• PRK vs LASEK Eye Surgery

PRK vs LASEK

If you do any research these days into your refrac­tive surgery options, you will inevitably see the terms “LASEK”, “PRK” and occa­sion­al­ly “advanced sur­face abla­tion” (ASA) being bat­ted around. What is PRK, what’s LASEK, what is the dif­fer­ence, and how does ASA relate to these?

First, very sim­ply, the above pro­ce­dures reshape the cornea to reduce or elim­i­nate your need for glass­es and con­tacts just like LASIK and Intralase do, but they do so with­out cre­at­ing a flap. With PRK and LASEK, the reshap­ing of your cornea takes place just under the thin loose sur­face lay­er of your cornea, called the epithe­li­um. In both pro­ce­dures, a con­tact lens is placed on the eye to pro­tect the new cells as the heal.

LASEK OVERVIEW

A lot of the infor­ma­tion avail­able to you on the inter­net regard­ing LASEK is at the very least con­fus­ing, so I think it’s impor­tant that you get the facts, based on peer-reviewed stud­ies and clin­i­cal expe­ri­ence that have guid­ed thought­ful sur­geons over the last decade on this sub­ject.

Terminology

PRK stands for “pho­to-refrac­tive ker­a­te­c­to­my” while LASEK stands for “laser assist­ed epithe­lial ker­a­te­c­to­my” ( the last word, “ker­a­te­c­to­my”, which means removal of corneal tis­sue, being used in favor of the orig­i­nal descrip­tive term giv­en to the LASEK acronym “ker­atomileu­sis”, mean­ing “to manip­u­late with­in.”

A Brief History

LASEK was first coined by sur­geon, Dr Mas­si­mo Camellin of Italy, who first described the LASEK pro­ce­dure in 1998, and he and ear­ly pio­neers like Dr. Shah in the UK were hope­ful over 15 years ago that it might pro­duce improved heal­ing and less risk of corneal haze (scar­ring.)

More recent­ly, “LASEK with Epithe­lial flap removal”, which is, in fact, PRK by anoth­er name, is now wide­ly rec­og­nized as pro­vid­ing not just bet­ter ini­tial vision than tra­di­tion­al LASEK dur­ing the 3–4 day epithe­lial heal­ing peri­od, but often sig­nif­i­cant­ly less pain than was observed in LASEK patients who had their epithe­lial flaps replaced back over their corneas. One of the bet­ter stud­ies demon­strat­ing this was con­duct­ed by Liu et al and appears in Cel­lu­lar Bio­chem­istry and Bio­physics, May 2010 issue and involved one-year fol­low-up of over 1000 eyes.

The Procedure behind LASEK and PRK

Let’s look at how LASEK and PRK dif­fer in terms of how the treat­ments are per­formed:

PRK procedure 

  • The sur­face cells (epithe­li­um) are removed either with a high-speed mechan­i­cal brush, with dilut­ed alco­hol, or with the excimer laser itself (trans- epithe­lial), and the laser then reshapes the stronger lay­er under­neath (the stro­ma). More recent­ly, some sur­geons per­form­ing LASEK may use an epithe­lial micro-ker­atome to mechan­i­cal­ly sep­a­rate the sur­face lay­er from the stro­ma (deep­er lay­er) and then remove or, less fre­quent­ly, replace this thin sur­face lay­er fol­low­ing the laser reshap­ing.

Historic LASEK procedure

  • The sur­face cells were loos­ened with a dilut­ed alco­hol solu­tion and then moved to the side in one sheet, away from the pupil. After the same laser treat­ment which one would have in PRK, the epithe­lial sheet of now non-viable sur­face cells were replaced back over the pupil to cov­er as well as could be their orig­i­nal posi­tion on the cornea.

Comparing PRK and LASEK

There are two main dif­fer­ences when com­par­ing PRK vs LASEK that are observ­able both in the pro­ce­dures them­selves and how they affect patients that under­go these treat­ments.

  1. Epithelial Flap Replacement

    What was observed when com­par­ing the 2 meth­ods was that replac­ing the epithe­lial flap back over the pupil fre­quent­ly caused delayed and irreg­u­lar heal­ing of the sur­face lay­er and the vision patients had while this heal­ing was tak­ing place was fre­quent­ly worse than that of their coun­ter­parts who had PRK or “LASEK with flap removal, which has become pre­ferred over the old LASEK method, for the above rea­sons.

  2. Post-Operative Pain

    Post-oper­a­tive pain dur­ing the first 3 days after tra­di­tion­al LASEK was often found to be worse than after PRK. The the­o­ry behind this is that the dead epithe­lial cells may trap cytokines and oth­er biprod­ucts of cell death which may cre­ate a greater inflam­ma­to­ry reac­tion on the cornea, con­tribut­ing to increased pain per­cep­tion as well as a delayed/irregular heal­ing process. Oth­ers have pos­tu­lat­ed that some of the dilut­ed alco­hol might remain in some con­cen­tra­tion with­in the retained flap, which could fur­ther irri­tate the eye if replaced on the corneal sur­face.

    Keep in mind, how­ev­er, that new­er LASEK tech­niques which involve the use of an epithe­lial micro-ker­atome may allow for increased cell via­bil­i­ty and thus not cre­ate the increased post op pain that was fre­quent­ly seen in alco­hol-assist­ed LASEK, espe­cial­ly if the flap had been replaced.

The Current Stance on LASEK?

So why was tra­di­tion­al LASEK embraced by a host of sur­geons 10–15 years ago, and then quick­ly aban­doned by most sur­geons? The hope was that LASEK might reduce the risk of corneal haze beyond PRK, which before the more con­sis­tent use of mit­o­mycin (an anti-scar­ring agent) and bet­ter post-oper­a­tive top­i­cal steroid reg­i­mens, was a more sig­nif­i­cant and feared prob­lem with sur­face abla­tions. How­ev­er, the risk of haze was not found to be improved after many com­par­i­son stud­ies between LASEK and PRK , and now the risk of haze after sur­face abla­tion is very low, espe­cial­ly if patients fol­low their post oper­a­tive reg­i­men.

Through years of refine­ment, expe­ri­enced sur­geons obtain won­der­ful out­comes using an Amoils brush PRK tech­nique or a “LASEK with epithe­lial flap removal” tech­nique. We at Dia­mond Vision gen­er­al­ly pre­fer Amoils brush PRK, which when cou­pled with a cus­tomized wave­front-guid­ed or topog­ra­phy-guid­ed treat­ment pro­duces phe­nom­e­nal results, and is referred to as advanced ser­vice abla­tion.

As always, we look for­ward to help­ing guide you in your deci­sion-mak­ing as you deter­mine the best vision cor­rec­tion pro­ce­dures for you!

July 24th, 2015|0 Comments

About the Author:

Born in Connecticut and raised in Upstate New York , Dr. Stetson graduated Cum Laude from Colgate University in New York, and then earned an MD degree with honors at the University of Vermont College of Medicine. He distinguished himself again in residency at the Albany Medical Center, where he obtained the highest percentile in the Ophthalmology Knowledge Assessment Examinations. Dr. Stetson has performed more than 50,000 refractive surgeries and has been on staff at Diamond Vision since 2004, before becoming Medical Director in 2006.

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