How a very high prescription affects your vision
Most people with nearsightedness (myopia) or farsightedness (hyperopia) see well in ordinary glasses or soft contact lenses. As the prescription gets stronger, glasses start to cause problems of their own:
- Thick, heavy lenses. Strong prescriptions need thick lenses, at the edges for myopia and in the center for hyperopia.
- A changed view of the world. Strong minus lenses make things look smaller. Strong plus lenses make them look bigger and narrow the clear field of view.
- Distortion away from the center. Looking through the edge of a strong lens bends straight lines and shifts objects.
- Unequal eyes. If one eye needs a much stronger prescription than the other, glasses can make the two eyes see images of different sizes. A small study of 18 people found contact lenses kept that size difference to a minimum.[4]
High myopia is common and rising. A global review estimated that 2.7% of the world’s population, about 163 million people, had high myopia in 2000 (a prescription of -5.00 or stronger). It projected 9.8% by 2050.[2]
Aphakia is the extreme case for farsightedness. Aphakia means the eye has no natural lens. It can follow cataract surgery without a lens implant, an injury, or a lens that has dislocated. It leaves a very strong plus prescription. Because of the optical effects of high-plus glasses, people with aphakia may be offered contact lenses or a lens implant first.[3]
How a scleral lens helps
A lens that sits on the eye moves with it. You look through the optical center wherever you look, so most of the problems of thick glasses fall away. That’s true of any contact lens, not just scleral lenses.
A scleral lens is a large rigid gas-permeable lens. It rests on the sclera (the white of the eye) and arches over the cornea without touching it. Before insertion it is filled with sterile saline, so a layer of fluid sits between the lens and the cornea. Its large size and resting point on the white of the eye mean it stays centered, which matters when a strong prescription has to line up with the pupil.
The question is when you need a scleral lens rather than a simpler one. For an eye with a normal cornea, soft lenses and smaller rigid lenses often work. Scleral lenses tend to come in when:
- smaller lenses won’t stay centered or aren’t comfortable
- the cornea is also irregular, scarred, or damaged
- the eye surface needs the protection of the fluid layer as well
What the research shows
This is a small use of scleral lenses. In an international survey describing 259 scleral lens patients, only 4% were wearing them for uncomplicated refractive error. 87% wore them for corneal irregularity.[1] In a series of 140 eyes fitted at one clinic, three eyes (2%) were fitted for high refractive error. Their median vision with the lenses was 20/32.[8]
The role has shrunk over time. At one specialist scleral lens clinic between 1988 and 1993, when most lenses were molded hard plastic, aphakia accounted for 18.4% of scleral lens cases and high myopia for 12.8%.[6] By 1999 to 2003, among eyes still wearing scleral lenses at Moorfields Eye Hospital in London, aphakia accounted for 2.1% and myopia for 2.6%.[7]
People with regular corneas stop more often. In a prospective study of 95 scleral lens wearers, 58% of those with regular corneas were still wearing their lenses after a year, compared with 77% of those with irregular corneas. Handling problems and discomfort were the main reasons people stopped.[5] The study didn’t break out high prescriptions specifically, but it’s a useful guide: when glasses or soft lenses already give decent vision, the effort of a scleral lens has to be worth it.
Aphakia with a damaged cornea can do well. In a series of eight eyes with aphakia and severe corneal damage after injury, which couldn’t be corrected with smaller rigid lenses, average vision with mini-scleral lenses was 0.05 logMAR (about 20/22). People wore them comfortably for an average of 11.6 hours a day.[9]
Children are a special case. For infants left without a natural lens after cataract surgery, the contact lens group of the Infant Aphakia Treatment Study, babies with one affected eye, wore silicone elastomer lenses, rigid gas-permeable lenses, or both at different times.[11] Scleral lenses have been fitted to children with aphakia in small series, alongside other indications.[10]
Other options, compared
| Option | What it does | Typically suited to |
|---|---|---|
| Glasses | Correct focus from a distance in front of the eye | Most prescriptions; less comfortable as strength rises |
| Soft contact lenses | Correct focus on the eye | Many high prescriptions with a normal cornea |
| Corneal rigid gas-permeable lenses | Correct focus on the eye with crisp optics | High prescriptions where the lens centers and is comfortable |
| Scleral lenses | Correct focus on the eye, centered on the white | Failure of smaller lenses, or an irregular or damaged cornea as well |
| Lens implant or refractive surgery | Changes the eye’s focusing power permanently | Selected adults; ask a surgeon about suitability and risks |
Questions to ask a scleral lens fitter
- Have I tried soft and smaller rigid lenses, and why might a scleral lens work better for me?
- Is there anything about my cornea or eye surface that makes a scleral lens a better fit?
- How many patients with high prescriptions or aphakia do you fit with scleral lenses?
- How will I put the lens in if I can barely see without it?
- How many visits does a fit usually take, and what do the fees cover?
- Do you bill my insurance directly, or give me a superbill to submit myself?
- What signs mean I should remove the lens and call you the same day?
Common questions
How strong does a prescription have to be for a scleral lens?
There's no set cut-off. Prescription strength alone rarely decides it. Scleral lenses are usually considered when glasses, soft lenses, and smaller rigid lenses haven't worked, or when the eye has another problem such as an irregular or damaged cornea.
Are scleral lenses better than glasses for high myopia?
Not better in every way, but different. Any contact lens avoids the thick edges, the shrinking of objects, and the distortion toward the edge of strong glasses. Many people with high myopia get those benefits from soft or smaller rigid lenses, which are simpler to handle.
I had cataract surgery without a lens implant. Can scleral lenses help?
They can. Contact lenses are a standard way to correct aphakia, and scleral lenses have been used when the cornea is also damaged or smaller lenses won't stay in place. A lens implant placed in a later operation is another option. Your surgeon can tell you whether that is possible for your eye.
Do scleral lenses protect against the eye problems linked to high myopia?
No. A lens corrects focus. It doesn't change the length of the eye or the strain on the retina that comes with high myopia. Keep up with regular dilated eye exams as your eye doctor advises.
Can I wear one scleral lens if only one eye has a high prescription?
Yes, a lens can be fitted to one eye. When the two eyes' prescriptions differ a lot, contact lenses can reduce the difference in image size between the eyes that glasses create.
Will I still need reading glasses with scleral lenses?
Often, yes, especially as near vision fades with age. Many wearers use reading glasses over their lenses, and some use one eye for distance and the other for near. Multifocal scleral lenses exist but are uncommon, so ask your fitter what suits your eyes.
My eyes feel tired after a few hours of wear. Could the prescription be wrong?
It's possible. With a strong prescription, a lens power that is slightly off can cause eye strain, and a fit problem can cause discomfort too. Tell your fitter when the tiredness starts, because adjusting the power or the fit often helps.
Can I try a scleral lens before committing to one?
Usually, yes. Most fitters start with a trial lens in the office, which lets you feel how the lens sits and try handling it. Ask about trial options, follow-up visits, and what the fees cover before you start.
Will insurance cover scleral lenses for a high prescription?
Sometimes. Some plans cover medically necessary contact lenses when they give clearly better vision than glasses, but the rules vary and a high prescription alone doesn't always qualify. Ask your plan what it requires and ask your fitter to document how your vision compares in glasses and in lenses.