Guide · complex lenses
Keratoconus: what it is, and what scleral lenses do
Keratoconus is the cornea thinning and bulging into a cone. Glasses stop working because the surface is no longer smooth. A scleral lens makes a new smooth surface — and for most people gives back vision they thought was gone.
What it is
The cornea — the clear front window of the eye — thins and pushes outwards into a cone shape, usually starting in the teens or twenties. Vision gets blurred and distorted in a way that new glasses don’t fix, because glasses correct a regular surface and this one isn’t. It’s not rare; we see it every month. It’s usually picked up when the prescription keeps changing oddly, or the astigmatism jumps.
What the lenses do
A rigid lens holds its shape. Put one over an irregular cornea and the tears fill the gap between them; the eye now looks through a smooth lens surface and a smooth tear layer, and the distortion goes. Scleral lenses are the large version: they rest on the white of the eye and vault right over the cornea without touching it, with a reservoir of fluid underneath. Mini-scleral lenses do the same in a smaller size, easier to handle and often the first choice; full scleral lenses are for the most irregular corneas. We fit both, and RGP and hybrid lenses, at every practice. Comfortable on corneas that can’t tolerate a small lens, and steady all day.
What the fitting involves
A corneal map (topography), then trial lenses chosen from the map, then adjustment over several visits until vision and comfort are right. Complex fittings take three to five visits; the assessment is £95 and everything after it is quoted in writing before ordering.
Beyond lenses
If the cone is progressing, the hospital can stiffen the cornea with cross-linking to stop it getting worse; we refer for that and fit lenses alongside. Cross-linking stops progression; lenses give the vision.
Where
Fitted at Cheadle and Middleton, aftercare at any practice. The specialist clinic →
The short version
- The cornea cones; glasses stop working because the surface isn’t smooth
- Rigid or scleral lenses create a smooth surface and give the vision back
- Fitting from a corneal map, three to five visits, quoted before ordering
- If it’s progressing, the hospital can cross-link; we fit alongside