Investigations by the Hong Kong Civil Aviation Department are underway after two Cathay Pacific pilots lost their vision while flying for the airline. In both cases, the first officers on board safely landed the aircraft.
Investigations are taking place into two cases of sudden sight loss suffered by pilots of commercial planes. According to the Hong Kong Civil Aviation Department (CAD), two captains of Cathay Pacific flights lost their sight in two completely unrelated incidents.
The most recent incident involved an Airbus A350 with 270 passengers on board, which was flying between Perth, Australia and Hong Kong on February 21st this year. While passing over Manilla, the captain complained of breathing difficulties and said his vision was impaired, leaving the first officer to take over control of the aircraft.
The captain was given oxygen and the plane descended to normalize the air pressure on board. The first officer requested priority approach to Hong Kong Airport, where the aircraft was met by paramedic.
The CAD report stated that:
“The condition of the Captain stabilized with the supply of medical oxygen. The Captain remained conscious and in communication with the first office and the senior purser throughout the occurrence, although the Captain was officially designated as incapacitated,”
The second incident took place on January 26th, when the captain of a Boeing 777 carrying 348 passengers from Sapporo to Hong Kong suffered problems with his eyesight. In this case, the captain voluntarily strapped himself into his seat to ‘prevent any possible interruption with the operation of the aircraft’, according to a report.
In both cases, thankfully, the first officers managed to land the aircraft safely, and we understand the vision impairment to be temporary in both pilots.
Can flying cause problems with eyesight?
Although flying is getting safer with every year that passes, placing your body in a metal tube thousands of feet in the air still comes with its risks to health. On older aircraft where humidity is not actively controlled, the environment on board is drier than in the world’s most arid deserts. The recirculated air is pumped in incredibly cold, often at around 10°C, and the pressure is similar to that at the top of an 8,000ft tall mountain.
These combined forces can cause a drop in blood oxygen levels to as low as 6 – 25%. In a hospital, oxygen saturation this low would have the doctors running for the supplementary O2 mask. However, for healthy passengers, it’s usually not a problem, although older people or those with pre-existing conditions may feel some effects.
However, according to the BBC, this hypoxic environment has been shown to have emotional effects on even the healthiest of travelers, making some feel more anxious, stressed or uncomfortable. Hypoxia related fatigue is common, and cognitive deficits can become more noticeable. The only eyesight issue noted, though, is a deterioration in night vision by 5 – 10% at altitudes over 5,000ft.
That doesn’t explain the vision problems encountered by the Cathay pilots, however. As one was complaining of shortness of breath, the blurred vision was likely related to dizziness from the lack of oxygen. The other had no such complaint but could have been suffering with vision issues before boarding the plane.
The dry environment of an aircraft has been shown to exacerbate dry eye symptoms, so if they were suffering prior to the trip, the arid cabin could have made it worse. Similarly, an RAF pilot from the UK lost sight during a training exercise in 2016, which was thought to have been caused by the rapid deterioration of a pre-existing eye infection.
Are the cases linked?
Both cases, while classed as ‘serious’ by the CAD, are rare in occurrence. As they happened on two separate flights and on different types of aircraft, it’s unlikely that they are connected.
As both incidents have been classified as ‘flight crew incapacitation’ and ‘serious incidents’ by CAD, a full investigation will take place to rule out any link between the two. Each investigation is expected to take around 12 months, with the CAD quoted by the South China Morning Post as saying:
“The [authority] will continue to collect and study all relevant information in order to determine the circumstances and causes of the serious incidents. More in-depth investigation and analysis have to be conducted before any conclusion can be drawn.”
As with any airline, Cathay Pacific expect pilots to undergo a full medical every year. Although this would pick up any significant illnesses or impairments, a temporary sickness such as an infection would not be identified. We await to hear the outcome of the investigations.