If your having to have biscuits between meals to keep your bg levels up then it could be that your basal insulin needs adjusting.
Regards to your vision, book an eye appointment and have them checked, sometimes cataracts develop as we get older which can cloud vision, either that or wait until your next retinopathy check.
Maybe aim for 5 -9 or 5 - 8.5mmol/l and see if that makes any difference vision wise, by injecting ahead of your food you can reduce the postprandial spikes.