How PRK can affect your vision
PRK (photorefractive keratectomy) is a laser vision surgery. Unlike LASIK, it doesn’t cut a flap. The surgeon removes the whole surface layer of the cornea and reshapes the tissue beneath it with an excimer laser. The surface layer then grows back over the following days.[2]
Most people end up seeing well. When vision isn’t good after PRK, it is usually for one of these reasons:
- Haze. Haze is cloudiness in the cornea caused by an abnormal healing response. It scatters light, so vision can look foggy, with glare. In the early days of PRK it was very common: one 1992 study using older broad-beam lasers, without the anti-scarring drug mitomycin C or steroid drops, reported haze in 92% of eyes. In a large 2017 single-center study using mitomycin C and steroid drops, the rate was 1.3%.[1] Larger corrections (more than 5 diopters of nearsightedness, or farsightedness) and higher astigmatism are linked to a higher risk.[1]
- An uneven or off-center treatment. If the laser zone is decentered or the surface heals unevenly, the cornea can end up with irregular astigmatism. That kind of distortion causes ghosting and halos that glasses can’t fully correct. A Canadian series of custom scleral lenses listed a decentered PRK treatment among the reasons people were fitted.[6]
- Ectasia. Rarely, the cornea weakens and bulges forward after surgery. A 2021 review of published reports estimated this at 20 per 100,000 PRK eyes without known risk factors, compared with 90 per 100,000 after LASIK.[3] Our post-LASIK ectasia page covers ectasia after any laser surgery in detail.
- Dryness and pain. Refractive surgery can lead to significant dry eye and, in some people, nerve-related pain (corneal neuralgia).[8]
How a scleral lens helps
A scleral lens is a large rigid gas-permeable lens. It rests on the sclera (the white of the eye) and arches over the whole cornea without touching it. Before insertion it is filled with sterile saline, which sits between the lens and the cornea while it is worn.
- It replaces an uneven surface optically. Light passes through the smooth front of the lens and the even layer of saline before it reaches the cornea. The saline fills in surface irregularities, which largely cancels them out.
- It doesn’t rely on the cornea’s shape for fit. Small rigid lenses sit on the cornea, so a reshaped or uneven cornea can make them hard to center and keep comfortable. A scleral lens lands on the white of the eye instead.
- It keeps the surface wet. Reviews describe scleral lenses being used after refractive surgery for leftover prescription, slow surface healing, and dry eye, partly because the saline layer protects and hydrates the surface.[9]
What a lens can’t do is make cloudy tissue clear. If most of your blur comes from haze rather than surface shape, a lens may help less. Your eye doctor can often tell from an exam and corneal imaging, and a trial lens is a practical test.
What the research shows
There is very little research on PRK by itself. Studies of scleral lenses after refractive surgery mostly group PRK with LASIK and radial keratotomy. A 2015 review noted that published series include refractive surgery patients but don’t report their outcomes separately.[7]
The closest study is small. At French centers, 35 eyes of 19 people with irregular corneas after refractive surgery were fitted with scleral lenses after conventional contact lenses had failed. Average best-corrected vision improved from 0.33 to 0.08 logMAR (roughly 20/40 to 20/25). Scores on a dry eye questionnaire improved from 66.2 to 42.4, where lower is better, and measured optical distortion roughly halved.[4] The abstract doesn’t say how many eyes had PRK, and one author advises the lens’s manufacturer.
One large series had only two PRK eyes. An academic center in Houston reviewed 825 eyes fitted with PROSE, a type of custom scleral lens. Every group with irregular corneas improved significantly except the post-PRK group, which had just 2 eyes.[5] Two eyes is far too few to draw any conclusion, but it shows how thin the evidence is.
Custom-designed lenses have been used for decentered treatments. In a Canadian series of 14 eyes fitted with an impression-based scleral lens, a decentered PRK treatment was one of the indications. Across the whole group, average vision improved from 20/36 to 20/21.[6] Results weren’t reported for the PRK eye on its own.
Other options, compared
What makes sense depends on why your vision is off. Haze, an irregular surface, and ectasia each have their own treatments.
| Option | What it does | Typically suited to |
|---|---|---|
| Glasses or soft lenses | Correct regular leftover prescription | Under- or over-correction without irregularity |
| Steroid drops | Calm the healing response | Early haze, as prescribed by your surgeon[1] |
| Removing haze (debridement or phototherapeutic laser), often with mitomycin C | Clears cloudy tissue and lowers the chance it returns | Haze that persists or is deep[1] |
| Corneal rigid gas-permeable or hybrid lenses | Give a smooth optical surface on the cornea | Mild irregularity, if the lens centers well |
| Scleral lenses | Vault the cornea over a saline layer | Irregular astigmatism, decentered treatments, ectasia, or dry eye after surgery |
| Corneal cross-linking | Strengthens the cornea | Progressive ectasia; doesn’t replace vision correction |
Questions to ask a scleral lens fitter
- Is my blur mostly from haze or from the shape of my cornea? How can we tell?
- Have you fitted people after PRK, and what did you have to adjust?
- Should I see my surgeon about treating the haze before we try a lens?
- Do my corneal maps show any sign of ectasia?
- If my eyes are dry or painful, do you think a scleral lens will help, and how will we know?
- How many visits does a fit usually take, and what do the fees cover?
Common questions
Can a scleral lens clear up haze after PRK?
Not directly. Haze is cloudiness inside the cornea, and a lens sits in front of it. A lens can sharpen vision if the surface has also become uneven. Haze itself is usually treated with steroid drops or, if it persists, by a surgeon removing it.
Is PRK more likely than LASIK to need a scleral lens later?
There's no study that compares them on this. For ectasia, the one problem that has been counted, a 2021 review estimated it happens about four and a half times less often after PRK than after LASIK. Both rates are low.
My vision after PRK is blurry but my eye doctor says the surgery went fine. Could a scleral lens help?
Possibly, but find out why first. Leftover prescription can often be corrected with glasses or ordinary contact lenses. Irregular astigmatism, an off-center treatment, or ectasia are the situations where a rigid or scleral lens is usually considered. Corneal mapping can tell these apart.
Can a scleral lens help with dryness or pain after PRK?
Scleral lenses keep the cornea bathed in saline, and one small study of people with irregular corneas after refractive surgery reported better dry eye scores with them. Pain that is out of proportion to what your eye doctor sees can be neuropathic, which is a different problem. A lens helps some of those people and is poorly tolerated by others.
Should I have more laser surgery instead?
Sometimes that's the better route, for example a phototherapeutic laser treatment to remove haze. A scleral lens avoids more surgery and can be stopped at any time. A cornea specialist can tell you which options fit your eye.