What size actually changes
Scleral lenses come in a wide range of diameters. In an international survey of fitters, the average lens was 16.2 mm across, with lenses ranging from 11.8 mm to 23.0 mm.[1] The smaller end is often called mini-scleral; what are mini-scleral lenses? explains how sizes are classified against your own eye.
Changing the diameter changes a few things:
- Coverage. A larger lens covers more of the white of the eye (the sclera and the thin conjunctiva over it). If the uncovered parts of your eye dry out and burn, more coverage can help.
- Where the weight lands. A larger lens rests farther from the cornea and spreads its weight over more tissue. Some wearers with pressure or edge awareness find that helps.
- Handling. A larger lens needs your lids held wider, holds more saline, and can be harder to insert without a bubble and harder to remove.
- How it meets your lids. On some eyes a larger edge sits under the lids more comfortably. On others, it catches or rubs.
What size doesn’t fix
- Front-surface fog and smearing. These usually come from the tear film over the lens, which relates to dry eye, eyelid disease, and lens surface wetting. See midday fogging and blepharitis and MGD.
- Solution reactions. Burning from a cleaner or fill saline won’t change with size. See the solution troubleshooter.
- A fit problem elsewhere. A lens that’s too tight in one area may need a reshaped landing zone, not a bigger lens.
- Nerve pain. Burning from neuropathic corneal pain may persist whatever the size.
Shape, not just size
Eyes aren’t perfectly round, and a dry patch or a bump like a pinguecula is often in one place. Options include:
- Toric or quadrant-specific landing zones, shaped differently in different directions so the lens rests evenly. See what is a toric landing zone? In the same survey, most landing zones were spherical, with toric, quadrant-specific and custom designs in the minority.[1]
- Oval or custom-shaped lenses, which some impression-based and scan-based designs allow, to cover a dry corner without enlarging the whole lens. See impression-based, scan-based, PROSE or standard.
- Notches or channels to clear a raised area.
What wearers say
Experiences point in both directions. Many wearers with dry eye describe moving to a larger lens and finding the burning at the corners or the whites of the eye eased, and a few needed to go quite large before they felt real relief. Some with redness or pressure found that a larger diameter spread the load and calmed things down.
Others had the opposite experience. Some found a smaller lens rubbed less, especially with loose folds of conjunctiva (conjunctivochalasis), eyelid scarring, or a lid that caught the edge. Some felt a larger lens caused more redness until other changes were made. And many people with severe dry eye wear smaller lenses comfortably all day.
Wearers also agree on the trade-off: larger lenses are harder to handle, at least at first. Several say it was worth it; a few went back down a size for easier insertion. The advice most often repeated is that size is one factor among many, and a skilled fitter weighs it with everything else.
When to ask about a different size
Raise it with your fitter if:
- The uncovered whites or corners of your eye stay dry, red, or burning while the lens is in.
- You feel pressure or see redness in one area that adjustments haven’t fixed.
- Your lids catch the edge or the lens pushes your lower lid out.
- Handling is so hard that it’s limiting your wear.
What to ask your fitter
- “Would more coverage help my symptoms, or is the cause something else?”
- “Could a shaped landing zone or an oval design do what a larger lens would?”
- “What are the handling trade-offs for me if we go larger?”
- “Would a smaller lens be easier on my lids or conjunctiva?”
When it’s not normal
Common questions
Is a mini-scleral a 'real' scleral lens?
Yes. A mini-scleral still vaults over the cornea and rests on the white of the eye with a fluid layer underneath. It simply extends less far past the cornea. See our page on mini-scleral lenses for how sizes are classified.
Will a bigger lens stop my lens from fogging?
Not reliably. Wearers who asked about this mostly found that fit, solutions, and dry eye or eyelid treatment mattered more than size. Fogging has its own causes and fixes, covered in our midday fogging guide.
Do larger lenses need a different case?
Often. Larger scleral lenses may not fit a standard peroxide case basket without being squeezed, which can damage them. Ask your fitter which case suits your lens size.
Can I keep two sizes and choose by the day?
A few wearers have done this with their fitter's agreement, but most wear the one size their fitter has designed for them. Don't swap sizes without asking.