Scleral Lens Sizes: Corneoscleral, Mini-Scleral, and Full

What do the scleral size classes mean?

They name which tissue carries the lens: all cornea, cornea and sclera together, or sclera alone.

The Scleral Lens Education Society nomenclature statement (June 2013) sets the rule: bearing is the defining feature. A lens resting completely on the cornea is a corneal lens. A lens resting partly on the cornea, centrally or peripherally, and partly on the sclera is a corneo-scleral lens. A lens resting entirely on the sclera is a scleral lens, in the society’s words, “no matter how large that lens is.” Within that scleral group, the further distinction is made against corneal size rather than against an absolute number: a lens up to 6 mm larger than the visible iris diameter — roughly 3 mm of bearing on each side — is a mini-scleral, and a lens more than 6 mm larger is a large scleral.

Alongside that bearing rule sits a set of diameter conventions that predate it and remain in wide use. Eef van der Worp’s A Guide to Scleral Lens Fitting tabulates them, and notes that it may be better to classify by purpose and landing-zone area precisely because those are independent of eyeball size.

Those ranges are van der Worp’s terminology table as published. Contact Lens Spectrum’s 2010 scleral fitting guide uses a slightly different cut, describing scleral lenses as large-diameter GP lenses ranging from 13 mm to more than 20 mm, and putting corneo-scleral lenses at 13.0–15.5 mm with most under 15 mm. The two conventions disagree at the boundaries, which is the point: they are conventions, not a standard.

Why does the nomenclature body argue against classifying by diameter?

Because the same diameter is a different class on a different eye.

The society gives the worked example itself: an 18 mm lens bearing exclusively on the sclera is a mini-scleral on an eye with a 12 mm corneal diameter, and anything larger than 18 mm on that same eye is a large scleral. Move to a bigger or smaller cornea and the boundary moves with it. It also notes the converse case — lens designs classified as corneo-scleral by diameter sometimes rest entirely on the sclera, and under the recommended nomenclature those are scleral lenses despite their relatively small diameters.

The practical reading is that a class name in a report tells you about a fitting relationship, and a millimetre figure on an order form tells you about a lens. They are different facts, and only one of them survives being moved to another patient.

What does changing diameter actually change?

Diameter moves where the lens lands, how its weight is spread, and how much scleral shape it has to match — and it moves sagittal depth with it.

• Weight distribution. A larger lens has a wider landing zone, so the same weight sits on more conjunctiva. Ariel Cerenzie reports the consequence in Contact Lens Spectrum (September 2021): larger-diameter lenses settle less over time than smaller ones, because there is less force per unit area on the bulbar conjunctiva and Tenon’s capsule beneath.
• Scleral toricity encountered. Lynette K. Johns notes in the 2010 guide that toricity increases peripherally from the limbus — so the larger the diameter, the more scleral toricity the landing zone meets, and the more likely a toric or quadrant-specific periphery becomes.
• Obstacles. A larger lens lands further out, which can carry the edge onto pinguecula, scarring or elevations; a smaller lens can avoid them. Johns describes an edge just abutting a pinguecula causing inflammation, and diameter chosen deliberately to clear it or to sit past it.
• Sagittal depth. Diameter is one of the inputs that produces sag: for a given surface, a larger chord means a deeper vault. That relationship is defined on Sagittal Depth of Contact Lenses, and the University of Iowa atlas states it plainly for this case — larger-diameter sclerals typically have deeper sag.

Because those move together, diameter is not a free variable late in a fit. Johns describes ordering 0.5 mm larger or smaller than the trial lens, and finding that changes greater than 0.5 mm produce a significantly different fit. The sequence those decisions sit in is on Scleral Lens Fitting Process.

What this page is not

It is not the diameter you order for a soft lens, and it is not a size to buy.

The DIA printed on a soft lens box, the usual 13.80–14.50 mm window, and how diameter is fitted with base curve are on Diameter of Contact Lenses. That page owns the diameter parameter on this site; this one only names the scleral bearing classes and hands the reader back.

One disambiguation is worth stating outright, because the word collides. Cosmetic full-eye lenses sold as “sclera lenses” — the black-out and costume designs marketed for photography and Halloween — are not scleral lenses in the sense used here. They are a different product with different intent, and nothing on this page describes them. A scleral lens in this section is a prescribed medical device fitted by a practitioner and made to the shape of one person’s anterior eye.

This page also names no lens brand, publishes no laboratory parameter grid, and lists no fitting set. Design names are a manufacturer matter; the site is manufacturer-agnostic.

Starting parameters are not a prescription

A size class is a description of a fit, not an instruction to order one.

Read the site-wide bound on Starting Contact Lens Parameters Are Not a Prescription. For the parameter set this class sits inside, read Scleral Lens Parameters; for what the diameter produces on eye, read Scleral Lens Vault.

Sources

Clinical claims on this page are attributed to the publications below.

• Scleral Lens Education Society — Scleral Lens Nomenclature(June 2013) — bearing as the defining feature; corneal, corneo-scleral and scleral definitions; mini-scleral up to 6 mm larger than visible iris diameter and large scleral more than 6 mm larger; the 18 mm on a 12 mm cornea worked example; the advice against diameter classification; small-diameter designs that bear entirely on sclera being scleral lenses.
• Eef van der Worp — A Guide to Scleral Lens Fitting(Pacific University College of Optometry, open access) — terminology table giving corneal 8.0–12.5 mm, corneo-scleral 12.5–15.0 mm with alternative names, mini-scleral 15.0–18.0 mm and large scleral 18.0–25.0 mm, with bearing and tear reservoir capacity per class; the argument for classifying by purpose and landing-zone area rather than diameter.
• Contact Lens Spectrum — Scleral Contact Lens Fitting Guide(Jason Jedlicka, Lynette K. Johns and Stephen P. Byrnes, October 2010) — scleral lenses as large-diameter GP lenses from 13 mm to more than 20 mm; corneo-scleral 13.0–15.5 mm with most under 15 mm; scleral toricity increasing peripherally from the limbus; pinguecula and edge-impingement considerations; ordering 0.5 mm from the trial diameter with larger changes producing a significantly different fit.
• Contact Lens Spectrum — Alright Folks, Let’s Settle Down(Ariel Cerenzie, OD; September 2021) — larger-diameter lenses settling less because a wider landing zone distributes weight over more conjunctiva.