Scleral versus RGP lenses for keratoconus: which one suits you

Why glasses stopped doing the job

If you are reading this, you have probably had the conversation where new glasses were tried and the letters were still smeared. That is not a failure of the prescription. Keratoconus leaves the cornea unevenly curved, and a lens in a frame can only correct a curve that is the same across the whole surface.

A rigid contact lens solves it differently. It sits in front of the cornea and holds its own shape, and the tears trapped beneath it fill in the dips. Light now passes through a smooth front surface, so the distortion is bypassed rather than compensated for. Both lens types in this guide do this; they differ in where they sit and how they feel.

If you are new to the condition, start with what keratoconus is. This guide assumes you know the diagnosis and are weighing up lens options.

Corneal RGP lenses: small, sharp, and a learning curve

A corneal rigid gas-permeable lens is a hard lens smaller than your iris. It rests on the cornea itself and moves slightly with each blink. The American Academy of Ophthalmology's EyeWiki notes that rigid lenses are more durable and can provide better optical clarity than soft lenses, and that they suit keratoconus because they do not conform to the cornea.

The trade-off is sensation. Because the lens sits on the most sensitive surface of the eye, you feel it at first, and EyeWiki notes rigid lenses take longer to adapt to than soft ones. Some people adapt well and wear them for years. Others never get past the awareness of the lens, or find it dislodges in wind or sport. A cone that is steep or sits low on the cornea can also make a small lens hard to centre.

Handling is simple once learned: a small lens is quick to put in and take out and needs no fluid filling. The lenses last a long time with proper cleaning, which EyeWiki notes tends to make them less expensive over time than lenses that are replaced often.

Scleral lenses: bigger, vaulting, fluid-filled

A scleral lens is also rigid, but much larger. It vaults right over the cornea without touching it and lands on the sclera, the white of the eye, which is far less sensitive. Before you put it in, you fill the bowl with sterile saline. That fluid stays between the lens and the cornea all day.

That design is why people who could not tolerate a corneal RGP often manage a scleral. EyeWiki describes the vault as providing a smooth surface for correcting high astigmatism and ectatic corneal disease, and the liquid reservoir as useful for severe dry eye. The lens does not move much, so vision tends to be steady and the lens is less likely to pop out during sport.

The costs are in handling and fitting. Insertion needs a filled lens placed squarely without bubbles, and removal uses a small plunger, so there is more to learn. The lenses are custom-made, so more trial lenses and follow-up visits are usual before the final pair. Our scleral lens page walks through that fitting process.

Hybrid and specialty soft lenses

Two other designs sit between the rigid options. A hybrid lens has a rigid centre with a soft skirt, which EyeWiki describes as combining the optics of a hard lens with the comfort of a soft one, and as especially useful for irregular corneas. Specialty soft lenses for keratoconus are thicker than ordinary soft lenses so they drape less; Health New Zealand notes specially designed soft lenses can work well as the cornea becomes more distorted.

Both can suit milder cones or people who cannot manage rigid lens handling. Their limit is that a softer surface follows the cornea more, so as the cone steepens the sharpness tends to fall away sooner than with a rigid lens. They are also replaced more often, which changes the running cost. In short:

• Corneal RGP: small, durable, sharp, sits on the cornea, takes adapting to, can dislodge.
• Scleral: large, vaults the cornea on fluid, steadier and often more comfortable, more to learn and more fitting visits.
• Hybrid: rigid centre, soft edge, a middle path on comfort and sharpness.
• Specialty soft: easiest to adapt to, suits milder irregularity, replaced more often.

What drives the cost, and where the subsidy fits

We do not print lens prices here because the right answer depends on the fit. The things that move the figure are the lens design, how many trial lenses and follow-up visits your cornea needs, and how often the lens is replaced. Custom scleral lenses usually involve more fitting work than a corneal RGP; soft and hybrid lenses cost less per lens but are replaced more often. Our consultation fees page lists the published fees, and scleral fitting is quoted after assessment.

Health New Zealand runs a contact lens subsidy for lenses supplied for medical need. It is claimed by an optometrist or dispensing optician who holds an agreement with Health New Zealand, it covers lenses rather than an examination on its own, and the criteria and amounts are set by Health New Zealand. The Health New Zealand page in the sources has the current rules. Our insurance and funding page explains how claims are handled here and what health insurance may cover.

One thing lenses never change: the cornea underneath. A Moorfields Eye Hospital leaflet puts it plainly: contact lenses do not make keratoconus worse or better, they just improve your vision while you are wearing them. Slowing the disease is a separate decision about cross-linking, covered in after a keratoconus diagnosis.

When this practice is the wrong place

Call 111 or go to the nearest hospital emergency department, not an optometry appointment, for sudden loss of vision, a shadow or curtain across your vision, flashes with a sudden shower of floaters, a chemical splash, a red and painful eye with light sensitivity, or an eye injury.

Two situations are specific to lens wearers with keratoconus. A sudden painful drop in vision with a cloudy patch on the cornea may be acute corneal hydrops, where fluid floods a very thin cornea; Healthify NZ advises seeing a doctor immediately for sudden severely blurred vision or for severe light sensitivity, redness and pain. And any red, painful, light-sensitive eye in a contact lens wearer needs same-day assessment: take the lens out and seek care rather than waiting for a routine slot. Healthline on 0800 611 116 is free and open 24 hours if you are unsure where to go.

We can refit lenses after an episode has settled, but the acute event belongs with the hospital eye clinic.

How the decision is made

The choice is made on your eye, not on a chart. Corneal topography shows how steep the cone is and where it sits; the slit lamp shows thinning, scarring and how dry the surface is; your history tells us whether you have worn rigid lenses before and what you do for work and sport. From that, a trial lens goes on, and what you see and feel decides the next step.

Our optometrists fit both corneal (micro-corneal) RGP and scleral lenses, so the recommendation follows the fit rather than the stock. Read our scleral lens post for the case for sclerals, and keratoconus treatment and management in Auckland for how fitting sits within the wider plan. Book a keratoconus assessment when you are ready.