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@#AIM: To analyze the effectiveness of transepithelial-corneal collagen cross-linking for 1a after the treatment of progressive keratoconus and discuss its clinical significance. <p>METHODS:A total of 45 cases(48 eyes)of progressive keratoconus who underwent accelerated transepithelial-corneal collagen cross-linking in our hospital from Jan. 2017 to Dec. 2018 were collected. After 1a of postoperative follow-up, the changes of visual acuity, corneal thinnest point thickness, corneal endothelial cell count, corneal cross-linking line depth, Km of anterior corneal curvature and corneal biomechanical parameters before and after surgery were analyzed.<p>RESULTS:Compared with preoperative, the uncorrected visual acuity(UCVA)was improved obviously postoperative in this group patients(<i>P</i><0.05), but the best-corrected visual acuity(BCVA), corneal thinnest point thickness and corneal endothelial cell counts were no significant change(<i>P</i>>0.05). At 6mo and 1a postoperative, Km of anterior corneal curvature(48.54±2.57, 48.77±2.29D)are decreased significantly, the first flatten width of corneal biomechanical parameters(1.52±0.21, 1.57±0.22mm)were significantly lower(<i>P</i><0.05). The absolute value of the second flattening velocity(0.82±0.09, 0.82±0.18m/s)was significantly increased(all <i>P</i><0.05).<p>CONCLUSION:Accelerated transepithelial-corneal collagen cross-linking surgery for progressive keratoconus can significantly improve the UCVA and corneal biomechanics postoperative, but the BCVA was not significantly improved.
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Objective To measure biomechanical parameters of the cornea after keratoconus and laser corneal refractive surgery by Scheimpflug noncontact tonometry (Corvis ST),and analyze the changes and differences in these parameters.Methods From April 2011 to November 2016,63 patients (96 eyes) with clinically diagnosed as keratoconus were selected as the keratoconus group,and 60 patients (120 eyes) underwent laser corneal refractive surgery between November 2016 to March 2017 were selected as postoperative cornea group,and totally 51 healthy person (102 eyes) who received physical examination during the same period were selected as healthy cornea group.Scheimpflug noncontact tonometry (Corvis ST) was performed to measure the length of appl 1,length of appl 2,velocity of appl 1,velocity of appl 2,maximum deformation amplitude,apex distance and radius of curvature in the three groups.Total comparison of biomechanical parameters was performed using ANOVA test among the three groups,while pairwise comparison was performed to analyze the difference of these parameters by SNK methods.Pearson or Spearman correlation analysis was applied to assess the differences in corneal morphological and biomechanical parameters.Results There was no significant difference in length of appl 1,length of appl 2 of the three groups (all P ＞ 0.05).And velocity of appl 1 in the keratoconus group was significantly higher than that of the healthy cornea group [(0.189 ± 0.230) m · s-1 vs.(0.151 ± 0.017)m · s-1] (P ＜ 0.05).As for velocity of appl 2,the keratoconus group was larger than the healthy cornea group,both which were larger than the postoperative cornea group,and the differences were significant (all P ＜ 0.05).And this was true of maximum deformation amplitude in the three groups,with the significant differences(all P ＜ 0.05).The apex distance in the keratoconus group was significantly longer than that in the healthy cornea group (P ＜ 0.05).The radius of curvature of the keratoconus group,postoperative cornea group and healthy cornea group were (5.696 ± 0.881) mm,(7.129 ± 0.681) mm and (7.012 ± 0.728) ram,respectively,which approached significant differences(all P ＜ 0.05).There was significant correlation between the anterior surface refractive power (Km) and apex distance and radius of curvature in the keratoconus group (r =-0.205,0.1 84;P =0.023,0.041),and maximum posterior surface elevation had a statistically significant correlation with velocity of appl 2,maximum deformation amplitude and radius of curvature (r =-0.579,-0.307,0.256,P =0.022,0.002,0.000).For the eyes in the postoperative cornea group,there were no significance correlation between the anterior surface refractive power (Km) and biomechanical properties (P ＞ 0.05),but significant correlation with length of appl 2 (r =-0.297,P =0.026).There were no significant correlation between maximum posterior surface elevation and biomechanical properties (P ＞ 0.05).Conclusion The corneal biomechanical parameters are decreased in eyes after keratoconus and laser corneal refractive surgery,and Corvis ST can become an auxiliary examination tool for earlier diagnosis of secondary keratoconus after corneal refractive surgery.
