Your concerns are nothing new. Back in 1986, I went to Satellite Operations Officer training with a captain who'd just transfered to the career field following a tour of duty at Wright-Patterson AFB, OH. His responsibilities there included developing laser eye protection devices for pilots. He told me of an incident a few years before where a soldier had swept a crowded area with an Army laser target designator. Several people were hit in the face but apparently none suffered permanent eye damage. However, their vision was affected for quite some time.

Laser weapons can take several forms. The one everyone thinks of is a laser powerful enough to shoot down a plane or a missile. However, there is a much easier way. You can cause an attacking plane to miss its target and perhaps even crash if you can blind the pilot even for a short period, say 30 seconds. It doesn't take a lot of laser energy to do that, perhaps even less than a watt. As a result of his work, a lot of planes and even some ground vehicles are equipped with laser eye protection devices. Of course, there's always the possibility of increasing the power levels to overload the devices.

You asked the question, The Geneva convention forbids use of blinding weapons- but this really applies only to weapons whose _intent_ is to blind- but what about a weapon that blinds as a side effect?

There are all sorts of weapons that can cause blindness as a side effect, including just about any exploding warhead. Shrapnel blinds a lot of soldiers. Based on that, I don't think laser weapons that are intended for other purposes would be outlawed.