Changes in corneal biomechanics and posterior corneal surface elevation after FS-LASIK.

AIM: To investigate the changes in corneal biomechanics and posterior corneal surface elevation after femtosecond laser-assisted in situ keratomileusis (FS-LASIK). METHODS: Totally 197 eyes of 100 patients who underwent the FS-LASIK from April 2022 to November 2022 were included. They were divided into three groups according to the ratio of residual corneal stroma thickness/corneal thickness (RCST/CT): Group I (50%≤RCST/CT<55%, 63 eyes of 32 patients), Group II (55%≤RCST/CT<60%, 67 eyes of 34 patients), and Group III (RCST/CT≥60%, 67 eyes of 34 patients). The intraocular pressure (IOP), corneal compensated IOP (IOPcc), corneal hysteresis (CH) and corneal resistance factor (CRF) were measured immediately, 1, and 3mo postoperatively by ocular response analyzer (ORA) and the posterior elevation difference (PED) was measured by Pentacam. RESULTS: After operation, IOP, CH, CRF, and PED were statistically different among the three groups (F=12.99, 31.148, 23.998, all P<0.0001). There was no statistically significant difference in IOPcc among the three groups (F=0.603, P>0.05). The IOP, IOPcc, CH, and CRF were statistical changed after surgery (F=699.635, 104.125, 308.474, 640.145, all P<0.0001). The PED of Group I was significantly higher than that of Group II (P<0.05), and Group II was significantly higher than that of Group III (P<0.05). The PED value of 3mo after surgery decreased in each group compared with 1mo after surgery, but there was no statistical difference (Group I: t=0.82, P=0.41; Group II: t=0.17, P=0.87; Group III: t=1.35, P=0.18). The correlation analysis of corneal biomechanical parameter changes with PED at 1mo and 3mo after surgery showed that ΔIOP, ΔIOPcc, ΔCH, and ΔCRF were not correlated with PED value in three groups (P>0.05). CONCLUSION: The smaller the RCST/CT, the greater effect on corneal biomechanics and posterior surface elevation. There is no correlation between changes in corneal biomechanics and posterior corneal surface elevation in the range of RCST/CT≥50%.

One-year clinical efficacy evaluation of selective corneal wavefront aberration-guided FS-LASIK correction in patients with high myopia.

AIM: To evaluate the effectiveness, safety, predictability, precision and changes of higher-order aberrations (HOAs) on corneal front surface of selective corneal wavefront aberration-guided femtosecond laser-assisted in situ keratomileusis (CW-FS-LASIK) in patients with high myopia 1-year postoperatively. METHODS: Totally 74 eyes of 37 patients with high myopia or myopic astigmatism in both the eyes who underwent the CW-FS-LASIK procedure in Xi'an Gaoxin Hospital from January 2021 to June 2021 were included. The changes of uncorrected distance visual acuity (UDVA), best corrected visual acuity (BCVA), spherical equivalent refraction (SER), astigmatism, HOAs and Strehl ratio (SR) on the anterior surface of the cornea after 1y of the surgery were analyzed. RESULTS: At postoperative 1y, the UDVA (logMAR) of 74 eyes (100%) reached 0 or better, including 0 in 8 eyes (10.81%), -0.1 in 45 eyes (60.81%), and -0.2 in 21 eyes (28.38%). The effectiveness index was 1.29±0.134. There was no decrease in postoperative BCVA compared with preoperative BCVA in all patients. Postoperative BCVA was the same in 44 eyes (59.46%) as preoperative BCVA, increased by 1 line in 23 eyes (31.08%) and increased by 2 lines in 7 eyes (9.46%) compared with preoperative BCVA. The safety index was 1.11±0.159. The estimated corrected SER before surgery was (-7.76±1.21) D, and the actual corrected SER was (-7.83±1.25) D (Y=0.9811X+0.2156, R2=0.9084). There was a high correlation between the estimated corrected SER and the actual corrected SER. The postoperative SER in 74 eyes (100%) was within ±0.75 D. The postoperative astigmatism of all was within -0.75 D to 0. Root mean square (RMS) HOAs of spherical aberration and SR within 5 mm of the corneal front surface were all increased compared with those before operation (P<0.01). The total coma, horizontal coma and vertical coma were all decreased compared with those before operation (P<0.01). There was no statistically significant difference in horizontal trefoil and vertical trefoil compared with preoperative ones (P>0.05). CONCLUSION: Selective CW-FS-LASIK for correction of high myopia is effective, safe, predictive, and accurate. For patients with preoperative RMS HOAs over 0.25 defocus equivalent, postoperative coma aberration can be significantly reduced, and SR value can be increased, thus corneal imaging quality can be improved.

