It sounds like when the extra vessels you get with proliferative retinopathy bleed - when I had my bleeds most looked a bit like black blobs / dots at first, which kind of blurred & smeared a bit like ink/oil in water as the blood dissipated. The worst bleed was like a big paint brush smear if blood across my vision. I think the normal treatment is as LeeLee says, 'pan retinal photocoagulation' where they laser the extreme edge to kind of 'switch off' the signal that's triggering the vessels to grow (that's how it was explained to me anyway 🙂 )
The lasering is usually done at a 'slit lamp' table - ie you're sat up, you put your head forward into the chin rest & forehead rest. The laser is a focussed cone so it can't go too deep as it were (sounds daft, but I was worried til I heard that lol)...it's a very bright green light, & the doc will stop the patient blinking by using a great big contact lens which keeps your eye lids open - you do get drops to help with the discomfort of this. As for the lasering itself...it's 'unconfortable' (basically your eye's being kept open whilst dilated & a very bright light fired in after all) & the more you have the less comfortable it is, but it's not unbearable. Taking some paracetemol beforehand might help reduce any post laser headache - tell your friend someone else will need to drive home & dark glasses will be ger friend.
Now for the good news - although lasering is not fun, it IS effective. I think there are some stats on the duk website but it's certainly worth putting up with to save sight. Best of luck & ((((hugs)))) to your friend / her daughter - I know how scary it is hearing that news. Xxxx