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ADVANCED SURFACE ABLATIONS

PRK. FDA approval:1995. LASIK. FDA approval:1999. Evolution of surface treatments for the correction of ametropias. Postoperative pain Late visual recovery Risk of Haze. Epithelial injury. Intrastromal incision In a deep plane in the stroma. Risk of corneal ectasia Unpredictable

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ADVANCED SURFACE ABLATIONS

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  1. PRK FDA approval:1995 LASIK FDA approval:1999 Evolution of surface treatments for the correction of ametropias Postoperative pain Late visual recovery Risk of Haze Epithelial injury Intrastromal incision In a deep plane in the stroma Risk of corneal ectasia Unpredictable flap induced aberrations ADVANCED SURFACE ABLATIONS

  2. Advanced Surface Ablations The term “advanced surface ablations”: • was coined as a way to explain the evolution in surface ablation techniques from the earlier PRK days • covers several techniques such as: • PRK with the intraoperative use of mitomycin-C (MMC) (PRK-MMC) • laser epithelial keratomileusis (LASEK) • epipolis LASIK (Epi-LASIK)

  3. Advanced Surface Ablations Advanced surface ablation techniques offer several advantages over conventional PRK such as: • increased quality of vision • reduced postoperative pain • minimized corneal haze

  4. Advanced Surface Ablations Reasons for selecting a surface treatment: • Thin corneas for attempted correction (corneal thickness < 500μm, residual bed thickness < 300μm) • Preoperative Dry Eye • Epithelial basement membrane dystrophies • Flat or steep corneas • No risk of flap-related complications and flap-induced aberrations • Deep set eyes - small palpebral apertures • History of recurrent epithelial erosions • Contact sports

  5. Epithelial Removal The epithelium can be removed with several ways: • Mechanical removal of the epithelium with a blade or a rotating brush (PRK) • Epithelial removal with the use of alcohol (alcohol-assisted epithelial debridement, LASEK) • Epithelial removal with the laser ablation (transepithelial phototherapeutic keratectomy, t-PTK) • Epithelial removal with the use of epikeratome (Epi-LASIK, off-flap Epi-LASIK) • In cases of LASEK and Epi-LASIK the epithelium is separated and preserved

  6. Evolution ofAdvanced Surface Ablations • Introduction to the retained epithelial flaps (LASEK, Epi-LASIK): • Allow for decreased incidence of haze • Offer with better tolerance of patients • Mechanical epithelial separation provides with the benefit of avoiding alcohol toxicity

  7. PRK-MMC • 0.02% for up to 1.5 min depending on the attempted correction (delay in epithelial healing at 2 min) • Reduction of myofibroblast activity / haze (compared to corticosteroids) • Faster visual recovery and confocal microscopic normalization • Safety up to about 10 yrs max experience

  8. LASEK • A dilute solution (20%) is used on the eye in a holding cup (8.5mm diameter) for approximately 30 seconds in order to loosen the epithelium and creates a complete epithelial flap • After the loosened epithelium is slid to the side and the stromal surface is treated with the laser • The epithelium is replaced (LASEK) or can be directly removed (alcohol-assisted epithelial debridement)

  9. Epi-LASIK • Surface ablation (epi-polis superficial) • Epithelium is separated as a sheet and replaced on the ablated stroma (Epi-LASIK) • Special device (Epikeratome) - automated procedure • No use of alcohol • Dealing with drawbacks of PRK (postoperative pain/ discomfort, late visual recovery, haze) and avoiding risks of LASIK • Suitable for thin corneas • Epithelium is separated as a sheet with the use of the epikeratome and not retained on the ablated stroma (“off-flap” Epi-LASIK)

  10. CONCLUSIONS • Prefer surface ablation treatment if there is any suspicion for corneal ectasia • Advanced surface ablation techniques offer several advantages over conventional PRK such as: • reduced postoperative pain • minimized corneal haze • increased quality of vision • There are several studies with controversial results concerning postoperative pain levels, corneal healing and visual recovery after surface ablations procedures O'Doherty M et al. JRS 2007 Feb;23:133-8 Gamaly TO et al. JRS 2007;23:S1015-20 Torres LF JRS 2007;23:126-32 Lee HK et al. Am J Ophthalmol 2005;139:56-63

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