Oh, it's worse than that. With an app and a phone with a high-res screen, a simple device[1] (BOM of a few dollars) could give you spherical and cylindrical nu

Oh, it's worse than that. With an app and a phone with a high-res screen, a simple device[1] (BOM of a few dollars) could give you spherical and cylindrical numbers. Nice for the developing world and, err, other nations with impaired health care systems. Of course, MIT patented it, and SV made it into low-order-hundred dollar devices, with mandatory annual per-person subscriptions, but oh well. Looks like there's a current indiegogo, fwiw.[2] Amazon reviews are mixed. At least it's apparently no longer necessary in the US to pretend it's not used to get glasses - yay progress. An optical trial lens set is another option.[3] [1] https://www.eyeque.com/pvt/ https://www.eyeque.com/pvt/ [2] https://www.indiegogo.com/projects/smartphone-vision-tests-order-new-glasses#/ https://www.indiegogo.com/projects/smartphone-vision-tests-o... [3] https://www.amazon.com/s?k=optical+trial+lens+set https://www.amazon.com/s?k=optical+trial+lens+set