Statistics from Altmetric.com
Radial optic neurotomy was recently introduced as a treatment option in patients with central retinal vein occlusion.1 As described by Opremcak et al,1 central retinal vein occlusion might be related to increased pressure on the central retinal artery and vein as well as on optic nerve fibres in the confined space provided by the scleral ring. It was therefore suggested that a relaxation of the scleral outlet by a radial optic neurotomy might be an effective surgical treatment option. In the light of this information we hypothesised, that radial optic neurotomy may also be applicable in patients with visual field defects and deterioration of visual acuity associated with optic nerve drusen, where compression induced damage to optic nerve fibres is the underlying pathogenetic principle2
A 27 year old female patient presented with extensive bilateral optic nerve drusen (fig 1A). While visual acuity was light perception on the right eye over 4 years, she had experienced an acute and rapid deterioration of visual acuity from 20/32 to 20/500 and a progressive visual field loss within the past 6 weeks before she was seen in our institution (fig 1B). The progressive visual field defect had been documented carefully by the referring ophthalmologist. Besides the optic nerve drusen, there was no other ophthalmic pathology, no history of glaucoma, or any other relevant disease. With respect to the rapid functional deterioration we discussed radial optic neurotomy as a potential treatment option. Surgery was performed, after written informed consent, by one of the authors (AK) and consisted of standard three port pars plana vitrectomy and radial optic neurotomy. The incision was performed at the nasal edge of the optic disc in a radial fashion avoiding major retinal vessels. There were no intraoperative complications except a small haemorrhage at the incision site. The patient was then carefully followed postoperatively at 3 week intervals. Already at the first follow up visit a regression of the visual field defect and slight improvement of visual acuity was noted (fig 2A). At last presentation 10 weeks after surgery, the visual field defect was limited to the inferior nasal quadrant and visual acuity had improved to 20/32 (fig 2B). Funduscopy revealed a scar at the incision site, but no other pathologies (fig 2C).
Drusen of the optic nerve are the result of axonal degeneration of retinal ganglion cells and are composed of acellular concentric calcified laminations.3 While most cases are idiopathic, drusen have been described in association with several acquired conditions such as hypertensive retinopathy, vascular occlusion, optic atrophy, or chronic papilloedema.4 If drusen are located deep in the optic nerve, progressive enlargement may result in pressure induced atrophy of adjacent nerve fibres producing visual field constriction and anterior ischaemic optic neuropathy.2 Drusen have also been reported to occur predominantly in eyes with abnormally small optic discs.5 It had been previously hypothesised,1 that a radial incision at the nasal edge of the optic disc might result in a decompression of the scleral outlet and the associated neurovascular compression in patients with central retinal vein occlusion. Transferring this hypothesis to our patient, radial optic neurotomy seemed a reasonable therapeutic approach to us, as a relaxation or decompression of the scleral outlet might counteract the relevant pathogenetic principles of progressive visual field defect in optic nerve drusen. To our knowledge, radial optic neurotomy has not been used for the treatment of progressive visual field defects in association with optic nerve drusen before. We were very aware of the experimental character of this surgical intervention and carefully informed the patient before the operation. However, with respect to the rapid deterioration of visual acuity and progression of visual field constriction, there seemed to be no other treatment option available and the surgical intervention appeared justified.
The validity of the “scleral outlet compartment syndrome” concept in central retinal vein occlusion, as well as the effect of the radial neurotomy, has been questioned6 by Hayreh and is currently under discussion. However, the excellent functional outcome in this case may suggest that radial optic neurotomy potentially provides a relaxation and decompression of the optic nerve, allowing a recovery in conditions associated with pressure induced nerve fibre damage as in the case presented. In retinal vein occlusion, other additional mechanisms of action, such as the formation of chorioretinal shunts as a result of radial optic neurotomy, were described to contribute to visual recovery.7
In summary, this case reports indicates that radial optic neurotomy might be considered in patients presenting with sudden visual loss and constriction of visual field in association with optic nerve drusen. We considered the surgical approach in this single case, as there was no other treatment option we could offer the patient that might restore vision.
Financial interest: none.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.