PfcAJ
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It takes a ridiculous amount of diving for that to happen.
Hyperoxic myopia in a closed-circuit mix... [Undersea Hyperb Med. 1999] - PubMed - NCBI
18 days, 4hrs of dive time/ day (avg) with a ppo2 of 1.3. Thats a lot.
Super Long Shallow Water Diving
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It takes a ridiculous amount of diving for that to happen.
Hyperoxic myopia in a closed-circuit mix... [Undersea Hyperb Med. 1999] - PubMed - NCBI
18 days, 4hrs of dive time/ day (avg) with a ppo2 of 1.3. Thats a lot.
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ermaclob
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Not so much... Sandra and several of the other macro photographers are at the bridge 4 times per week, sometimes for several in a row. Three to 4 hour dives, with 36 to 38 percent mix, was what Sandra had been doing, when she got her hyperoxic myopia incident...
Even though it resolved in 48 hours, it is an indication that it is not ideal to use Nitrox on long duration shallow dives, particularly if you dive often at a place like BHB.
For shallow dives, air costs less, air causes less free radical formation than 38% Nitrox, and air is NOT going to cause the myopia.
We went to Nitrox for boat dives to extend allowable bottom time without going into deco, and or, shortening the surface interval so the dive boats could run more efficient trips ( two or more trips per day). For the BHB, none of this is of any value.
I put on twin steel 130s and an AL80 stage (for a whopping 340 cubic feet of gas) and then I go play for a few hours at 20 feet in my local reservoir.
Here in the mountains there really isn't that much opportunity for good diving, so I get what I can. There's nothing but mud and tree stumps, so it's not very interesting. Below 30 feet there is a pronounced thermocline and the temperature drops into the 40s. Below 60 feet it is totally dark. And the viz is about 12 inches, so it doesn't make sense to go with a buddy.
Generally I just do a lot of drills for those 2 to 3 hours. I practice regulator removal & replacement, buoyancy drills, mask-off drills, stage bottle procedures, kicks, laying cave line, etc., etc.
Lost-line drills can really eat up a lot of time, but they have really increased my confidence. This visibility is pretty poor anyway, and it gets worse after I've stirred up the muddy bottom. After setting my main line, I close my eyes, spin around and loop a few times, swim away for a bit, then settle on the bottom for a lost line drill. The viz really goes to zero after I've mucked around for a while. I can eat up 2 hours just doing lost-line drills.
Occasionally I get really bored and I head out into the deeps. The reservoir is over 300 feet deep. Sometimes the viz gets better at depth, sometimes worse. On one trip into the deeps the viz dropped to about 2 inches, just enough to see your gauges if you held them up to your mask. Of course, it was totally dark anyway. I finger-walked slowly along the bottom for reference. At 120 feet I ran into a vertical drop-off. My heart was thumping, I tell you! I popped over the drop and headed down for a while. It was really cold and I began to wish that I had my 400gm Thinsulate and dry gloves. My hands got too cold and painful, so I called it quits. Sometimes I carry 50% instead of 32 for deco, I think on this day I had 50%. I did my stops on the way back up the warm water at 20 feet.
I have found that I am most often limited by cold, hunger and hypoglycemia more than anyting else. I carry some Gu packets now, and try to over-dress a bit. If I get too warm at 20 feet then I can always drop down below the thermocline for a while.
In Mexico, I've done 2-1/2 hour cave dives with twin AL80s and an AL80 stage because the caves are so shallow.
Here in the mountains there really isn't that much opportunity for good diving, so I get what I can. There's nothing but mud and tree stumps, so it's not very interesting. Below 30 feet there is a pronounced thermocline and the temperature drops into the 40s. Below 60 feet it is totally dark. And the viz is about 12 inches, so it doesn't make sense to go with a buddy.
Generally I just do a lot of drills for those 2 to 3 hours. I practice regulator removal & replacement, buoyancy drills, mask-off drills, stage bottle procedures, kicks, laying cave line, etc., etc.
Lost-line drills can really eat up a lot of time, but they have really increased my confidence. This visibility is pretty poor anyway, and it gets worse after I've stirred up the muddy bottom. After setting my main line, I close my eyes, spin around and loop a few times, swim away for a bit, then settle on the bottom for a lost line drill. The viz really goes to zero after I've mucked around for a while. I can eat up 2 hours just doing lost-line drills.
Occasionally I get really bored and I head out into the deeps. The reservoir is over 300 feet deep. Sometimes the viz gets better at depth, sometimes worse. On one trip into the deeps the viz dropped to about 2 inches, just enough to see your gauges if you held them up to your mask. Of course, it was totally dark anyway. I finger-walked slowly along the bottom for reference. At 120 feet I ran into a vertical drop-off. My heart was thumping, I tell you! I popped over the drop and headed down for a while. It was really cold and I began to wish that I had my 400gm Thinsulate and dry gloves. My hands got too cold and painful, so I called it quits. Sometimes I carry 50% instead of 32 for deco, I think on this day I had 50%. I did my stops on the way back up the warm water at 20 feet.
I have found that I am most often limited by cold, hunger and hypoglycemia more than anyting else. I carry some Gu packets now, and try to over-dress a bit. If I get too warm at 20 feet then I can always drop down below the thermocline for a while.
In Mexico, I've done 2-1/2 hour cave dives with twin AL80s and an AL80 stage because the caves are so shallow.
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Scubagolf
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