Diabetic retinopathy is a type of secondary consequence of diabetes that affects the back of the patient's eye or the retina. The circulation in the blood vessels of the retina changes, resulting in bleeding and fluid accumulations. These disorders can result in a loss of visual acuity, which can cause blindness in some situations.

Diabetic retinopathy classification

Diabetic retinopathy is characterized based on changes in the eye fundus. 

The intensity and amount of damage determine how the condition is classified:

• Mild non-proliferative: Slight alterations to the fundus of the eye.
  
• Moderate non-proliferative: Severe alterations, but not impacting the entire fundus.
  
• Non-proliferative severe: Changes that are extreme in all parts of the fundus.
  
• Proliferative: The emergence of new blood vessels and/or internal bleeding is referred to as proliferative.
  

It is also categorized based on whether or not fluid has accumulated in the central section of the retina, i.e., whether or not diabetic macular oedema exists:

• Without diabetic macular oedema.
  
• With diabetic macular oedema.
  

How many people suffer from diabetic retinopathy?

Diabetic retinopathy is a common consequence of diabetes; it affects one out of every ten patients with the disease. This means that 3–4 out of every 100 Europeans have diabetic retinopathy. In fact, it is the leading cause of blindness among adults of working age worldwide.

Diabetic Retinopathy Causes

Diabetic retinopathy is caused by abnormalities in blood circulation that occur in people with diabetes (above all, when they have a high blood sugar level). These alterations cause damage to the retina's blood vessels, resulting in bleeding, fluid leaks, and fat deposits.

Factors Contributing to Diabetic Retinopathy

• Diabetes duration: The chance of getting diabetic retinopathy, or of it worsening, rises with age.
  
• Blood sugar control: Strict glycaemic monitoring (blood sugar levels) with well-controlled glycosylated haemoglobin (HbA1C) values lowers the development of retinopathy.
  
• Blood lipid levels (dyslipidaemia and hypercholesterolaemia): An increased level of lipids (cholesterol and triglycerides) in the blood can cause an increase in the deposition of exudates, which are deposits of proteins filtered in the retina. This disorder is linked to a higher chance of moderate vision loss.
  
• Microalbuminuria and diabetic nephropathy: Microalbuminuria is caused by a protein called albumin, which, if found in the patient's urine, may indicate diabetic retinopathy. The situation is indicative of developing renal disease.
  

Diabetic retinopathy indications

• Visual acuity loss (blurred vision):
  
• Myodesopsia is an abbreviation for Myodesopsia (appearance of floating spots): Patients with proliferative diabetic retinopathy and modest internal haemorrhage have floaters (vitreous haemorrhage).
  
• Pain in the eyes: Eye pain can occur in severe cases of proliferative retinopathy when intraocular pressure rises significantly due to massive haemorrhages (neovascular glaucoma).
  

Diabetic retinopathy symptoms

• Microaneurysms: These small dilatations in the retina's blood vessels are the first and mildest signs of the disease.
  
• Intraretinal haemorrhages: small amounts of localized bleeding coming from the damaged blood vessels within the retina.
  
• Lipid exudates: Accumulations of fat leaking from the damaged retinal blood vessels.
  
• Macular oedema: Swelling of the retina due to fluids leaking from the abnormal vessels.
  
• Intraretinal microvascular abnormalities: The abnormal growth of blood vessels within the retina.
  
• Retinal neovascularisation: The abnormal growth of blood vessels outside the retina and inside the vitreous cavity (interior of the eye).
  
• Vitreous haemorrhages: Significant bleeding inside the vitreous cavity due to retinal neovascularization.
  
• Vitreomacular traction: Stretching and deformation of the retina caused by the growth of large areas of retinal neovascularisation.
  
• Neovascularisation in the iris: The abnormal growth of blood vessels inside the iris and trabecular meshwork increases intraocular pressure because they obstruct drainage.
  

Diabetic Retinopathy Treatment

The treatment is based on the findings made by the ophthalmologist when examining the patient's eyes. It could include:

• Controlling blood sugar levels: Sometimes, simply increasing a patient's metabolic control might enhance their vision.
  

• Laser: This lowers the number of aberrant blood vessels as well as those that cause oedema.
  

• Intraocular injections: Different medicines are injected into the eye or the vitreous body (also known as intravitreal injections) to reduce the amount of fluid in the macula.
  

• Vitrectomy: Surgical intervention that eliminates any blood inside the eye. It is also the technique used to repair a retinal detachment.
  

• Non-drug therapy: To avoid or treat the early stages of retinopathy, patients should maintain reasonable metabolic control and lower risk factors such as high blood pressure, dyslipidaemia, and/or obesity.
  

Therapeutic education: Therapeutic education is critical for promoting diabetes control and minimizing complications. Lifestyle modification programmes that involve the health team, the patient, and their family produce better weight control, assist patients in quitting harmful habits (such as smoking) and encourage them to accept their diabetes. 

Patients who are well-informed about their diabetes, self-care skills, and medication management are more likely to participate actively and thus achieve better results.

Medical nutrition therapy: Diet is a fundamental component of diabetes treatment. It must be nutritionally sound, with each meal comprising a moderate number of carbohydrate-rich foods (milk, floury foods and fruit). Each patient's body weight, drug therapy (insulin or tablets), physical activity, eating habits, and blood sugar profile must be considered.

