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ETIOLOGY AND INCIDENCE OF EPITHELIAL DEFECT
Femtosecond and Microkeratome LASIK
An epithelial defect is defined as an area of epithelium with a break or loose cells greater than 2 mm. Trauma to the epithelium seems significantly less likely with the femtosecond laser compared with the microkeratome laser. It can still occur during several docking attempts, or especially when inexperienced surgeons have difficulty inserting the dissecting spatula under the flap edge. Epithelial defects tend to occur in patients with predisposing risk factors such as epithelial basement membrane dystrophy or a history of recurrent corneal erosion syndrome. They are also more commonly seen in older patients, in patients with large flap diameters, and with excessive topical anesthetic use. Epithelial defects also tend to occur when lifting the flap for LASIK refractive enhancement. The main advantage of the femtosecond laser is the absence of the keratome rotational movement that can lead to tearing or shearing of the epithelium. The incidence of epithelial defect with femtosecond LASIK is approximately 0.6%,1–3 while the incidence with microkeratome is between 1% and 8.65%, depending on the type of microkeratome used.1–3
Figure 10-1. Iatrogenic epithelial defect induced during a flap lift.
Figure 10-2. Excimer laser treatment was uneventful.
FEMTOSECOND LASIK COMPLICATIONS AND IMMEDIATE SOLUTIONS
Complication #1: Epithelial Defect During Flap Lift
Video section: 0 minutes 5 seconds
Platform: WaveLight FS200 (Alcon Labs)
Flap diameter: 9.3 mm
Flap target depth: 100 microns (µm)
The initial surgery on the left eye resulted in an epithelial defect from an inadvertent epithelial flap lift (video 10; time: 0 minutes 5 seconds; Figures 10-1, 10-2, and 10-3).
Figure 10-3. Epithelial defect was repositioned, and a contact lens was placed at the end.
Some practical measures are as follows:
- Apply excimer laser treatment.
- Try to reposition the epithelial defect.
- Place a contact lens at the end of the procedure.
Complication #2: Epithelial Defect During Flap Repositioning
Video section: 3 minutes 9 seconds
Platform: WaveLight FS200
Flap diameter: 9.3 mm
Flap target depth: 100 µm
The initial surgery on the left eye resulted in an epithelial defect from flap repositioning (video 10; time: 3 minutes 9 seconds; Figures 10-4 and 10-5).
Some practical measures are as follows:
- Try to reposition the epithelial defect.
- Place a contact lens at the end of the procedure.
Figure 10-4. Iatrogenic epithelial defect induced during flap repositioning (red arrow).
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