EyeQue Personal Vision Tracker: This great little device is available here http://www.eyeque.com/home from US$29.99 (July 2017)
You can use this device to ascertain your correct eyeglass prescription. Repeated self-tests will make you more and more accurate. Users report it gives as good or better result than their optometrist. It is very handy for on-line ordering eg from http://www.zennioptical.com/ where you can buy a pair of flexible titanium progressive glasses for $US50 or less.
I have been buying my glasses from Zenni for years. The only time I have had a bad result is when the prescription was wrong. This device should allow me to check my optometrist’s prescription before I order. I will still be having a regular eye check up to make sure I am not developing any other eye problems – such as glaucoma, which blinds you before you are aware of it unless you have a regular visual field test and use it to keep track of your visual field index. Be warned. My wife lost more than half her eyesight before her glaucoma was diagnosed.
I have ordered one of these devices and will download the App to go with it.
PS: You can do the same thing with your hearing aids to save even more money.
Here is a good way to prevent you losing your hearing aids in the bush. It has saved me thousands: http://www.theultralighthiker.com/securing-hearing-aids/