The Effect of Repeated Use of the Disposable Blade in Automated Microkeratome on the Corneal Flap Dimensions and Cut Quality

PURPOSE: To evaluate changes in the blade, flap dimensions, and stromal bed with repeated use of disposable blade in LASIK (laser in situ keratomileusis) surgery. METHODS: A keratome was used to make a corneal flap in pig cadaver eyes, with the blades being reused up to five times. The thickness and diameter of each corneal flap was measured. Scanning electron microscopy of the stromal beds and blade cutting edges was performed to determine the effect that repeated use of the blade had on the stromal bed, and on the cutting edge of the blade. RESULTS: The thickness/diameter of flap was 169.73 +/- 7.55 micro meter/8.60 +/- 0.23 mm after single use and 142.93 +/- 13.10 micro meter/8.72 +/- 0.20 mm after being used five times, with both demensions decreasing as the blade was used more. The edge of the blade became blunt and irregular and the cutting surface rough and irregular with continual use. CONCLUSIONS: During LASIK surgery, reused blades became blunt, causing a thin flap, rough cutting face, and complications such as irregular astigmatism clinically.

The Effect of Preoperative Keratometric Value on Corneal Flap Dimensions in LASIK

PURPOSE: To evaluate the effect of preoperative keratometric value on corneal flap dimensions, records of 81 eyes of 45 patients who had LASIK were analyzed retrospectively. METHOD: Corneal thickness and diameter , and keratometric value were measured preoperatively. RESULTS: In this study, SCMD Turbokeratome was set for making a corneal flap with 150 micron thickness and 8.25 mm diameter. In reality, however, the mean corneal flap thickness was 110.7+/-15.7 micron and the mean corneal flap diameter was 7.89+/-0.33 mm. The lower mean preoperative keratometric value, the thicker(r=-0.325, p=0.003) and the smaller(r=0.460, p=0.009) diameter flap was made. When we divided eyes into three groups according to their keratometric values, eyes with keratometric values lower than 42.5 D resulted in corneal flap with 116.70+/-12.6 micron thickness and 7.65(0.28mm diameter as opposed to 102.16+/-13.41 micron thickness and 8.05+/-0.37 mm diameter flap in corneas having keratometric values above 44.5 D(p<0.05). CONCLUSION: When a LASIK flap was made using SCMD manual keratome, steeper corneas tend to have larger and thinner corneal flaps. In conclusion, for making the corneal flap according to the intended thickness and diameter in LASIK, preoperative keratometric value should be considered carefully.