The short version of the evidence
A 2016 review of the published literature found reports of infection with scleral lenses, often in severely compromised corneas, while oxygen-related and inflammatory complications were rarely reported. It also noted problems unique to scleral lenses, such as the conjunctiva bulging into the space under the lens, swelling of the corneal surface layer, midday fogging, and the lens edge pressing on the limbus.[2]
The best single snapshot comes from a US retrospective study of 157 keratoconus eyes that had worn scleral lenses successfully for at least a year:[1]
| Event | Share of eyes[1] |
|---|---|
| Any physiological adverse event | 9.6% |
| Hydrops (sudden swelling from a break in the cornea’s inner layer, part of keratoconus itself) | 3.2% |
| Corneal abrasion | 1.3% |
| Contact lens acute red eye | 1.3% |
| Corneal infiltrates (inflammation spots) | 1.3% |
| Pingueculitis (inflamed bump on the white of the eye) | 1.3% |
| Microbial keratitis (corneal infection) | 0.6% |
| Phlyctenulosis (an inflammatory nodule) | 0.6% |
| Any lens-related event | 55.4% |
| Broken lens | 26.1% |
| Deposits | 8.9% |
| Lens intolerance | 7.6% |
| Reservoir fogging | 7.0% |
| Handling problems | 3.8% |
| Poor wetting | 1.9% |
Two caveats. The study only included eyes that were successfully fitted, and it can’t show which events were caused by the lens rather than by keratoconus. Still, the pattern is clear: problems with the lens itself were far more common than problems with the eye.
In a prospective one-year study of 95 wearers, none of the 26 people who stopped did so because of an adverse event.[3]
Infection
Microbial keratitis, an infection of the cornea, is the most serious risk of any contact lens. Scleral lenses aren’t exempt. Large studies of how often it happens in scleral wearers don’t exist yet; what’s published is mostly case reports and small series.
- In the 157-eye keratoconus study, microbial keratitis occurred in 0.6% of eyes.[1]
- In a series of 31 people wearing scleral lenses after a full-thickness transplant, followed for an average of 5.2 years, two eyes (6%) had an episode of microbial keratitis.[8]
- Acanthamoeba keratitis, a serious corneal infection caused by an amoeba, was reported in three scleral lens wearers with keratoconus. The authors listed possible contributing factors: reduced oxygen and tear exchange, the large volumes of saline used, storing lenses overnight in saline instead of disinfecting solution, not rubbing the lens during cleaning, and the reservoir as a space where organisms could multiply. They recommended sterile, preferably single-use saline, rubbing the lens, cleaning the plunger, and fresh disinfecting solution each night without topping off.[4]
- Three infections in grafted eyes were described in people who also had dry eye or exposure problems and were taking immune-suppressing medicines. The authors noted that several factors, including the lens, may have contributed.[5]
- Case reports describe an infection after poor lens care in a man with neurotrophic keratitis[6] and a microsporidial and bacterial infection in a woman with Sjögren’s syndrome and ocular cicatricial pemphigoid.[7]
The common thread: infections tend to occur in eyes that are already vulnerable, and often alongside a gap in lens care. That’s why the care routine matters. See the daily routine guide.
Corneal swelling and oxygen
A scleral lens and its fluid layer reduce the oxygen reaching the cornea, and the cornea responds by swelling slightly.
