Bilateral simultaneous non-arteritic ischaemic optic neuropathy: a rare complication of idiopathic systemic capillary leak syndrome (SCLS)

Abstract

We report a case of bilateral symmetrical superior visual field defects in a 72-year-old man first reported during the recovery from systemic capillary leak syndrome (SCLS). During the acute illness, he required extensive and prolonged fluid replacement and mechanical ventilation for severe hypotension, shock and multiorgan dysfunction. His visual field defect and optic nerve changes were consistent with a diagnosis of ischaemic optic neuropathy. These remained unchanged over 3 years and he retained excellent 6/7.5 visual acuity bilaterally. We hypothesised the mechanism of bilateral segmental infarction of the optic nerve head to be caused by the hypercoagulable and hypovolaemic state, in addition to pre-existing vascular disease and hypertension. This case highlights the importance of including optic nerve examination in the management plan of SCLS, particularly in individuals with underlying vascular risk factors.

Background

Complications of systemic capillary leak syndrome (SCLS) commonly include limb compartment syndrome, pulmonary oedema, cerebral oedema and acute renal failure.¹ Progression of monoclonal gammopathy to multiple myeloma is also well documented.² Increased vascular permeability during the leak phase can result in marked polycythaemia and tremendously increased blood viscosity.¹ This can subsequently lead to a hypercoagulable state which may lead to deep venous thrombosis and ischaemic stroke. To our knowledge, there are no reported ophthalmic complications of SCLS to date in the literature.

Case presentation

A 72-year-old man was referred to the ophthalmology department with bilateral symmetrical superior visual field defects. Prior to this, he had been admitted to the intensive care unit with severe shock and multiorgan dysfunction, preceded by low-grade fever, hypotension and collapse. At some point during his acute illness, he had required intubation, mechanical ventilation and large volume fluid replacement therapy. He was diagnosed with SCLS, based on the classical presentation of generalised oedema, leakage of fluid in the third space with associated pericardial and pleural effusions, haemoconcentration and the ongoing need for large volume fluid replacement. He was managed with 2 g/kg body weight of intravenous immunoglobulin (IVIg) in addition to intravenous hydrocortisone. The condition was thought to have been triggered by influenza B, subsequently confirmed on molecular testing. A paraprotein (IgG lambda, 2.0 g/L) was also identified on serum testing. As the patient regained consciousness, he reported a superior visual field defect, which was confirmed 4 months later on formal visual field testing.

His medical history included moderate aortic stenosis, minor coronary artery disease and hypertension. His best-corrected visual acuity was 6/7.5 in each eye at presentation. Colour vision was full, and pupils were equal, round and reactive to light with no relative afferent defect. Fundus examination revealed bilateral distinct inferior optic disc pallor, but the rest of the posterior segment findings were unremarkable. His extraocular muscle movements were full in all nine directions of gaze. In addition to the above, there was no focal neurological deficit.

Investigations and management

Humphrey’s visual fields showed bilateral symmetrical superior altitudinal visual field defects (figure 1A). Optical coherence tomography (OCT) of the optic nerve heads showed thinning of the retinal nerve fibre layer inferiorly in both eyes consistent with the visual fields (figure 2) and OCT imaging of the maculae was unremarkable. MRI of the head and orbits showed no focal infarct or space occupying lesion, and an ultrasound B-scan of the optic nerve head showed incidental small drusen with a normal optic disc diameter in both eyes.

Figure 1.

Humphrey’s 24-2 visual field showing symmetrical superior arcuate visual field defect at presentation (A) in the left (OS) and right (OD) eye which did not show any signs of progression over the course of 3 years (B).

Figure 2.

Optical coherence tomography of the optic nerve heads showing inferior retinal nerve fibre layer thinning in the left (OS) and right (OD) eye which remained unchanged over the course of 3 years.

Outcome and follow-up

The visual fields were repeated yearly after the initial presentation and showed no progression over a follow-up period of 3 years (figure 1B), and visual acuities had remained stable throughout this period. Systemically, the patient continues to remain stable on regular IVIg therapy.

