Research On The Changes In Corneal Sensitivity And Tear Film Stability After LASIK Affected By Ablation Depth Of Corneal Stroma

PurposeTo investigate the changes in comeal sensitivity and tear film stability in the early stage after LASIK affected by ablation depth of comeal stroma( ADCS).Method132 myopic eyes underwent LASIK were checked with comeal sensitivity and no - invasive tear break - up time ( NIBUT) before and 1 week, 2weeks, 4weeks after operation. They were assigned to four groups according to different ablation depth of corneal stroma; Groupl (range; <36μm,mean: 30.53 ±4.12 μm) Group2 (range <72 ~ 108μm,mean: 55. 58 ±9.49μm) Group3 (range36 ~72μm,mean: 84.16 ±8.56μm),Group4 (range > 108μm,mean: 119.22 ± 11. 73μm). The corneal stromal thickness was measured with A ultrasonic phacometer before and afer laser ablating.Result1. The changes of corneal sensitivity and tear film stability of all patients in the early stage after LASIK: (1)The mean comeal sensitivity: Before operation: 58.11 ±2.43 mm; 1 week after operation: 17.01 ±3.65 mm; 2 weeks after operation :30. 15 ±3.97 mm;4 weeks after operation:50. 57 ±3. 94 mm; There were significant differences between preoperative corneal sensitivity values and postoperative comeal sensitivity values (1 weak,2weeks and 4 weeks after oper-ation) (P < 0. 01). (2)The mean NIBUT: Before operation: 19. 17 ±3. 10 seconds; 1 week after operation :8. 05 ±2.47 seconds;2 weeks after operation:10.80 ± 2. 51 seconds;4 weeks after operation: 14. 32 ± 2. 78 seconds. There were significant differences between preoperative NIBUT values and postoperative NIBUT values (1 weakN2weeks and 4 weeks after operation) (P <0.01).2. The comeal sensitivity of the different comeal stromal ablation depth groups :(l) The mean comeal sensitivity before operation: Groupl: 58. 44 ± 2.36 mm; Group2:58. 06 ±2.47 mm; Group3:58. 13 ±2. 46 mm; Group4:57.81 ±2.52 mm;There were not significant differences in comeal sensitivity a-mong four groups befoe operation ( P > 0. 05 ). (2) The mean comeal sensitivity values:d)l week after operation : Groupl : 17.03 ±4.73 mm; Group2: 16.53±3. 12 mm; Group3: 16. 88 ±3. 30 mm; Group4: 17. 06 ±3. 36 mm;d)2 weeks after operation : Groupl: 29. 06 ±4. 10 mm; Group2: 30. 42 ±4. 37 mm; Group3: 29.93 ±3.20 mm; Group4: 30.41 ±3.98 mm; ?4 weeks after operation : Groupl: 49.53 ±4. 64mm; Group2: 50.99 ±3.55 mm; Group3: 50.31 ±3. 09 mm; Group4: 50. 59 ± 3. 94 mm; There were not significant differences in comeal sensitivity values among four groups 1 weak N2weeks and 4 weeks after operation( P > 0.05 ).3. The NIBUT of the different corneal stromal ablation depth groups: (1) The mean NIBUT before operation*, groupl : 19. 58 ±3. 50 seconds; group 2: 19.24 ±2.76 seconds; group3: 19.26 ±3.47 seconds; group4: 18.57 ±2.67 seconds;There were not significant differences in NIBUT among four groups befoe operation(P >0.05) ;(2) The mean NIBUT values:01 week after operation : Groupl: 7.73 ± 1.76 seconds; group2: 7.86 ±2.40 seconds; group 3: 9.02 ±2.69 seconds; Group4: 7.80 ±2.41 seconds;There were significant differences in NIBUT values among four groups 1 week after operation( P <0.05 ) ; (D 2 weeks after operation : groupl: 10.15 ± 1.88 seconds; Group2 10.58 ±2.55 seconds; Group3: 11.78 ±2.46seconds; Group4: 10.91 ±2.54seconds;There were significant differences in NIBUT values among four groups ;2 weeks after operation( P < 0. 05 ) ; ?4 weeks after operation : Groupl: 13. 90 ± 2.37sec-onds;Group2 : 14.58 ±2.58seconds;Group3: 14.31 ±2.74seconds; Group4: 14.20 ±3.02 seconds;There were not significant differences in NIBUT values a-mong four groups 4 weeks after operation( P > 0.05 ).4. The correlation between the NIBUT and the comeal sensitivity in the early stage after LASIK: (1)1 week after operation r = 0.089, P < 0.05;