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B.A. Nassaralla, J.J. Nassaralla; The Effect of Hinge Position and Depth Plate in Corneal Sensation Following LASIK . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2661.
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Purpose: To evaluate the effect of hinge position and depth plate in corneal sensation following excimer laser in situ keratomileusis (LASIK) for the correction of very low myopia. Methods: In a prospective study, 40 eyes of 40 patients underwent LASIK to correct myopia ranging from –1.00 to –2.50 diopters. Corneal sensitivity was measured preoperatively and at every month after surgery, until recovery of the preoperative level. Sensitivity measurements were made with the Cochet-Bonnet esthesiometer at central, temporal, inferior, nasal and superior points on the corneal flap. The nasal hinged ACS microkeratome (NH) with depth plates of 130 or 160µm and the superior hinged Hansatome microkeratome (SH) with depth plates of 160 or 180 µm were used for corneal flap creation. The eyes were divided into 4 groups according to the hinge position and depth plate (DP): Group 1, NH and 130µm DP; Group 2, NH and 160µm DP; Group 3, SH and 160µm DP; Group 4, SH and 180µm DP. Results: Corneal sensitivity returned to preoperative level after 3.3 (± 0.48), 4.3 (± 0.48), 5.4 (± 0.84) and 6.1 (± 1.10) months respectively in groups 1, 2, 3 and 4. Statistically significant differences (P>0.05) were found between all groups, except between groups 3 and 4 (P<0.05). In all groups, the recovery of sensitivity increased slowly and gradually. Sensitivity of the hinge area was higher than other areas at every time point. The central area was the latest to recover preoperative level of sensitivity. Conclusions: The results suggest that after LASIK for very low myopia, the hinge position and depth plate seems to be important factors in the temporary decrease of corneal sensitivity as well as in its recovery. Faster recovery was found in the NH groups. There was a positive correlation between the depth plate and the time for full return of corneal sensation.
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