Surface ablation yields excellent outcomes with buttonholes

Chicago-LASIK should be aborted and the flap replaced in eyes when a buttonhole occurs during flap creation. Excellent visual outcomes, however, can be achieved if these eyes are followed closely and managed according to a simple treatment algorithm based on surface ablation, said Samir Melki, MD, PhD, at the annual meeting of the American Society of Cataract and Refractive Surgery.

Dr. Melki's comments were based on the findings from a retrospective study that identified 15 eyes (0.59%) with a buttonhole or "near buttonhole" out of a series of 2,629 LASIK cases. A near buttonhole was defined as a partial-thickness buttonhole where the epithelium was not broken, said Dr. Melki, attending physician at the cornea and refractive surgery service, Massachusetts Eye & Ear Infirmary, Boston.

Six eyes presented with no epithelial ingrowth and received no further treatment. The remaining nine eyes underwent treatment that involved phototherapeutic keratectomy (PTK) with PRK and mitomycin-C (MMC); epithelial ingrowth was absent in eight of the nine eyes.

Outcomes analysis showed that the treatment resulted in overcorrection in three eyes, although only one needed to be re-treated for hyperopia. Haze developed in two eyes but resolved spontaneously.

Uncorrected visual acuity was 20/25 or better in all nine treated eyes and 20/20 or better in six (67%). All of the eyes returned to 20/20 or better best corrected visual acuity (BCVA) without any loss compared with preoperative BCVA. One patient who elected against further treatment experienced a 1-line loss of BCVA, Dr. Melki said.

"Buttonholes are among the most feared complications of LASIK flap creation because of the risk for developing epithelial ingrowth, irregular astigmatism, and loss of vision," he said. "However, our experience shows that outcomes can be favorable using an algorithmic approach taking into account the severity of the presentation and using PTK/PRK ablation rather than alcohol epithelial removal followed by PRK."

Two mechanical microkeratomes (Hansatome, Bausch & Lomb; M2, Moria) were used to create more than 2,600 flaps. The first device was used in about two-thirds of cases, and the latter was used in the rest. The incidence of buttonholes was similar in the two microkeratome groups. Dr. Melki observed that in cases where the Hansatome microkeratome was used, the buttonhole had a triangular shape with the apex facing the surgeon.

"We have been considering whether the shape of the buttonhole associated with the Hansatome microkeratome holds any clue to the etiology of the complication. So far, its significance remains unclear," Dr. Melki said.

The eyes with a buttonhole had an average corneal thickness of 552 Μm and an average K of 45 D.

"We did not find that a steep K predisposed eyes to buttonholes, and this observation is consistent with other recently published papers," Dr. Melki said.

Explaining the algorithm for treatment in eyes with buttonholes, Dr. Melki noted the eyes are divided into three groups or stages defined by severity of epithelial ingrowth. In stage-one eyes, epithelial ingrowth is absent. Stage-two eyes present with progressing ingrowth at the edge of the buttonhole, and stage three represents eyes in which the ingrowth has advanced to the development of stromal melting and irregular astigmatism.

The management approach for stage-one eyes involves waiting for about 3 months to allow the epithelium to smooth the surface. Then a 50-μm PTK procedure is performed followed by PRK to treat the existing refractive error and using intraoperative MMC 0.02% for 60 seconds.

When epithelial ingrowth is progressing, immediate intervention is warranted. A 50-μm PTK is performed initially, and the depth is increased as needed to ablate the ingrowth. Later, refractive error is treated with PRK and MMC.

"Resolution of the ingrowth, not correction of refractive error, is the initial treatment goal for stage-two eyes," Dr. Melki said. "When more than a 50-μm PTK is performed, the PRK procedure should be delayed because there is a risk of overcorrection."

Of the nine eyes that were treated in his series, eight were categorized as stage one and one was stage two. The stage-one eyes underwent PTK/PRK/MMC-treatment at an average of 12 weeks postLASIK, and the stage-two eye was treated at 10 days.

"Eyes that present at stage three have usually either been mismanaged initially or the patient delayed returning for follow-up," Dr. Melki said. "The management approach in these eyes needs to be individualized."