Signs and symptoms

• Microaneurysms: In most cases, these are the earliest clinical abnormality detected. They appear as minute, discrete, circular, dark red spots near to but apparently separate from the retinal vessels [9].
• Hemorrhages: They characteristically occur in the deeper layers of the retina, are round and regular in shape, and are called 'blot' hemorrhages. In hypertensive patients, superficial flame-shaped hemorrhages may also occur.
• Hard exudates: These are characteristic of diabetic retinopathy [9]. They result from leakage of plasma from abnormal retinal capillaries and can vary in size from tiny specks to large patches.
• Cotton-wool spots: Most often seen in rapidly progressive retinopathy and hypertension, these spots represent arteriolar occlusions.
• Venous beading: Sausage-like dilatation and increased looping of veins indicate widespread capillary nonperfusion.

Presenting complaints

A patient may initially complain of blurred or fluctuating vision and difficulty in color perception. This may be more evident in one eye than in the other. The patient may then complain of empty or dark areas and floating spots or lines in his vision. In severe form of this condition, the patient may eventually suffer from complete loss of vision.

Workup includes a complete history and physical examination. The following tests should be conducted:

Laboratory tests

• Complete blood count
• Resting blood sugar
• Fasting blood sugar
• HbA1c levels
• Liver function tests

Imaging

• Fluorescein angiography: This is a test in which pupils are dilated and photographs of the vessels are taken. Then a radiocontrast dye is injected and photographs are taken again once the dye has perfused to all eye vessels.
• Optical Coherence Tomography (OCT): OCT provides us with cross-sectional images of the retina which help in both identifying retinal thickening if any, as well as monitoring the progress of treatment.
• B-scan Ultrasonography may also be done.

Medications

Multiple doses of intravitreal injections of anti-VEGF drugs such as bevacizumab show good results [10]. Similar drugs like Ranibizumab and a corticosteroid Triamcinolone may also be given.

Photocoagulation

In cases of nonproliferative DR, laser photocoagulation may be used to treat macular edema due to vascular leakage.
In patients with proliferative diabetic retinopathy, pan-retinal photocoagulation is used to spare the macular area and treat the entire diseased retina.

Vitrectomy

This procedure may be used in some patients with proliferative diabetic retinopathy.

Cryotherapy

This procedure may be used when the patient already suffers from other eye diseases like cataracts, etc.

Blood sugar level control

This is the primary mode of controlling the progression of retinopathy. By bringing blood glucose to normal levels, edema and other such conditions involved in diabetic retinopathy can be lessened.

The longer a person has diabetes, the higher his chances of developing diabetic retinopathy [8]. If a person has been diagnosed early, he would have well-defined leakage and good perifoveal perfusion. His vision loss would be mild and exudates would be minimal. In such cases, the prognosis is favorable as with the right control and treatment, the progression of the disease may be halted.

If on the other hand, a patient with diabetic retinopathy also has hypertension and/or kidney disease, and has already suffered from irreversible macular ischemia and edema, the prognosis is bad.

Complications

Complications include all the factors that may worsen the ischemic state of the eye such as:

• Hypertension
• Smoking
• Hyperlipidemia
• Renal diseases
• Cataract formation
• Glaucoma

As the name indicates, the primary cause of diabetic retinopathy is diabetes. In type I diabetes mellitus, the chances of developing this condition are comparatively less. In patients with type II diabetes mellitus, however, the incidence of this condition is directly proportional to disease duration.

Other causes include hypertension and hyperlipidemia which may exacerbate preexisting diabetes and increase the risk of developing diabetic retinopathy. Studies reveal that pregnant women that have this condition have a 4-5% chance of progression to a more severe stage.

Diabetes is responsible for approximately 8000 eyes becoming blinded each year, meaning diabetes is responsible for 12% of blindness [2].

A recent estimate of the prevalence of diabetic retinopathy in the US showed a high prevalence of 28.5% among those with diabetes aged 40 years or older [3]. Clearly the longer a person has diabetes, i.e the older a person is, the more likely he is of developing retinopathy.

The retinal vasculopathy of diabetes mellitus can be classified into the background (pre-profilerative) diabetic retinopathy and proliferative diabetic retinopathy [4].

Pre-proliferative diabetic retinopathy

Hyperglycaemia induced intramural pericyte death and thickening of the basement membrane leads to vascular wall incompetence. These damages change the formation of the blood-retinal barrier and also make the retinal blood vessels more permeable [5]. Smaller vessels may occlude and the weakened walls of the larger vessels may dilate. As a result, microaneurysms and macular edema occur.

Proliferative diabetic retinopathy

Retinal ischemia can result in the up-regulation of pro-angiogenesis factors such as VEGF and lead to retinal angiogenesis [6]. Retinal neovascularization may be accompanied by the development of a neovascular membrane on the iris surface, presumable secondary to increased levels of VEGF in the aqueous humor [7]. Gradually, scar tissue develops which may cause retinal detachment and/or build up of intraorbital pressure leading to glaucoma and optic nerve damage.

Diabetes mellitus is a metabolic disorder that results in excess glucose in the blood. This excess amount of glucose causes widespread complications.

The most common and potentially most blinding of these complications, however, is diabetic retinopathy (DR) [1]. In this condition, a person's retinal vessels suffer ischemia and damage due to high blood glucose levels resulting in visual loss and in the worst case - blindness.

Diabetic retinopathy is a complication of long-standing, and often uncontrolled, diabetes mellitus. It is caused due to raised glucose levels in the blood which damage the blood vessels of the eyes, leading to first blurred vision and finally blindness. If you are diabetic and feel that your visual power has decreased, you should schedule a consultation with an eye specialist immediately.