The short answer is yes. In my practice, approximately 80% of our scleral lens patients achieve 20/20 vision or better.
However, that figure requires context. The patients walking through our doors for scleral lenses are not typical spectacle wearers seeking an upgrade. They are individuals living with keratoconus, severe corneal irregularities, or post-surgical complications who cannot achieve functional vision with conventional spectacles or soft contact lenses. If we were fitting a standard spectacle-wearing population with sclerals, the proportion achieving 20/20 vision would be well above 80%.
When evaluating whether scleral lenses can deliver 20/20 vision, it helps to look at how these lenses interact with irregular eyes, what limits visual acuity, and how true success is measured in an exam room.
How Scleral Lenses Create Sharp Vision
To understand why scleral lenses work when spectacles fail, consider how an optical system functions. Whether you look through a camera lens, a pair of binoculars, or a living room window, the optical surface must be smooth for light to pass through without distortion.
When I show patients a 3D picture of their corneal topography, their irregular cornea looks anything but smooth. It resembles a landscape of steep hills, valleys, and distortions. Conventional spectacles and soft contact lenses drape or sit across these irregularities, leaving the distorted optical surface largely intact.
A scleral lens works by completely vaulting over the cornea. It rests gently on the sclera, the white part of the eye, trapping a reservoir of sterile saline solution between the back of the lens and the front of the eye. Because liquid naturally fills every microscopic crevice, this fluid layer cancels out the uneven cornea beneath it.
Instead of light scattering across an irregular surface, the fluid acts like the calm, mirror-flat surface of a lake. The front surface of the rigid lens becomes the eye’s new, optically regular refractive surface, allowing clean, undistorted light to focus directly onto the retina.
Defining Visual Success Beyond the 20/20 Chart
Whilst 20/20 is always our primary target, treating complex corneal disease means defining visual success according to the patient’s functional transformation rather than an arbitrary chart line.
We frequently see patients who present with less than 5% functional vision when corrected with spectacles before sclerals. If an eye has sustained structural irregularities or scarring and a scleral lens elevates that eye to 60% or 75% best-corrected visual acuity, that is considered a significant clinical success. For that patient, moving from severe visual impairment to driving, reading, and working independently transforms their life.
Visual balance between both eyes is another critical factor. Many patients present with one eye significantly worse than the other, such as one eye with advanced keratoconus or a dense corneal scar alongside a relatively stable fellow eye. A scleral lens will naturally deliver far better visual acuity to the clearer eye than the scarred one.
Even so, fitting both eyes remains fully justified. Restoring functional vision in the weaker eye balances binocular vision, improves depth perception, and delivers a superior overall visual experience compared to relying solely on a single corrected eye.
Biological Limits to 20/20 Vision
A scleral lens can only correct the optical pathway at the front of the eye. If there are biological or structural barriers deeper in the ocular system, 20/20 vision may not be attainable:
- Corneal Scarring: Dense scars physically impede light from reaching the back of the eye. However, whether a scar prevents clear vision depends entirely on its optical density and position. We routinely fit patients with corneal scarring, and if we achieve acceptable visual outcomes, the lens is justified.
- Higher-Order Aberrations (HOAs): Standard optics correct simple prescription errors like short-sightedness and regular astigmatism, but complex irregular corneas often produce higher-order aberrations. In our practice, we utilise specialised HOA scleral lens designs that can cancel out these higher-order aberrations and achieve good vision where standard rigid lenses fall short.
- Retinal and Neurological Health: If conditions like amblyopia, optic nerve damage, or retinal disease are present, the eye’s internal sensor cannot resolve fine detail, regardless of how clear the image is at the corneal plane.
The Design Philosophy: Prioritising Corneal Health and Oxygen
Achieving 20/20 vision is pointless if the lens compromises the underlying health of the eye. A successful fit requires an uncompromising design philosophy focused on three non-negotiables: maximum oxygen delivery, comfort, and sharp vision.
Many competitors fit mini-sclerals, which are smaller in diameter due to design constraints. These smaller lenses often press directly on the limbus, the delicate junction between the cornea and sclera where corneal epithelial stem cells reside. Over time, mechanical compression in this area can restrict metabolic exchange and lead to corneal hypoxia.
Our design philosophy differs fundamentally:
- Complete Limbal Vaulting: Our designs always vault the limbal stem cell area entirely, preventing mechanical pressure and ensuring maximum oxygen delivery to the cornea.
- Highest Oxygen Permeability: We manufacture lenses using materials with the highest possible oxygen permeability (Dk) so the cornea can breathe normally throughout long wearing days.
- Stable Centration: Vaulting the cornea evenly eliminates rotation and rocking, ensuring visual acuity remains stable without fluctuating with every blink.
The Common Misconception: Scleral Lenses Are Not Just an Option
One of the most persistent misconceptions among people who are ideal candidates for sclerals, such as those with keratoconus or corneal transplants, is the belief that scleral lenses are merely one of many available options to improve their vision. In reality, there often are no other viable optical options.
Many patients believe that surgical procedures are intended to restore crisp visual acuity:
- Corneal Cross-Linking (CXL) is performed to halt the progression of keratoconus by stiffening the corneal tissue. It does not directly result in significant improvement in visual acuity.
- Intacs (corneal ring segments) are surgically inserted to reshape the cone and make the eye slightly easier to fit, but they rarely deliver sharp unassisted vision on their own.
- Corneal Transplants replace diseased tissue to restore ocular integrity, yet the resulting graft is almost always irregular and heavily astigmatic.
These procedures stabilise or reconstruct the eye’s anatomy, but they do not eliminate irregular optics. For individuals with compromised, irregular corneas, scleral lenses are not merely an alternative among many; they are frequently the only optical device capable of directly restoring functional, high-definition sight.
Book a Scleral Lens Assessment
If glasses or standard contact lenses are failing to give you the crisp, comfortable vision you need, scleral lenses could transform how you see the world.
Whether you are managing keratoconus, recovering from a corneal transplant, or dealing with corneal scarring, our specialist team designs bespoke lenses tailored precisely to the unique contours of your eyes.
Explore our scleral lens services and book an assessment today to find out what level of vision your eyes can truly achieve.
Paul Moldovanos Optometrist is a family optometry practice in Roodepoort, Johannesburg, caring for patients since 1990.
Read next: Scleral Lenses: Five FAQ.