We noticed you’re blocking ads

Thanks for visiting CRSToday. Our advertisers are important supporters of this site, and content cannot be accessed if ad-blocking software is activated.

In order to avoid adverse performance issues with this site, please white list https://crstoday.com in your ad blocker then refresh this page.

Need help? Click here for instructions.

Up Front | Nov 2001

Managing Stromal Free Cap

Avoiding laser treatment after an irregular flap offers an excellent prognosis in LASIK.

A 28-year-old white female was referred to me 3 months after an attempted LASIK procedure in her left eye. The patient's preoperative refraction was -3.75 sphere, and the pachymetry was 520 µm. According to the videotape provided by the surgeon, there was an elliptical free cap measuring approximately 3 mm X 4 mm. The surgeon decided to reposition the flap without laser treatment.

Upon slit lamp examination, the patient presented with an apparently well-positioned free cap and some debris in the interface without any signs of epithelial ingrowth. Her manifest refraction taken under bright light was -5.00 -3.75 X 180, achieving best spectacle-corrected visual acuity (BSCVA) of 20/400. The patient's topography revealed irregular astigmatism with curvatures varying in the horizontal meridian, from 47.00 D temporally, to 39.00 D nasally. Differential maps from preoperative data showed an increase in curvature of more than 5 D temporally.

Considering that no laser treatment was carried out, and no ectasia was present (the videotape revealed a flap of normal thickness), the only explanation for the induced irregular astigmatism was flap positioning. Assuming that a small free cap was related to loss of suction during the procedure, the entrance side of the blade should be thicker than the exit side. As the shape of the flap was elliptical, there were two ways that this flap could be repositioned: either the way in which it was executed, or 180º apart.

After discussing the alternatives with the patient, we decided to lift and rotate the flap 180º. To avoid misalignment, two distinct marks were placed at the border of the flap. These marks were placed horizontally to guide the surgeon in order to rotate the flap exactly 180º, in such a way that the temporal mark of the uncut cornea would align with the nasal mark of the flap after the procedure. Epithelium was removed from an area of 2 mm at the border of the flap with a blunt spatula, and a cyclodialysis spatula was placed underneath the flap to lift it with centrifugal movements. After the flap was lifted, it was placed aside with the epithelium facing downward to avoid epithelialization of its stromal face. The interface was thoroughly irrigated and washed with the help of a microsponge. The flap was then realigned as described, and the border was left to dry for at least 4 minutes. A therapeutic contact lens was placed for 24 hours.

Five months after the flap repositioning, the patient presented with a manifest refraction of -3.25 -1.00 X 020 achieving 20/20 BSCVA. Her topography was more regular and revealed a subtle round area of steepening that corresponded to the border of the flap. Biomicroscopy showed a faint, round scar around the pupil where we noticed an epithelial plug . No epithelialization of the interface was observed; there were no striae or folds, and the interface was clear.

The STARS display shows that the post- (superior right) and preoperative (superior left) topographies were very similar and the changes of the topography can be observed after the attemped LASIK procedure (inferior left) and after flap repositioning (inferior right). The surgeon suggested the possibility of LASIK to the patient; however, she opted against reoperation.

Preoperative epithelial marks in LASIK are very important and should extend all the way to the center of the cornea. In fact, the marks used in this patient's first attempted LASIK procedure were present, however, they did not cross the border of a small free cap, rendering them useless.

Avoiding laser treatment after an irregular flap offers a better prognosis, and all patients should be alerted to this possibility before the surgery.
Wallace Chamon, MD, is the President of the Brazilian Laser Ophthalmological Surgery Society in Sao Paulo, Brazil. Dr. Chamon may be reached at +55-11-507-18888;VISUS@pobox.com
Advertisement - Issue Continues Below
Publication Ad Publication Ad
End of Advertisement - Issue Continues Below

NEXT IN THIS ISSUE