ABSTRACT
Objective:To evaluate the effect of mushroom-like pattern femtosecond laser enabled penetrating keratoplasty with different laser energies on the ring incision and corneal endothelial cells, and compare with conventional penetrating keratoplasty.Methods:According to the point/line separation and blasting energy, 48 porcine corneas were randomly divided into 6 groups by using a random number table.In group A, B, C, D and E, the point/line separation was 4/4, 4/4, 8/8, 8/8 and 4/2 μm, and the blasting energy was 1.5, 2.0, 1.5, 2.0 and 2.0 μJ; In group F, a negative pressure ring drill was used to make penetrating incisions.There were 8 porcine corneas in each group.Femtosecond laser of 200 kHz was used to make corresponding mushroom-shaped penetrating incisions on the porcine corneas, and compared with porcine corneas incisions with a ring drill.The optical and scanning electron microscope images were used to evaluate the glossiness of ring incisions.Four human corneas used femtosecond laser for mushroom-like penetrating incisions with point/line separation 8/8 μm, and blasting energy 2.0 μJ as the experimental group; three human corneas received a negative pressure ring drill for penetrating incisions as the control group.The loss rate of corneal endothelial cells was observed and compared between experimental group and control group.The donor guardians agreed to the acquisition and use of the donors' cornea and signed informed consents.This study protocol was approved by the Ethics Committee of Nanjing First Hospital.Results:Femtosecond laser mushroom penetrating ring incision completion rate was 100%.The corneal ring incision in each group was stepped, and sections of ring incisions in group A and group E were glossiest by the light microscope.Sections of ring incisions in group E were glossiest by the laser scanning electron microscope.The overall glossiness scores of the corneal ring incisions among various groups were statistically significantly different by the light microscopy ( F=22.75, P<0.01). Among them, the glossiness scores in the group A were higher than those in the group B, and the glossiness scores in the group C were higher than those in the group D, with statistically significant differences (both P<0.05). The overall glossiness scores of corneal ring incisions among various groups were statistically significantly different by laser scanning electron microscopey ( F=122.33, P<0.01). Among them, the glossiness scores in the group A were higher than those in the group B, and the the glossiness scores in the group C were higher than those in the group D, with statistically significant differences (both P<0.05). The corneal endothelial cells showed regular shape and tight arrangement in the experimental group, and irregular shape and loose connections were seen in the control group.The average corneal endothelial cell loss rate in the experimental group was (2.2±1.3)%, lower than (6.7±2.1)% of the control group, with a significant difference between them ( t=3.569, P<0.05). Conclusions:Femtosecond laser can produce perfect mushroom configuration, and the ring incision glossiness is better in comparison with trephine cutting.Femtosecond laser ring cut can lessen corneal endothelial loss.
ABSTRACT
Background The instability of tear film in dry eye often affects the visual quality after femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK).The prediction for visual quality following FS-LASIK was difficult in the past because of the limiting of examination method.OQAS-Ⅱ is a quantitative checking system of visual quality,which is helpful for the evaluation of the relationship between tear stability and visual quality following FS-LASIK.Objective This study was to investigate the predicting effects of the quality of tear film on visual quality after LASIK.Methods A prospective cohort study was performed.One hundred and twenty eyes of 120 myopic patients who wanted to receive FS-LASIK were enrolled in Nanjing First Hospital from August to December 2015 after informed consent.The objective scattering index (OSI) was 1.2 in the patients.The patients were divided into mild dry eye group (71 eyes) and non-dry eye group (49 eyes) based on the Expert Consensus on Clinical Diagnosis and Treatment of Dry Eye(2013).FS-LASIK was performed in the non-dry eye group,and 0.1％ sodium hyaluronate eye drops was topically administered for 1 month firstly and then the operation was carried out in the same way in the mild dry eye group.Slit lamp microscope,uncorrected visual acuity (UCVA),best corrected visual acuity (BCVA),spherical equivalent (SE) were examined,and the safety index and availability index were assessed.OQASTM Ⅱ analysis system was employed for the defection of Schirmer Ⅰ test (S Ⅰ t),breakup time of tear film (BUT),modulation transfer function cut-off frequency (MTF cut off) and mean OSI before and after surgery.Results The safety index was 1.05 ±0.11 and 1.03 ±0.09,and the availability index was 1.02±0.14 and 1.01 ± 0.12 in the non-dry eye group and mild dry eye group,respectively,showing significant differences between the two groups (t =0.391,0.147,both at P＞0.05).The BUT was evidently shortened 1 month and 3 months after surgery in comparison with before surgery in both non-dry eye group and mild dry eye group,and BUT in the mild dry eye group was shorter than that in the non-dry eye group in postoperative 3 months,with a significant differences between them (P＜0.05).The mean OSI was increased and MTF cutoff was reduced 1 month,3 months and 6 months after surgery in comparison with before surgery in both mild dry eye group and none-dry eye group,and mean OSI was higher and MTF cutoff was lower in the mild dry eye group than that in the non-dry eye group,with significant differences between them (all at P＜0.05).In postoperative 12 months,BUT,mean OSI and MTF cutoff were near normal in both groups.Conclusions FS-LASIK can improve objective visual quality,and preoperative tear film quality is associated with objective visual quality after FS-LASIK.The unstable tear film affects visual quality after FS-LASIK.OQASTM Ⅱ system can diagnose and monitor tear change of dry eyes,which is helpful for the screening of indicator of FS-LASIK and rational prediction of postoperative visual quality.
ABSTRACT
Cornea is a very important component of the human eyeball wall.It maintains the physiological structure of eyeball and provides protection for eye content and it is an important part of refractive media.As human inhomogeneous viscoelastic material, the cornea possesses many biomechanical properties such as the elastic, viscosity and non linear elastic.Currently, ocular response an-alyzer and corneal visualization scheimpflug technology are often used in vivo measurement and analysis to assist in the diagnosis and treatment of clinical diseases such as keratoconus, and to assess the feasibility and prognosis of refractive surgery.The latest progress of corneal biomechanical measurement and its clinical application are reviewed in this paper.