The eye test is a retinal screening test where they take an image of your eyes. It is nothing like an eyesight test. First of all they get you to read one of those opticians letter boards at a distance, then they put some drops in your eyes. You then wait about 10 minutes before having the images taken. The images take about a minute. The reason for the drops is to enlarge your pupils so they can get a better view. Sometimes the drops sting a little bit, but nothing horrendous, and with some people it can make your sight a bit blurry for an hour or two (although it never has done with me). It is better if you wear sunglasses if the weather is bright and sunny, and better if you are not driving in case you get the blurriness. All in all about 15 minutes plus any waiting time to be seen. You should get the results by letter withing a few weeks. They usually say 6 weeks, but it has never been as long as that in my case, usually just a couple of weeks.
Well done on your home testing levels. When you say "random" tests, when do you mean? Are you testing before you eat and again a couple of hours later? Random tests taken at any time are a bit meaningless.