A scleral lens never touches your cornea. It vaults over it entirely and rests on the white of the eye, holding a reservoir of sterile saline underneath. That single design choice is why they work for eyes that no other lens can fit — and why they are often more comfortable than a small rigid lens despite being much larger.
How they work
A scleral lens is rigid and gas permeable, but far wider than a corneal RGP — typically 14 to 20 mm, so it lands on the sclera rather than the cornea.
The space between lens and cornea is filled with preservative-free sterile saline before insertion. That fluid does two things:
- It creates a new, perfectly smooth optical surface, neutralising whatever irregularity your cornea has
- It keeps the cornea continuously bathed all day, which is why they help in severe dry eye
Because the sclera has far less sensation than the cornea, many people find them comfortable almost immediately — a genuine surprise given the size.
Who they are for
- Keratoconus and pellucid marginal degeneration
- Post-surgical corneas — after transplant, RK, or complicated LASIK
- Corneal scarring from injury or infection
- Severe dry eye, including Sjögren’s and graft-versus-host disease, where the fluid reservoir is the treatment
- High or irregular astigmatism that nothing else stabilises
- Anyone who cannot tolerate a corneal rigid lens
They can also carry multifocal optics for presbyopia, which matters for people who need both.
Insertion and removal
Different enough to need learning properly.
In: fill the bowl to the brim with preservative-free saline, lean forward so your face is parallel to the floor, and bring the lens straight up to the eye with a plunger or a tripod of fingers. Looking straight down is what stops the fluid escaping.
A bubble means starting again. Trapped air blurs vision and leaves a dry patch of cornea underneath. It is not something to tolerate.
Out: break the seal first — press the lower lid margin up under the bottom edge to admit air — then apply the removal plunger to the lower third of the lens, never the centre.
The saline rule
This is the one non-negotiable. The filling solution must be preservative-free sterile saline, because it sits against your cornea for the whole day.
Never tap water, never distilled water, never homemade saline, never a preserved solution. The sterility requirement here is stricter than anywhere else in contact lens wear — see contacts and water and solutions compared.
What to expect from the fitting
Longer and more involved than any other lens fitting, usually several appointments. The fitter is assessing corneal clearance, how the edge lands on the sclera, and whether the lens settles through the day.
Many sclerals are made to order from corneal topography or a scan, which is why they cost considerably more upfront. They also last well — often a year or more — and for medically necessary indications may be covered far more generously than elective lenses. Check the criteria in medically necessary contact lenses; keratoconus and post-surgical corneas frequently qualify.
Midday fogging and settling
Two things worth knowing in advance rather than discovering:
Midday fogging — debris accumulating in the reservoir, blurring vision after some hours. Usually fixed by removing, rinsing and refilling. If it happens daily, the fit or the edge profile can be adjusted.
Settling — the lens sinks slightly into the conjunctiva over the first hours. A good fit accounts for it; that is why fittings are assessed after the lens has been on for a while, not immediately.
Neither is a reason to give up on them. Both are reasons to go back.
General information, not a substitute for a specialist fitting. Reviewed by Dr. Teresita Bollar, OD.
