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Measurement of Retinal Vein Calibre as a Proxy of Cavernous Sinus Pressure Using Portable Digital Opthalmoscopy

The inexorable drive of diagnostic equipment towards miniaturisation and accessibility has quickened the pace of high-altitude research, allowing the researcher to collect quality data at low-cost and with relative ease. One area that shows promise is digital retinal imaging. The eye is the one place in the body where you can directly see veins and arteries with your own eyes, and can be used to diagnose a huge number of conditions. Digital fundus imaging is already showing great potential as a form of telemedicine in the remote areas of Africa and Alaska.

Acute Mountain Sickness (AMS), also known as altitude sickness, is an unpleasant condition involving headache, nausea, vomiting and insomnia. It is also linked to High Altitude Cerebral Oedema, a condition where the brain begins to swell, eventually leading to death if the climber is not evacuated. The problem is that doctors don't know yet why some people develop this and some don't. One theory is that the problem lies in the ability of the brain to get the blood out, which backs-up at high altitude, leading to brain swelling. If this is the case then the retina, which drains its blood back into the brain into a big vessel called the cavernous sinus, should also show this increase in pressure. We want to use this effect and see if it is linked to the severity of AMS or the development of cerebral oedema.

For 10 days in July we will be climbing to the Margherita Hut, located in the Italian alps on Monte Rosa at 4,554m above sea level, the highest building in Europe. This will give us a great opportunity to capture as many images of the back of the eye as we can, which we can then analyse for changes associated with AMS and cerebral oedema. The plan is to then present at the World Extreme Medicine Expo later on this year in London.

The Margherita Hut (4,554m), Monte Rosa, Italy   (

The Margherita Hut (4,554m), Monte Rosa, Italy (credit: Andy Slough)