Surface Ablation Still Useful

Corneal session at Refractive Surgery Course discusses development of surface ablation. Priscilla Lynch reports

There is still room for surface ablation, despite the rise of LASIK in recent decades, Jesper Hjortdal MD, PhD, Denmark, told the 25th ESCRS Winter Meeting Virtual 2021.

Speaking during the Refractive Surgery Course— Corneal Session, Prof Hjortdal outlined the development of surface ablation; the first excimer laser-based procedure for changing the refractive power of the cornea.

The original photorefractive keratectomy (PRK) technique had issues with slow wound healing and visual recovery, pain until the epithelium had healed, and haze, however, he noted.

There was a shift towards LASIK in the mid-1990s, with its faster healing and visual recovery benefits, but refinements of the original surface ablation technique have improved outcomes as well as pharmacological modification, i.e. the addition of mitomycin-C, which reduces haze risk, Prof Hjortdal explained.

The surgical improvements are mainly due to technological perfection of the excimer lasers with respect to optimising the ablation profiles and eye-tracking during treatment.

“There are certain advantages of surface ablation compared to LASIK; there is no flap so that is the main advantage, you don’t have surgical complications—no flap folds, epithelial ingrowth, trauma, late dislocation, or ectasia, which can happen after LASIK,” he said.

Concluding, he said it is still worth considering surface ablation in thin corneas, irregular corneas, dry eyes, young patients, lower range of refractive errors, and Epithelial Basement Membrane Dystrophy.

BEST PROFILE FOR STANDARD LASIK Also speaking during this session, Dr Roberto Bellucci MD, Italy, said that a wavefront-optimised profile should be the standard ablation technique for LASIK in corneal refractive surgery.

While newer technology and more advanced protocols of ablation (wavefront optimised, wavefront guided, ray tracing, etc.) have improved some of the inconveniences with the original ‘Munnerlyn’s ablation protocol’, they consume more tissue, and are exposed to factors limiting their precision and efficacy: laser/tissue interaction, micro eye movements, epithelial healing, etc., he noted. “They are complex and frequently require complex and expensive devices, and confounding factors include dry eye, corneal, and epithelial variation. The cornea may not be thick enough because the ablation depth increases with all advanced profiles.”

However, the original protocol just achieves good results in certain situations; “so should only be used for specific eyes and conditions like thin cornea, low defects, and small pupils,” Dr Bellucci maintained.

He concluded that “wavefront-optimised profiles should be the standard, while wavefront-guided profiles can be used in eyes with high order aberrations above 0.3 microns at 7mm optical zone.”

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