Eyeworld

24 January 2018 EW NEWS & OPINION by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer Presentation spotlight Bad memories of flap complications A large corneal scar after microkeratome LASIK where the blade likely made a disconnected double cut in the cornea A LASIK buttonhole flap that had epithelial ingrowth through the buttonhole region Flap stria emanating from the flap hinge area Source: J. Bradley Randleman, MD For surgeons who have switched to the femto laser, severe flap irregularities are a distant memory. For those using mechanical microkeratomes, flap crisis management is essential know-how M icrokeratome flap complications make a good case for adopt- ing the femtosecond laser, according to J. Bradley Randleman, MD, professor of ophthalmology, Keck School of Medicine, University of Southern California (USC), and director of cornea and refractive surgery, USC Roski Eye Institute, Los Angeles, during a presentation he gave at the 2017 ASCRS•ASOA Symposium & Congress. "While femtosecond flap creation has its own set of compli- cations, microkeratome flap issues can be more urgent and still require our attention," Dr. Randleman said. "I was a late adopter of the femto- second laser for flap creation. The flap creation techniques and flap morphology and architecture were reasonable with mechanical micro- keratomes, and I was comfortable using them. OCT studies showed us we were getting exactly what we were anticipating for our flaps. That said, some of the more sig- nificant complications you can get with microkeratomes are harder to manage than those you can get with femto flaps. You are not going to get a bisected flap or a true buttonhole with a femtosecond laser. Also, with most lasers, you can watch the flap creation process, which is an advan- tage. I have now moved exclusively to the femtosecond laser. It does not mean you can't get complications with femtosecond flaps—you can and will—but I do think they are a little easier to manage." Free caps and buttonholes Dr. Randleman discussed classic, microkeratome-related compli- cations from different cases that he experienced in his practice, in particular the creation of a free cap. Microkeratomes are used to create a hinged corneal flap to expose the stromal bed for laser ablation. In eyes with small corneas or deep orbits, or when the microkeratome achieves poor suction, decentered ring placement, or has faulty blades, the flap can detach and thereby cre- ate a free-floating cap, which under certain circumstances can change the course of the surgery. "A free cap is one of the things we are concerned about with me- chanical devices," Dr. Randleman explained. "When a free cap is created, the surgeon has to decide whether it is best to carry out the excimer laser ablation or abort. The most important thing is to find the cap. First and foremost, you want to make sure that you have the flap tissue and that you have a normal optical zone. The next treatment step is somewhat controversial. Al- though I would say that the major- ity of surgeons do feel comfortable going ahead and completing the laser ablation, once the free cap has been identified and is seen to have a normal thickness, surgeons prefer to abort if the stromal bed is irregular. In situations with difficult suction, some surgeons may opt to abort from the start. If the surgeon continues with ablation, the cap is replaced in position afterward, either with or without sutures. If the surgeon chooses to abort, the flap is replaced and allowed to heal. When you can't find the cap, I would argue against laser ablation at that time. Performing an ablation without replacing a free cap can lead to dire outcomes and complications, such as severely decentered ablations with the development of irregular astigmatism. I would allow the cor- nea to heal and then possibly treat with PRK later if possible." Flap buttonholes are caused by an abnormal lamellar cut during the creation of the LASIK flap, in which there is a connection between the flap interface and the corneal surface. Although uncommon, they need to be identified to avoid creat- ing an irregular corneal surface and further complicate visual outcomes for the patient due to a flap stromal bed contour mismatching, which is likely to result from proceeding with laser ablation in this scenar- io. Surgeons should be cautious in patients with steep corneal curva- ture preoperatively, previous ocular surgery, and targeted thin flap

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