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C. Lagunas-Quiroz, O. Baca, R. Velasco, A. Babayan, C. Johnson; Ultrabiomicroscopic (UBM) Findings in Patients after Lasik. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3877.
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Ultrasonic Biomicroscopy (UBM) provides high resolution images of the anterior segment in a non-invasive fashion. The purpose of the study is to describe the ultrabiomicroscopic findings in post-LASIK patients and determine the utility of such technology in refractive surgery and compare with the Orbscan® values.
We included patients who underwent refractive surgery (LASIK) with the Hansatome microkeratome® (160 mm flap thickness) between July and October 2006 and were evaluated with UBM 2 to 4 weeks after refractive surgery. We used the 50 mHz transductor and performed by a single physician. Measurements were done at 2 mm from the edge of the corneal flap to the center of the cornea. We measured the thickness of the flap and the thickness of the residual stromal bed. We determined corneal pachymetry by adding the two previous values and it was compared to the post-operative Orbscan values.
17 eyes of 9 patients were included. The mean flap thickness was 160.17 microns. Eyes in which the flap thickness was greater than 160 microns, the mean thickness excess was 13.2 microns. Eyes in which the flap thickness was lower than 160 microns, the mean thickness was around 9.6 microns. In one patient the measurement was made outside the area of laser ablation. The total corneal thickness obtained by UBM was compared to the post-operative pachymetry obtained by Orbscan®. The measurements with UBM were greater than the Orbscan values.
The Hansatome® microkeratome provides flaps of 160 microns of mean thickness. UBM is able to assess the quantitative but not the qualitative characteristics of the corneal flap. The corneal interphase is difficult to assess in the center of the cornea. UBM over estimates corneal pachymetry compared to Orbscan II topography.
Fundaciòn Hospital Nuestra Señora de la Luz
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