Outpatient records and imaging collected over 9 years in three hospitals were reviewed to gain a detailed history. Bilateral background diabetic retinopathy had first been detected 9 years earlier. Five years earlier visual acuity (VA) fell to 6/9 bilaterally, with evidence of bilateral macular oedema, which was treated with bilateral focal argon laser therapy following fundus fluorescein angiography (fig 1). This resulted in improvement of the right eye’s VA to 6/6, but had no impact on the left eye, which gradually deteriorated over 12 months to counting fingers vision. Later that year the patient presented with a 5 day history of reduced right VA (6/24), and bilateral fullness of the optic discs was noted, with dilation of superficial disc capillaries. Elevated intracranial pressure was not suspected, but he was empirically commenced on the carbonic anhydrase inhibitor acetazolamide, 250 mg daily, perhaps to improve perfusion of the swollen discs through reduction of aqueous production and lowering of intraocular pressure. During the following month the right VA normalised, and the dose was reduced to 125 mg.

At follow-up the next year, the right VA was 6/7.5 and the left VA had improved slightly to 3/60. He received multiple focal argon laser treatments to both eyes, the left in particular, for active diabetic maculopathy. Pronounced disc swelling persisted bilaterally, so the acetazolamide was increased again to 250 mg, and a computed tomography (CT) scan of the head and orbits without contrast was performed to exclude intracranial pathology. This was reported as normal, along with subsequent magnetic resonance imaging (MRI) of the head and a Doppler ultrasound study of the carotid arteries. Lumbar puncture was not performed.

At routine follow-up the next year (3 years before referral to our hospital), the right VA had deteriorated to 6/12, despite no increase in maculopathy, and increased swelling and pallor of the right disc was noted. The cause of this deterioration was uncertain, but non-arteritic ischaemic optic neuropathy or diabetic papillopathy were suspected, and the acetazolamide dose was further increased to 250 mg twice daily. Over the next 12 months the right VA fluctuated around 6/12 and 6/18. At the patient’s request, repeat trials of tapered systemic prednisolone were tried, followed by repeat intraorbital triamcinolone (40 mg), and then a 3 month trial of hyperbaric oxygen therapy, though the rationale for these is unclear: systemic steroids frequently worsen glycaemic control and can precipitate intracranial hypertension on withdrawal, among other side effects. The right eye vision continued to deteriorate to 6/60.

Four months before admission, bilateral disc pallor and swelling were noted, with a left relative afferent pupillary defect, and visual acuities of 1/60 on the right, and ‘hand movements’ on the left. Around this time, the patient discontinued acetazolamide, after 4 years, as he felt it was not helping. Two months before admission his vision had further deteriorated, to no perception of light in the left eye, and light perception only in the right. On admission he had no perception of light in either eye. No previous visual field records were available for review.

The patient volunteered no associated symptoms, but on direct questioning admitted to neck ache on waking most mornings for several months, which he attributed to his pillow and poor sleeping position. He admitted a long history of snoring, and more recent daytime somnolence. He had been overweight for many years, and had recently gained further weight. There were no other symptoms.

In addition to well controlled type 2 diabetes and hypertension, his previous medical history included tooth extraction 30 years earlier, complicated by an oro-maxillary sinus communication and recurrent sinusitis until a repair operation and nasal septoplasty 7 years later. He was otherwise fit and well. His regular medications included sertraline, aspirin, doxazosin, valsartan, rosiglitazone, glimepiride, metformin, alpha lipoic acid and ginkobiloba. He had no allergies, and there was no family history of note. He had worked with computers until 18 months previously, when declining vision in his better eye forced him to retire. He lived alone, managing with help from neighbours. He was an ex-smoker with a 15 pack-year history, and consumed approximately 14 units of alcohol per week.

General examination revealed a body mass index (BMI) of 31 kg/m², but was otherwise unremarkable. Ophthalmic examination showed a mild convergent squint, and reduced VA to no perception of light bilaterally. The pupil reactions were absent to light and present to accommodation. Digital colour photographs of the fundi are shown in ​infigsfigs 2 and 3. The intraocular pressures were normal.