Q:I have a patient with optic nerve drusen who is exhibiting progressive nerve fiber layer loss over time. What can I do?
“In the absence of any substantive medical literature, I don’t treat drusen of the nerve head,” says Bob Vandervort, OD, of Heartland Eye Consultants in Omaha, Neb. In some cases, the literature suggests treating drusen with prophylactic glaucoma medications, but I do not in patients who have no risk factors for glaucoma. Drusen of the optic nerve is a relatively common condition, he says, and, according to the literature, they occur around 1% of the time, though family history increases the incidence. “These incidence reports do not state the amount or grade of drusen. When nerve heads are carefully examined using indirect illumination with a condensing lens at the slit lamp, clinicians sometimes observe isolated or minimal drusen in patients with small optic nerves.”
This purported association, and the concurrent belief that smaller optic nerves may be more susceptible to damage, prompts clinicians to consider some type of prophylactic treatment to slow or halt progressive nerve damage from drusen, according to Dr. Vandervort.
|Prominent optic nerve drusen creates a pseudopapilledematous appearance.
This case brings to the forefront the vexing question of whether clinicians have justification to treat patients in the absence of evidence. Factors to consider:
A life sentence. Drusen of the optic nerve, no matter how severe, rarely if ever cause any symptomatic vision or visual field loss, says Dr. Vandervort. “Do we recommend a 16-year-old adhere to a lifetime regimen of glaucoma medications in the hope that lowering the IOP will slow or halt their progressive nerve damage? Bear in mind, the nerve loss is likely never to have any meaningful negative impact on the person’s quality of life,” says Dr. Vandervort.
Correlation is not causation. “In patients with symptomatic loss and moderate to severe drusen, is there something else going on?” asks Dr. Vandervort. “Patients are entitled to a diagnosis of more than one disease at a time, and great care needs to be taken to make sure concurrent optic nerve disease such as an active or old optic neuritis did not cause the damage,” he explains.
Evidence is a must. While the literature does not support the notion that lowering IOP will stop progressive nerve damage from optic nerve drusen, “it’s commonplace and accepted” to treat patients with significant ocular hypertension and significant concurrent optic nerve drusen to lower their risk of glaucomatous loss, since the nerve is already compromised from the drusen, says Dr. Vandervort.
Second opinions. Dr. Vandervort surveyed the Keystone Group, a group of highly experienced secondary care optometrists, on how they would manage a patient with progressive loss of nerve fiber and IOPs of 18mm Hg and 19mm Hg. Opinions varied from no treatment and close observation to treatment with glaucoma medications. The consensus was to obtain a second opinion from a neuro-ophthalmologist if at all possible. “And, if the patient suffers any symptomatic vision loss or loss of visual acuity, neuroimaging would be indicated.”
“I have encountered many patients with moderate to severe drusen of the optic nerve who are 50 years of age or older with significant visual field loss and nerve damage, some with afferent pupillary defects. They’ve been living their lives without visual complaints or disability,” says Dr. Vandervort.
Optometrists should only treat if concurrent glaucoma or risk factors for normal tension glaucoma or primary open-angle glaucoma exist. “It is unfortunate that someone has lost and will probably continue to lose small amounts of nerve tissue, but the loss has no meaningful impact on their lives.”