Since fluorescein angiographic (FA) criteria for differentiating optic disc drusen (ODD) from optic disc edema (ODE) have been unclear, the authors of this study reviewed FA findings in ODD cases to identify distinguishing features. They report in the March issue of the Journal of Neuro-Ophthalmology that early and late FA features reliably distinguish ODD from ODE and may be particularly useful when the conditions coexist. They conclude that in patients with surface or buried ODD suspected of also having ODE, full-sequence FA analysis plays a valuable role in establishing the correct diagnosis.
The authors identified 62 cases of ODD (116 eyes) seen at one university medical center during a 20-year period. Ten cases of papilledema and eight of coexistent drusen and edema were selected for comparison.
Twenty-three eyes were classified as surface ODD. Of these, 90 percent demonstrated early nodular staining of the disc, with late nodular staining in 90 percent and late circumferential peripapillary staining in 22 percent. Autofluorescence was visible in 93 percent with preinjection photography.
Eighty-three eyes were classified as buried ODD. Of these, 25 percent demonstrated early nodular staining, with late nodular staining in 29 percent and late circumferential peripapillary staining in 80 percent. Autofluorescence was visible in 12 percent of those with preinjection photography.
In nine eyes, buried ODD were present with superimposed true optic nerve edema. In these eyes, early dye leakage, late nodular hyperfluorescence and late leakage were present.
Buried ODD are characterized by either no early staining (75 percent) or a characteristic early nodular staining (25 percent). They also often show late peripapillary staining, either nodular (29 percent) or circumferential (80 percent) or both, which is not seen in ODE.
The clinical features of buried ODD include optic disc elevation, blurred optic disc margins without obscuration of peripapillary retinal vessels, and nodular border of the optic disc, all in the absence of features of ODE, including retinal nerve fiber opacification with obscuration of retinal vessels, microvascular abnormalities, such as optic disc surface capillary net dilation, telangiectasia, retinal hemorrhages, and exudates.
While the detection of autofluorescence of the optic disc on preinjection photography is confirmatory for ODD, with the technique most effective when ODD are on or near the disc surface, for buried ODD, sensitivity is low. The present study corroborates previous studies confirming the limited role for ultrasonography in detection of buried ODD.
The authors conclude that when ODD are visible on the optic disc surface, identification is straightforward, although it does not rule out the presence of superimposed ODE. In cases of suspected coexistent ODE, the appearance of early or late leakage confirms the presence of ODE. However, they say that at times it may be difficult to distinguish ODD from ODE with certainty.