A study was published that looked at the safety and accuracy of glasses ordered online - including children's glasses: "Safety and compliance of prescription spectacles ordered by the public via the Internet", by Karl Citek, published in Optometry, vol. 82, iss. 9, pages 549-555, Sept 2011.
The full text of the article is available here.
The study found that nearly half of the glasses ordered were either the wrong prescription, the wrong lens style, or the lenses failed impact testing. In many cases, eyewear was shipped with features the purchaser did not want or without features the purchaser ordered.
Overall, the study found that nearly half of all glasses they ordered online had a problem, either with the prescription being wrong, the lens type (single vision vs. bifocal) being wrong, or with the lenses not passing impact resistance testing -- and that problem existed regardless of the cost of those glasses online. Probably the most disturbing finding of the study was that in 25% of the glasses for children, the lenses failed impact testing. Given how active kids can be, it's extremely important for our children's glasses to not shatter on impact. The study did find that all of the polycarbonate lenses that were ordered did pass the impact resistance testing. Some of the children's glasses also had incorrect prescriptions.
A couple of interesting pieces from that study include the fact that the rate of problems with prescription errors was similar to the error rate at traditional optical labs, it's just that when you order glasses through a traditional optical dispensary, there are additional checkpoints, and nearly all the problems have been caught and corrected before the glasses even make it to the dispensary. In this manner, the active, personal, "hands-on", dispensing process could protect the patient from spectacles that might not meet applicable requirements.
We believe that the dispensing process remains a vital and necessary step in the manufacture and delivery of eyewear to best ensure the health and safety of patients who wear spectacles. Ordering glasses online, without the benefit of this dispensing process, can come with a significant risk of error in providing the correct type of lenses needed or ordered.