[Three Different Digestion Methods to Separate Neonatal Rat Cardiomyocytes].

OBJECTIVES: To investigate the efficacy of three different digestion methods for the separation of neonatal rat cardiomyocytes. METHODS: We employed three different digestion methods to separate neonatal rat cardiomyocytes. Group A was 0.08% trypsin digestion alone, group B was 0.08% trypsin+0.08% type 2 collagenase mixed digestion, group C was 0.08% trypsin and 0.08% type 2 collagenase isolated digestion. The number of cells and cell viability after differential adhesion were recorded. The purity of cardiomyocytes was evaluated by immunofluorescence staining. The cell vitality was assessed by the detection of mitochondrial membrane potential with JC-1 staining, and the ratio of red to green fluorescence intensity by laser scanning confocal microscope. RESULTS: There was nostatistically significant difference in the number of cells between three groups (P >0.05).The rate of cell viability in group C was significantly higher than that in group A (P <0.01). No statistically significant difference was found in the purity of cardiomyocytes between three groups (P >0.05). The ratio of red to green fluorescence intensity in group A, B and C were 0.928±0.078, 0.943±0.099 and 1.160±0.089, respectively; the ratio in group C was significantly higher than that in group A and group B (P <0.01). CONCLUSION: The cell isolation method with 0.08% trypsin and 0.08% type 2 collagenase isolated digestion could be served as conventional method to separate neonatal rat cardiomyocytes.

The influence factors and management of anterior chamber gas bubble emergence during femtosecond flap creation for LASIK / 国际眼科杂志(Guoji Yanke Zazhi)

·AIM:To study the influence factors and management of anterior chamber gas bubble during femtosecond flap creation for laser-assisted in situ keratomileusis ( LASIK) .·METHODS: Totally 9671 eyes of 4859 patients with femtosecond LASIK were included in this study. Preoperative, intraoperative and postoperative parameters of anterior chamber gas bubble patients were analyzed and compared.·RESULTS:A total of 51 cases (0. 53%) occurred anterior chamber gas bubble during femtosecond flap creation. There was no statistical difference between uncorrected visual acuity of postoperative 1mo (-0. 076 ± 0. 09 ) and preoperative best corrected visual acuity (-0. 08±0. 04; t=-0. 34,P=0. 74). And 33 eyes (65%) did not affect the pupil tracking, but there were 18 eyes ( 35%) unable to track the pupil successfully. There was no statistical difference in uncorrected visual acuity of postoperative 1mo between trace group (-0. 06 ± 0. 08 ) and no trace group(-0. 11 ± 0. 09; t = 1. 82, P = 0. 07). The highest incidence of anterior chamber gas bubble was at 9 point, followed by 3 point. There were no statistical differences in spherical equivalent refraction, corneal curvature, corneal diameter, anterior chamber volume, anterior chamber depth and intraoperative femtosecond laser energy between anterior chamber gas bubble eyes and the contralateral eyes (P>0. 05).·CONCLUSION: Anterior chamber gas bubble formation during femtosecond flap creation for LASIK is an uncommon event. It may affect the eye tracking. There is no obvious effect on early postoperative visual acuity if intraoperative disposed properly. The direct or indirect factors of anterior chamber gas bubble formation are unclear.

[Effect of early caffeine treatment on the need for respirator therapy in preterm infants with respiratory distress syndrome].

OBJECTIVE: To study the efficacy of early caffeine treatment in preterm infants with respiratory distress syndrome (RDS). METHODS: A prospective controlled clinical trial was performed. A total of 59 preterm infants with RDS were enrolled and divided into a caffeine group (30 infants) and a control group (29 infants). Caffeine was administered in the caffeine group and control group at the same dosage at 12-24 hours after birth and before extubation respectively. The respirator parameters and the incidence rates of ventilator-associated pneumonia (VAP) and apnea were compared between the two groups. RESULTS: Compared with the control group, the caffeine group had significantly lower peak inspiratory pressure, peak fraction of inspired oxygen, and incidence rate of VAP (p<0.05), as well as significantly shorter intubation time, NCPAP time, and total duration of oxygen supply (p<0.05). In addition, the caffeine group had a significantly longer time to first onset of apnea after extubation (p<0.05) and significantly fewer times of onset of apnea 1-2 days after extubation (p<0.01), as compared with the control group. CONCLUSIONS: Early caffeine treatment can reduce the need for assisted ventilation in preterm infants with RDS, help with early extubation and ventilator weaning, reduce the oxygen time in the late stage, reduce the incidence of VAP, and prevent the development of apnea after extubation.