Choosin’ the Drusen; Differentiating Disc Drusen

A diagnostic challenge

Always a diagnostic challenge is the hyperopic early teen who presents with mom in tow and brings along a history of increased headaches and blurred vision….and on fundus examination there appear to be full discs. And you begin to question whether or not this is papilledema. And if so, do I get a scan? But maybe its disc drusen, and all is fine. But if it’s not drusen, how in the world do I discuss this with mom, whose job it is to be hyper-protective?

How to differentiate disc drusen

Differentiating disc drusen, especially those that are buried and not visible ophthalmoscopically, from papilledema in young hyperopic teens can be difficult. But with an understanding of some of the clinical signs that differentiate these two conditions, navigating through the visit becomes easier.

Of course, the easy case is the patient with visible disc drusen…they are generally a slam dunk. But remember, in young teens, often times the disc drusen have not yet calcified, and therefore they are more difficult to observe fundoscopically. For buried drusen that have calcified, we have a couple of options clinically to help visualize the drusen: fundus autofluorescence (FAF) and B-scans. In deep, buried drusen, it is not uncommon for FAF to not visualize the drusen, and we must rely on B-scan. Having ultrasound technology in your practice is certainly very helpful in these cases. But again, until the drusen become more calcified with time, sometimes even B scans don’t show buried drusen well.

The best tool we have to evaluate these patients is our OCT. I would suggest that you not examine the optic nerve utilizing your OCT in the typical imaging mode looking at the RNFL circle scans. While they may show mild elevation changes in the perioptic RNFL, the action in these cases is in the neuroretinal rim in the optic canal. I would, therefore, suggest you run a series of high-resolution rasters of the optic nerve.

There are several characteristics that can help differentiate non-calcified drusen from papilledema on OCT imaging.

Minimal RNFL elevation:

With disc drusen, there is not much RNFL elevation, though that is not always the case especially with a very small disc with multiple drusen.

Small central cup:

In the presence of disc drusen, there is usually a small remaining central cup, but this too is not always the case, especially in small discs with drusen.

Reflectance of Hyaline and Shadowing beneath:

This is seen commonly in patients with disc drusen and it is not seen in cases of papilledema

Separation of the neurosensory retina from the RPE:

This is a pathognomonic OCT finding in drusen that is not seen in apilledema. Due to the fact that drusen are essentially space occupying, and therefore are ‘crammed’ into a small space, there is separation of the overlying neurosensory retina from the RPE as you approach the optic canal, as seen below:

A Flat RPE/Bruch’s Membrane complex:

This too is pathognomonic of disc drusen, and the reverse is pathognomonic of papilledema. In disc drusen, since there is no elevation of ICP, there is no forward pressure on the back of the optic nerve, and there is no deflection of the RPE forward. The reverse is true when increased ICP exists, as the translaminar pressure gradient is much higher in the optic nerve sheath than it is inside the eye, with forward bowing of the RPE/Bruch’s membrane complex. Papilledema is seen in the image below, and note the bowing forward of this complex:

While the teenager presenting with full discs and headaches can be challenging, utilization of our OCT technologies can help differentiate readily the difference between papilledema and pseudopapilledema, thereby making the clinical diagnosis easier to make, and subsequently improving care.