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Decentered Flaps

ETIOLOGY AND INCIDENCE OF DECENTERED FLAPS

Appropriate flap centration is crucial for the success of LASIK. Creating a flap with an adequate diameter is necessary to create a bed that is sufficient for excimer laser treatment. A decentered flap is a complication that occurs during the LASIK procedure that can affect the visual and refractive outcome, causing the loss of best-corrected visual acuity if not managed properly. It is important to be prepared to abort the procedure if the exposed stroma cannot accommodate the planned ablation zone.

Patient and surgeon factors can influence flap creation. Head position, ring position, and applanation can all influence the procedure. Decentered flaps have been reported as a complication with mechanical microkeratomes. They mainly occur when the vacuum ring slowly shifts between the application of suction and the initiation of the keratome pass. This is a phenomenon referred to as oozing; it can be missed if the surgeon is not attentive to it. Decentered flaps have been reported with less frequency with the femtosecond laser. The femtosecond laser allows small adjustments in flap centration prior to ablation to permit the realignment of the flap. This is not possible with a microkeratome laser. The incidence of decentered flaps after microkeratome LASIK has been reported to be approximately 0.6%.1–3 Only one study in the literature reports the rate of decentration with femtosecond LASIK at approximately 0.1%.^2–4

FEMTOSECOND LASIK COMPLICATIONS AND IMMEDIATE SOLUTIONS

Complication #1: Difficult Docking Resulting in Decentered Flap

Video section: 0 minutes 10 seconds

Platform: WaveLight FS200 (Alcon Labs)

Flap diameter: 9.3 mm

Flap target depth: 110 microns (µm)

The initial surgery resulted in a decentered flap (video 12; time: 0 minutes 10 seconds; Figures 12-1, 12-2, and 12-3).

Some practical measures are as follows:

• Assess the available stroma for excimer laser treatment.
  
• Abort the procedure in cases of severely decentered flaps (ie, situation where a 6.0-mm stromal ablation zone is not attainable under the flap).
  
• Plan for a future surface refractive procedure.

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