46 states do not require optometrists to include pupillary distance on prescriptions, trapping consumers into buying from the prescribing office

Only four US states (Kansas, Massachusetts, Alaska, and New Mexico) mandate that optometrists include pupillary distance (PD) measurements on eyeglass prescriptions, meaning patients in the other 46 states cannot order glasses online without separately obtaining their PD -- a measurement their doctor already took but is not required to share. Why it matters: consumers who want to buy cheaper glasses online from Zenni ($69 median), Warby Parker, or other competitors cannot do so without PD, so they are effectively locked into buying from the prescribing optometrist's in-house optical shop at 3-5x higher prices, so the 164 million Americans who need corrective lenses overpay by hundreds of dollars per purchase, so low-income consumers either buy ill-fitting glasses with self-measured PD or forgo online savings entirely, so the online eyewear market that could provide real price competition remains artificially suppressed. The structural root cause is that optometrists derive 40-60% of practice revenue from optical sales, creating a financial incentive to withhold PD measurements, and state optometry boards -- staffed by practicing optometrists -- set the rules governing what must be included on prescriptions, creating a regulatory capture situation where the regulated parties write their own rules.