I think REASOMABLE is the key word. Granted, many goals are hard to measure in a quantitative way, but that shouldn't necessarily exlude them--things like self-advocacy, staying on task, responding appropriately, etc.
My funny IEP story--for my middle daughter who had emotional/mental health issues, not albinism, was that she would be on task and respond appropriately to adults and others 100% of the time!! Excuse me, but for a sixth grader? Is there a 6th grader anywhere in the world that is on task and responds appropriately 100% of the time? That would make someone perfect. Fortunately, the principal of the school, who was a former special ed. teacher hinmself and a very, knowledgeable and kind person, agreed completely with me on the unreasonableness of that and convinced them (he always attended the IEP meetings) to modify it, I think they went with 80%. We had a good laugh over that one! Again, this is a goal that is difficult to measure mathematically, but the goal itself and the issue addressed were appropriate and reasonable.
As an adult with albinism, one of the suggestions I have for inclusion in the IEP is adequate keyboard instruction. I know that almost all schools include keyboarding at various points throughout a students school career, but for those of us with low vision, it is a much more necessary skill at a much younger age. Being as old as I am, it was called typing, but I was taught in fourth grade, and not just the cursory treatment most schools give keyboarding in the younger grades now. Particularly if your child has poor handwriting. (OK, so I make typos, it is just because I am too lazy to correct things before I post!) Another is Introduction to various low vision aids, if it hasn't already been done--different magnifiers, monoculars and even screen enlargement software(the last is pricey but free trials are available from the manufacturer--ZoomText offers a 60 day trial). At first try, many peole will say these things aren't helpful for them. I believe it is because the right power hasn't been found, or that in some instances people need to be taught how to use them correctly. Ultimately, though, it is more of an awareness of knowing what is available when you need it, and some never need it. A teacher can't just hand a kid a random magnifying glass and say "Use this, because it is specified in your IEP" It could be the worst magnifier in the world for that child and they may not be aware there are other options.
OK, I ramble. Good luck!
Joni