Optical coherence tomography demonstrating macular retinal nerve fiber thinning in advanced optic disc drusen.

Optic disc drusen (ODD) are extracellular proteinaceous excrescences in the optic nerve head. They enlarge over time and can cause damage to nerve fibers with resulting loss of visual field. The authors report a case of advanced ODD in which macular optical coherence tomography demonstrated retinal nerve fiber thinning. A single case report of a 42-year-old woman with known ODD presented to the eye clinic with worsening field of vision which was impacting on her daily life. The patient was subject to full ophthalmic examination as well as Goldmann visual field testing, optic disc photography and optical coherence tomography (OCT) of both her optic discs and maculae. ODD although rare, can be visually devastating. No treatment is currently available however patients should be counseled about progressive nature of ODD and the potential for visual loss. OCT imaging of the maculae as well as optic discs may serve a role in monitoring the damage disc drusen cause to the eye.

Introduction

Optic disc drusen (ODD) are recognized to cause visual field defects. Enlarging drusen within the tight space of the lamina cribosa can impart compressive force on the retinal nerve fibers exiting the eye here. We present a case of bilateral advanced ODD causing visual field constriction in which optical coherence tomography (OCT) demonstrated both peripapillary and macular retinal nerve fiber layer (RNFL) thinning.

Case Report

A 42-year-old Caucasian female with bilateral ODD was referred by her optician with worsening visual field loss particularly affecting her right eye. She had previously been functioning normally, however the recent visual field deterioration meant she was no longer confident driving. There was no notable medical history.

Best corrected distance visual acuity (Snellen) was 6/6 -3 OD and 6/5 + 2 OS, near acuity was N5 bilaterally. A mild right relative afferent pupillary defect was noted. Examination of both anterior segments was unremarkable and Goldmann applanation tonometry revealed pressures of 12 mmHg in each eye.

Fundal examination revealed healthy appearing maculae and retinae; however, each optic disc had a large number of visible confluent drusen occupying the entirety of the nerve head [Figure 1].

Figure 1

(Top) Right and left optic disc color photographs showing multiple excrescences of drusen covering the entire optic nerve head. (Bottom) Fluoroscopy showing autofluorescence of the right and left optic disc drusen

Goldmann visual field tests demonstrated gross constriction particularly affecting the right eye [Figure 2]. Optical coherence tomography (OCT, Cirrus HD-OCT Model 400, Carl Zeiss Meditec, US) of the optic discs and maculae were performed; these demonstrated both peripapillary and macular RNFL thinning bilaterally [Figures 3 and 4].

Figure 2

Goldmann visual field plots showing bilateral advanced constriction

Figure 3

OCT of both optic nerves showing elevated optic nerve heads and peripapillary RNFL thinning

Figure 4

OCT showing thinning of the neuroretinal layers at each macula; the maculopapular bundle is particularly attenuated. Note the central foveal thickness is normal

Discussion

ODD are pre-laminar excrescences of extracellular proteinaceous material anterior to the lamina cribrosa in the optic nerve head.[1] Drusen can enlarge and calcify over time compressing the optic nerve and damaging the nerve fibers.[2] Peripapillary retinal nerve fiber loss has been demonstrated in patients with ODD using a number of imaging modalities including fundal photography,[3] scanning laser polarimetry[4] and optical coherence tomography.[5] The damage caused to the peripapillary RNFL has been linked to the loss of visual field in ODD.[567]

ODD have been linked to cases of hemorrhagic and serous retinopathy, which can involve the macula;[8] however, the authors could not find any publication describing the pathological effects of ODD on the macular RNFL. In our case, the OCT demonstrated bilateral thinning of the macular nerve fiber layer in each eye; in particular, gross attenuation of the maculopapular bundle is noted. We note that the fovea, which is free of a retinal nerve fiber layer, was of normal thickness on the macular OCT for each eye.

This case demonstrates the use of OCT for observing the effects of advanced ODD on the RNFL both around the optic disc and at the macula. This case also reminds us of the severity of some cases of ODD and the potential for the condition to cause serious sight impairment.