Diseases
Overview
Age-Related Macular Degeneration
Diabetic Retinopathy
Retinal Vein and Artery Occlusions
Flashes of Light and Floaters
Retinal Tears and Retinal Detachments
Macular Pucker (Epiretinal Membrane)
Macular Hole
Vitreomacular Traction
Uveitis (Inflammation in the Eye)

Diabetic Retinopathy

What is Diabetic Retinopathy?
Diabetes and elevated blood glucose levels cause blood vessel damage throughout the body. The damage is most severe to small blood vessels, especially in the eye, kidney, fingers and toes, heart, and brain. As long as the blood glucose is elevated, there is microscopic damage to the cells that line the walls of small blood vessels and microaneurysms form. These are focal areas of weakness in the walls of the blood vessels that can then bleed or leak fluid and lipid into the retina as the earliest signs of diabetic retinopathy. The beginning stages are known as Non-Proliferative Diabetic Retinopathy (NPDR) and is graded based on severity; mild, moderate, and severe. As the damage progresses, the vessels in the periphery of the retina become unable to carry blood to supply the nutritional needs of the retina and eventually the retina responds with the development of new blood vessels, a process known as neovascularization. When new blood vessels form it is termed Proliferative Diabetic Retinopathy. Diabetes damage accumulates over a lifetime and is not the result of one short period of elevated blood glucose. Consequently most people will develop some diabetic retinopathy in their lifetime.

Mild, moderate, and severe Nonproliferative Diabetic Retinopathy

How do I prevent Diabetic Retinopathy?
Since diabetic retinopathy occurs as the result of chronically elevated blood glucose, controlling blood glucose is essential to preventing vascular damage. Keeping blood glucose levels below 120 mg/dL and Hemoglobin A1C at 6.5% greatly reduce the risk of developing retinopathy. Additionally, controlling underlying hypertension reduces the amount of vascular damage.


How is Diabetic Retinopathy diagnosed?
It is recommended that all patients with diabetes get routine, dilated examination to check for retinopathy. Since Type 1 diabetes present suddenly, screening is performed within 5 years of diagnosis. Type 2 diabetes however may have been present for a long period of time before diagnosis, consequently screening is recommended at the time of diagnosis for these patients. The initial stages of diabetic retinopathy typically do not have any symptoms. For early diagnosis and treatment screening is extremely important. 

The screening exam consists of a full, dilated examination of the eye and retina. By carefully looking at the retina the amount of diabetic retinopathy can be assessed and the risk for progression to vision loss determined. If any complications are present they can be detected and the properly treated. Often a scan of the retina is performed by Optical Coherence Tomography (OCT) to allow the retinal structure to be examined, this is particularly helpful for macular edema as the measurement can be used to follow the response to treatment. Sometimes a Fluorescein Angiogram (FA) is performed, this test uses a special dye to check the blood flow in the retina and identify areas of leakage. 



What are the complications from Diabetic Retinopathy?

Diabetic Macular Edema
If microaneurysms are present in the central retina, the macula, the leaking fluid and swelling can lead to decreased vision and is termed, Diabetic Macular Edema. Since the macula is responsible for central vision, a small amount of damage cause can cause significant decrease in vision.



Vitreous Hemorrhage
In proliferative diabetic retinopathy the neovascularization can lead to bleeding that fills the inside of the eye causing decreased vision, known as Vitreous Hemorrhage. 

Tractional Retinal Detachment
Neovascularization in PDR can also lead to scar tissue development and if progresses without control it can pull on the retina and cause a Tractional Retinal Detachment. This complication of diabetic retinopathy is very serious lead to complete blindness. 

 

Neovascular Glaucoma
Neovascularization can take place in the front of the eye as well as in the retina, and can block the normal fluid drainage network of the eye causing elevated eye pressure, termed Neovascular Glaucoma (NVG). NVG results in very elevated intraocular pressure and bleeding in the front of the eye that can occur suddenly resulting in severe eye pain and redness. If the eye pressure is not controlled there can be complete and irreversible loss of vision.


