Hybrid Contact Lens Design: GP Center and Soft Skirt

What is a hybrid contact lens?

A hybrid contact lens has a rigid GP centre that is surrounded by and fused to a soft skirt.

That definition is from Contact Lens Spectrum, Hybrid Lens Strategies for Regular and Irregular Corneas (Giancarlo Montani, October 2018), which also records the design intent from the first patent on this lens type, filed in 1973 by Louis J. Page: to provide the visual acuity of the hard lens and the comfort of the hydrophilic lens, with the possibility of incorporating multifocal correction. Montani notes that forty-five years later the aims of the lens type were still the same.

Cracking the Cone: Fitting Contact Lenses for Keratoconus (Clark Chang, OD, MS, and Kriti Bhagat, OD, Review of Cornea & Contact Lenses, September 2025) gives the same structure from the irregular-cornea side: a GP centre chemically bound to a surrounding soft lens skirt, offering a balance of comfort and visual clarity through improved GP centration and clearance over the corneal apex.

Optically, the lens is a GP lens. Mechanically, it behaves like a soft one. That is the whole proposition, and the parameters follow from it.

How does the GP-centre to soft-skirt junction work?

The junction is a lift region between the rigid optic and the soft skirt, and on irregular-cornea designs the depth of that lift is the fitting parameter.

Montani describes the current generation of hybrid lenses for regular corneas as having a prolate optical zone and a junction lift area with a flatter radius than the reverse curvature of the soft skirt — a back-surface design intended to distribute forces between lens and cornea and so improve tear exchange and lens movement.

For irregular corneas the geometry is reversed and the parameter set changes with it. Montani states that this family incorporates reverse-geometry designs to vault over ectatic surfaces without bearing, and that these lenses have two fitting parameters:

• Vault, which replaces the base curve. It corresponds to the rigid portion of the lens and defines its relative depth, measured in microns.
• Soft skirt curvature, which is the only part of the design that touches the anterior segment and which modulates the cornea-to-lens relationship at the rigid–soft junction zone.

Montani also describes the lift curve that connects the vault to the rigid landing zone as fixed up to a vault of 250 µm and variable from 300 µm upward, to accommodate the increasing need for depth. And in the prolate irregular design he notes a positive correlation between the vault and the corneal sagittal depth over an 8.5 mm chord, with a lower correlation to the sagittal depth of the anterior segment as a whole — because the soft skirt conforms to a scleral shape that differs on every eye.

That correlation is the reason sagittal depth appears in a hybrid conversation at all: the lens is specified by height over a chord, exactly as a scleral lens is. Read Sagittal Depth of Contact Lenses for that geometry, and Base Curve of Contact Lenses for the radius it replaces.

How is a hybrid fitted on a regular cornea?

On a regular cornea, a hybrid is fitted so the rigid portion aligns with the cornea, and the skirt is chosen from corneal diameter.

Montani gives the initial-selection method for the regular-cornea family: it can be fitted empirically from keratometry, subjective manifest refraction and horizontal visible iris diameter, without a fitting set. The stated rules are:

• Base curve 0.10 mm, or 0.50 D, steeper than the flat meridian.
• Skirt from HVID — a medium (8.1 mm) skirt for HVID ≥ 11.8 mm, a flat (8.4 mm) skirt for HVID < 11.8 mm.
• Power by adding −0.50 D to the sphere of the subjective manifest refraction — Montani's worked examples are −1.00 −1.00 × 180 ordering as −1.50 D, and +1.00 −1.00 × 180 ordering as +0.50 D — with vertex compensation still required at higher powers.

That last clause is this site's territory: at higher refractive powers the spectacle sphere must be moved to the corneal plane before any design rule is applied. Convert it on the Contact Lens Conversion Calculator or per meridian on the Vertex Distance Calculator first.

Montani's optimal fit on a regular cornea is good centration with the optic zone over the pupil, 0.5 mm to 1.00 mm of movement per blink, and the GP portion in alignment with the cornea. The skirt is the control: too steep and the lens bears on a small area, producing central pooling and possible seal-off; too flat and the GP portion settles heavily onto the cornea, producing central bearing and decentration.

How is a hybrid fitted on an irregular cornea?

On an irregular cornea the target reverses: the rigid portion must clear the apex rather than align with it, and the vault is adjusted to achieve that clearance.

