* Spill. A hiker, spelunker or whatever uses both his peripheral vision as well as being focused on what is ahead. This is why most flashlights and headlights, aside from the bright spot, also have a lot of light that spills over. A surgeon does not use his peripheral vision much. If he is using loupes, he cant use his peripheral vision becuase he is totally concentrated on what is within the field of view of the loupe. The ideal surgical headlamp must have a very concentrated cone of light focused a handlength away, with little or no spill. Spilled light just wastes energy.
* Comfort. A surgical headlight must be utterly comfortable. I've used headlights that cause headaches when used for a long time unless you move it around. Surgeons can be wearing the headlight for hours so it has to be utterly comfortable. A surgeon cannot adjust the headlight by himself because he is sterile so there better be no pressure points that can cause pain and skin ulcers.
* Tilt adjustment. The led lenser headlights are notorious for this. The hinge has ratchets so the tilt can only be adjusted to a certain number of angles. If you are not wearing loupes you can just tilt your eyeballs up or down so that your field of vision conicides with the focus of the light. If you are wearing loupes you cant do that. A work around is to move the headlamp up or down on the forehead. And the light better stay pointed where it is set. A surgeon can't easily adjust a headlamp once he is sterile.
* Coaxiality. If you're a hiker it doesnt matter if your light is a meter away from your eyes. You can still see. If however you are looking down a small pipe, then you need the light to be near your eyes. Most surgical lights have the emitter in between or maybe slightly above the line of sight
* Intensity. For a hiker, most likely it would be night time so even a weak light will help. A surgeon using a headlamp already has the operating light shining on the patient so his pupils will be already contracted. So the intensity needs to be high. Photographers would be familiar with this. Try photographing the contents of a tin can in bright sunlight without a flash, with the interior of the can in shadow. Thats what surgeons deal with all the time. Plus loupes tend to decrease the aparrent light intensity. However there are times when a weak headlight will work. These include office or bedside procedures or surgeries where the surgical light is focused on some other part of the body, as long as the headlamp does not have to fight against an operating room light. Of course you could just turn down the operating room light. But then your assistan and the nurses cant see anything unless you get them their own lights.
* Switch. A surgical headlamp ideally would have a switch that the surgeon can turn on and off without breaking sterility. You can macgyver this by installing a switch at say belt level. Just press the switch through your sterile gown.
* Modes. Most often you only need 2 modes, OFF and MAXIMUM. A normal user would maybe need other modes like flashing or low modes.
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