Optometry today is something like 95% politics. It’s trying to take over, state by state in the US, as much of ophthalmology as it can, while still trying to hang onto measurment of eyes for contact-lens and even spectacle-lens correction of ordinary spherical and cylindrical defocusing over the full distance range of normal eyesight. Contact lenses require data on the shape of the cornea and involve considerable medical concern in their use adjacent to the tissues of the eye; however, spectacle optometry and corrective prescription is just optics-lab optics, together with proper instructions to the client as to how to make the measurements himself.
If optometrists hadn’t arranged state/provincial laws against such, in order to sustain their incomes, many more versions of focus-correcting eyeglasses would be available today in drugstores and supermarkets. As it is, only a few non-astigmatism-correcting, single-vision, plus-lens glasses are grandfathered as OK to sell over the counter. Optometrists, of course, will give you all kinds of stories about how they have to fuss with you, and use all kinds of inefficient routines to get your best-vision prescription or whatever prescript he or you wants. In fact and normative law, they have no business claiming eyeglasses must be sold on prescription, because there are no safety considerations involved in choosing lens powers and other parameters of eyeglasses.
I have experienced, throughout my adult life, continual screw-ups by optometrists and ophthalmologists in getting the proper correction for my simply presbyopic and moderately astigmatic eyes. I have recently spent some time on the Usenet newsgroup sci.med.vision tangling with optometrists and opticians over lots of the nonsense they feed the public.
Yanking these guys’ laws away from them would produce many more OTC eyeglasses variations but not the full range needed to cover all spherical and cylindrical optical correction. However, I claim that something like 90-95% of eyeglass prescriptions could be accomplished today by self-service automatic, non-contact optical instrumentation and that much superior instrumentation for this purpose would be quickly forthcoming, given a free market in this area. I have heard that some years back there were such prescriptions so determined for free, by the customer – in Kowloon, HK, for instance – only on the requirement of ordering the specs from the place having the machine. The only private report on the results such a transaction, which was heard from a customer of this storefront, was full satisfaction; and the transaction, in his case, occurred after his having gotten poor results from optometrists. So the free self-prescription in K-Marts has definitely been feasible for years, given an overhaul of state/provincial and national laws.
The next logical question is how much and what kind of optics would be needed for an optometric accessory for a home PC in order to do the same job. The price on such optical hardware, which would probably involve deformable lenses, is apt be more than most people would be willing to pay. So, the next question is:
Is it not possible to measure simple spherical and/or cylindrical defocusing of the human eye’s lens system by subjective methods alone, employing DSP software on a standard PC with no optics in front of it? Can one not, in the case of a user of a PC who suffers a range of spherical and cylindrical eye defocussing, have him run such software so as to control sophisticated dot patterns on his monitor, viewable one eye at a time; and have him manipulate these patterns by keyboard and mouse in such manner as to end up with some definitive indication on his monitor, such as a clearer pattern of dots, that would inform him that numerical readings, also displayed on the monitor, now provide him with accurate values of the toric optical parameters needed for his eyeglass prescription. If so, such software could have separate additional modes for bifocal and trifocal lenses. Other tests of light sensitivity, color sensation, convergence and field integrity, all presently feasible, could also be included, for pursuing other problems of eye health and functionality.