Montani states this as a fitting pearl — the rigid portion must align with the cornea on regular-cornea hybrids, whereas clearance over the apex is necessary to maintain comfort, tear exchange and corneal health on irregular-cornea hybrids. The stated procedure:

• These lenses are fitted from a diagnostic set, starting at a 250 µm vault with a medium skirt curvature.
• The bowl is filled to the top with preservative-free saline and fluorescein before application, to prevent bubbles under the lens.
• Fit is assessed after a minimum of 30 minutes and confirmed at about three hours, because settling behaves like a scleral lens: 50% of settling in the first hour, stabilising after three.
• Optimal apical clearance is 100–150 µm on application and about 50 µm once settled.
• Clearance is adjusted with the vault, not the skirt. Too much vault and a ring of bearing appears under the rigid landing zone, causing seal-off and reduced tear exchange; too little and the rigid portion bears on the apex.

For the oblate irregular design — the one used on post-refractive corneas — Montani gives a starting vault of 255 µm with a medium skirt, an ideal of 50–100 µm of clearance 30 minutes after the initial fit, and a titration: increase the vault in 100 µm steps until fluorescein is observed, or decrease in 100 µm steps until bearing appears and then add 50–100 µm back for clearance. The corneal shape that design is written for is on Contact Lenses After LASIK.

One check belongs at the end of every hybrid fit. Montani notes that on removal there may be a light, transient indentation ring at the junction of the soft and GP portions — and that a deep impression ring may indicate a tight fit and should be modified.

Hybrid vs scleral lenses: what actually differs?

A hybrid and a scleral both vault an irregular cornea. They differ in what lands on the eye, how much fluid sits behind the optic, and how they are handled.

Montani's comparison against scleral lenses lists the hybrid advantages as a soft skirt that conforms to the scleral shape, less chance of seal-off, a reduced fogging effect from tear debris trapped behind the lens, lower clearance, optics closer to the entrance pupil and increased oxygen transmission — and the disadvantages as being more difficult to fit on very asymmetric profiles or very irregular corneas, needing more frequent replacement, and taking longer to settle.

Chang and Bhagat state the same boundary from the keratoconus side: hybrids are viable for mild to early-severe irregularity, while sclerals are described as particularly well suited to moderate and advanced irregularity. The scleral design system itself — optic, limbal and landing zones, vault and settling — is on Scleral Lens Parameters, and design selection by corneal shape is on Keratoconus Contact Lens Options.

What are the disadvantages of hybrid lenses?

The trade-offs are handling, settling time, replacement frequency and fitting difficulty — and they are documented rather than incidental.

Against corneal GP lenses, Montani lists hybrids as more difficult to apply and remove, longer to settle, and needing more frequent replacement. Against soft lenses, he lists higher cost, more difficult fitting, more careful evaluation of the lens-to-anterior-segment relationship, and more difficult application and removal. Against piggyback systems, the listed cons are the need for careful lens-to-anterior-segment evaluation and the inability to substitute different lens materials — you cannot swap the soft component the way you can under a piggyback.

Chang and Bhagat add the clinical caution: a soft skirt may not conform well to an asymmetric corneal curvature or may induce mechanical stress on the limbus and peripheral cornea, and inadequate junctional clearance risks epithelial binding and deposit build-up.

Cost is a real factor and is named as one in the source. This site does not publish prices, and a lens cost is a conversation with the practice fitting the lens, not a parameter.

How long do hybrid contact lenses last, and how are they cared for?

Montani names a recommended replacement schedule of every six months for modern hybrid lenses.

The care routine he describes is a soft-lens routine applied to a two-material lens: digital rubbing of both the front and back surfaces in the palm with a multipurpose solution or a non-alcohol, non-abrasive soft lens daily cleaner, rinsed off with saline before disinfection; then chemical disinfection with a multipurpose system or a hydrogen peroxide system for disinfection and storage. He notes explicitly that certain multipurpose and hydrogen peroxide systems are not recommended with the hybrid lenses available in the United States — meaning the solution is a fitted decision like the lens, not a shelf choice.

Two handling points recur in that article because they are where new wearers fail. The bowl must be filled with fluid on application or bubbles form under the lens; and applying with excessive pressure can create a vacuum in the post-lens tear reservoir, causing seal-off and an indentation ring. Removal is described as a narrow pinch with the tips of thumb and forefinger at the 5 and 7 o'clock positions of the soft skirt, just outside the GP portion, with dry fingers.