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Objective To compare the dry-eye features of normal cornea and keratoconus at different stages using non-invasive dry-eye integrated analyzer (Keratograph) and it clinical significance.Methods A case-control study was conducted in 35 patients (44 eyes) with keratoconus who were treated in our hospital from May 2015 to December 2016 as keratoconus group and 45 patients (45 eyes) who received laser corneal refractive surgery as normal cornea group;and subjects in the keratoconus group were subgrouped into mild group (19 eyes),moderate group (15 eyes) and severe group (10 eyes) according to Amsler-Krumeich grading method.The first tear break-up time (first BUT),mean BUT,tear meniscus height (TMH) and conjunctival hyperemia scoring (CHS) of the both eyes in all groups were measured by Keratograph,and the diagnostic values of these variables for keratoconus at different stages were analyzed by ROC curve.Results The levels of horizontal central curvature,vertical center curvature,surface variation index,keratoconus index,posterior corneal surface height and CHS of the keratoconus group were higher than those of the normal cornea,and the difference were statistically significant (all P ＜ 0.05).The non-invasive first BUT,mean BUT and TMH in the keratoconus group were significantly lower than those of the normal cornea group,approaching significant difference (all P ＜ 0.05).The differences in horizontal central curvature,vertical center curvature,surface variation index,keratoconus index,posterior corneal surface height,first BUT and mean BUT among subgroups of keratoconus patients had statistically significance (all P ＜ 0.05).The first BUT and mean BUT in the moderate and severe group were lower than those in the mild group,the difference was statistically significant (all P ＜ 0.05),but there was no significant difference between the moderate and severe group (all P ＞ 0.05).In addition,the mean BUT was negatively correlated with horizontal central curvature,vertical center curvature,surface variation index,keratoconus index and posterior corneal surface height,but had no significant correlation with TMH and CHS (all P ＞ 0.05).ROC curve analysis showed that keratoconus index had the highest diagnostic value for keratoconus than other variables (AUC =0.790,95％ CI:0.689-0.892;P ＜ 0.001).Conclusion The Keratograph dry-eye analyzer can effectively measure the dry-eye parameters of the cornea and the mean BUT in the measurement parameters is the most valuable for the diagnosis of keratoconus,and it is more meaningful for the diagnosis of mild keratoconus.
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Background The application of femtosecond laser in the corneal refractive surgery has made great progression recent years,but the morphology characteristic of corneal stroma surface after making-flap of femtosecond laser is closely concerned.Objective This study was to analyze the influence of photodisrnption of femtosecond laser on the corneal stroma surface and to investigate the effect of different laser pulse energy on the sudace ultrastructure of corneal stroma.Methods Corneal flaps were made with Visu Max femtosecond laser in 16 fresh porcine eyes with the pulse energy 125 nJ,155 nJ and 195 nJ respectively,and Moria-M2 microkeratome was used as control.Scanning electron microscopy (S-3400N Hitachi High-Technologies Corp) was used to observe and compare the ultrastructural characteristic of corneal stroma bed surface after making of corneal flap.Results The corneal strnma was evaporated and created a smooth surface when photodisrnption happened in the femtosecond laser group.Residual tissue bridges could been exhibited among the cavitation bubbles under the scanning electron microscope.Corneal strnma surface was smooth in the 125 nJ pulse energy group,but some tissue bridges still were visible.In the 155 nJ pulse energy group,much more smooth surface was seen without tissue bridges and mechanical damages on the corneal surface.However,the surface quality was worse and many tissue bridges and grooves existed in the 195 nJ pulse energy group.In addition,different sizes of slots caused by big cavitation bubbles were visible with the round and oval shape.The edges were regular and sharp with small damage zone after cutting with femtoseeond laser.However,many elevated fibril tissues could be seen on the corneal surface after making of flap with microkeratome.Many crimp and irregularity tissues were found on the surface.Blunt surface and indentations appeared in the cutting edge.Conclusions The mierostrueture of corneal stroma surface is more smoother after making of corneal flap with fentosecond laser in comparison with microkeratome.Pulse energy of 155 nJ is preferably during the making-flap with femtosecond laser.
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Background As a newly developed refractive surgery,femtosecond laser in situ keratomileusis (LASIK) receives more and more attention.Changes in ocular stray light after femtosecond LASIK is an important problem that impacts visual quality.Some relevant research has been performed before,but the outcomes are conflicting.Objective This primary study was to investigate the change of stray light values before and after femtosecond LASIK and analyze the relevant factors underlying the change.Methods Clinical data from 109 eyes of 55 myopic patients who underwent femtosecond LASIK in Tianjin Eye Hospital from December,2010 through February,2011 were included in this study.Stray light values were measured and recorded by C-Quant stray light meter preoperatively,and 1 day,1 week,1 month and 6 months postoperatively.The stray light data were compared by repeated measures ANOVA,and the correlations among the stray light values with preoperative factors,such as age,equivalent sphere,pupil diameter and central corneal thickness(CCT),as well as with postoperative factors,such as residual bed thickness(RBT),RBT/CCT,ablation depth,ablation ratio,flap thickness,flap diameter flap base width and exiting energy,were analyzed statistically.Written informed consent was obtained from each individual at initial of this study.Results The stray light values were 0.90±0.19,1.10±0.19,1.02±0.18,0.96±0.16 and 0.94±0.15 pre-operation,and 1 day,1 week,1 month and 6 months after femtosecond LASIK.The stray light values increased significantly 1 day,1 week,and 1 month after surgery,showing significant differences among the various time points (F=17.699,P=0.000).The mean stray light value was higher in 1 week than that in 6 months after operation (t=2.412,P=0.017).No significant differences were found in the stray light values between 6 months and 1 month or pre-operation (t =0.779,P =0.437 ; t =-1.877,P =0.062).No significant correlations were seen between preoperative and postoperative stray light values with age,preoperative refractive diopter,pupil diameter or CCT (P＞0.05).The changes in stray light values 1 week,1 month and 6 months after surgery were negatively correlated with ablation depth(r=-0.226,-0.228,-0.241 ;P＜0.05) and ablation ratio(r =-0.149,-0.219,-0.255 ;P＜0.05).Conclusions Stray light values increase within 1 month and return to normal 6 months after femtosecond LASIK.Stray light values may be related to multiple setting laser parameters and factors during femtosecond LASIK.