Incidence, possible risk factors, and potential effects of an opaque bubble layer created by a femtosecond laser.

PURPOSE: To describe the incidence, characteristics, risk factors, and sequelae of an opaque bubble layer created by the IntraLase (15 Khz) femtosecond laser (IntraLase, Corp.).

SETTING

Private laser center and the Department of Ophthalmology, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada.

METHODS

This study comprised 79 consecutive patients (149 eyes) who had laser in situ keratomileusis for myopic astigmatism. The preoperative visual acuity, refraction, keratometry, pachymetry, and intraoperative data including flap size and thickness were documented. A computerized system was used to calculate the total area of the opaque bubble layer.

RESULTS

Eighty-four eyes (56.4%) developed an opaque bubble layer. The layer pattern was diffuse in 32.2% of eyes and hard in 24.2%. The diffuse opaque bubble layer covered a mean of 13.4%+/-10% of the corneal flap and the hard opaque bubble layer, a mean of 21.6%+/-10% (P= .0004). A significant correlation was noted between the corneal steep curvature and central corneal thickness (CCT) and the area of opaque bubble layer. Multivariate logistic regression found that flap diameter (P= .04) and CCT (P = .045) affected the occurrence and area of the opaque bubble layer (P= .04 and P= .05, respectively). Postoperative diffuse lamellar keratitis was not associated with an opaque bubble layer. Three months postoperatively, visual acuity and refraction were not affected by the bubble layer. There was an increase in trefoil aberrations in eyes with a hard opaque bubble layer (P= .01).

CONCLUSIONS

Thicker corneas and smaller flaps were associated with a more opaque bubble layer. The presence of an opaque bubble layer did not seem to have detrimental long-term sequelae, although a small harmful effect could not be ruled out.