Discussion

A combination of several clinical findings is highly suggestive of PION. Patients typically present with a sudden and painless loss of vision, usually of one eye, with no light perception and pupils non-reactive to light. They also typically show normal fundus and optic nerve on initial ophthalmoscopy, with optic nerve atrophy in subsequent weeks and months.5 All of these conditions were present in this patient except for the monolateral manifestation.

DKA as a severe complication of diabetes mellitus is rarely associated with an optic nerve atrophy: the first case we found was a 15-year-old diabetic patient who survived DKA, complicated by acute severe encephalopathy, hypopituitarism and atrophy of the optic nerve.6 The next case was an 82-year-old woman who developed bilateral optic neuropathy following a massive gastrointestinal haemorrhage, resulting in myocardial and cerebral infarction and complicated by DKA.7 Another case was a 50-year-old man who lost vision of his right eye after severe DKA and only retained partial vision in his left eye. Bilateral optic atrophy was diagnosed.8 Another case is a 58-year-old man with insulin-dependent diabetes mellitus and myocardial infarction, who was admitted with the diagnosis of acute pancreatitis complicated by sepsis and DKA. Bilateral ischaemic optic neuropathy was diagnosed.9 The most recent case found was a 35-year-old man with DKA who developed rhabdomyolysis, and acute renal and respiratory failure. Bilateral PION was diagnosed.10

The pathogenesis behind non-arteritic and perioperative PION is not completely clear. The central portion of the retrobulbar part of the optic nerve has a very poor vascularisation, which makes it more vulnerable to ischaemia during hypotension.11 Ischaemic optic atrophy after surgery is a rare disease and was only significantly associated with age, male gender and surgery type.12 Bilateral involvement was present in 70% of perioperative cases, and patients’ loss of vision was worse than that in non-arteritic cases.4 Many authors discuss the effects of severe hypotension and anaemia as being the main factors for perioperative PION.13 ,14 Other pathogenic factors described for ischaemic optic neuropathy include use of vasopressors and prolonged cardiopulmonary bypass time in open-heart operations.15

In our case, DKA was accompanied with the need for resuscitation, which leads to severe hypotension. That might be the main cause for the PION, but the use of catecholamines and ECMO might also be important factors.

Patients with non-arteritic PION are older than patients with a perioperative PION. They usually have only one eye affected, and they present with evidence of a systemic vascular disease or vascular disease risk factors, including hypertension, diabetes mellitus, hypercholesterolaemia, cardiac and cerebrovascular disease.4 This patient had no other known risk factors for atherosclerosis than his type 1 diabetes, and no documented diabetic organ manifestation. In synopsis, our patient presented a more typical clinical picture of a patient with perioperative PION than non-arteritic PION. However, to prevent further vascular events, we initiated a prophylactic anticoagulation with low-dose acetylsalicylic acid.

The prognosis depends upon the subtype of PION. Perioperative PION is usually bilateral, severe and irreversible,16 and no effective treatment has been found.17 On the other hand, non-arteritic and arteritic PION is improved by the use of systemic steroid therapy, and there have been cases of spontaneous improvement in vision.17 ,18 The vision of our patient did not improve after the high-dose steroid therapy.