Estimating Drusen Size

Overview

Described here is a simple way to estimate drusen size using anatomical cues, a skill that is necessary for the accurate classification of AMD.

The diameter of the central retinal vein at the optic disc margin is approximately 125µm and this is used to give us a point of comparison.

- Small drusen are less than 63µm - that is, less than half the vein diameter as it crosses the edge of the optic disc.

- Medium drusen are between 63µm and 125µm - that is, more than half but less than the full diameter of the vein

- Large drusen are larger than 125µm - that is, they have a diameter larger than the vein

Case Examples

  • Small drusen

    Small drusen (drupelets) are smaller than 63µm in diameter.

    Fundus photo showing a drupelet

    More info

    Fundus photo showing a drupelet

    In this image, the yellow dot indicated by the arrow is half the diameter of the retinal vein as it crosses the edge of the optic disc (63µm). A drupelet is identified by the second yellow dot. It can be seen that this second dot is smaller than the first, classifying it as a drupelet.

  • Medium drusen

    Medium drusen are between 63µm and 125µm in diameter.

    Fundus photo showing a medium druse

    More info

    Fundus photo showing a medium druse

    In this image, the reference circle is 125µm (the same diameter as the retinal vein as it crosses the inferior edge of the optic disc. The medium druse identified in the retina is smaller than this reference circle, but larger than half the size of this same circle, making it a medium druse.

  • Large drusen

    Large drusen have a diameter greater than 125µm.

    Fundus photo showing a large druse

    More info

    Fundus photo showing a large druse

    In this image, the reference circle is larger than the retinal vein crossing the inferior edge of the optic disc. The druse identified by the second circle is the same size as this reference circle.