Retinopathy, Diabetic

For further information, see CMDT Part 7-20: Retinal Disorders Associated with Systemic Diseases

Essentials of Diagnosis

• Present in about 33% of all diagnosed diabetic patients

• Present in about 20% of type 2 diabetic patients at diagnosis of diabetes

• Retinopathy is not detectable in type 1 diabetic patients for the first 5 years after diagnosis

• By 20 years after diagnosis of diabetes, 99% of type 1 diabetic patients and 60% of type 2 diabetic patients will have diabetic retinopathy

• Nonproliferative diabetic retinopathy

  • Can be mild, moderate or severe

  • Microvascular changes are limited to the retina

• Proliferative diabetic retinopathy: new blood vessels grow on the surface of the retina, optic nerve, or iris

• Diabetic macular edema

  • Central retinal swelling

  • Can occur with any severity level of diabetic retinopathy

  • Reduces visual acuity if center involved

General Considerations

• Worldwide, there are approximately 93 million people with diabetic retinopathy, including 28 million with vision-threatening disease

• The leading cause of new blindness among adults aged 20–65 years

• The number of affected individuals aged 65 years or older is increasing

• Retinopathy increases in prevalence and severity with increasing duration and poorer control of diabetes

• Broadly classified as

  • Nonproliferative, which is subclassified as mild, moderate or severe

  • Proliferative, which is less common but causes more severe visual loss

• Maculopathy and proliferative retinopathy may coexist, particularly in severe disease

• Nonproliferative retinopathy manifests as

  • Microaneurysms

  • Retinal hemorrhages

  • Venous beading

  • Retinal edema

  • Hard exudates

• In mild nonproliferative retinopathy, there are retinal abnormalities without visual loss

• Reduction of vision is most commonly due to diabetic macular edema, which may be focal or diffuse, but it can also be due to macular ischemia

• Macular involvement is the most common cause of legal blindness in type 2 diabetes

• Macular edema may be associated with treatment with thiazolidinediones (glitazones)

• Proliferative retinopathy

  • Characterized by neovascularization, arising from either the optic disk or the major vascular arcades

  • Vitreous hemorrhage is a common sequel

  • Proliferation into the vitreous of blood vessels, with associated fibrosis, may lead to vitreous hemorrhage and tractional retinal detachment

• Patients with diabetes should undergo regular screening, including

  • Fundus photography, preferably after pupillary dilation (mydriasis)

  • Slit-lamp examination after pupillary dilation

• More frequent monitoring is required in women during pregnancy and in those planning pregnancy

• Patients with type 2 diabetes mellitus should have a complete ophthalmologic examination shortly after diagnosis

• Assessment of maculopathy requires

  • Visual acuity testing

  • Stereoscopic examination of the retina

  • Retinal imaging with optical coherence tomography

  • Fluorescein angiography (occasionally)

• Optimize blood glucose, blood pressure, kidney function, and serum lipids

Medications

• VEGF inhibitor (ranibizumab [Lucentis], bevacizumab [Avastin], or aflibercept [VEGF Trap-Eye, Eylea]) or corticosteroids used for macular edema and exudates

  • VEGF inhibitor therapy improves diabetic retinopathy severity in eyes at all levels of nonproliferative diabetic retinopathy and is the mainstay of treatment for diabetic macular edema

• Proliferative retinopathy is usually treated by intravitreal injection of a VEGF inhibitor or panretinal laser photocoagulation, preferably before vitreous hemorrhage or tractional detachment has occurred

• Proliferative diabetic retinopathy, especially after successful laser treatment, is not a contraindication to treatment with thrombolytic agents, aspirin, or warfarin unless there has been recent intraocular hemorrhage

Therapeutic Procedures

• Laser photocoagulation or vitrectomy may be helpful in macular edema and exudates but not in ischemia

• Fluorescein angiography in patients with severe nonproliferative retinopathy can help determine whether panretinal laser photocoagulation should be undertaken prophylactically by determining the extent of retinal ischemia

• Panretinal laser photocoagulation

  • Used to treat proliferative retinopathy

  • Should be done before vitreous hemorrhage or tractional detachment has occurred

  • Determining the extent of retinal ischemia on fluorescein angiography helps determine whether panretinal laser photocoagulation should be undertaken prophylactically for pre-proliferative retinopathy

• Vitrectomy is necessary for

  • Removing persistent vitreous hemorrhage

  • Improving vision and allowing panretinal laser photocoagulation for the underlying retinal neovascularization

  • Treating tractional retinal detachment involving the macula

  • Managing rapidly progressive proliferative retinopathy

Prognosis

• Untreated, the visual prognosis in proliferative retinopathy is generally much worse than in nonproliferative retinopathy

When to Refer

• All diabetic patients with sudden loss of vision or retinal detachment should be referred emergently to an ophthalmologist

• Proliferative retinopathy or macular involvement requires urgent referral to an ophthalmologist

• Severe nonproliferative retinopathy or unexplained reduction of visual acuity requires early referral to an ophthalmologist