Early changes in corneal densitometry after FS-LASIK combined with accelerated corneal cross-linking for correction of high myopia

AIM:To observe the effects of femtosecond laserassisted excimer laser in situ keratomileusis combined with accelerated corneal cross-linking(FS-LASIK Xtra)on corneal densitometry after correcting for high myopia.METHODS:In this prospectively study,130 patients underwent FS-LASIK or FS-LASIK Xtra for high myopia.Their right eyes were selected for inclusion in the study,of which 65 cases of 65 eyes in the FS-LASIK group,65 patients with 65 eyes in the FS-LASIK Xtra group.Patients were evaluated for corneal densitometry at 1,3,and 6mo postoperatively using Pentacam Scheimpflug imaging.RESULTS:Preoperative differences in corneal densitometry between the FS-LASIK and FS-LASIK Xtra groups in different ranges were not statistically significant(P>0.05).Layer-by-layer analysis revealed statistically significant differences in the anterior(120μm),central,and total layer corneal densitometry between the FS-LASIK and FS-LASIK Xtra groups at 1 and 3mo postoperatively(all P<0.05),the FS-LASIK Xtra group is higher than that of the FS-LASIK group.Analysis of different diameter ranges showed statistically significant differences between the FS-LASIK group and the FS-LASIK Xtra group at 1mo postoperatively in the ranges of 0–2,2–6,and 6–10 mm(both P<0.05);At 3mo postoperatively,the FS-LASIK Xtra group is higher than that of the FS-LASIK group in the ranges of 0–2 and 2–6 mm(P<0.05).At 6mo postoperatively,there were no statistically significant differences in corneal densitometry between the FS-LASIK group and the FS-LASIK Xtra group in different diameter ranges(all P>0.05).CONCLUSION:There is an increase in internal corneal densitometry during the early postoperative period after FS-LASIK Xtra for correction of high myopia.However,the densitometry values decreased to the level of conventional FS-LASIK at 6mo after surgery,with the most significant changes observed in the superficial central zone.

Ten-year observation of corneal densitometry and associated factors following small incision lenticule extraction

●AIM:To investigate the long-term changes of corneal densitometry(CD)and its contributing elements after small incision lenticule extraction(SMILE).●METHODS:Totally 31 eyes of 31 patients with mean spherical equivalent of-6.46±1.50 D and mean age 28.23±7.38y were enrolled.Full-scale examinations were conducted on all patients preoperatively and during followup.Visual acuity,manifest refraction,axial length,corneal thickness,corneal higher-order aberrations,and CD were evaluated.●RESULTS:All surgeries were completed successfully without complications or adverse events.Ten-year safety index was 1.17±0.20 and efficacy 1.04±0.28.CD value of 0–6 mm zones in central layer was statistically significantly lower 10y postoperatively,compared with preoperative values(0–2 mmΔ=-1.62,2–6 mmΔ=-1.24,P<0.01).There were no correlations between CD values and factors evaluated.●CONCLUSION:SMILE is a safe and efficient procedure for myopia on a long-term basis.CD values get lower 10y postoperatively,whose mechanism is to be further discussed.

One-step viscoelastic agent technique for ICL V4c implantation for myopia

AIM:To investigate the safety and efficacy of using a onestep viscoelastic agent technique for posterior chamber phakic implantable collamer lens with a central hole(ICL V4 c)implantation for myopia correction.METHODS:The one-step viscoelastic agent technique for ICL V4 c implantation was used in 100 eyes of 52 patients.Refractive outcomes,intraocular pressure(IOP),corneal endothelial cell,and corneal densitometry values were evaluated at 1 d,1 wk,1 and 3 mo postoperatively.RESULTS:All the surgeries were uneventful.No corrected distance visual acuity was lost after 3 mo.IOP was 16.12±3.18 mm Hg before surgery,and 14.74±3.08 mm Hg at 1d and 14.50±2.56 mm Hg at 3 mo after surgery(P<0.05).Corneal endothelial cell density was 2580±242 cell/mm^(2),the coefficient of variation in cell size was 42.11%±7.92%,and the percentage of hexagonal cells was 40.98%±9.46%before surgery.No significant difference was found when these outcomes were compared between the studied time points(P>0.05).The corneal densitometry values of the central 2 mm and 2 to 6 mm areas showed similar regularities.After surgery,the values significantly increased at 1 d,then decreased to the preoperative values at 1 wk,and then continued to decrease at 3 mo(P<0.05).CONCLUSION:The one-step viscoelastic agent technique for ICL V4c implantation is found to be safe and effective for myopia correction and causes little disturbance to the cornea.

Corneal biomechanical changes in allergic conjunctivitis

Background:To explore corneal biomechanical changes,identify related factors and determine early indicators of keratoconus(KC)development risk in allergic conjunctivitis(AC)patients.Methods:A total of 50 patients,including 20 eyes without AC and 30 eyes with AC were enrolled in this study.All patients underwent a complete ocular examination,including evaluations of clinical manifestations of AC,corneal tomography and densitometry by Pentacam,corneal biomechanics by Corvis ST,and corneal and epithelial thickness mapping by RTvue optical coherence tomography(OCT).Results:The index of surface variance(ISV),index of vertical asymmetry(IVA),keratoconus index(KI),index of height decentration(IHD)and Belin/Ambrosio enhanced ectasia total deviation index(BAD-D)were significantly higher in the AC group than in the non-allergic conjunctivitis(NAC)group(P<0.05).The tomography and biomechanical index(TBI)was also significantly higher in the AC group(P=0.04).The average epithelial thickness in the 2-7mm annulus was significantly thinner in the AC group than in the NAC group(P<0.05).The average densitometry of the total cornea and the anterior layer were higher in the AC group than in the NAC group(P<0.001).The ISV,IVA,KI,IHD and BAD-D were significantly correlated with the TBI and changes in corneal epithelial thickness in AC patients(P<0.05).The changes in epithelial thickness were closely related to the eye rubbing frequency and allergic sign scores(P<0.05).Conclusions:AC patients should be advised to routinely undergo corneal tomographic and biomechanical measurements,and the TBI could be used as an indicator of KC development risk in AC patients.

