Diabetic Retinopathy

Diabetic Retinopathy

Diabetic complications in the eye are known to be one of the leading causes of legal blindness between the ages of 25 to 65 years. It is recognised as having important economic significance because the majority affected belong to the “working age”.

Diabetic retinopathy is a direct consequence of raised glucose levels in the small blood vessels of the retina. People with diabetic retinopathy may not have any symptoms of vision impairment (asymptomatic).

When people have the most advanced form of diabetic retinopathy, they can suddenly develop severe vision impairment or blindness because of bleeding from abnormal retinal vessels into the eye.

Type 1 diabetic individuals between the age group of 33 to 40 years are more commonly affected because of diabetic retinopathy, with an incidence of nearly 83 percent. People with diabetes for more than 20 years duration, almost all Type 1 and about 60 percent of Type 2 patients manifest some degree of retinopathy.

STAGING AND PROGRESSION OF THE DISEASE

Natural history of diabetic retinopathy was put forward by Diabetic Retinopathy Study (DRS) and Early Treatment Diabetic Retinopathy Study (ETDRS) as:

• Background retinopathy
• Maculopathy
• Pre-proliferative diabetic retinopathy
• Proliferative diabetic retinopathy
• Advanced diabetic eye disease
• End stage diabetic eye disease

CLINICAL CLASSIFICATION OF DIABETIC RETINOPATHY

• No disease visible
• Mild non-proliferative diabetic retinopathy
• Moderate non-proliferative diabetic retinopathy
• Severe non-proliferative diabetic retinopathy
• Proliferative diabetic retinopathy

Involvement of the most important part of the retina that contributes to visual acuity – the macula is called macular edema. The classification of macular edema is:

• No visible macular edema
• Non-centre involving macular edema
• Centre involving macular edema

The classification distinguishes between retinopathy and maculopathy because they can progress at different rates and the changes in the macula can occur in all grades of severity of diabetic retinopathy.

RATIONALE FOR DIABETIC RETINOPATHY SCREENING

Screening for diabetic retinopathy is important because of the lack of symptoms until there is a drop in visual acuity following macular involvement. This involvement of the macula is called diabetic macular edema or maculopathy.

It has been well-established that laser photocoagulation and/or vascular endothelial growth factor (VEGF) inhibitors injections into the vitreous cavity, are effective modalities of treatment for macular edema. However, these therapies are more beneficial in preventing further visual loss than reversing diminished visual acuity.

Thus, early detection through screening programs and timely therapy are important to preserve vision in patients with diabetic retinopathy.

METHOD FOR SCREENING DIABETIC RETINOPATHY

Screening can be effectively accomplished with a dilated retinal examination or retinal photography.

The retinal examination is a part of our routine eye examination in the out-patient department.

Every patient is given a colour coded diagram of his/her retina. A yearly examination of the retina with reference to the previous colour coded diagram will help the ophthalmologist and the patient know if there is a progression of the disease. A retinal photograph can also be used for a similar purpose but a retinal colour coded diagram is more than sufficient and cost-effective for the patient as well.

FREQUENCY OF SCREENING

Most studies have concluded that the screening interval or frequency of rescreening should be between one and two years.

An ideal approach would be to suggest individualizing the length of time between screenings, adjusting the screening interval according to the person’s glycaemic control and retinopathy or by the severity of the retinopathy. This would improve the cost effectiveness and affordability of the screening programme.

EMERGING TECHNOLOGIES IN DIABETIC RETINOPATHY SCREENING

New technologies, such as automated image-grading systems and hand-held cameras, are being developed alongside diabetic retinopathy screening techniques and may offer new methods for screening in the future.

Diabetic retinopathy screening is also likely to benefit from further developments in artificial intelligence-based technologies for image capture and analysis, offering opportunities to improve the quality of imaging and grading.

In addition to currently used diabetic retinopathy grading criteria, analysing retinal vessels might provide an enhanced understanding of cardiovascular/cerebrovascular risk for developing complications.

PREVENTION AND TREATMENT OF DIABETIC RETINOPATHY

Good blood glucose level control along with stable blood pressure and normal lipid profile reduces the risk of new-onset diabetic retinopathy and slows the progression of existing diabetic retinopathy. This has been well established by the “Diabetes Control and Complications Trial” research group. This approach should be carried out for all diabetic retinopathy patients to prevent and treat their retinopathy.

Laser treatment using argon green laser is the mainstay of treatment for proliferative diabetic retinopathy and can also be used for the treatment of diabetic macular edema.

Anti-VEGF (vascular endothelial growth factor) agents and steroids injected into the vitreous cavity of the eye can reduce the progression of the disease and preserve visual function in diabetic macular oedema. The commonly used and approved anti-VEGF agent is ranibizumab. Steroid implant of dexamethasone is known to have anti-inflammatory and anti-VEGF properties that can be used to treat diabetic macular edema in advanced cases.

Vitrectomy, a surgical procedure, can restore useful vision in eyes with non-resolving vitreous haemorrhage and traction retinal detachment of the macula.