What is the risk of laser eye treatment?

Impaired vision. Lasik surgery can result in inadequate or over correction which may require additional procedures. If correct for distance vision you may still need correction for near vision. You may have problems with visual accuracy in low light. Your vision may be permanently impaired by complications of surgery or equipment. Other standard risks include infection and scarring.
Varies. There are many lasers that we use in ophthalmology, including some for the front part of the eye for glaucoma, for refractive surgery, after cataract surgery, etc. As well as others that we use in the back of the eye (ie. Retina). The risks will vary depending on which type of laser. Your eye doctor will be able to fully explain the risks before performing any laser eye treatment.
Too vague. Lasik? For diabetes/glaucoma? For lasik, it depends a lot on how much astigmatism, how thin your cornea, how myopic you are. Risk of blindness, or dry eye, or glare/halos etc.? You need to speak to the surgeon and then get a 2nd opinion- this forum is not ideal.
Many but unlikely. There are many (usually minimal) risks. For a full discussion of this- go to my website www.Contieyecare.Eyemd.Org.