Microvascular retinal disease from chronic hyperglycemia — leading cause of new-onset blindness in working-age adults.
Also known as: diabetic retinopathy, DR, NPDR, PDR, non-proliferative diabetic retinopathy, proliferative diabetic retinopathy, diabetic macular edema, DME
Overview
Microvascular complication of diabetes mellitus characterized by progressive retinal microaneurysms, hemorrhages, exudates, ischemia, and ultimately neovascularization. Classified as non-proliferative (NPDR — mild, moderate, severe) and proliferative (PDR — new vessels at the disc, NVD, or elsewhere, NVE). Diabetic macular edema (DME) — fluid in the central macula — can occur at any stage.
Epidemiology
Leading cause of new-onset blindness in US adults aged 20-74. Nearly all patients with type 1 diabetes for >20 years and most with type 2 develop some degree of retinopathy. Prevalence of vision-threatening retinopathy ~5-10% of diabetic patients.
Try two board-style Diabetic Retinopathy questions
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Question 1EENTEasy
A 55-year-old diabetic female has fundoscopy showing dot/blot hemorrhages, hard exudates, microaneurysms, and cotton wool spots bilaterally without neovascularization. A circinate hard exudate ring surrounds the right fovea, with optical coherence tomography (OCT) showing 310 micron central subfield thickness. Visual acuity 20/50 OD. Which of the following is the most likely diagnosis?
AMild non-proliferative retinopathy without macular edema
BProliferative retinopathy with disc neovascularization
Why non-proliferative retinopathy with center-involving macular edema is correct
Center-involving diabetic macular edema (CI-DME) is defined as fluid within 500 microns of the foveal center and is the most vision-threatening form
Optical coherence tomography (OCT) is the gold standard for diagnosis; this patient's central subfield thickness of 310 microns confirms macular edema
The circinate hard exudate ring surrounding the fovea and visual acuity of 20/50 OD are consistent with center-involving disease
Absence of neovascularization rules out proliferative diabetic retinopathy; extensive findings (cotton wool spots, multiple dot/blot hemorrhages, microaneurysms) exclude the mild and non-center-involving categories
Why the others are wrong
Mild non-proliferative retinopathy without macular edema — limited to a few microaneurysms; cotton wool spots, hard exudates, and macular edema place this in a more advanced category (premature closure)
Proliferative retinopathy with disc neovascularization — requires neovascularization of the disc or retina, which is absent here (anchoring on severity)
Non-proliferative retinopathy, non-center-involving macular edema — macular edema is present but here involves the foveal center on OCT with VA loss (confused-with non-center-involving)
Additional high-yield points
Treatment for CI-DME: intravitreal anti-vascular endothelial growth factor (anti-VEGF) first-line
DRCR.net Protocol T: aflibercept is superior when visual acuity is 20/50 or worse
Systemic targets: A1c <7%, BP <130/80, statin therapy for hard exudates
Question 2EENTMedium
A 58-year-old man with a 22-year history of type 2 diabetes presents with sudden, painless loss of vision in his right eye that began this morning, preceded by a shower of new floaters. His most recent A1c was 9.4%, and he has not had a dilated eye exam in 6 years. Visual acuity in the right eye is limited to counting fingers. On attempted fundoscopy, a dense vitreous hemorrhage completely obscures the view of the retina. Which of the following is the most appropriate next diagnostic test?
AB-scan ocular ultrasonography
BOptical coherence tomography
CRetinal fluorescein angiography
DWide-field fundus photography
Reveal answer & full explanation
Correct answer: A — B-scan ocular ultrasonography
AB-scan ocular ultrasonography✓
BOptical coherence tomography
CRetinal fluorescein angiography
DWide-field fundus photography
Why B-scan ocular ultrasonography is correct
A dense vitreous hemorrhage obscures the fundus, so any test that depends on a clear optical view of the retina is useless until the media clears.
B-scan ultrasound does not require an optical window; it images through the opaque vitreous to detect a tractional retinal detachment, the feared complication of proliferative diabetic retinopathy that changes management (urgent vitrectomy) versus simple observation of the hemorrhage.
AAO guidance: when media opacity prevents fundus visualization in a diabetic with vitreous hemorrhage, B-scan is the study of choice to rule out retinal detachment.
