleed causing blood to accumulate in the vitreous.

A vitreous hemorrhage can cause dramatic loss of vision as it physically may block light from hitting the retina.  It is not an emergency despite the significant loss of vision.  As long as the retina is attached, the hemorrhage may be observed for weeks or even months.  It causes no damage, just anxiety.

A vitreous hemorrhage may also be caused by a tear in the retina.  Retinal tears may occur in anyone.  So, in diabetic patients with a vitreous hemorrhage……….As long as the retina is attached and without a tear, we can wait.

Laser treatment to the retina is the antidote for proliferative diabetic retinopathy.  If there is too much blood in the vitreous, it may not be possible to laser the retina.  Sometimes we can wait for the hemorrhage to absorb and then treat with laser in the office.  Other times, the hemorrhage does not clear and we may choose to operate, that is, perform a “vitrectomy.”  In this case, the blood is mechanically removed and then the retina is treated with laser during the operation.

Sub-Retinal Hemorrhage – Blood underneath the retina is called a sub-retinal hemorrhage.

A sub-retinal hemorrhage may occur in patients with wet macular degeneration.  Abnormal blood vessels,  called choroidal neovascularization, may develop within the layers of the retina in “wet” macular degeneration.  Patients with “wet” macular degeneration, by definition, have developed neovascularization underneath the retina.

The blood underneath the retina, too, is benign.  It does no harm to the retina. The neovascular tissue; however, may be causing some damage and efforts are made to quickly arrest further progression of the abnormal blood vessels.

Once the presence of neovascularization is confirmed underneath the retina by a fluorescein angiogram, the treatment of choice may be anti-VEGF medications such as Avastin®, Lucentis® or Macugen®.


Randall V. Wong, M.D.
Ophthalmologist, Retina Specialist

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How I Practice

Why Diabetics Need to Get Eye Exams

Whether or not you are newly diagnosed or a veteran of diabetes, you need to get your eyes checked at least once a year.

Recommendations by the ADA and the AAO are that every diabetic get a complete eye exam, including a dilated exam (pupils get dilated) to allow proper examination of the retina.

If you are newly diagnosed, you may have noticed blurry vision recently. Large fluctuations of your serum glucose (blood sugar) can change the water content of your lens and cause transient blurry vision. Most likely, since diagnosis, your blood glucose is now lower than it has been in a long time; changing the water content of your natural lens. The refractive power of the eye is now changed and it changes the power of the glasses or contact lenses that you may need.

We are most concerned about diabetic changes in the retina.  Most diabetics (over 80%) will develop some degree of diabetic retinopathy in their lifetime.  The most common stage of diabetic retinopathy is the so-called “background” or “non-proliferative” phase.  Doctors are looking for signs of swelling near the macula, the functional center of the retina.  The goal is to prevent swelling in the macula and thus preserve vision. If macular edema has already developed, the goal is to treat the retina with laser or sometimes medicines, to reduce the amount of swelling.  This may lead to better vision.  Sometimes the gest we can do is to simply limit additional swelling.

Unfortunately, diabetics can NOT self monitor themselves. It is better not to wait for changes in the vision before seeking medical attention.  In a perfect world, it is ideal if a patient is still 20/20, yet needs treatment.  The chances of preserving the perfect vision are better than trying to regain lost vision.

About 20% of patients that have developed diabetic retinopathy progress to the prolifertive phase of the disease.  In this phase, abnormal blood vessels develop on the surface of the retina and other parts of the eye.  This retinal neovascularization can cause hemorrhaging into the vitreous and cause significant loss of vision.  More importantly, a diabetic retinal detachment can occur.  The neovascularization (aka “neovascularization elsewhere”) can grow on the retina surface much like ivy on the forest floor.  It can grow from one point to another and start to contract.  This pulling on the retina can lead to retinal detachment if not caught in time.  This is the mechanism by which diabetics go blind.

The treatment for proliferative diabetic retinopathy is panretinal photocoagulation, that is, diffuse laser photocoagulation to the peripheral or side vision.  Proliferative diabetic retinopathy occurs when the retina is “ischemic.”  To say another way, ischemia results when the demand for oxygen is greater than the supply.  In this state, a growth factor is produced by the retina causing abnormal proliferation of blood vessels.  Laser photocoagulation, in this setting, is aimed at “killing” or reducing the need for oxygen in the peripheral or side retina.  When the demand for oxygen is reduced sufficiently, the growth factor is no longer produced causing regression of the abnormal blood vessls.  The proliferative phase the disease is now stabilized.

Advanced cases may require vitrectomy surgery.

What does this mean to you? Regardless of the number of years that you have been diabetic, make sure you get a dilated eye exam at least annually.  Vision does not correlate with the severity of the disease, nor does the disease correlate with sugar control (you can be well controlled, but still suffer from diabetic retinopathy).  We, as eye doctors, do a much better job at treating you early and preventing vision loss than vice versa.


Randall V. Wong, M.D.
Ophthalmologist, Retina Specialist

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