SURFACE ABLATION

Surface ablation remains an evolving science and may yet keep pace with recent advances in intrastromal techniques , asserted Ioannis Pallikaris MD, University Hospital of Crete, Heraklion, Crete, Greece, at the 19th ESCRS Winter Meeting in Istanbul.

Reviewing the history of lasers in corneal refractive surgery, Dr Pallikaris noted that photorefractive keratectomy (PRK) was introduced in the 1980s. Its minimally invasive nature and predictable results initially made it a very attractive option. However, the procedure as originally designed caused postoperative pain and haze and there was regression of effect. That in turn led to the development of LASIK.

LASIK involved less pain than conventional PRK and provided faster rehabilitation. But as with PRK, unforeseen complications emerged, in this case corneal ectasia and unpredictable flap-induced aberrations. That in turn led to the development of advanced surface ablation.

Dr Pallikaris noted that advanced surface ablation is a term covering a variety of procedures, including standard PRK but with the addition of mitomycin –C to prevent haze, LASEK, which involves the use of epithelial flap loosened by alcohol as a sort of bandage for the stromal surface, and epi-LASIK, where an epikeratome is used instead of alcohol to create an epithelial flap.

“In the case of LASEK, the retained epithelial flaps allow for a reduced incidence of haze, and it is better tolerated by patients. With epi-LASIK, the use of the epikeratome provides the benefit of avoiding alcohol toxicity,” Dr Pallikaris said.

Advanced surface ablation techniques offer several advantages over conventional PRK, such as an increased quality of vision, a reduction of postoperative pain and minimal corneal haze. In addition, like conventional PRK, they have the advantage of having no risk of flap-related complications, ectasia or flap-induced aberrations.

Furthermore, surface ablations are a very useful option in deep set eyes with small palpebral aperture. They also have safety advantages for patients with a history of recurrent epithelial erosions, and participants in contact sports. Other indications for surface treatments include eyes with thin corneas, those with preoperative dry eye, epithelial basement membrane dystrophies, or flat or steep corneas.

Dr Pallikaris said that one problem that remains with surface ablations is the compensatory smoothing of the ocular surface by the epithelium as it regrows. However, ablation algorithms could be developed to compensate for that, and new masking agents used in the manner of the photoablatable lenticular modulator (PALM) technique may also play an important role in the future of surface ablations.

The PALM technique refers to corneal excimer laser phototherapeutic keratectomy through a gel used as a masking agent.

Ioannis Pallikaris: pallikar@med.uoc.gr