Loose Rivets Only too happy to answer your question,as opposed to getting sarcasm from people whose only knowledge seems to be cutting and pasting links.
Normally an opthalmologist would start to treat at a lower power than 'usual' settings.For most retinopathy a start spot size of 200 microns is used and a power of around 100mW and an exposure of 0.1-0.2 secs.What the opthalmologist is first looking for is effect eg a blanching of the sight over the vessel which is leaking and just enough to seal but not overburn on the sight.So by slowly altering the parameters for this effect the operation is carried out.Sometimes upto 2500 shots will be done at one sitting.Originally Argon lasers at 488nM-520nM were used but it was found that it was treated better and less painful for the patient if the blue light was filtered out and the green light component at 514-518nM was used.
Dye lasers at 585nM have been used as some opthalmologists think yellow light is the way to go and in fact the company I used to work for managed this using a Krypton tube with a different high reflector and filter to achieve this 561nM.
Red light can also be used to treat areas of the macula at 657nM.
No longer do diabetics have to go blind thankfully.