Acetazolamide

Okay, so after my last experience with altitude I thought I would get prepared for the next time I went that high. I recently took a trip around Tibet, where the majority of the travel was above 4000m and the highest point was at Mt Quomolonga (Mt Everest) base camp at 5200m.

Before leaving Lhasa I thought I would try to track down some Acetazolamide (trade name Diamox), which works to lessen the severity of AMS through allowing hyperventilation and hence increasing the oxygenation of the blood. I checked many pharmacies all over Lhasa before being directed to the Peoples Hospital, where I managed to purchase a bottle of 100 tablets for 14 RMB. The reason I made the effort to get the tablets was that there was a nights sleep planned at the Rhongphu Monastery guesthouse, Wikipedia says that its at 5200m, however while we were there someones altimeter watch said it was around 5000m. Either way, its damn high. Sleeping at altitude is very difficult, and I didn't want a repeat of my last altitude experience.

I should mention that I have actually tried Diamox before, while I was sick up at Namtso. I didn't mention it in the last post, but one of the people I was with gave me a few tablets which I swallowed with no immediate effect. This makes sense of course, as Diamox takes 6 - 12 hours to become effective. The one thing I did notice was the side effects the next day, my face tingled intensely for half a day.

The first half of the trip involved sleeping around 4000 meters, and that all seemed to be okay. I was a little short of breath while exerting myself, but nothing too serious. Then we got to Shigar.

Shigar is a picturesque Tibetan town in the shadow of a monastery and ruined hill fort, after leaving our bags at a guesthouse we decided to check out said monastery and ruined hill fort. (see left for monastery and right for hill fort)

The town is at 4400 meters, and the top of the fort was about 300 meters above the town. It was very hard work getting to the top, out of 8 of us that attempted it, me and 2 others made it. It was probably a bad idea but the view was fantastic.

In the evening I started to feel a little ill, a familiar altitude headache was coming on. I think I made the same mistake as I did at Lake Karakul, by going up high then climbing higher. Given that the day after we had planned to go to Everest base camp, I decided to start taking the Diamox. I felt pretty average in the night, and at one point my oxygen starved brain thought there was a small Tibetan child hanging from the roof of our dormitory (it was a jacket).

I expected to wake up with a tingling face, as that was a side effect I had experienced before. I also expected to wake up with my vision intact. That was not the case. As soon as I woke I found that the whole room was blurry. I rubbed my eyes a few times to no avail, I couldn't see more than a foot in front of me clearly. I could only read text if it was a few inches from my eyes and as for seeing into the distance, forget it. I had read somewhere that blurred vision was a possible side effect of Diamox so I wasn't totally freaking out, however since I had hoped to see Everest that afternoon I was a little concerned. We had a 5 hour bus trip up to Rhongphu Monastery and Everest base camp, in which I spent the beginning vainly attempting to discern the scenery we were passing through. One of the women on the bus offered me her prescription glasses saying they were a 3.5 correction factor, whatever that means. I tried the glasses, and to my amazement everything suddenly regained sharp focus. Praise the lord, I could see!

The mountains and valleys that had been just coloured shapes now had texture and contours, and I didn't have to guess who people were by their general body shape and clothing colour.

The woman in question was wearing contact lenses, so I borrowed her glasses for the day. It would have looked quite amusing, me wearing narrow euro-style women's glasses, but for clear vision it was worth the price. I used the glasses several times during the bus trip to see various sights of merit, but I didn't keep them on continuously as I didn't know if they would adversely affect my vision in the long term.

My vision slowly recovered over the day, to the point where I could see Everest without the glasses in the afternoon. (Everest image below)

The real proof my vision had returned was that in the evening wearing the glasses made everything blurred. I had a decent nights sleep, and the next day stopped taking the Diamox.

It was a very interesting experience having impaired vision, especially as it seemed to mimic the common sight disorder of myopia. It only lasted 6 hours or so, however I really noticed how much lack of sight affected my life. I couldn't read signs or tell the time. It would have been interesting (albeit annoying) if the side effects had lasted for longer, so I could have seen how I adapted to blurred living.