Benign idiopathic haemorrhagic retinotherapy

Sir,

In their recent paper, Baker and Grey described five cases of benign ‘idiopathic’ haemorrhagic retinopathy.¹ I would argue, however, that Case 2 is almost certainly suffering from altitude retinopathy. The 44-year-old woman described had 2 days previously flown in a pressurized aircraft from Australia. The authors dismiss altitude retinopathy because altitude sickness ‘does not occur in pressurized aircraft’ and does not have a ‘delayed onset’. In fact, cabin pressures in commercial aircraft are usually equivalent to 9000 ft, representing a fall in inspired pO₂ of 30%.² The mild anaemia of Case 2 and the long duration of flight may have made her particularly susceptible to this hypoxia. Also altitude retinopathy has been shown to occur in the absence of altitude sickness in a prospective study analysing these conditions independently at altitude.³ Moreover, in Case 2 most of the retinal haemorrhages shown were centred on the optic disc and orientated in the nerve fibre layer. The published fluorescein angiogram showed mild venous dilatation but no disc leakage. These features are entirely consistent with altitude retinopathy and a fluorescein angiogram of a climber taken 5 days after descent from Mount Everest is shown for comparison (Figure 1). This climber also had no symptoms of altitude sickness and the haemorrhages cleared without long-term sequellae.

Figure 1

Altitude retinopathy: a late phase right fundus fluorescein angiogram of a mountaineer taken 5 days after descent from 7500 m. Haemorrhages are seen orientated in the nerve fibre layer. There is mild venous dilatation, but a normal capillary network and no sign of disc oedema.

Altitude retinopathy is a poorly understood condition, due in part to the remoteness at which it usually occurs and the difficulties in performing invasive ophthalmological tests at altitude. It may be that the authors need to be congratulated for the first reported case following travel in a commercial jet aircraft.