Feeling nervous about my Cataract operation

I went on 21st June to see the Consultant, but they couldn't do the biometry measurement (whatever that is) that day, as someone was using the room where the equipment is housed, I now have to go for that on 17th July.  I asked how long the waiting list was, he said realistically, he wouldn't be able to do it before September, so I  told him that I could go in at short notice if someone cancels, so I'm hoping they have recorded that.