Corneal biomechanical changes in allergic conjunctivitis

Background:To explore corneal biomechanical changes,identify related factors and determine early indicators of keratoconus(KC)development risk in allergic conjunctivitis(AC)patients.Methods:A total of 50 patients,including 20 eyes without AC and 30 eyes with AC were enrolled in this study.All patients underwent a complete ocular examination,including evaluations of clinical manifestations of AC,corneal tomography and densitometry by Pentacam,corneal biomechanics by Corvis ST,and corneal and epithelial thickness mapping by RTvue optical coherence tomography(OCT).Results:The index of surface variance(ISV),index of vertical asymmetry(IVA),keratoconus index(KI),index of height decentration(IHD)and Belin/Ambrosio enhanced ectasia total deviation index(BAD-D)were significantly higher in the AC group than in the non-allergic conjunctivitis(NAC)group(P<0.05).The tomography and biomechanical index(TBl)was also significantly higher in the AC group(P=0.04).The average epithelial thickness in the 2-7 mm annulus was significantly thinner in the AC group than in the NAC group(P<0.05).The average densitometry of the total cornea and the anterior layer were higher in the AC group than in the NAC group(P<0.001).The ISV,IVA,KI,IHD and BAD-D were significantly correlated with the TBI and changes in corneal epithelial thickness in AC patients(P<0.05).The changes in epithelial thickness were closely related to the eye rubbing frequency and allergic sign scores(P<0.05).Conclusions:AC patients should be advised to routinely undergo corneal tomographic and biomechanical measurements,and the TBl could be used as an indicator of KC development risk in AC patients.Trial registration:Corneal Biomechanical Changes of Allergic Conjunctivitis,NCT04299399.Registered March 3,2020-Retrospectively registered.

Investigation of corneal topographic and densitometric properties of Wilson's disease patients with or without a Kayser-Fleischer

Background:To investigate the topographic measurements and densitometry of corneas in Wilson's disease(WD)patients with or without a Kayser-Fleischer ring(KF-r)compared to healthy individuals.Methods:This cross-sectional study included 20 WD patients without a KF-r(group I),18 WD patients with a KF-r(groupⅠ),and 20 age-matched controls(group Ⅱ).The Pentacam high-resolution imaging system is used to determine corneal topographic measurements and densitometry.Results:Mean age for groups Ⅰ,Ⅱ and Ⅲ was 25.40±6.43 years(14-36 years),25.38±6.96 years(16-39 years),and 23.60±6.56 years(17-35 years),respectively(P=0.623).There was no significant difference between the groups in terms of the anterior corneal densitometry values(P>0.05),while the 6-10 mm and 10-12 mm midstroma and the 2-6 mm,6-10 mm,and 10-12 mm posterior corneal densitometry values in group Ⅱ were significantly higher than those in groups Ⅰ and Ⅱ(for all values,P<0.05).However,the 10-12 mm posterior corneal densitometry values in group Ⅰ were also significantly higher than those in group Ⅲ(P=0.038).The central corneal thickness(CCT),thinnest corneal thickness(tCT),and corneal volume(CV)values in groups Ⅰ and Ⅱ were significantly lower than those in group Ⅱ(for CCT values,P=0.011 and P=0.009;for tCT values,P=0.010 and P=0.005;for CV values,P=0.043 and P=0.029).Conclusion:In WD patients with a KF-r,corneal transparency decreased in the peripheral posterior and midstromal corneal layers;for these patients,corneal transparency may be impaired not only in the peripheral cornea but also in the paracentral cornea.

Investigation of corneal topographic and densitometric properties of Wilson's disease patients with or without a Kayser-Fleischer ring

Background:To investigate the topographic measurements and densitometry of corneas in Wilson’s disease(WD)patients with or without a Kayser-Fleischer ring(KF-r)compared to healthy individuals.Methods:This cross-sectional study included 20 WD patients without a KF-r(group I),18 WD patients with a KF-r(group II),and 20 age-matched controls(group III).The Pentacam high resolution imaging system is used to determine corneal topographic measurements and densitometry.Results:Mean age for groups I,II and III was 25.40±6.43 years(14-36 years),25.38±6.96 years(16-39 years),23.60±6.56 years(17-35 years),respectively(P=0.623).There was no significant difference between the groups in terms of the anterior corneal densitometry values(P>0.05),while the 6-10mm and 10-12 mm mid stroma and the 2-6 mm,6-10 mm,and 10-12 mm posterior corneal densitometry values in group II were significantly higher than those in groups I and III(for all values,P<0.05).However,the 10-12mm posterior corneal densitometry values in group I were also significantly higher than those in group III(P=0.038).The central corneal thickness(CCT),thinnest corneal thickness(tCT),and corneal volume(CV)values in groups I and II were significantly lower than those in group III(for CCT values,P=0.011 and P=0.009;for tCT values,P=0.010 and P=0.005;for CV values,P=0.043 and P=0.029).Conclusion:In WD patients with a KF-r,corneal transparency decreased in the peripheral posterior and mid stromal corneal layers;for these patients,corneal transparency may be impaired not only in the peripheral cornea but also in the paracentral cornea.