Physical activity: Physical activity is another essential component of treatment, particularly for type 2 diabetes. Patients should engage in at least 150 minutes of physical exercise per week, spaced out across three to five days. Patients must adapt their food and pharmacological therapy based on the time and intensity of their activities. (Relationship with diabetes / physical activity)

Contraindications for physical exercise:

• Patients with moderate non-proliferative retinopathy should avoid very vigorous exercises that increase blood pressure, such as weightlifting.
  
• In unstable diabetic retinopathy, patients must also avoid activities that raise blood pressure, such as jumping and those involving sudden head movements.
  
• Patients with vitreous haemorrhage are advised to avoid all types of physical activity.
  

Oral diabetes medications lower blood glucose levels, which can assist improve diabetic retinopathy. Drugs that have a direct effect on diabetic retinopathy, on the other hand, are injected into the eye. Currently, two types of intraocular medicines are available:

Anti-VEGF drugs. These inhibit the function of a molecule implicated in diabetic macular oedema. They are liquid drugs that must be injected multiple times a year because they are only effective for a few months.

Corticosteroids. These reduce the ocular inflammation that accompanies diabetic macular oedema. They are solid medicines (implants) that continue working inside the eye for several months, requiring fewer injections.

Surgical treatment

A surgical intervention (pars plana vitrectomy) is usually required to treat advanced stages of diabetic retinopathy, such as proliferative retinopathy. Three main situations require an operation: very dense or recurrent vitreous haemorrhage, tractional retinal detachment, and treatment-resistant macular oedema. The procedure consists of inserting tiny instruments (e.g., suction devices, forceps or lasers) inside the eye's vitreous body while illuminating the retina and maintaining the internal eye pressure constant. It is a very delicate procedure, but it has evolved a lot in recent years and can often be completed without the need for stitches.

Vitreous haemorrhages that do not heal fully or reoccur may require a vitrectomy to remove the blood and treat the damaged vessels causing the bleeding. If severe cases of vitreous haemorrhage go untreated for long periods, the eye's pressure may increase and even cause pain, a condition known as neovascular glaucoma.

Tractional retinal detachment occurs when the inner retina wrinkles up due to the pulling action of membranes and filaments, thus causing vision loss and the appearance of wavy lines. Vitrectomy tends to help this problem, but vision may be permanently affected depending on the extent of damage to the inner retina.

Cases of macular oedema that do not respond to drug therapies may require surgery to clean the membranes growing on the macula. However, the patient does not always recover their entire vision.

Intravitreal injections

The intravitreal injection has become a popular technique for treating several conditions affecting the retina. Every day, retina specialists apply the procedure to several of their patients. The specialist must provide a detailed explanation of the risks, benefits and alternatives for this treatment.

• There are very few risks, but there is always the possibility of infection which can develop into a severe condition. However, it occurs rarely as it affects less than 1 in every 1,000 patients.
  
• The benefits of these injections depend on the eye disease being treated, but they include improved vision or a reduced chance of deterioration.
  
• Alternative treatments can include simply waiting to see if the condition improves with better control over blood sugar levels, surgery (vitrectomy) or laser treatment, depending on the eye disease. However, intravitreal injections are undoubtedly the best option if the specialist recommends them, and the alternatives are often clinically worse from the outset.
  

Finally, it is critical to remember specific injection-related recommendations. Depending on the center, the therapy will take place in a consultation room or a tiny operating theatre, and there is no need to fast or stop taking any other drugs. Patients are usually not required to conduct any previous preparation. Nonetheless, depending on the specialist's advice, patients may need to apply eye drops for a few days after the injections. Patients frequently notice floaters for a few days following the injections (these may be due to a small air bubble or eye drops). However, if you experience pain or have red eyes, you should see an emergency ophthalmologist.

New therapies

While laser therapy for diabetic retinopathy has not improved significantly in recent years, treatments for diabetic macular oedema has. Laser treatment is now accompanied by several options, including intravitreal medication therapy. In terms of enhancing patients' vision, these new treatments have produced more significant and satisfying effects. Current treatment, for example, with anti-VEGF medicines and corticosteroids, have entirely transformed diabetic macular oedema, but there is still a subset of patients with treatment-resistant oedema. As a result, new treatment procedures are being researched to discover medicines that require fewer injections. Researchers are investigating new anti-VEGF compounds, such as those that remain active inside the eye for a more extended period. In contrast, new corticosteroid implants that can last up to three years have just been accessible for persistent diabetic macular oedema patients.

Treatment complications

Laser photocoagulation can be complicated by the development of haemorrhages and scarring in the retina if too much energy is applied to the eye fundus. Depending on the situation, this can produce some dark spots in the patient's vision. Patients may also notice a decline in their nocturnal vision and color vision.

The most severe effect of intravitreal medication therapy is an infection inside the eye, known as endophthalmitis, which can result in total vision loss in some instances. Although the frequency varies, it is usually very low, with less than one infection occurring in every 1,000 persons who receive this medication. Other problems include haemorrhages inside the eye and retinal detachment, both of which are extremely rare. Finally, the use of corticosteroids increases the risk of developing cataracts and raising intraocular pressure.
Complications associated with surgery are the same as those for intravitreal injections (e.g., intraocular infection, haemorrhage and retinal detachment).

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