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J Gallar, MC Acosta, J Moilanen, C Belmonte, T Tervo; Recovery Of Corneal Sensitivity To Mechanical And Chemical Stimuli After Lasik Surgery . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2106.
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Purpose: Corneal nerves are damaged during LASIK surgery. The purpose of this work was to evaluate the time course of corneal sensitivity values to mechanical and chemical stimulation following LASIK surgery. Methods: Patients who had undergone LASIK surgery at various times before the experiment were investigated: Group 1, 2 days (n=1). Group 2, 7-9 days (n=2). Group 3, 2-6 months (n=3). Group 4, 2 years (n=6). Seven unoperated patients served as control. Corneal sensitivity was measured using a gas esthesiometer (Belmonte et al., 1999; IOVS, 40, 513-519). Chemical (20-80% CO2 in air) and mechanical (0-200 ml/min) stimuli were applied to the center of the cornea. The intensity and attributes of the evoked sensation were represented at the end of the pulse in a 10-cm, continuous visual analog scale (VAS). Threshold for the sensation was expressed as the first intensity that evoked a VAS value ≷0.5. Results: Mechanical and chemical sensitivity were greatly reduced 2 days after surgery. One week later, threshold sensitivity and response curves to both stimuli were higher than normal. 2-5 months after LASIK, sensitivity curves to both stimuli flattened. After 2 years, sensitivity curves were similar to control. Conclusion: Nerve injury caused by LASIK surgery reduced corneal sensitivity for several months, with a transient hyperalgesic period at the end of the first week presumably due to sprouting and sensitization of injured nerve terminals. Two years after surgery corneal sensitivity had returned to virtually normal values.
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