How radial keratotomy changes your vision
Radial keratotomy (RK) was a surgery for nearsightedness, widely done in the 1980s and 1990s.[12] The surgeon made deep, spoke-like cuts in the cornea (the clear front window of the eye), leaving a clear zone in the center. The cuts let the cornea’s middle flatten, which reduced nearsightedness.
For many people it worked well for years. In the PERK study, which followed 793 treated eyes for 10 years, 70% of patients who had both eyes done reported not wearing glasses or contacts for distance.[1] But the cornea often doesn’t stay put, and three long-term problems are common.
A slow drift toward farsightedness. In the PERK study, the first-operated eyes averaged -0.36 D six months after surgery and +0.51 D at 10 years. 43% shifted in the farsighted direction by 1.00 D or more, and the shift continued throughout the study. It was linked to the diameter of the clear central zone.[1]
Vision that changes through the day. Many RK eyes grow more nearsighted from morning to evening. Eleven years after surgery, 51% of PERK eyes shifted by 0.50 to 1.62 D between a morning and an evening exam, and 13% lost two to seven lines of uncorrected vision over the day. For most people the change is small, and the authors concluded it may be permanent in some.[2] A related study found the cornea itself steepens over the day, and that eye pressure may contribute.[3]
An irregular surface. The incisions and scars can leave the cornea uneven, which causes glare and blur that glasses can’t fully correct. A Japanese hospital reviewing patients 20 to 30 years after RK found that some kind of refractive or medical help was possible in 59% of those whose vision had worsened. In the other 41%, no intervention was possible.[4]
How a scleral lens works after RK
A scleral lens is a large rigid gas-permeable lens. Instead of sitting on the cornea, it rests on the sclera (the white of the eye) and arches over the entire cornea without touching it. Before insertion the lens is filled with sterile saline, so a layer of fluid sits between the lens and the cornea.
That arrangement helps an RK eye in three ways:
- It replaces the eye’s irregular front surface. Light passes through the smooth front of the lens and the even layer of fluid before it reaches the cornea. The fluid fills in the irregularities, which largely cancels them out optically.
- It corrects the accumulated prescription. The lens can correct both the refractive error that has built up since surgery and irregular astigmatism.[5]
- It keeps weight off the cornea. Smaller rigid lenses sit on the cornea and can be hard to center on a flattened, uneven surface. A scleral lens lands on the white of the eye instead.
Rigid lenses are a common way to restore vision after RK. At the Japanese hospital above, a rigid gas-permeable lens fit was the most common refractive intervention, and it was effective in 36% of cases.[4]
What the research shows
Most mini-scleral fits improve vision, but not all. A Taiwanese hospital reviewed 36 eyes fitted with mini-scleral lenses after RK. Average best vision improved from 0.47 logMAR in glasses to 0.19 logMAR with the lenses (lower is sharper). 64% of fits met the study’s definition of success, a gain of three or more lines on the eye chart.[5]
Where the incisions sit matters. In that study, fits worked better when the RK treatment zone was well centered on the eye. Small central clear zones, from incisions or scars close to the center, made results worse.[5]
The evidence base is small. A 2015 review found high success rates reported for scleral lenses after refractive surgery, including RK, but noted that outcomes for refractive surgery patients were not reported separately.[6]
Scleral lenses can help even after serious complications. In a Belgian case, a woman’s cornea opened spontaneously along an old incision 29 years after RK. After the wound healed with the help of soft bandage lenses, a scleral lens restored her vision to 20/20.[9]
Other options, compared
A few procedures aim at the cornea’s instability rather than at vision correction.
