| PrefaceLaser in situ keratomileusis ( LASIK) is a new - developed effective method to treat myopia and is being accepted by more and more doctors and patients due to its safety, stability and predictability. However, we founded that some patients suffered from eye - dry symptom , which affected the postoperative effect to some degree. The exact mechanism is not clear up to now, about which there were few of literatures and the literatures arent consistent[3-7]. In our experiment, the difference from predecessors was quantificationally measuring the tear film stability, the tear flow and the cornea! sensitivity at the same time preoperatively and postoperatively in order to investigate the change regulation and the relationship among them.ObjectiveTo investigate the relationship between the change of tear film and comeal sensitivity after LASIK and the reason of postoperative eye dry.Methods100 eyes of 50 patients undergone LASIK were chosen at random, whose mean age was 26. 5 years (range 18 to 35 years) and the mean equivalent spherical diopter was 1.25D~ -11.37D. The crite-rions to choose cases is: (1) The patients never wore contact lens or hadnt worn contact lens for 1 month; (2) The diopter was stable more than 2 years; ( 3 ) The patients never were administrated by the drugs that affected tear secretion and tear film stability, such as anti - glaucoma drugs, glucocorticoid and so on; (4) The patients examined by slit lamp microscope and ophthalmofundoscope were excluded other ophthalmic diseases such as keratoconus, chronic dacryocystisis, viral keratitis, glaucoma, retinal disease and optic nerve disease; ( 5 ) The patients were excluded systemic connective tissue disease and autoimmune disease such as systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, severe diabetes mellitus and conception. The routine examination included unaided vision, subjective and objective optometry, slit lamp microscope examination, ocular fundus examination by ophthalmofundoscope, corneal topography, ultrasonic corneal pachymeter and measure of intra - ocular pressure. The special examination included; ( 1) The corneal central sensitivity of all objects were measured by Cochet Bonnet Aesthesiometer. (2) Non -invasive break up time of tear film (NIBUT) measured by KEELER tear scop; ( 3 ) Schirmer I tear secretion test measured by CLEMENT-CLARK tear flow test paper . The criterions above were measured before operation, 1 week, 2 weeks and 4 weeks after operation.Results1. The mean corneal central sensitivity value was 55.60 8.18 mm preoperatively, 24. 78 19. 82 mm and 34. 02 19. 28 mm 1 week and 2 weeks postoperatively, and there was significant difference compared with preoperative corneal sensitivity (p <0.05) ; The meancorneal central sensitivity value was 53. 30 ?10. 38mm 4 weeks post-operatively and there was no significant difference compared with pre-operative corneal sensitivity (p >0. 05). 2. The mean NIBUT value was 26. 20 15. 12 seconds before operation, 18. 56 15. 24 seconds and 18.90 11. 64 seconds and 24. 10 14. 24 seconds 1 week and 2 weeks and 4 weeks after operation, and there was significant difference compared with preoperative NIBUT (p <0. 05) ; 3. The mean tear secretion value measured by Schirmer I tear secretion test was 20. 92 10. 80mm before LASIK, 17. 83 10. 64 mm, 20. 06 11. 42 mm and 20. 44 11. 68 mm 1 week, 2 weeks and 4 weeks afterLASIK, and there was no significant difference between them according to paired t - test ( p > 0.05 ). 4. According to die results of Pearson correlation analysis by SPSS 10. 0 software, the NIBUT and the corneal central sensitivity appeared positive correlation (r =0.48,p < 0.05) , and there wasnt correlation between the tear secretion value and the corneal sensitivity ( r =0.029, p >0.05).Discussion1. The change of corneal sensitivity after LASIK: the study showed that the corneal central sensitivity decreased in the early stage after LASIK and then recovered gradually. 1 month postoperatively... |
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