Diabetic retinopathy

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Diabetic retinopathy is a vascular disease of the retina that is usually asymptomatic in the early stages but can lead to visual impairment and blindness as the disease progresses. The majority of cases of diabetic retinopathy are detected during screening examinations. Further tests (optical coherence tomography, fluorescein angiography) may be performed to determine severity or identify complications. Management for all patients includes optimization of treatment for diabetes, managing risk factors for atherosclerotic cardiovascular disease (ASCVD), and referral to an ophthalmologist for further management and monitoring. Further treatment depends on the subtype (nonproliferative diabetic retinopathy or proliferative diabetic retinopathy), presence of macular edema, and severity of diabetic retinopathy and includes panretinal photocoagulation (PRP), intravitreal anti-vascular endothelial growth factor (VEGF) and vitrectomy.

Diabetic retinopathy is usually detected on routine screening, and then classified and treated based on the presence of neovascularization, retinal thickening, and disease severity. ^[2]

Vitrectomy may be required for patients with complications, e.g., tractional retinal detachment, vitreous hemorrhage ^[2]

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• After 15 years, approx. 80% of patients with type 1 diabetes will develop retinopathy. ^[2]
• Among patients > 30 years old with type 2 diabetes: ^[2]
  • Patients not requiring insulin
    • Approx. 25% will develop retinopathy within 5 years of diagnosis.
    • Approx. 50% will develop retinopathy within 19 years.
  • Patients requiring insulin
    • Approx. 40% will develop retinopathy within 5 years of diagnosis.
    • Approx. 85% will develop retinopathy within 19 years.
• Diabetic retinopathy is the most common cause of visual impairment and blindness in patients aged 20–74 years. ^[5]

Epidemiological data refers to the US, unless otherwise specified.

Development and progression of diabetic retinopathy is associated with: ^[3][5]

• Diabetes-related factors
  • Poor glycemic control
  • Increased duration of diabetes
  • Presence of diabetic nephropathy
• Other cardiovascular risk factors
  • Hypertension
  • Dyslipidemia
• Puberty
• Pregnancy
• History of cataract surgery

• Early stages: usually asymptomatic ^[3]
• Patients may experience symptoms of associated complications, e.g., macular edema, vitreous hemorrhage, and retinal detachment. ^[6]
  • Blurred vision
  • Floaters
  • Photopsia
  • Scotoma
  • Sudden, painless vision loss
• Later stages: significant visual impairment progressing to blindness

• Modalities ^[2][5]
  • Dilated comprehensive eye examination performed by an ophthalmologist/optometrist
  • Retinal photography
• Onset
  • Type 1 DM: within 5 years of the onset of disease ^[2][7]
  • Type 2 DM: at the time of diagnosis ^[2]
• Interval: every year ^[2]

Less frequent retinopathy screening (e.g., every 2 years) may be considered in consultation with an ophthalmologist or optometrist for patients with diabetes who have a normal initial eye exam and good glycemic control. ^[5][7]

General principles ^[2][5]

• Usually detected on screening
• Symptomatic patients should undergo a comprehensive eye examination (including slit lamp examination and fundoscopy) with the pupil dilated.
• Ancillary testing, e.g., optical coherence tomography (OCT), fluorescein angiography, may be performed to:
  • Assess disease severity.
  • Determine treatment approach and assess response.
  • Exclude differential diagnoses of sudden vision loss.

Retinal findings

Approach ^[2][5]

• Refer all patients with diabetic retinopathy to an ophthalmologist.
• Optimize glycemic control with: ^[9]
  • Antihyperglycemic treatment of diabetes
  • Lifestyle recommendations for patients with diabetes mellitus
• Manage ASCVD risk factors.
  • Treat hypertension if present (see “Approach to management of hypertension”).
  • Initiate treatment for lipid disorders as indicated (see “Guidelines for lipid-lowering therapy”).
  • Continue aspirin if indicated for another condition. ^[2]
• Screen for additional microvascular complications of diabetes because of the high risk of co-occurrence.
• Arrange follow-up eye exams at regular intervals. ^[2]
• For patients with significant vision impairment, consider:
  • Referral for vision rehabilitation
  • Assessment for fitness to drive

Early detection and treatment of diabetic retinopathy can prevent 90% of blindness. ^[2]

Treatment by retinopathy subtype ^[2][5]

• Nonproliferative retinopathy
  • Mild NPDR to moderate NPDR: Observation only; repeat dilated comprehensive eye examination every 6–12 months.
  • Severe NPDR: Treat as proliferative retinopathy with panretinal laser photocoagulation (PRP) and/or anti-VEGF therapy.
• Proliferative retinopathy: PRP and/or anti-VEGF therapy
  • Both PRP and anti-VEGF therapy are equally effective.
  • PRP is usually preferred as treatment occurs in a single session (reduces risk of loss to follow-up). ^[2]
  • Anti-VEGF injections alone can be considered for patients who are highly motivated and have no barriers to follow-up.
  • Additional treatments should be utilized if after initial treatment, any of the following are present:
    • New vitreous hemorrhage or neovascularization
    • Failure of existing neovascularization to regress
• Macular edema ^[2]
  • Center-involving macular edema
    • First line: Intravitreal anti-VEGF therapy
    • Consider PRP or focal and/or grid laser depending on severity of retinopathy.
  • Noncenter-involving macular edema: PRP, anti-VEGF, or focal and/or grid laser therapy may be used depending on severity of retinopathy.
• Refractory disease or severe complications (e.g., tractional retinal detachment, vitreal hemorrhage): Consider vitrectomy.

• Optimize management of diabetes to ensure patients meet glycemic targets for DM. ^[2][5]
• Manage ASCVD risk factors. ^[5]
• Educate patients on the importance of screening for complications of diabetes. ^[10]
  • Ensure patients are aware that they may not experience symptoms until the disease is advanced.
  • Address risk factors for poor adherence (see “Managing chronic conditions”).
• Advise patients to seek immediate medical attention if they notice any changes in their vision.

Advise patients to attend regular screenings as microvascular complications are usually asymptomatic until significant damage has occurred. ^[2]

Diabetic retinopathy in pregnancy ^[2][5][9]

• Pregnancy can precipitate or aggravate diabetic retinopathy in patients with type 1 DM and type 2 DM.
• Diagnostics and management of diabetic retinopathy are largely the same as for nonpregnant patients with the following changes:
  • Patients should undergo additional screening: ^[5]
    • Prior to conception
    • Once during each trimester
    • During the first year postpartum ^[2]
  • While PRP is safe in pregnancy, anti-VEGF therapy should be avoided due to theoretical risks to the fetus. ^[5]

Routine screening for diabetic retinopathy is not recommended for patients with gestational diabetes mellitus. ^[2][5]