Two rigid lenses, two very different places to sit
A corneal rigid gas permeable (RGP) lens is a small, firm lens that sits directly on the cornea, the clear front window of the eye. It floats on your tears and moves a little with each blink. Because it’s rigid, it holds its own smooth shape, and the tears that fill the gap between the lens and an irregular cornea help even out the bumps. For decades it has been the standard lens for keratoconus. In the large CLEK study of 1,209 people with keratoconus, 65% wore RGP lenses, and 73% of those said their lenses were comfortable.[3]
A scleral lens is made from the same kind of rigid, oxygen-permeable material, but it’s much larger. It rests on the sclera (the white of the eye) and arches over the whole cornea without touching it. You fill it with sterile saline before putting it in, so the cornea sits under a pool of fluid. In an international survey of scleral lens prescriptions, the average diameter was 16.2 mm, with a range from 11.8 to 23.0 mm.[6]
In between sit corneo-scleral lenses, which are designed to share their weight between the outer edge of the cornea and the white of the eye. Terms vary, so if your fitter proposes one, ask where it lands.
Side by side
| Corneal RGP | Scleral lens | |
|---|---|---|
| Rests on | The cornea, floating on your tears | The white of the eye (sclera), over the conjunctiva |
| Touches the cornea | Yes, by design | No. It vaults the cornea over a layer of saline |
| Irregular corneas | Works well for many. Can be hard to keep centered or comfortable on a very steep or uneven cornea | Works across a wide range, because the cornea’s shape matters less to how the lens sits |
| Dry eye | Relies on your own tears | Keeps the cornea bathed in saline while worn |
| Comfort | Many wearers are comfortable. Some feel the lens edge or get irritation where it bears on the cornea | Rated more comfortable on average in a randomized trial |
| Handling | Small. Put in and taken out with a fingertip | Larger. Filled with saline and usually put in with a plunger or tripod of fingers. Handling is the most common reason people stop |
| Cost drivers | Custom parameters, number of lenses tried, follow-up visits | Fully custom design, more chair time, often more than one lens ordered before the fit is final, plus saline and care products |
| Who it suits | Mild to moderate irregularity where the lens centers and is comfortable | Moderate to severe irregularity, people who can’t tolerate corneal lenses, or eyes that also need surface protection |
What the research shows
In a head-to-head trial, comfort differed but vision didn’t. A randomized crossover trial enrolled 34 people with keratoconus or similar conditions who were already successful corneal RGP wearers. Each person tried both a new corneal RGP and a scleral lens, in random order. Of the 30 who finished, scleral lenses scored significantly higher for comfort. Vision, contrast, and vision-related quality of life showed no significant difference between the two. At the end, 53% chose corneal lenses and 47% chose scleral lenses, a split that wasn’t statistically different.[1]
The same trial found that people who rated their corneal RGP comfort below 7 out of 10 were the ones likely to find scleral lenses more comfortable.[1] That’s a useful rule of thumb to raise with your fitter, though it comes from one trial of 30 people.
For irregular corneas with dry eye, the picture is mixed. A small pilot randomized study in China fitted 40 people (78 eyes) who had both an irregular cornea and dry eye with either mini-scleral lenses or RGPs and followed them for six months. Both groups saw better in lenses than in glasses. The RGP group had a larger gain in visual acuity, while the mini-scleral group reported lower dry eye symptom scores and fewer episodes of fluctuating vision.[2] The authors call for larger studies before drawing firm conclusions.
Practitioners lean toward sclerals for irregular corneas, but not unanimously. In a survey of 778 scleral lens prescribers, 42% ranked scleral lenses as their first choice for corneal irregularity, compared with 20% for corneal RGPs.[4] Bear in mind that the people surveyed were all scleral lens fitters.
Neither lens fully matches a healthy eye. A 2025 review explains that corneal RGPs often leave some residual distortion, mainly from the back surface of the cornea, which a lens on the front can’t reach. Changes to the lens design, including adjustments to scleral lens vault, can reduce it.[5]
Comfort matters for more than comfort. In the CLEK study, poorer contact lens comfort and flatter contact lens fits at the start of the study were among the factors linked to a higher chance of later needing a corneal transplant.[9] That’s an association, not proof that a different lens would have changed the outcome.
How to decide
Corneal RGPs tend to make sense when your cornea is irregular but the lens still centers, stays put, and is comfortable for a full day. They’re small, quick to handle, and don’t need a saline reservoir.
Scleral lenses tend to make sense when a corneal lens won’t center on a steep or uneven cornea, when it’s uncomfortable or keeps popping out, when you can’t wear it long enough to get through your day, or when your eye surface also needs protection, as in severe dry eye.
Many people start in one and move to the other as their eyes or needs change. Your fitter may suggest trying both. If you’d like to see how a scleral fit works first, read what a scleral lens fitting involves. If you have keratoconus, our keratoconus page covers the wider set of options.
Questions to ask your fitter
- Why are you recommending a corneal lens or a scleral lens for my eye specifically?
- If I’m comfortable in my current RGPs, what would I gain by switching?
- Can I try both before I decide?
- What happens to the fee if the first lens type doesn’t work out?
Common questions
Is a scleral lens just a bigger RGP?
They're made from the same family of rigid gas permeable materials, but they work differently. A corneal RGP rests on the cornea and floats on your tears. A scleral lens rests on the white of the eye, is filled with saline before it goes in, and is designed to clear the cornea completely.
I already wear RGPs. Should I switch to sclerals?
Not necessarily. In a randomized trial of people already succeeding with corneal RGPs, vision and quality of life were about the same in both lenses, and roughly half preferred to stay with their corneal lenses. Switching is worth discussing if your RGPs are uncomfortable, won't stay centered, or you can't wear them long enough each day.
Which one gives sharper vision?
For most people with an irregular cornea, both can give a large improvement over glasses. Studies comparing them directly have found similar vision on average. Your own result depends on your cornea, so your fitter may suggest trying both.
What is a corneo-scleral lens?
It's an in-between size: larger than a corneal RGP, smaller than most scleral lenses, and designed to share its weight between the edge of the cornea and the white of the eye. Some fitters use the term for the smallest scleral designs. Ask your fitter which size they're proposing and why.
Are RGPs cheaper than scleral lenses?
Fees vary too much between practices to generalize. What drives cost is how much custom design and chair time the fit needs, how many lenses are ordered before the fit is final, and what's included in the fitting fee. Ask each practice for its fees in writing.