Histopathological and ultrastructural features of preclinical drusen deposits
| Deposit type | LM appearance | EM appearance | Size | Clinical correlation |
|---|---|---|---|---|
| Entrapment sites | smallest not detectable, hyalinised | smallest only seen on EM, intact and ruptured | up to ½ RPE cell high | not found in eyes with many drusen |
| CMBB | ||||
| Amorphous | all hyalinised stain red on P-M | all amorphous electron dense | may be found in all eyes | |
| (i) iridescent plaques | all amorphous electron dense | up to 10 μm | ||
| (ii) globular drusen root-like extensions | all amorphous electron dense | all sizes may reach clinical size >30 μm | ||
| (iii) microdrusen over which small globular drusen may develop | all amorphous electron dense | small 1–2 μm form rows up to 10 RPE cells in length | found in eyes with many drusen | |
| Mixed | hyalinised heterogeneous stain on P-M | entrapment site material with amorphous material | maximum: 30 μm diameter up to 1 RPE cell high | not found in eyes with many drusen |
LM = light microscopy; EM = transmission electron microscopy; CMBB = coated membrane bound bodies; RPE = retinal pigment epithelium; P-M = Picro-Mallory stain.