It will really depend on which clinic they'll be sending you to. In my case, the nurse's and doctor's level of english was quite good and I had no problem communicating with them. I cannot speak for other clinics though, but I'll take a look at my screening documents and PM you the clinics contact number if I find these. Give me one or two days for that. Again, if you want the direct link to the JCAB's medical standards (in Japanese) PM me your email and I'll send you the translated version of the eye/vision requirements as well.
Upspeed.