How do you treat Diabetic Macular Edema?
As the vessels in the central retina, the macula, develop damage and microaneurysms form the leaking of blood, fluid, and protein into the retina cause it to swell and distort the retinal structure causing decreased vision. Standard therapy has been to treat the microaneursyms with Focal Laser Photocoagulation to seal the leaking areas. While effective, patients can have a variable treatment response and the laser has the risk of causing damage to the surrounding retina. More recently, pharmacologic agents have been developed to block Vascular Endothelial Growth Factor (VEGF), a molecule in the eye that leads to increased vascular permeability. These agents are bevacizumab (Avastin), ranibizumab (Lucentis), aflibercept (Eylea) and are antibodies against the VEGF molecule. Lucentis and Eylea are FDA approved for the treatment of diabetic macular edema while Avastin is not. These medications are injected directly into the eye, called Intravitreal Injection, and are effective for 4-6 weeks. Response to the medication is variable and there is no way to predict how many treatments will be necessary. In some patients the response is inadequate to anti-VEGF molecules and steroids can be used to control the vessel leaking and can be administered by injection into the eye or next to the eye. Triamcinolone is the most common steroid used and the FDA has approved Ozurdex (dexamethasone) implant that can slowly release steroid for up to 3 months.

 
How is Proliferative Diabetic Retinopathy treated?
When the peripheral retina does not receive adequate blood supply from the damaged vessels it begins forming abnormal blood vessels, known as neovascularization. The retina causing the neovascularization is significantly damaged from ischemia and does not function for vision. Unfortunately, there is no way to undo the damage or restore the blood flow and laser photocoagulation is used to burn this retina, termed Pan-Retinal Photocoagulation (PRP). After PRP, the nutritional requirement of the peripheral retina is decreased and once balance is achieved between retina and blood supply the neovascularization process will stabilize. Sometimes this can be achieved with only one session of laser, but often multiple sessions are required to control the disease. If diabetes damage worsens from continued uncontrolled blood glucose the treatment may need to be repeated in the future.

 
How do you treat Vitreous Hemorrhage?
When the eye has bleeding from neovascularization it prevents light passing through the eye and causes decreased vision. Mild bleeding will cause floaters or strings in the vision and very dense bleeding can cause significant vision loss.  With enough time, the blood will be broken down and absorbed by the eye but the underlying cause of the bleeding needs to be treated. If the bleeding is not severe, PRP treatment can be applied through the blood in the clinic to control the underlying disease and then the vitreous hemorrhage can be safely monitored as it clears. If the bleeding is too dense to apply PRP in the clinic, the underlying disease is not controlled and waiting becomes dangerous. To clear the blood manually requires surgery, known as Pars Plana Vitrectomy (PPV). A PPV is performed in the operating room under sterile conditions, and involves making small incisions in the eye and using specialized equipment removing the blood along with the vitreous gel that fills the eye. During the procedure, PRP laser is applied to stabilize the diabetic retinopathy.

 
How is a Tractional Retinal Detachment treated?
If scarring along the retina becomes severe the traction can pull the delicate retina and cause separation from the wall of the eye. This is very damaging to the retina and can result in significant vision loss. If the retinopathy is stabilized with PRP treatments, the amount of scarring can stop but will not reverse itself. To remove the scar tissue and repair the retina surgery is required, the surgery is known as Pars Plana Vitrectomy (PPV). This surgery is performed in the operating room and involves making small incisions in the eye and using specialized equipment to remove the vitreous gel. Under high magnification from a microscope the scar tissue is delicately separated from the retina and removes the traction allowing the retina to reattach to the wall of the eye. PRP treatment is applied at the same time to ensure that the underlying retinopathy is stabilized. Often the retina will need internal support during the healing process and an intraocular gas bubble is placed. If a gas bubble is necessary, then the head and eye will need to be positioned face down toward the ground to allow the gas bubble to support the retina, this may be necessary for several weeks after surgery.

 
What is the treatment for Neovascular Glaucoma?
The same process that causes neovascularization of the retina can cause neovascularization of the iris, and these blood vessels can block the normal drainage network of the eye causing buildup of fluid in the eye and elevating eye pressure. This can occur suddenly and result in very high internal pressure and significant eye pain. Elevated intraocular pressure causes damage to the optic nerve that carries the signal from the eye to the brain, this damage is irreversible. Control of both the eye pressure and the retinopathy is necessary. To initially control the neovascularization, medication is injected into the eye to block the signal that causes the blood vessel growth, the medication is bevacizumab (Avastin), and will cause the abnormal blood vessels to stabilize and regress. The medication is only temporary until full PRP can be applied. If the process is early then the intraocular pressure can normalize, often however, the neovascularization results in scarring of the fluid drainage network in the eye and causes persistently elevated pressure. Treating with topical and often oral medications may be necessary to control the eye pressure but, if insufficient, surgery may be necessary to shunt the fluid out of the eye and is performed by a surgeon specializing in glaucoma surgery. 
 
Dr Kruti Dajee Dr Jawad Qureshi Dr Johnathan Warminski