Discussion

Superior visual field defects respecting the horizontal midline corresponded anatomically to the distinct pallor of the inferior half of the optic discs in our patient. The OCT also confirmed thinning of the inferior neuroretinal rim. These clinical features were consistent with a clinical picture of non-arteritic ischaemic optic neuropathy (NAION). While we cannot confirm the presence or absence of optic disc swelling during the acute illness, the established optic nerve pallor with corresponding visual field defects are in keeping with the diagnosis.

Risk factors for ischaemic optic neuropathy (ION) include diabetes, hypertension, atherosclerosis, hyperlipidaemia, haemoconcentration, haemodilution and hypercoagulable states. Morphologically, a small crowded disc is more at risk of NAION too.³ Both anterior and posterior perioperative ischaemic optic neuropathy are well documented following prolonged spinal surgery or coronary bypass grafting.⁴ The term ‘shock-induced anterior ischaemic optic neuropathy’ has also been used to describe optic nerve swelling with visual loss occurring following severe blood loss, anaemia and hypovolaemia.⁴ ION associated with SCLS has not been described in the literature, but can be explained in our case based on the associated hypercoagulable and hypovolaemic state, in addition to pre-existing vascular disease and hypertension.

The mechanism of segmental infarction of the optic nerve head as a complication of hypovolaemia can be explained by the anatomy of the optic nerve head circulation. The optic nerve head receives its blood supply through the ciliary system and not from the retinal circulation. The posterior ciliary arteries supply the optic disc in a sectoral manner, making the optic nerve susceptible to sectoral ischaemia and nerve-fibre bundle infarction.⁵ The blood vessels supplying the optic disc go through the peripapillary choroid, which is under the influence of the intraocular pressure. The normal intraocular pressure equates to relatively high tissue pressure, which in turn may favour selective flow via anastomotic channels away from the optic disc area.⁶ These vessels are end arteries and create a watershed zone in the posterior part of the optic nerve that is susceptible to ischaemia.⁷ Therefore, the occurrence of shock, as noted in our case, may have precipitated segmental infraction and a subsequent ION in both eyes. It is important to note that bilateral simultaneous NAION as described in our case is very rare, and cases previously reported were mainly in relation to severe arterial hypotension during cardiopulmonary or extensive surgery with significant blood loss.^{8 9}

Interestingly, our patient had not suffered profound visual loss but data relating to the visual acuity levels following an ION secondary to hypovolaemia are variable.^10–12 A major review of perioperative ION reported a vision of count fingers or worse in 75% of eyes and no perception of light in 53% of eyes.¹¹ In our case, the optic nerve head appearance, visual field defect and visual acuity had remained static over a period of 3 years. In contrast, the Ischaemic Optic Neuropathy Decompression Trial, which studied the natural history of NAION, reported that 43% of patients experienced an improvement of three or more lines of visual acuity at 6 months, with a corresponding 12% who lost three or more lines of visual acuity.¹²

In summary, we report an extremely rare case of bilateral simultaneous symmetric ischaemic optic neuropathy without any significant loss of central visual acuity in association with SCLS. Our case highlights the need to assess visual acuity and visual fields as well as to include the optic nerve in the recognised list of organs at risk in SCLS.

Patient’s perspective.

It was both surprising and distressing to find my vision to be affected during my admission to the intensive care unit for systemic capillary leak syndrome. The clinicians looking after me and myself were surprised to learn that the optic nerve could be affected with this condition as it was not common. Unfortunately, the delay in me getting referred to the ophthalmology department given the nature of my condition at that time had possibly resulted in my vision being permanently affected. This has impacted on my ability to drive despite a reasonable vision in both eyes due to the visual field defects. I would just like to extend my thanks to all the members of staff from Whipps Cross University Hospital for the excellent follow-up care that I received, and the support given. I hope this case would benefit future clinicians when managing patients with systemic capillary leak syndrome.

Learning points.

• Anterior ischaemic optic neuropathy can occur in patient with systemic capillary leak syndrome (SCLS).

• It is prudent for clinicians to include assessment of optic nerve function in the management plan for patients presenting with SCLS.

• Clinicians should have a low threshold of referring patient with SCLS who complains of visual disturbance to the ophthalmology team.