A. Diabetes Mellitus is a chronic disease characterized by inability to burn up the sugars (carbohydrates) that have been ingested.  It is caused by insufficient production of insulin by the pancreas. The patient may feel excessive thirst and frequent urination. Diabetes can affect vision due to cataracts, glaucoma, optic nerve problems and most significantly by causing damage to the blood vessels of the retina which results in Diabetic Retinopathy. Diabetes can affect adults and children as well.

What is Diabetic Retinopathy?

Diabetic Retinopathy is a complication of Diabetes Mellitus that affects the inner lining of the eye called the retina. Diabetes causes changes in the blood vessels of the retina that leak fluid and/or blood.

The risk of developing Diabetic Retinopathy increases the longer the patient has diabetes. Diabetic Retinopathy is also more aggressive and starts at an earlier time, the younger the onset of diabetes especially if the condition was diagnosed during childhood or during the teenage years.

Diabetic Retinopathy is a chronic, progressive disease; that is, there is no known cure for Diabetic Retinopathy. It causes blurring of vision that cannot be relieved by eyeglass prescriptions. Diabetic Retinopathy is also one of the leading causes of blindness, especially if undetected or left untreated.

What is the Retina?

The retina is the part of the eye that is affected in Diabetic Retinopathy. It is the innermost lining of the eye and is responsible for receiving visual images for transmission to the brain. The retina is likened to the “white meat” in a coconut and is intimately related to its outer shell. Blood vessels pass through the retina and these are affected by diabetes.

The “bull’s eye” of the retina is the very center of the retina. Its ophthalmological term is macula.

What happens in Diabetic Retinopathy?
 
In Diabetic Retinopathy, changes are seen in the blood vessels that occur the longer the duration of diabetes, more especially if the blood sugar levels have been inadequately controlled.

The smaller blood vessels called capillaries become narrowed and/or obstructed while others form balloon-like sacs. These changes cause the vessels to leak blood and fluid, seen in the retina as hemorrhages, exudates and/or swelling. These changes can be slow to progress if blood sugar is well controlled. Despite good control, however, the retinopathy tends to progress slowly and steadily over time.

What are the types of Diabetic Retinopathy?

There are two basic types: 1) Non-proliferative Diabetic Retinopathy (NPDR) and 2) Proliferative Diabetic Retinopathy (PDR).

Non-proliferative Diabetic Retinopathy is seen in the retina as red dots and blots of hemorrhages or as yellow dots which are lipid (fatty) leakages. If the macula of the retina is affected, swelling can occur which would cause blurring of vision that cannot be fully corrected with eyeglass prescriptions.

These retinal changes increase in number and cover a wider area the longer the patient has diabetes. The retinopathy will progress even though the blood sugar is well controlled. The speed with which the retinopathy deteriorates will, however, be slower if there is strict control of the patient’s blood sugar.

Proliferative Diabetic Retinopathy is the more advanced stage where abnormal, new blood vessels begin to grow on the surface of the retina. A simple analogy is to think of the roots of a tree which continually branch and grow looking for sources of nutrients. These abnormal blood vessels continue to branch and multiply.  Because their vessel walls are weaker, they may rupture and or leak causing hemorrhage and swelling which could result in severe blurring of vision or blindness.

In the earlier stages of the proliferation, the blood vessels grow on the surface of the retina. If one thinks of the coconut, the blood vessels are creeping along the surface of the “white coconut meat”. Later, however, these blood vessels begin to extend upwards and grow into the fluid of the eye called the vitreous. This would be like having blood vessels grow out of the “white coconut meat” into the fluid compartment. If these blood vessels bleed, the extent of hemorrhage could be severe, replacing the fluid with blood.

What are the symptoms of Diabetic Retinopathy?

The most common symptom is gradual, continuous blurring of vision. This can be due to the swelling of the macula or macular edema. The blurring may be mild to quite severe depending on the seriousness of the retinopathy. In the Proliferative Diabetic Retinopathy stage, the blurring may be sudden and severe due to the bleeding of the vessels into the fluid or vitreous of the eye.

Many times, the patients can describe the start of the vitreous hemorrhage. In the beginning, they see black spots or dots called “floaters”. These dots occasionally become elongated like strands of hair which eventually become denser and more black.  The vision then becomes quite poor as the blood increases and fills the vitreous.

Blurring of vision, may however, also be due to a gradually thickening cataract.

Other symptoms include: double vision (most often due to a temporary weakness of a nerve) and a painful eye (due to glaucoma).

How is Diabetic Retinopathy detected?

To detect Diabetic Retinopathy, an eye exam is performed  by a retina specialist which would include testing the vision, checking for cataracts and glaucoma and doing a retina screening.  A retina screening involves dilating the pupil in order to be able to see the retina adequately via Indirect Ophthalmoscopy.

If Diabetic Retinopathy is noted, color photographs and/or Fluorescein Angiography are recommended. Fluorescein Angiography (FA) is a special technique performed which allows detailed analysis of the blood vessels of the retina and helps determine the seriousness of the retinopathy to plan for the mode of management. Optical Coherence Tomography (OCT) may also be recommended. This exam evaluates the severity of the macular edema

Who should have eye checks?

All diabetics should go for eye checks which include evaluation of the retina by a qualified retinologist.

Children who have been diagnosed to have diabetes should have retina checks as soon as they reach puberty.

Adults who have been diagnosed to have Diabetes Mellitus should have their retinal checks as soon as they are diagnosed to have diabetes.
 
Diabetics who become pregnant and those diagnosed with gestational diabetes should have retinal checks at every trimester or as recommended by the retinologist.

What is the treatment for Diabetic Retinopathy?

Treatment depends on the stage of the retinopathy. If the retinopathy is still in the early Non-proliferative Diabetic Retinopathy stage, repeated eye checks are recommended.

If the Diabetic Retinopathy is progressing, retinal photos and a Fluorescein Angiography (FA) may be requested to document the stage of the disease. This exam involves injecting a dye into the arm vein and taking photos of the retina to see which vessels are leaking or which areas lack oxygen. Moreover, an FA may help decide if laser treatment for the retinopathy is needed and how soon the laser treatment should be started.

At the appropriate stage, PRP or Pan-Retinal Photocoagulation (laser of the retina) is performed to prevent the blood vessels from growing continuously, thereby preventing bleeding. Most significantly, appropriate timing of PRP can prevent blindness.

If cataracts are present, a cataract operation may be recommended.

If blood is noted in the vitreous, a surgical procedure called Pars Plana Vitrectomy may be recommended to remove the blood and apply laser treatment if not done yet.

It must be emphasized that despite laser and surgery, there is no guarantee that the retina will be okay or that no more further laser or surgery will be needed. As mentioned earlier, Diabetic Retinopathy is a chronic, progressive disease and there is no known cure for it.

What can be done to prevent Diabetic Retinopathy?

A multicenter USA study called the “Diabetes Complications Control Trial” showed that prevention can best be done by a very tight control of blood sugar and by early detection of Diabetic Retinopathy which can be achieved by regular retina checks by retina specialists.

It is important that the patient comply with the schedule recommended by the retina doctor for follow up visits even if the patient does not feel any symptoms. This is because diabetic retinopathy will more often than not start quietly and the patient may experience symptoms only when the disease is in its more advanced stages.