The problem it solves
A scleral lens vaults over your cornea and rests on the white of your eye, the sclera, which is covered by a thin clear membrane called the conjunctiva. The part of the lens that touches down is the landing zone, sometimes called the haptic.
The simplest landing zone is spherical: curved the same way all around. That works well when the sclera is evenly curved. But many eyes are steeper along one direction than another, which fitters call scleral toricity. On those eyes, a spherical landing zone presses harder in some spots and lifts away in others. In a study of 10 healthy young adults, eyes with more scleral toricity showed more uneven contact between the lens and the eye, and more lens flexing.[3]
Uneven landing can show up as pressure or blanched blood vessels in one area, an edge that lifts and lets in bubbles or debris, lens rotation, or vision that varies.
Types of landing zones
- Spherical: the same curve all the way around.
- Toric: two different curves at right angles, matching a sclera that is steeper in one direction.
- Quadrant-specific: each quarter of the landing zone can be adjusted separately, for less regular shapes.
- Custom or free-form: designed from a scan or a mold of the eye’s surface. See scleral profilometry and impression-based lenses.
How often each is used varies by practice. In an international survey describing 419 eyes, landing zones were spherical in 64%, toric in 26%, quadrant-specific in 7%, and custom in 3%.[1] The authors noted that relatively few patients were wearing these advanced designs.[1] By contrast, a single large specialty practice in the Netherlands reported that 99.8% of the 27,430 scleral lenses it ordered between 2016 and 2022 had toric landing zones.[6]
What the studies show
The research is mostly small studies in healthy eyes, so treat it as early evidence:
- Less flexing and rotation. Ten young, healthy participants wore lenses with landing zone toricity from none up to 200 microns. Toric landing zones reduced lens flexure by about 62% and rotation by about 77% compared with a spherical landing zone, but didn’t change how far the lens sat off-center.[2] Lens flexure matters because a lens that bends on the eye can add unwanted astigmatism to your vision.
- Centering. In 20 young adults with regular corneas, a toric landing zone lens centered better after two hours of wear than a spherical one, though it didn’t eliminate decentration.[5]
- Tear exchange. In nine healthy participants, a lens with a toric landing zone allowed more fresh tear fluid to flow in behind it than an otherwise identical spherical lens.[4]
Lens size also plays a part. Smaller, mini-scleral lenses are less affected by scleral toricity, while larger lenses more often benefit from a toric back surface to avoid pressure points, bubbles, and decentration.[7]
What to ask your fitter
- Does my lens have a spherical, toric, or more customized landing zone, and why?
- How will we know if it’s landing evenly?
- If I notice redness in one spot, pressure, or a rotating lens, what would you change?
If a lens leaves a red ring or pressure mark that doesn’t fade soon after removal, see red ring after removal and tell your fitter.
Common questions
How do I know if I need a toric landing zone?
Your fitter decides based on how a trial lens sits on your eye, signs like blanching of blood vessels or edge lift in certain spots, and in some practices a scan of your sclera. You might notice the problem as pressure, redness in one area, a lens that rotates, or vision that varies, but those can have other causes too.
Does a toric landing zone correct astigmatism?
No. The landing zone is about how the lens sits on the white of your eye. Astigmatism correction comes from the optics in the center of the lens. A toric landing zone can help by keeping the lens from rotating, which matters if your lens has toric optics on its front surface.
Does it matter which way the lens goes in?
It can. A lens that isn't evenly shaped all the way around may need to sit at a particular angle. Ask your fitter whether your lens has an orientation mark and how to line it up when you insert it.