D -12 and counting...

Retinal Hemorrhage.

Did you know... about half of all people who venture beyond 5000M above sea level will experience a retinal hemorrhage? Most of these people won't even know they have had one. This is because very few of these small bleeds occur in the macula (central visual field).

Where a bleed occurs in the peripheral retina, it is often not noticed - unless it is painful. The vast majority of bleeds are not painful.

It is important to have a retina scan done after returning from altitude, so any continuing bleeds (rare) can be managed and these will be covered by your travel insurance. If you want to prove it was not there before the visit to altitude, then it is also important to have a scan beforehand.