Dry Macular Degeneration (DMD) Lecture Notes

Key Topics Covered

1. RPE Abnormalities and Drusen
2. Retinal Abnormalities and Drusen Types
3. Reticular Pseudodrusen
4. RPE and Retinal Abnormalities Classification

RPE Abnormalities

• Types of Drusen: Soft, Calcified, Atrophic, etc.
  • Soft Drusen: Characterized by a bright RPE line over the drusen deposits.
  • Druzenoid PEDs: 350 microns across.
  • Shallow Irregular RPE Elevations (SIRE): Greater than 1000 microns, often containing neovascular membranes.
• Pigment Abnormalities: Focal hyperpigmentation, hypopigmentation, and geographic atrophy.
  • Focal Hyperpigmentation: Intra-retinal hyper reflective spots.
  • Geographic Atrophy: Loss of retinal layers, increased light transmission.

Retinal Abnormalities

• Types of Drusen
  • Soft Drusen: Double layer sign due to Brooks membrane visibility.
  • Confluent Drusen: Soft drusen running together.
• Reticular Pseudodrusen: Seen in elderly patients, appear as small bumps in front of the RPE line on OCT.

OCT (Optical Coherence Tomography) Findings

• External Limiting Membrane: Important marker, tricky due to variability.
• Reticular Pseudodrusen: Distinct from soft drusen, common in patients 85 years and older.
• SIRE: Non-exudative neovascular complexes, risk of converting to exudative AMD.

Image Examples (Not included, referenced in lecture)

• Soft Drusen: Bright RPE line, deposits under RPE.
• Confluent Drusen: Multiple soft drusen merging together.
• Reticular Pseudodrusen: Spots on infrared image, bumps on OCT.

RPE Abnormalities Classification

• Focal Hyperpigmentation: Intra-retinal hyper reflective spots, sign of pigment migration.
• Focal Hypopigmentation: Small atrophy spots over drusen.
• Geographic Atrophy: Loss of retinal layers, hyper transmission of light.
  • Characteristics: Loss of outer nuclear layer, shadowing.
  • Examples: 94-year-old patient with mild vision loss.

Other Findings and Considerations

• Pattern Dystrophy: Deposits in front of RPE (Pseudo vitelli-form lesion).
• Outer Retinal Tubulation: Hyper reflective tubes, not cysts, visible in OCT.
• Sub-retinal Fluid in Dry AMD: Caution required; distinguished between DMD fluid and other conditions (e.g., diabetic macular edema).
• Outer Retinal Atrophy: Loss of nuclear layer and external limiting membrane, key marker for assessing vision loss.

Conclusion

• Imaging and OCT: Critical in differentiating between types and stages of DMD.
• Understanding Variability: Key to correct diagnosis and treatment strategy. Ensure thorough assessment to differentiate DMD from other diseases.