This article is more than 5 years old. Information may no longer be current.
Surface ablation procedures still viable options in refractive surgery
N/A
 Béatrice Cochener |
LASIK was designed 20 years ago to compete with and even replace PRK in bilateral surgery due to fast visual recovery and optimal patient comfort, but its use has declined with the occurrence of secondary ectasia. This complication, mostly attributed to an improper indication of a lamellar cut on the fragile cornea, has led to an inversion of indications, with a preference for LASIK in low refractive error and a return to surface ablation for moderate ametropia and/or a cornea with risk factors.
In Europe and especially in France, PRK never completely disappeared and represents 20% to 80% of corneal surgery, according to the surgical volume and the quality of equipment in clinics. The main reason for the lasting popularity of surface ablation is probably not based on the reputation of social conditions in Europe allowing less pressure to go back to work and a slower pace of life, but rather on the security aspect of an older procedure being easier to control than LASIK and less costly in equipment and procedure price.
Ablation benefits
Refinements of ablation profiles (smoothing process, progressive transitional zone), use of alcohol rendering epithelial removal easier, the advent of mitomycin C for wound healing modulation and prevention of haze in extreme indications (moderate and high ametropia, re-treatments) have all expanded the field of applications for surface ablation.
Moreover, postoperative management combining a lens shield, topical NSAIDs and innovative lubricants has considerably improved patient comfort when adjusted excimer profiles have optimized time for recovery and wound healing, as well as stability and predictability.
Surgeons with minimal experience might feel more secure performing an easy and well-controlled procedure instead of exposing the patient to complications of the flap cut with a learning curve. In addition, when considering custom ablation, PRK avoids the amount of higher-order aberrations related to a flap and therefore does not need nomogram adjustment.
Finally, the ocular surface has been shown to play an important role in refractive surgery, but LASIK induces more dryness, which could justify surface ablation in cases of preoperatively identified ocular surface disease.
Ablation indications
A variability of indications exists according to the conviction and the experience of the surgeon, but we can say in broad outline that in refractive centers with high volumes of patients, two-thirds to three-fourths of procedures are LASIK. This is especially the case because of the advent of the femtosecond laser, allowing for the creation of a thin flap, which should, theoretically, better respect the biomechanics of the cornea than a mechanical cut. However, the thin flap is created without eliminating secondary ectasia.
PRK is reserved for patients in professions or sports with contraindications for a lamellar cut. It is also reserved for fine retouches and for corneas that present with risks factors, including abnormal irregularity, viscoelasticity and/or thickness.
We should also consider surface ablation because of an apprehension of the LASIK cut for more demanding patients and because of the higher cost of a surgical procedure that provides the same end result: removal of glasses.
Where are we now with surface photoablation procedures? Variations of PRK include LASEK (performing a chemical lifting of the epithelium) and epi-LASIK (performing a mechanical separation of the epithelial flap). Indeed, different arguments have not changed the basic facts with LASIK. There is no scientific evidence of positive action of living cells from the flap, a shortening of the healing period or better postoperative comfort compared with PRK associated with a lens shield. Moreover, the epithelium will inexorably disappear, needing, even in premature loss of the lens, a removal of the flap because of acute pain.
In addition, the extra cost induced by specific instrumentation, particularly for epi-LASIK, seems to not be justified. Concerning the intraoperative use of mitomycin C 20 mg/mL for the majority of surgeons, it is not systematical but is nearly unanimously approved for re-treatment, high ametropia, haze and/or ablation on radial keratotomy.
In conclusion, PRK is definitely not obsolete. It maintains not a competitive place but a complementary position with LASIK. Admittedly, perspectives of transepithelial ablation are the most investigated, giving a growing and promising place to the femtosecond laser. If this approach shows the same or even better efficacy, predictability and stability than PRK, without surface alteration and with fewer traumas for the cornea, the future of photoablation could be threatened for both PRK and LASIK.
- Béatrice Cochener, MD, PhD, can be reached at the Department of Ophthalmology, University of Brest, CHU Morvan - 5, Av. Foch, 29609 Brest Cedex, France; email: beatrice.cochener-lamard@chu-brest.fr.
- Disclosure: Dr. Cochener has no relevant financial disclosures.