What is recorded above is a published description, not an instruction to a wearer, and this page issues no handling, cleaning, solution or replacement advice of its own. That is the same refusal this site applies everywhere: the application and removal technique, the care system and the replacement interval for a specific lens are set by the practitioner who fitted it and by that lens's own labeling, and Montani's own note that certain solutions are not recommended is exactly why a generic instruction taken from a third party can be the wrong one for the lens in front of you.

Does the ordered power come from the spectacle prescription?

The spectacle refraction gets you to a starting power. The ordered power comes from an over-refraction over the settled lens.

On regular-cornea hybrids Montani's starting rule is arithmetic — manifest sphere plus −0.50 D, with vertex compensation at higher powers — and then an over-refraction at follow-up to determine any necessary power change, along with an assessment of whether residual astigmatism exceeds what the difference between refractive and corneal astigmatism predicts.

On irregular-cornea hybrids the instruction is stricter: calculate the power from an over-refraction only once during a fitting, even if several trial lenses are used. Montani also notes a design consequence worth knowing before an order is placed — because of the flat curvatures used in the irregular-cornea designs, the negative power ordered is lower than the power that would be needed in a corneal GP lens on the same eye. A hybrid order is not a GP order transcribed.

Convert the spectacle refraction to the corneal plane on the Contact Lens Conversion Calculator, and turn the residual refraction into the next ordered power on the Over-Refraction Calculator. Neither of those steps chooses a vault or a skirt. The bound that applies across this site is on Starting Contact Lens Parameters Are Not a Prescription, and the GP parameter set a hybrid borrows its optics from is on RGP Contact Lens Parameters and Starting Power.

What does this page not cover?

This page describes a design class.

It names no manufacturer, publishes no brand parameter table or fitting-set nomogram, quotes no prices, and issues no handling, application, cleaning or care-system instruction. Availability, diagnostic sets, solution compatibility and lens ordering are practice-level decisions taken with the lab and the licensed practitioner fitting the lens. Corneal shape and which design family it routes to are on Contact Lenses for an Irregular Cornea.

Sources

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

• Contact Lens Spectrum, Hybrid Lens Strategies for Regular and Irregular Corneas (Giancarlo Montani, October 2018) — hybrid definition as a rigid GP centre surrounded by and fused to a soft skirt; the 1973 Louis J. Page patent and its stated aim; prolate optic zone and junction lift area on regular-cornea designs; vault and soft skirt curvature as the two fitting parameters on irregular-cornea designs, with vault in microns replacing base curve; fixed lift curve to 250 µm and variable from 300 µm; vault correlated with corneal sagittal depth over an 8.5 mm chord; empirical selection from keratometry, manifest refraction and HVID; base curve 0.10 mm or 0.50 D steeper than the flat meridian; medium 8.1 mm skirt for HVID ≥ 11.8 mm and flat 8.4 mm skirt for HVID < 11.8 mm; power as manifest sphere plus −0.50 D with vertex compensation at higher powers; optimal regular-cornea fit with 0.5–1.00 mm movement per blink; skirt-too-steep and skirt-too-flat failure modes; diagnostic fitting from a 250 µm vault with a medium skirt; the bowl filled with preservative-free saline and fluorescein; assessment at 30 minutes and confirmation at three hours; 50% of settling in the first hour; 100–150 µm apical clearance on application and about 50 µm settled; vault adjusted rather than skirt; 255 µm starting vault and 50–100 µm clearance target on the oblate design with 100 µm titration steps; transient versus deep junction indentation rings; the comparison against GP, soft, piggyback and scleral designs; over-refraction once per fitting and lower ordered minus power than a corneal GP; six-month replacement schedule; the rub, rinse and disinfection routine with the note that certain solutions are not recommended; application bubble and seal-off cautions; the 5 and 7 o'clock removal pinch.
• Review of Cornea & Contact Lenses, Cracking the Cone: Fitting Contact Lenses for Keratoconus (Clark Chang, OD, MS, and Kriti Bhagat, OD, September 2025) — hybrid lenses as a GP centre chemically bound to a soft skirt with improved centration and apical clearance; wide sagittal height range; mild to early-severe suitability; soft-skirt conformity and limbal stress cautions; junctional clearance as critical to avoiding epithelial binding and deposit build-up.