What the research shows
No study can tell you your personal risk, but several give a sense of how often problems happen.
A large practitioner survey. Scleral lens fitters estimated what happened over one year among the 72,605 scleral lens wearers they saw. Wearers stopped because of corneal complications at these rates: corneal swelling (edema) 1.2%, new blood vessel growth into the cornea 0.53%, microbial keratitis (a corneal infection) 0.45%, and limbal stem cell deficiency 0.20%.[2] These are fitters’ estimates, not medical records, and they count only problems serious enough to stop wear.
A keratoconus study. A review of 157 eyes in 86 people with keratoconus, all of whom had worn scleral lenses successfully for at least a year, found that 9.6% of eyes had a physiological adverse event. Most were uncommon individually: microbial keratitis occurred in 0.6% of eyes, and corneal hydrops, a keratoconus complication, in 3.2%.[1] Lens problems were more frequent but mostly practical: broken lenses (26.1% of eyes), deposits (8.9%), and fogging (7.0%).[1] Because it included only successful wearers from one clinic, it doesn’t capture people who stopped early.
A year-long study of 95 wearers. Of the 27% who stopped during the year, none stopped because of an adverse event.[3]
Taken together: serious complications are uncommon in these studies, but they happen, and infection is the one that matters most.
Infection: the risk to take seriously
Any contact lens can lead to an eye infection. The FDA notes that contact lens wear carries a risk of serious infections and corneal ulcers, which can develop quickly and, in rare cases, cause blindness.[4]
Scleral lenses have some features worth knowing about. A report of three cases of Acanthamoeba keratitis, a hard-to-treat corneal infection, in scleral lens wearers with keratoconus listed possible risk factors: the large volume of saline involved, storing lenses overnight in saline instead of a disinfecting solution, not rubbing lenses during cleaning, and the fluid reservoir behind the lens.[5]
The stakes are higher for some people: those with only one working eye, and those with a corneal transplant. In a case series of three scleral lens wearers who developed infections after a full-thickness corneal transplant, all three also had ocular surface disease and were on medicines that suppress the immune system.[6] If either applies to you, have a specific conversation about risk with your eye doctor.
Oxygen, and why you never sleep in them
Your cornea gets oxygen from the air and the tears. A scleral lens covers the whole cornea, and because it’s large, little fresh tear fluid moves underneath it. The Acanthamoeba report lists reduced oxygen to the cornea as one possible risk factor.[5] Of the four corneal complications in the practitioner survey above, swelling was the most common reason wearers stopped.[2]
Closing your eyes over a lens cuts oxygen further. Across contact lenses in general, sleeping in lenses raises the risk of eye infection six- to eightfold, and even occasional overnight wear carries risk.[7] That’s why the rule is simple: never sleep in scleral lenses, not even a nap.
The habits that make the biggest difference
Most of the risk you can control comes down to a few habits:
- No water, ever. Keep tap, bottled, distilled, pool, lake, and ocean water off your lenses and out of your case. Remove lenses before swimming.[4]
- Sterile saline only, fresh each time. Fill with sterile, preservative-free saline, ideally from a single-use vial, and never reuse it.[5]
- Rub, don’t just soak. Rub and rinse your lenses as your fitter directs, and clean your plunger too.[5][4]
- Fresh solution in the case every night. Never top off old solution.[4]
- Let peroxide finish. If you use a hydrogen peroxide system such as Clear Care, leave lenses in for at least 6 hours or overnight, and never rinse a lens with it before insertion.[8]
- Replace your case every 3 months, or as your eye doctor directs.[4]
- Follow your wearing schedule and keep your follow-up visits, even when everything feels fine.
The full routine is in the scleral lens daily routine.
Warning signs
The FDA lists these as symptoms of eye irritation or infection: discomfort, excess tearing or discharge, unusual sensitivity to light, itching, burning or a gritty feeling, unusual redness, blurred vision, swelling, and pain. If you notice them, remove your lenses and contact your eye care professional. Keep the lenses in their case, since your doctor may want to examine them.[4]
Common questions
Can I take a nap in my scleral lenses?
No. Remove them before any sleep, including a short nap. Sleeping in contact lenses raises the risk of eye infection, and even occasional overnight wear carries risk. If you're likely to doze off, take the lenses out first.
Do scleral lenses get enough oxygen to the eye?
Scleral lenses are made from gas-permeable materials, but because they're large and little tear fluid moves under them, oxygen to the cornea is something fitters pay attention to. In a large practitioner survey, corneal swelling was the most common of the four corneal complications it asked about that led wearers to stop. Follow your wearing schedule and keep your follow-up visits so your fitter can check.
Can I shower or swim in scleral lenses?
Keep all water away from your lenses: tap, bottled, distilled, pool, hot tub, lake, and ocean. Remove your lenses before swimming. If water gets on a lens, remove it, clean and disinfect it as your fitter has shown you, and call if your eye becomes red or painful.
Are scleral lenses riskier if I've had a corneal transplant?
The stakes can be higher. In a small case series of infections in scleral lens wearers after a transplant, all three people also had ocular surface disease and took medicines that suppress the immune system. That doesn't rule out scleral lenses, but it's a decision to make carefully with your eye doctor.
What should I do if I think I have an infection?
Take the lens out and don't put it back in. Call your eye doctor the same day. Keep the lens in its case rather than throwing it away, because your doctor may want to examine it.