Eyeworld

25 EW NEWS & OPINION January 2018 creating a surface that needs to heal. If you decide to go back and lift this flap later, you are right back where you were on the operating table. There are arguments either way." Gaining the requisite clearance for good suction on the corneal surface is essential. Eyes with spatial limitations that, for example, do not creation. Also, microkeratome-re- lated risk factors can include the loss of suction, decrease of power in the microkeratome motor, or blade imperfections. If a buttonhole flap occurs, the case should be aborted without laser ablation; otherwise sever irregularity can result. Mechanical trouble Like any mechanical device, micro- keratomes are susceptible to block- age and space constraints on the surface of the eye. Dr. Randleman described the unwelcome scenario of the microkeratome freezing in place after swiping across the cornea. "With mechanical devices, you have to be very conscious about every step of the process as it is happen- ing. You can have a case with good suction and no free cap formation but find the device has stopped moving and will not go any further forward or backward," he said. Surgeons who find themselves in this situation should take action by removing suction and manually retracting the microkeratome blade. Investigating the morphology of the flap is important, which may either be incomplete or severed off, as well as the optical zone, which may be smaller than targeted at the start of treatment. Eyes presenting with a full optical zone are generally safe to undergo ablation, cautiously. Dr. Randleman advised against laser ablation with grossly incomplete flaps, however, to avoid inadvertent treatment of the undersurface of the flap or the possibility of certain stro- mal areas not being ablated, which could create irregular astigmatism and entail further, difficult refractive corrective measures. Smaller orbits present a unique set of problems for the surgeon. "Surgeons sometimes have trouble getting the device in place," Dr. Randleman. "You want to make sure you get good clearance and good fix- ation. What we sometimes see is the lid speculum positioned too close, relative to the end of the microker- atome pass, which can cause either a suction break or for the pass not to be where you anticipate it was going to be. This is going to give you a disrupted flap with a poor hinge or a free cap, something that you want to watch out for. The surgeon may opt at this point not to con- tinue treatment with excimer laser, although I would ablate as long as the flap is intact and its morphology close to what I anticipated it would be. Otherwise, you haven't done anything for the patient aside from continued on page 26

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