- In healthy corneas, a combined modeling and clinical study found that modern lenses with typical fits cause less than 2% swelling during open-eye wear. Closed-eye wear appeared clinically unsafe.[9]
- The thicker the fluid layer, the more swelling, up to a point. In 10 healthy volunteers, average swelling rose from 0.69% with a thin reservoir to 2.11% with a thick one, leveling off at about 600 microns.[10]
- A 2026 meta-analysis of 22 studies (830 eyes) found a small increase in central corneal thickness while the lens was on, about 8 microns, and no significant change after removal.[20]
The concern is greater for eyes whose corneal pump, the inner endothelial layer, is already weak:
- After full-thickness transplant, 9 eyes swelled about three times as much as healthy eyes after a few hours of wear, with more swelling toward the graft edge.[11]
- At one PROSE center, 6 of the 8 eyes that failed treatment had worsening corneal swelling, all in eyes with risk factors for a low endothelial cell count.[13]
- A three-center study of 31 grafted eyes, 90% originally grafted for keratoconus, found lower central endothelial cell density weakly linked to more swelling during lens wear, though all corneas stayed clear.[12]
- Three case reports describe sudden, painful corneal swelling in scleral wearers whose transplants were more than 30 years old. Similar events can happen in old grafts without lenses, but the timing after refitting suggested a possible link.[14]
Graft rejection is also a consideration. In the 31-patient post-transplant series, 30% of eyes had at least one rejection episode during follow-up.[8] That study had no comparison group, so it can’t show whether lens wear changed the risk.
Eye pressure
Researchers have asked whether the landing zone, pressing on the tissue over the eye’s drainage system, could raise pressure inside the eye. Measuring eye pressure with a lens covering the cornea is technically difficult, and a 2023 review called the results conflicting, with most studies short-term and in healthy eyes.[15]
- 2 hours, 29 healthy eyes: no difference in pressure after lens removal.[16]
- First 6 months, 32 new wearers: a slight upward trend of 1 mmHg or less after removal, not statistically or clinically significant.[17]
- 6 hours, 26 healthy adults: one instrument measured an average rise of 2 mmHg during wear; the authors concluded the effect on pressure and the optic nerve was minimal.[18]
- 1 to 2 minutes, 50 young adults: pressure rose in 96% right after insertion, by under 4 mmHg on average, returning to near baseline on removal. The authors couldn’t tell whether this was a true rise or a measurement artifact.[19]
- 2026 meta-analysis: no significant change in pressure measured after lens removal.[20]
The review authors advise ongoing monitoring of optic nerve structure and function in people at risk for glaucoma who need scleral lenses.[15]
Fogging and other everyday problems
Midday fogging, debris clouding the fluid layer, is the most common complaint. Studies have reported it in 26% to 46% of wearers.[21] In a survey where fitters described their most recent established scleral patient, 25.8% of those patients reported it. Fogging was more common in people who also reported redness or irritation, which suggests inflammation may play a part.[23]
In the study of 120 veterans, 55.0% had some difficulty with wear, most often eye irritation (20.0%) and midday fogging or bubbles (15.8%).[24]
For the benefits side of the picture, see scleral lens outcomes research.
Common questions
Are scleral lenses safe?
For most wearers, published studies report few serious problems, and modern high-oxygen materials have reduced many of the complications older scleral lenses caused. But no contact lens is risk-free. Infections have been reported, and some eyes, such as those with corneal transplants, need especially close monitoring.
Can scleral lenses cause an eye infection?
Yes, though published reports are uncommon. In a keratoconus study of 157 eyes, microbial keratitis occurred in 0.6%. Case reports describe infections, including Acanthamoeba, often linked to fragile corneas or to lapses in lens care such as non-sterile saline or not rubbing the lens clean.
Do scleral lenses raise eye pressure?
The evidence is mixed. Several short studies in healthy eyes found no meaningful change after the lens was removed, while others measured small rises during wear. Measuring pressure with the lens on is technically hard. If you have glaucoma or are at risk for it, ask how your optic nerve will be monitored.
Can scleral lenses damage a corneal transplant?
Grafted corneas can swell more under a scleral lens than healthy ones, and case reports describe problems in some long-standing grafts. Many people with transplants wear scleral lenses successfully, but they need careful fitting and regular checks of the graft.
What's the most common problem scleral wearers have?
Everyday lens problems rather than medical ones. In a keratoconus study, broken lenses affected 26.1% of eyes, deposits 8.9%, and reservoir fogging 7.0%. Surveys and reviews put midday fogging at roughly a quarter to nearly half of wearers.