Hi there Angie
I'm dithering about whether to write this because I agree entirely with Gareth's summary -- with rare conditions like Keratoconus (and then adding on top not universal events like acute hydrops) it's not, as Tom Jones would say, unusual to find even specialists to come out with comments like "that's at the poor end of the scale" or "that's quite severe" when actually it's probably not at the really, really bad end of the spectrum at all, it's more that the people concerned simply haven't encountered enough patients with our condition to accurately place it in context.
However (you knew there was a "however" coming I'm sure

), it might be worth at least getting your heads collectively around what to do if you're in the position of having to opt for a graft for Charlotte in order to regain usable vision in the affected eye or because the best advice you've received from the professionals is that Charlotte's cornea should not be left as-is. It might, of course, not come to that. The hydrops could heal and leave Charlotte with a scar-free cornea or even if there is scarring, it could be well out of the way of the centre of the eye and only affect peripheral vision slightly. And it is also a possibility that Charlotte's vision may be better post-hydrops than pre-hydrops because the scarring may even improve the geometry of the eye as a happy accident. If I remember correctly someone (might have been Anne) told me that in the dim and distant past, surgeons used to induce hydrops in Keratoconus patients because the outcomes sometimes were that vision improved. It was a desperate measure but there wasn't at the time anything else much to be done.
But, looking on the gloomy side, if a graft is suggested either to improve vision or because the cornea isn't thought to be stable in the long term how do you and Charlotte feel about that step ? It's quite okay in my view to not think at all about it until it happens, because it might not. Alternately, if you and the family want to at least ponder on it then you can (when Charlotte has her consultation with the specialist) have some points to discuss that you've already explored together. The main things to consider for anyone thinking about a graft are:
1) Am I doing it to improve vision or because the thinning of the cornea is such that it's likely to leave a residual risk of further hydops occurrences ? (your ophthalmologist can guide you on this one to a degree, but if vision is very poor, you can certainly consider a graft simply to try and improve the vision)
2) Will I be able to manage the immediate post-operative recovery period (eye patch wearing, not rubbing the eye
no matter what, medication regime (drops for several months), daily hygiene and hospital visits ?
3) Are the risks worth the potential benefits and will the short, medium and long term implications impact quality of life to an acceptable or unacceptable degree ?
As Keratoconus is a medical condition not uncommonly co-existing simultaneously with Down's, it would be great (and not all that unlikely) if the ophthalmologist has some experience with performing grafts on young people with Down's too. Wouldn't hurt to ask if s/he has.
Like I mentioned, I'm a bit conflicted as to whether it is even worth thinking about the possibility of a graft when it might not be required at all. The flip side of that is, if that's the big scary thing which is at the back of everyone's minds anyway, better to bring it out into the open and at least think through the implications consciously. I don't know if Charlotte has ever had to have a major operation and how it affected her... if not, then perhaps some gentle probing might elicit an initial reaction. If it's a big resounding "no way !" I've a hunch she'll let you know
Best wishes
Chris