What information is needed for an Early Treatment Diabetic Retinopathy Study (EDRS) assessment in a patient with diabetes?

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Information Needed for ETDRS Assessment

For an Early Treatment Diabetic Retinopathy Study (ETDRS) assessment, you need stereoscopic color fundus photographs using seven standard fields, visual acuity measurement using the ETDRS chart, and a comprehensive dilated fundus examination with slit-lamp biomicroscopy to evaluate retinal thickening. 1

Essential Clinical History

  • Duration of diabetes - this is the strongest predictor for development and progression of retinopathy 1
  • Past glycemic control (HbA1c levels) - higher HbA1c increases the hazard for diabetic retinopathy 1
  • Medical history including obesity, renal disease, systemic hypertension, serum lipid levels, pregnancy status, and neuropathy 1
  • Ocular history including trauma, other eye diseases, previous ocular injections, surgery (retinal laser treatment and refractive surgery) 1
  • Current medications 1

Required Examination Components

Visual Assessment

  • Visual acuity testing - the ETDRS used standardized visual acuity charts to define moderate visual loss as loss of 15 or more letters, or doubling of the visual angle 1

Anterior Segment Evaluation

  • Slit-lamp biomicroscopy to assess for iris neovascularization and other anterior segment changes 1
  • Intraocular pressure measurement 1
  • Gonioscopy before dilation when indicated - iris neovascularization is best recognized prior to dilation, and when present or suspected, or if IOP is elevated, undilated gonioscopy detects neovascularization in the anterior chamber angle 1
  • Pupillary assessment for optic nerve dysfunction 1

Posterior Segment Evaluation

  • Stereoscopic examination of the posterior pole - this three-dimensional assessment is essential for detecting retinal thickening from macular edema 1
  • Peripheral retinal examination via indirect ophthalmoscopy 1
  • Seven-standard field stereoscopic 30° fundus photography - this is the gold standard for ETDRS grading and is more sensitive at detecting retinopathy than clinical examination alone 1

Specific Retinal Features to Document

For Diabetic Retinopathy Severity Grading

  • Microaneurysms - their presence and number 1
  • Intraretinal hemorrhages - severity is assessed by counting hemorrhages in each quadrant (≥20 in each quadrant indicates severe NPDR) 1
  • Hard exudates - these are signs of current or previous macular edema 1
  • Cotton wool spots 1
  • Venous beading - definite venous beading in 2 quadrants indicates severe NPDR 1
  • Intraretinal microvascular abnormalities (IRMA) - presence in 1 quadrant indicates severe NPDR 1
  • Neovascularization at the disc (NVD) - compare to standard photograph 10A (approximately one-quarter to one-third disc area) 1
  • Neovascularization elsewhere (NVE) - location and extent 1
  • Vitreous or preretinal hemorrhage 1

For Macular Edema Assessment

  • Retinal thickening location - document whether it involves the central subfield zone (1 mm diameter) or is non-center-involved 1
  • Distance from center of macula - clinically significant macular edema (CSME) is defined as retinal thickening at or within 500 μm of the center of the macula, or hard exudates at or within 500 μm of the center with adjacent retinal thickening, or zones of retinal thickening 1 disc area in size within 1 disc diameter of the center 1

Ancillary Testing (When Available)

Optical Coherence Tomography

  • OCT is the most sensitive method for detecting and assessing DME - retinal map scans locate areas with retinal thickening, and single line scans detail specific morphologic changes such as intraretinal cysts, subretinal fluid, and vitreoretinal traction 1

Fluorescein Angiography

  • Not required to diagnose DR, PDR, or DME - all are diagnosed by fundus examination 1
  • Can be useful as a guide to evaluate retinal non-perfusion area, presence of retinal neovascularization, microaneurysms, or macular capillary nonperfusion in DME 1
  • May help differentiate IRMA from new blood vessels in PDR 1

Systemic Parameters to Document

  • Glycemic status (hemoglobin A1c) 1
  • Blood pressure 1
  • Serum lipid levels 1
  • Renal status 1
  • Pregnancy status - pregnancy can accelerate retinopathy changes 1

Common Pitfalls to Avoid

  • Do not rely on clinical examination alone - stereo fundus photography is more sensitive at detecting retinopathy than clinical examination, though clinical examination is superior for detecting retinal thickening from macular edema and early neovascularization 1
  • Do not skip stereoscopic examination - retinal thickening requires three-dimensional assessment best performed by dilated examination using slit-lamp biomicroscopy, stereo fundus photography, or both 1
  • Do not forget gonioscopy when neovascularization is suspected - neovascularization in the anterior chamber angle can lead to neovascular glaucoma 1
  • Do not assume good vision means no significant disease - patients may have good vision and no ocular symptoms but still have significant disease requiring treatment 1

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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