What is Diabetes?
Diabetes, or diabetes mellitus, is a condition that results from a deficiency or inefficiency of the insulin hormone, leading to high blood sugar levels. It is a microvascular disease that affects many organs.
Type 1 diabetes usually starts before the age of 30 and involves an insulin deficiency. Insulin injections are required.
Type 2 diabetes typically occurs after the age of 40, where the body either has insufficient insulin or has problems using it. It requires diet management, oral antidiabetic medications, and sometimes insulin injections.
How does Diabetes affect the eyes?
Diabetes affects many parts of the eye. Common eye diseases in diabetic patients include dry eyes, eye pressure issues, cataracts, and optic neuropathy. However, the part of the eye most affected by diabetes is the retina.
Diabetic retinopathy occurs when the small blood vessels in the retina (the light-sensitive layer at the back of the eye) are damaged due to high blood sugar, which can lead to blindness. Both eyes are usually affected. In the early stages, a patient may not experience any symptoms, and signs typically appear over time.
In any diabetic patient who has undergone an eye exam, the likelihood of retinopathy is about 40-45%. This rate may increase with the duration of the disease. Patients caught at an early stage have easier treatments and a lower risk of vision loss. Therefore, even if patients have no symptoms, retina exams should be done once a year. During puberty, pregnancy, cataract surgery, or when switching to insulin, these exams should be done more frequently.
Tight control of diabetes, transitioning to insulin when necessary, controlling blood lipids and cholesterol, managing other internal problems, and quitting smoking all help slow the progression of the disease, though they do not stop it. For this reason, retina exams should not be neglected even if blood sugar levels are well controlled.
Stages of Diabetic Retinopathy:
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Early Diabetic Retinopathy: This stage involves the blockage of retinal blood vessels, weakening of their walls, microaneurysms, and small retinal hemorrhages caused by the leakage of blood components. Yellow deposits called hard exudates may also be seen. There are usually no vision problems unless the macula (the sharp vision area) is affected.
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Maculopathy: Over time, when the blood vessels in the macula area are affected, it causes feeding problems (ischemia), fluid leakage (edema), and bleeding and exudates in the area, all of which affect vision. Patients may start to experience blurry and reduced vision.
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Proliferative Diabetic Retinopathy: This stage is less common but more severe. In response to ischemia, the retina forms signals and chemicals that encourage the growth of new, unwanted blood vessels. These new blood vessels can lead to intense bleeding inside the eye (vitreous hemorrhage), causing sudden vision loss. The pulling of the retina due to new vessels can lead to retinal detachment, and these vessels can cause glaucoma by obstructing the angle, raising eye pressure. These developments can result in blindness.
How is Diabetic Retinopathy Diagnosed?
Once diabetes is diagnosed, an eye consultation is requested to determine its effects on the organs. During the eye exam, the retinal blood vessels are examined to assess how much the organs are affected at the capillary level. The stage of retinopathy is also determined, which helps estimate how long the diabetes has been present and its severity. If vision-threatening retinal edema and bleeding are detected, treatment is started immediately. If there are bubbles, hemorrhages, or leaks in the retinal vessels, but they are not at a threatening size, the patient is monitored with follow-ups every 6 months or annually.
For diagnosis and staging of diabetic retinopathy, OCT (Optical Coherence Tomography) and FFA (Fluorescein Angiography) tests are conducted. OCT assesses the condition of the macula, while FFA involves injecting fluorescein dye into a vein and capturing retinal images to examine blood vessels, hemorrhages, leaks, and other abnormalities.
How is Diabetic Retinopathy Treated?
There are three main treatment methods:
- Argon Laser Photocoagulation
- Intraocular Injections
- Vitrectomy
How is Laser Photocoagulation Applied?
It is essential for patients to seek an eye doctor’s consultation even without symptoms. In the early stage, laser photocoagulation can prevent blindness in 80-90% of treated patients. The technique has been refined through 40 years of research. A contact lens is placed on the eye, and laser light is delivered to the treatment areas, creating burns. The procedure is usually tolerable, but some patients may experience pain, in which case painkillers are recommended.
The goal of laser treatment is to maintain vision at the level the patient presented with, though there may be slight vision reduction after the procedure. The laser affects only leaking areas and newly formed blood vessels, not blocked small vessels. The success of the treatment is directly related to the timing of the patient's visit.
Intraocular Injections (Injection Therapy)
In recent years, intraocular injections have become popular in treating macular edema, a condition that significantly reduces visual acuity. Initially, corticosteroid injections were used, but they were replaced by anti-VEGF injections (such as Avastin, Lucentis, Macugen) due to their ability to suppress new blood vessel growth and raise intraocular pressure. These injections, typically given monthly in 3 or more doses, can significantly improve vision by reducing edema and suppressing the formation of new blood vessels. Laser and injection therapies are often used together.
What is Vitrectomy Surgery?
Vitrectomy is performed when the disease has advanced, and laser treatment is no longer effective. During the surgery, specialized tools are used to enter the eye and remove hemorrhages and fibrous bands that cause retinal traction, aiming to restore the retina’s original anatomical structure. The eye is filled with saline or other fluids after the removal of the vitreous gel. The success of this surgery is time-dependent, and the final visual outcome depends on how much of the retina's nerve tissue is repaired.
Common side effects of vitrectomy include cataract formation and potential rebleeding, which may require additional surgery.