Ocular structure changes during vacuum by the Hansatome microkeratome suction ring

PURPOSE: To evaluate whether the vacuum of a microkeratome suction ring induces ocular structure changes. METHODS: A prospective case series using A-scan ultrasonography to measure anterior chamber depth, lens thickness, vitreous body, and axial length was performed. Measurements before and during application of a Hansatome microkeratome suction ring were performed on 69 eyes of 39 consecutive patients scheduled to undergo a first-time LASIK procedure with mechanical creation of a corneal flap. RESULTS: Mean patient age was 43 +/- 12.1 years. Of the 69 eyes, 63 (91.3%) had refractive myopia with a mean spherical equivalent refraction of -2.93 +/- 1.56 diopters (D) and 6 (8.7%) had refractive hyperopia with a mean spherical equivalent refraction of 1.37 +/- 0.31 D. Overall, the mean spherical equivalent refraction of all eyes was -2.56 +/- 1.94 D. Ultrasound measurements during suction revealed a decrease in the anterior chamber depth of -0.06 +/- 0.36 mm (P < .05) and lens thickness by -0.14 +/- 0.45 mm (P < .05) whereas the vitreous body increased 0.25 +/- 0.36 mm (P < .05). Although insignificant, a trend toward increasing axial length was noted. No measurements changed over time during the application of vacuum. CONCLUSIONS: Vacuum by a microkeratome suction ring induced a compression of the anterior chamber and lens with commensurate expansion of the vitreous body. The assessment of vacuum effects during LASIK suggests that measurements of intraocular compartments are more informative than axial length.