Photorefractive keratectomy, or PRK, is the original excimer laser vision correction, and it works by removing the epithelium and reshaping the anterior stroma without creating a flap.
It is also the procedure of choice for thin corneas, for eyes with anterior basement membrane disease, and for patients with a high risk of trauma (see LASIK).
The price is also a slower and more uncomfortable recovery.
How Photorefractive Keratectomy Is Done
- Surgeons remove the epithelium with alcohol, a brush, a blade, or the laser itself in the transepithelial method
- Then the excimer laser ablates the stroma according to the refractive error
- Surgeons may apply mitomycin C, 0.02 percent, for 12 to 30 seconds in higher corrections, to reduce haze (see the references)
- The surgeon places a bandage contact lens and starts antibiotic and steroid drops
The procedure takes a few minutes per eye under topical anesthesia.
Photorefractive Keratectomy: Recovery Timeline
Also, the epithelium heals in three to five days, and the bandage lens is removed at that point.
Pain is worst in the first two or three days, and cold compresses, lubricants, and oral analgesics relieve it.
Vision is blurry for several days, and most patients can work in a week, though sharp vision takes one to three months.
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From Choroida — the team behind this siteWho Is a Good Candidate?
- Thin corneas or borderline tomography
- Anterior basement membrane dystrophy or a history of recurrent erosion (see map-dot-fingerprint dystrophy)
- Contact sports, military, and law enforcement jobs
- Patients with a past history of flap problems
Patients with a low tolerance for pain or who must see well in days may prefer another method.
Results of Photorefractive Keratectomy
Most patients reach 20/25 or better, with high satisfaction in studies of large series, and the visual outcomes at 6 to 12 months are like those of LASIK (see the references).
In addition, stability is good, and regression is related to the size of the correction.
Complications of Photorefractive Keratectomy
- Haze: a subepithelial scar, rarer with lower corrections and with mitomycin (see PRK corneal haze)
- Regression and undercorrection
- Infection, though it is uncommon
- Steroid response, with a rise in pressure that needs monitoring
- Dry eye, glare, and halos, especially at night
Persistent pain, redness, or reduced vision need prompt review.
Follow-Up for Photorefractive Keratectomy
Examine at day 1 or 2, at the time of bandage lens removal, and at one, three, and six months, with the pressure checked while on steroid.
A taper over two to three months is also common, and it is tailored to the response.
Comparison With Other Procedures
LASIK and SMILE give quicker recovery and less pain, but they weaken the cornea more and carry flap or lenticule risks (see small incision lenticule extraction).
Counselling
Describe the discomfort of the first days, the slow recovery, and the importance of the drops, and agree on a plan to avoid driving until the vision is adequate.
An Example Case
A 24-year-old military recruit with -3.50 sphere and a corneal thickness of 480 micrometers is refused LASIK because of the thin cornea, and has PRK in both eyes at the same visit.
He has two days of pain managed with analgesics and cooling, and the bandage lens is removed on day 4.
At three months he sees 20/16 in both eyes, with no haze, and returns to duty without restrictions.
Practical Steps in the Clinic
- Warn patients about the pain in the first days, and give clear instructions
- Use topical steroid drops, and then check the pressure at each visit
- Teach patients to avoid rubbing and to wear sunglasses outdoors
- Use mitomycin C for higher corrections, following the surgeon’s protocol
Counselling
Tell patients that the recovery is slower than for LASIK, that they will need time off, and that final vision takes a few months.
Also, explain the benefits of no flap, and the risks of haze and regression.
Key Points to Remember
- No flap, so suited to thin corneas and surface disease
- Pain and slow recovery are the main drawbacks
- Haze is rare, and steroids or retreatment treat it
- Check the pressure during steroid use
Limits of the Procedure
Large corrections raise the risk of haze and regression, so patients with high myopia may need another option such as a phakic lens.
Choosing the Method of Epithelial Removal
Alcohol-assisted, mechanical, and laser transepithelial removal give similar final vision, and the choice depends on the surgeon and the patient’s eye.
Transepithelial laser methods may give less pain and faster healing in some studies, though results differ.
For the latest studies, see the PubMed results for photorefractive keratectomy.
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From Choroida — the team behind this siteReferences
- Seiler T, Holschbach A, Derse M, Jean B, Genth U. Complications of myopic photorefractive keratectomy with the excimer laser. Ophthalmology. 1994;101:153-160.
- Majmudar PA, Forstot SL, Dennis RF, et al. Topical mitomycin-C for subepithelial fibrosis after refractive corneal surgery. Ophthalmology. 2000;107:89-94.
- Sugar A, Hood CT, Mian SI. Patient-reported outcomes following LASIK: quality of life in the PROWL studies. JAMA. 2017;317:204-205.
- American Academy of Ophthalmology. Basic and Clinical Science Course, Section 13: Refractive Surgery. AAO; current edition.
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