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Sir,

Optic disc drusen are known to be associated with other ocular conditions such as angioid streaks and retinitis pigmentosa and are rarely complicated by peripapillary disciform degeneration, central retinal arterial and venous occlusions. We report a patient who presented with bilateral optic disc drusen associated with bilateral neovascularization of the optic discs (NVD).

Case report

A 54-year-old woman who was asymptomatic was referred following a visit to an optician for a routine eye check. Her visual acuity was 6/4 in the right eye. Her left eye was amblyopic and had a visual acuity of 6/36. The anterior segments were normal in both eyes with normal intraocular pressures. Posterior segment did not show any evidence of inflammation. Fundus examination showed presence of well-marked optic disc drusen in both eyes (Figure 1a, b). In addition, she had NVD in both eyes with a small optic disc haemorrhage in the left eye. The retinas appeared normal in both eyes. On fluorescein angiography, the preinjection photographs clearly showed autofluorescence from optic disc drusen in both eyes (Figure 2a, b). Fluorescein angiogram also confirmed the NVD (Figure 2c, d) on both sides with normal choroid and retina. Systemic evaluation was normal.

Figure 1
figure 1

(a, b) Colour fundus photographs showing optic disc drusen and NVD.

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Figure 2
figure 2

(a, b) Autofluorescence demonstrating optic disc drusen. (c, d) Leakage of fluorescein from NVD on the right optic disc. NVD—Neovascularization of optic disc.

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A detailed discussion with the patient about treatment resulted in a decision to perform panretinal photocoagulation in the right eye first. When the patient was reassessed in 4 weeks, the NVD had regressed completely. Encouraged by the response, she underwent panretinal photocoagulation in the left eye, which also showed a similar response in 4 weeks. Both her eyes remain stable since the treatment.

Comment

Optic disc drusen are calcified material in the substance of the optic nerve head. Sacks et al1 presented a hypothesis on the pathogenesis of disc drusen. The presence of drusen may cause blurring of optic disc margins and may be mistaken for papilloedema. The drusen are initially buried but later become visible as irregular, nodular lesions that are bilateral in approximately 75% of patients.2 Autofluorescence confirms these surface drusen in over 96% of cases. Buried drusen can be reliably detected by B-scan ultrasonography.3

Optic disc drusen are known to be associated with various vascular abnormalities in the eye.2 These include optociliary shunts, anterior ischaemic optic neuropathy, central retinal artery occlusion, central retinal vein occlusion, peripapillary disciform lesion, and retinal haemorrhage. Other associations include retinitis pigmentosa and angioid streaks. We are not aware of any association with neovascularization of the optic disc. Neovascularization of disc and peripheral retinal new vessels are associated with conditions causing retinal nonperfusion such as diabetic retinopathy. They may also be seen in the presence of intraocular inflammation without evidence of retinal nonperfusion. The possibility of these abnormal vessels being optociliary shunts was excluded by fluorescein angiography as there was leakage of dye from these vessels (Figure 2c, d).

NVD is thought to arise from the retinal circulation, but possible origin from the uveal circulation has been reported.4 The pathogenesis for NVD in this patient is unclear. The presence of enlarging drusen may cause ischaemia that may stimulate development of new vessels at the disc border. Peripapillary choroidal filling defects on fluorescein angiography have been described in patients with optic disc drusen.1 Growth factors such as vascular endothelial growth factor (VEGF) may also play a role. Expression of VEGF has been found to be more prominent in the nerve fibre layer near the optic disc in rat retinas.5 The patient was evaluated for the possibility of underlying causes such as diabetes, ocular ischaemia, vascular occlusion, and intraocular inflammation. We can only speculate on the pathogenesis of the development of NVD as our attempts to identify an underlying cause were unsuccessful.

In our patient, panretinal photocoagulation was effective in achieving regression of NVD within 4 weeks in each eye. The mode of action of panretinal photocoagulation in achieving successful regression of NVD is not clear. Our case highlights the usefulness of PRP in the treatment of NVD even when the pathogenesis is unclear.