- Corneal cross-linking has been tried to stabilize RK corneas. In a Toronto series of nine eyes, daily fluctuation stopped in eight between 6 and 12 months after cross-linking. Part of the early effect had faded by 12 months, and the authors called for longer follow-up.[10]
- Bowman layer onlay grafting places a thin layer of donor tissue on the cornea. In the first reported patient, her rating of visual fluctuation dropped from 10 to 3, while her best corrected vision stayed the same.[11]
- Cataract surgery is now common in people who had RK decades ago. Their altered corneas make it harder to calculate the implant lens power, and daily fluctuation adds to the challenge.[12]
| Option | What it does | Typically suited to |
|---|---|---|
| Glasses | Correct regular blur only | Eyes with a fairly regular surface and little daily change |
| Soft lenses | Correct prescription, mask little irregularity | Mild farsighted shift with a regular surface |
| Corneal rigid gas-permeable lenses | Give a smooth optical surface on the cornea | Irregular surfaces where the lens centers and is comfortable |
| Hybrid lenses | Rigid center with a soft skirt | People who can’t tolerate a corneal rigid lens |
| Scleral lenses | Vault the whole cornea over a fluid layer | Irregular corneas, or failure of the options above |
| Corneal cross-linking | Aims to stabilize the cornea | Fluctuation or progressive change; evidence in RK is limited |
| Corneal surgery (onlay graft, transplant) | Reinforces or replaces corneal tissue | Instability or damage not managed by lenses |
Questions to ask a scleral lens fitter
- How many patients with RK do you fit, and how do you handle daily fluctuation?
- How do you measure my eye: trial lenses, corneal mapping, or a 3D scan of the eye surface?
- How will you check for swelling or changes around my incisions?
- 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?
- Who do I call if I can’t get a lens out, or if my eye becomes painful?
- If I need cataract surgery later, how will the lens fit into that plan?
Common questions
Why is my vision different in the morning and the evening?
This is a known long-term effect of RK. In a large US study, about half of eyes grew more nearsighted between morning and evening more than a decade after surgery. For most people the change is small, but for some it is enough to notice.
My RK worked for years. Why am I farsighted now?
Many RK eyes keep shifting toward farsightedness for years after surgery. In the PERK study the shift continued through the whole 10 years of follow-up, and it was linked to the size of the untouched central zone.
Can a scleral lens stop the daily fluctuation?
It can steady your vision while you wear it, because the lens and fluid layer give the eye a new front surface. It doesn't change the cornea itself. Your fitter may still need to account for how your eye changes through the day.
Are scleral lenses safe on corneas with RK incisions?
Many people with RK wear them successfully, but the old incisions are weak points. Swelling under the lens has been measured near the incisions, and rare cases of the cornea opening along an old incision have been reported. Regular follow-up with your fitter matters.
I need cataract surgery. Does RK affect that?
Yes. RK changes the cornea in ways that make choosing the lens implant power harder, and daily fluctuation adds to that. Tell your cataract surgeon about your RK and ask how they plan for it.
Will scleral lenses help with glare and starbursts at night after RK?
Many people with RK say scleral lenses greatly reduce the doubling, glare, and starbursts they see at night. Some still notice mild starbursts, especially with scars near the center of the cornea. Tell your fitter what you see, since a refit or custom optics can sometimes reduce what's left.
Can I go back to scleral lenses after cataract surgery?
Many RK wearers do, once the surgeon says the eye has healed. The prescription changes after surgery, so expect a refit rather than reusing your old lens. Tell your surgeon beforehand that you rely on scleral lenses so they can plan with your fitter.
Will I still need reading glasses with my 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 and harder to get right on an irregular cornea, so ask your fitter what fits your eyes and needs.
My eye doctor says a scleral lens won't improve my vision. Should I get another opinion?
It can be worth it. A scleral lens can sometimes make vision steadier and reduce ghosting and glare even when the smallest line you can read doesn't change much. A second opinion from a fitter who sees many post-RK eyes can tell you whether a lens is likely to help you.
Why does an area near my RK scars hurt even with the lens in?
Pain can have several causes, including the lens pressing on one area or a sensitive spot on the cornea, and your fitter needs to look to tell which. Lens adjustments sometimes help. If the pain is severe, or comes with redness or blurrier vision, remove the lens and call your eye doctor today.