Why the others are wrong
Optical coherence tomography quantifies macular thickness and diabetic macular edema but requires a clear optical path to the retina; it cannot image through a dense vitreous hemorrhage.
Retinal fluorescein angiography maps capillary nonperfusion, leakage, and neovascularization, but the dye and camera both need an unobscured retinal view that the hemorrhage prevents.
Wide-field fundus photography is the primary teleretinal screening tool for asymptomatic patients, but it is a photographic image of the fundus and is blocked by the same opaque media.
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Pregnancy (can accelerate progression — exam at first prenatal visit)
Renal disease (proteinuria)
Smoking
Anemia, sleep apnea
Rapid intensive glycemic correction in long-standing poor control (transient worsening)
Pathophysiology
Chronic hyperglycemia drives advanced glycation end-product formation, polyol pathway flux, protein kinase C activation, and oxidative stress. These damage retinal capillary pericytes and endothelial cells, leading to microaneurysm formation, increased vascular permeability (edema and exudates), capillary nonperfusion (ischemia), and upregulation of VEGF. VEGF drives macular edema and, when ischemia is widespread, proliferative neovascularization. New vessels are fragile and grow along the posterior hyaloid, causing vitreous hemorrhage and tractional retinal detachment.
Clinical presentation
Symptoms
Often ASYMPTOMATIC until advanced or DME develops — emphasizes screening
Blurred or fluctuating vision (often with glycemic swings)
Floaters or sudden vision loss — vitreous hemorrhage from PDR
Curtain over vision — tractional retinal detachment
Central blurring or distortion — diabetic macular edema
ADA / AAO screening: dilated exam at diagnosis in type 2 DM and within 5 years of diagnosis in type 1 (and at puberty), then annually (or every 1-2 years if no retinopathy and good glycemic control). Pregnant diabetic patients: exam in first trimester and as indicated.
Labs
A1c, lipid panel, BMP, urine albumin-creatinine — for diabetic care, not specific to DR diagnosis
Diabetic macular edema (non-center-involving) — focal/grid laser per ETDRS
Intravitreal corticosteroid implant — dexamethasone (Ozurdex), fluocinolone (Iluvien) — for DME refractory to anti-VEGF or pseudophakic patients; cataract and IOP-rise risk
Proliferative DR — panretinal photocoagulation (PRP) — ablates peripheral ischemic retina to reduce VEGF drive (DRS); high-risk PDR is a class I indication
Anti-VEGF — non-inferior to PRP for PDR over 2 years (Protocol S), and preferred when DME coexists
Vitrectomy for non-clearing vitreous hemorrhage, tractional retinal detachment threatening macula, or combined tractional-rhegmatogenous detachment (DRVS)
Cataract progression and earlier need for cataract surgery
Worsened DR after rapid glycemic correction (transient — emphasize gradual normalization in chronically uncontrolled patients)
PANCE pearls
Early DR is silent — annual dilated exams or telehealth retinal photos are essential per ADA guidelines.
Macular edema can occur at any stage of DR — measure with OCT, not just slit-lamp.
PROLIFERATIVE DR = new vessels (NVD or NVE) and is the indication for PRP and/or anti-VEGF.
Anti-VEGF is now first-line for center-involving DME and is non-inferior to PRP for PDR, particularly when DME coexists (Protocol S).
Pregnancy can rapidly accelerate DR — screen at first prenatal visit and as indicated; gestational diabetes alone does not require retinal screening.
Fenofibrate slowed retinopathy progression independently of lipid effects in ACCORD Eye and FIELD — consider in patients with DR and dyslipidemia.
References
ADA 2024 — American Diabetes Association. Standards of Care in Diabetes — Retinopathy, Neuropathy, and Foot Care. Diabetes Care 2024;47(Suppl 1):S231-S243
AAO 2019 — American Academy of Ophthalmology. Diabetic Retinopathy Preferred Practice Pattern. Ophthalmology 2020;127(1):P66-P145
DCCT/EDIC — DCCT Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes. NEJM 1993;329(14):977-986
ETDRS — Early Treatment Diabetic Retinopathy Study Research Group. Photocoagulation for diabetic macular edema. ETDRS Report Number 1. Arch Ophthalmol 1985;103(12):1796-1806
Protocol S — Gross JG et al. Panretinal photocoagulation vs intravitreous ranibizumab for proliferative diabetic retinopathy. JAMA 2015;314(20):2137-2146
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