Comparison: PRK vs. LASIK
Posted on December 31, 2018 by Mark Mandel, MD
Eye Surgery Options
Most patients select LASIK eye surgery because clarity of vision occurs quickly and healing is rapid. However, Mark Mandel, MD at Optima Eye in the Bay Area offers PRK as an alternative to LASIK eye surgery.
It is important to realize that PRK uses exactly the same lasers and the same technology as LASIK. Additionally, there does not seem to be a significant difference in the percentage of patients achieving 20/20 to 20/40 vision at the end of six months between patients having PRK and patients having LASIK. The incidence of overcorrection or undercorrection, the need for enhancements (touch-ups), decreased correctable visual acuity, infection, rate of complications and long-term side effects are essentially equal.
Dr. Mandel charges the same for both LASIK and surface procedures. The Laser Center charges a little more for LASIK because of the special instrumentation required.
Length of PRK vs LASIK Procedure
Both LASIK and surface procedures are quite short. They each take about 6 minutes of actual treatment time for each eye. There is no discomfort during either procedure. With LASIK, there is a “pressure sensation” and a “graying” out of vision for about 60 seconds at the beginning of the procedure.
Complexity of the Surgery
Both are highly delicate microsurgical procedures that require the skill, knowledge and expertise of an experienced cornea and refractive surgeon.
In the majority of cases, the vision following LASIK is much better during the first three weeks than PRK. Discomfort is considerably less, achievement of visual acuity is faster, return to full activity is quicker, and the need for post-operative medications is greatly diminished with LASIK. Vision becomes “crisper” quicker and patients feel more comfortable during the early post-operative period. It takes up to one month for vision to become clear after PRK. This is why we recommend doing PRK on one eye at a time.
LASIK – a shield is worn over the eye the first 24 hours, and then nightly for 10 nights to prevent inadvertent rubbing of the eye. Eyedrops are begun the morning after surgery and are used for 4 days.
PRK – a therapeutic soft bandage contact lens is placed in the eye at the time of surgery and is worn for approximately six days to reduce discomfort. Anti-inflammatory, antibiotic and cortisone eyedrops are used twice a day while the lens is on. After contact lens removal, the topical cortisone is used four times a day for one month, then tapered over the next one to three months. Artificial tears are used frequently.
PRK and LASIK Side Effects
Both procedures have a low rate of side effects. These include mild irritation, glare or halos (more prominent at night), ghost images, and undercorrection or overcorrection or induction of astigmatism. Both LASIK and PRK can produce a slight decrease in the quality of night vision (decreased contrast sensitivity). These side effects have been minimized with software and hardware upgrades to the lasers that we employ including larger treatment zones, eye tracking, wavefront and iris registration.
Haze and/or scarring of the surface of the cornea may occur following PRK. However, it is rare with lower degrees of nearsightedness (less than 5.00 diopters). In all patients undergoing PRK I briefly place a small sterile sponge with a medication called Mitomycin-C on the surface of the treated cornea. This substantially decreases the chances for scarring or haze following PRK. However, if scarring occurs, it can permanently decrease vision. This occurs in less than 0.5% of cases in our hands.
About 13% of LASIK or PRK patients may require a retreatment (enhancement or touch-up) for undercorrection, overcorrection and/or induced astigmatism. Retreatment is more common in patients who are highly myopic, highly hyperopic, or who have a lot of astigmatism. With either PRK or LASIK regression and undercorrection is very uncommon with less than 3.00 diopters of myopia or hyperopia, or 2.00 diopters of astigmatism.
Irregular astigmatism (i.e., a “wavy” corneal surface) due to decentration of the laser optical zone or uneven healing is uncommon with both procedures (less than 1%).
Loss of best correctable (i.e. with glasses) vision worse than two lines on the vision chart is about 0.5% to 2% for both LASIK and PRK.
Recurrent corneal erosions are uncommon with both PRK and LASIK.
Infections are very rare, but may result in permanent loss of vision. Sterile inflammatory white blood cell infiltrates in the treated area occur rarely in surface PRK while wearing the therapeutic bandage soft contact lens. These usually respond well to treatment with topical antibiotics and cortisone. Sterile white blood cell infiltrates (DLK) below the flap can also be seen with LASIK.
Unlike LASIK, many PRK patients require topical cortisone for 1 to 4 months to reduce scarring and prevent regression. A small percentage of patients have a genetic tendency to develop high pressure in the eye when given cortisone topically for this long. When the cortisone drops are discontinued, the elevated pressure in the eye generally returns to normal. Rarely does the pressure remain elevated and require treatment. LASIK patients use cortisone drops for a few days and cannot develop cortisone-induced glaucoma. Cortisone can also cause cataracts, but fortunately they are rarely seen with four months or less of topical therapy. The rare patient may develop an early cataract requiring cessation of cortisone, at which time the cataract usually stops growing. LASIK patients use cortisone drops for only a few days and cannot develop cortisone-induced cataracts.
Complications Specific to LASIK
These include problems with the microkeratome which result in incomplete flaps, however we only use the microkeratome rarely as we primarily perform the All Laser LASIK procedure. Irregular flaps, flaps with thin spots or “holes” in it, or a flap that comes totally off is possible but very rare. These require the procedure to be aborted, and then redone in about three months. Rarely a flap may require suturing back in place, and even more rarely, a flap may be lost. If the flap is lost, a corneal transplant operation may be required.
Occasionally, adequate ring suction cannot be maintained and LASIK cannot be performed.
Other uncommon flap problems include material under the flap (which usually causes no problem), infection (very rare), or epithelial ingrowth beneath the flap (requiring repositioning and cleaning under the flap).
Folds (like the striations seen just before tearing a piece of cellophane off of a roll) occur in about 5% of LASIK flaps in people with high amounts of myopia (6.00 diopters of more), and occasionally lower myopes who require large zones of treatment. Most of the time the folds do not cause symptoms, but occasionally they can result in distorted vision, decreased vision, decrease in contrast appreciation and/or can increase glare and halos at night. If patients have symptoms from microfolds, the flaps must be lifted and an attempt to “iron-out” the folds undertaken. However, in some cases, the folds cannot be “ironed out” and patients may have persistent symptoms.
Blindness is an exceedingly rare complication of LASIK or PRK and can be caused by severe infection or a retinal, optic nerve or blood vessel problem occurring in the back of the eye during or after surgery.
Fortunately, refractive surgery procedures are safe and effective and complications are rare. However, like any operation, problems can occur and patients must always weigh the risk and the benefits before undergoing surgery.