Diabetic Retinopathy

Epidemiology

• 12% of new cases of blindness per year
• Most common cause of acquired blindness 20-65yo age group
• 700,000 adults in U.S. with PDR (65,000 new cases per year)
• 500,000 adults in U.S. with diabetic macular edema
• Type I diabetics tend to develop PDR (56% after 20 yrs)
• Type II diabetics tend to develop diabetic macular edema (28% after 20 yrs)

Pathology

• Pathogenesis a combination of:
  • Aldose Reductase
  • Vasoproliferative factors
  • Growth hormones
  • Platelets and blood viscosity
• Histopathology
  • Thickened capillary basement membrane (earliest changes in ciliary body)
  • Pericyte loss (normal pericyte:endothelial cell ratio is 1:1)

Systemic Factors that Influence Diabetic Retinopathy

• Glucose control
• Renal disease
• Hypertension
• Pregnancy
• Race
• Serum lipids
• Smoking

Classification

• Retinal Findings
  • Microaneurysms
    • First sign of diabetic changes
    • 12-125 microns (can see >30 microns)
    • Due to capillary closure and pericyte loss
  • Retinal Hemorrhages
    • Due to ruptured microaneurysms, capillaries, venules
    • Dot-Blot and flame-shaped hemorrhages
    • Resolve in 6weeks to 4 months
    • Located in posterior pole and/or periphery
    • If only flame-shaped hemorrhages, must consider other causes
  • Hard Exudates
    • Serum lipoproteins left behind after fluid reabsorbed
    • Eventually reabsorbed by macrophages
  • Macular Edema
    • Most common cause of decreased vision in diabetics
    • Due to abnormal permeability of blood vessels
    • Focal edema represents inner blood-retinal barrier dysfunction
    • Diffuse edema represents outer blood-retinal barrier dysfunction
  • Foveal Avascular Zone (FAZ) Abnormalities
    • FAZ is 350-750 microns (can be up to 1000 microns)
    • Irregular margins
    • Bridging vessels
  • IRMA (Intraretinal microvascular anomalies)
    • Represents diseased capillary beds
    • Abnormal connections seen between arterioles and venultes
    • Can show leakage on FA, but not as much as neovascularization
    • "Intraretinal neovascularization"
    • Associated wtih developing PDR
• Classification

Stage	Criteria	Follow-Up
NPDR Mild-Moderate	MA's Heme <4 quadrants Hard exudates Macular edema FAZ abnormalities No CWS	Without ME, 6-12 months With early ME, 4-6 months
NPDR Moderate-Severe	Cotton-Wool Spots Heme in 4 quadrants Venous Beading IRMA	3-4 months
Severe NPDR	Severe intraretinal heme in 4 quads Venous beading 2 quads Moderately severe IRMA 1 quad	3-4 months
Very Severe NPDR	Any 2 of the 3 criteria for severe NPDR	Consider treatment
Proliferative Diabetic Retinopathy	NVD up to 1 DD from disc NVE Preretinal heme Tractional RD NV of iris or angle	Early - Consider Treatment
High-Risk PDR	Any 3 of the following: Presence of new vessels Location of new vessels on disc Severity: If NVD > 1/4 to 1/3 disc area If NVE > 1/2 disc area Presence of both NVE and NVD Presence of preretinal or vitreous hemorrhage	Recommend Treatment
Also recommend treatment for Clinically-Signficant Macular Edema: Thickening of the retina at or within 500 microns of the center of the macula Hard exudate at or within 500 microns of the center of the macula with thickening of the adjacent retina A zone of retinal thickening equal to or larger than one disc area, any part of which is within one disc diameter of the center of the macula



• Management
• First DFE
• 0-30yo at onset, examine by 5 years after onset
• Over 30yo, examine at the time of diagnosis
• Pregnant diabetics need to be seen every trimester
• Pregnant women with gestational diabetes do not need to be seen
• Annual followup if no retinopathy or minimal disease
• Followup per table above for NPDR and PDR

Major Diabetic Eye Disease Studies