Orthokeratology is considered safe for both children and adults, with serious complications occurring at rates comparable to regular daily-wear soft contact lenses. In the largest study to date on the topic, involving 1,438 patients tracked over thousands of patient-years, the rate of serious eye infection was 5.4 per 10,000 patient-years. That’s roughly a 0.05% chance in any given year. The risks are real but low, and they drop further when you follow proper lens hygiene.
How Common Are Serious Infections?
The biggest concern with any overnight contact lens is microbial keratitis, a bacterial or parasitic infection of the cornea that can threaten vision if untreated. A multicenter study of 1,438 ortho-k wearers (average age 12.7, average wear time 5.2 years) found just four cases of microbial keratitis across 7,415 total patient-years of lens wear. That translates to an incidence of 5.4 per 10,000 patient-years, a rate the researchers described as comparable to or slightly lower than that of daily-wear soft contact lenses.
A separate 18-year follow-up study found zero cases of microbial keratitis in children, with only one case occurring in an adult wearer (6.8 per 10,000 patient-years). So while the risk isn’t zero, it’s in the same ballpark as the lenses millions of people already wear every day.
Minor Side Effects Are More Common
The most frequent complication is corneal staining, which refers to small areas of surface damage on the cornea visible under a special dye. Corneal staining is typically mild and resolves on its own or with a brief pause in lens wear. It occurs more often in adults than children and is more likely in people with higher prescriptions.
Long-term ortho-k use can also cause a faint iron-colored ring or arc on the cornea, a deposit that becomes more common the longer you wear the lenses. Some wearers develop more visible fine white lines on the cornea, thought to be nerve fibers becoming more apparent. Both of these findings are considered clinically insignificant, meaning they don’t affect your vision or eye health. Temporary changes in corneal stiffness have also been measured in studies but resolve after discontinuing treatment.
Safety in Children
Most ortho-k patients today are children, since the primary appeal is slowing the progression of nearsightedness during the years when eyes are still growing. The safety data for kids is reassuring. In the 18-year follow-up study, 65.7% of children experienced no complications at all, compared to 55.4% of adults. Children also had lower rates of corneal staining. The dropout rate during the first year was 17.2% for children versus 33% for adults, suggesting kids generally tolerate the lenses well.
Ortho-k lenses can slow the elongation of the eyeball (the physical change behind worsening nearsightedness) by roughly 70% over 12 months compared to regular glasses. That meaningful reduction in myopia progression is the main reason eye care professionals recommend ortho-k for children despite the small infection risk that comes with any contact lens worn overnight.
How Ortho-K Compares to Other Lenses
A systematic review and meta-analysis found that ortho-k wearers were up to 3.8 times more likely to experience an adverse event than conventional contact lens wearers. That sounds alarming, but context matters. The “adverse events” counted in these studies include minor corneal staining, not just serious infections. When you look specifically at microbial keratitis, the rates between ortho-k and daily soft lenses are similar. The higher overall adverse event rate reflects the fact that reshaping the cornea overnight is inherently more mechanically demanding than simply wearing a lens during the day.
Compared to people who wear no contact lenses at all (just glasses), ortho-k wearers had about 9.4 times more adverse events. Again, this is expected. Any contact lens introduces risk that glasses don’t.
Hygiene Habits That Prevent Problems
The single most important thing you can do to stay safe with ortho-k lenses is keep them away from water. Nearly 85% of Acanthamoeba keratitis cases (a particularly serious parasitic infection) occur in contact lens wearers, and the primary risk factor is exposing lenses to water. That includes tap water, pool water, hot tub water, and homemade saline. There are documented cases, including in children, where rinsing or storing ortho-k lenses with tap water led to Acanthamoeba infection.
Tap water harbors bacteria that stick to lens storage cases and form biofilms. Rinsing your case with tap water increases contamination with several species of harmful bacteria. To minimize risk:
- Never rinse lenses or cases with tap water. Use only the recommended lens care solution.
- Replace care solution daily. Don’t top off old solution in the case.
- Keep the storage case clean and replace it regularly.
- Wash and dry your hands before handling lenses.
Who Should Not Wear Ortho-K Lenses
Ortho-k isn’t appropriate for everyone. You’re generally not a candidate if you have dry eye disease, keratoconus (a condition where the cornea thins and bulges), corneal dystrophies or other corneal diseases, or moderate to severe allergic conjunctivitis. People who can’t commit to regular follow-up appointments or consistent hygiene routines are also poor candidates, since compliance is a major factor in staying safe.
Prescription limits also apply. FDA-cleared ortho-k lenses can correct up to 6.00 diopters of nearsightedness and up to 1.75 diopters of astigmatism. Higher prescriptions fall outside the approved range.
What Follow-Up Looks Like
Ortho-k requires more frequent eye exams than glasses or standard contact lenses. Your eye care provider will check the front surface of your eye at every visit, looking for corneal staining, signs of infection, and proper lens fit. The back of the eye is typically examined annually. The exact schedule of visits varies depending on how your eyes respond, but expect more frequent appointments in the first few months as the fit is dialed in, then periodic checkups after that. The American Optometric Association notes that “with adequate follow-up care, orthokeratology is a safe and effective procedure,” underscoring that ongoing monitoring is part of what makes it work safely.