Stromal lenticule addition keratoplasty with corneal crosslinking for corneal ectasia secondary to FS-LASIK:a case series

●AIM:To explore the clinical efficacy and safety of stromal lenticule addition keratoplasty(SLAK)with corneal crosslinking(CXL)on patients with corneal ectasia secondary to femtosecond laser-assisted in situ keratomileusis(FS-LASIK).●METHODS:A series of 5 patients undertaking SLAK with CXL for the treatment of corneal ectasia secondary to FS-LASIK were followed for 4-9mo.The lenticules were collected from patients undertaking small incision lenticule extraction(SMILE)for the correction of myopia.Adding a stromal lenticule was aimed at improving the corneal thickness for the safe application of crosslinking and compensating for the thin cornea to improve its mechanical strength.●RESULTS:All surgeries were conducted successfully with no significant complications.Their best corrected visual acuity(BCVA)ranged from 0.05 to 0.8-2 before surgery.The pre-operational total corneal thickness ranged from 345-404μm and maximum keratometry(Kmax)ranged from 50.8 to 86.3.After the combination surgery,both the corneal keratometry(range 55.9 to 92.8)and total corneal thickness(range 413-482μm)significantly increased.Four out of 5 patients had improvement of corneal biomechanical parameters(reflected by stiffness parameter A1 in Corvis ST).However,3 patients showed decreased BCVA after surgery due to the development of irregular astigmatism and transient haze.Despite the onset of corneal edema right after SLAK,the corneal topography and thickness generally stabilized after 3mo.●CONCLUSION:SLAK with CXL is a potentially beneficial and safe therapy for advanced corneal ectasia.Future work needs to address the poor predictability of corneal refractometry and compare the outcomes of different surgical modes.

Iontophoresis-assisted versus standard corneal crosslinking for progressive keratoconus

Background:To compare the safety and efficacy of iontophoresis-assisted epithelial-on corneal crosslinking(I-CXL)using 0.1%riboflavin-distilled water solution with standard epithelium-off corneal crosslinking(S-CXL)for progressive keratoconus.Methods:In a retrospective analysis,progressive keratoconus patients treated with I-CXL(17 eyes of 17 patients)or S-CXL(13 eyes of 13 patients)were included.All patients were followed up at least 12 months.All patients underwent detailed ophthalmologic examinations involving pre-and postoperative visual acuity,topographic parameters and pachymetry.Intra-and postoperative complications were recorded.Results:No statistically significant differences were observed between the two groups at baseline with respect to visual acuity,age and thinnest corneal thickness(TCT).The postoperative decreases of K1 and Kmean in the S-CXL group represented statistically significantly better results than in the I-CXL group(t=2.093 and 2.123,P=0.046 and 0.043,respectively).Alterations of other parameters showed no significant differences between the two groups.There were no failure cases in the two groups.Conclusions:I-CXL using 0.1%riboflavin-distilled water solution provided effective treatment for progressive keratoconus at 12-month follow-up.However,the decreases of K1 and Kmean caused by I-CXL were less than those by S-CXL.Although treatment time,postoperative patient pain and risk of infection in I-CXL are all less than those in S-CXL,I-CXL is unable to completely replace S-CXL for progressive keratoconus temporarily.

Comparative 2-year outcomes of conventional and accelerated corneal collagen crosslinking in progressive keratoconus

AIM:To compare the safety and efficacy of conventional versus accelerated(9 mW/cm^2)corneal collagen crosslinking(CXL)in progressive keratoconus at the 2-year follow-up.METHODS:In this prospective study,consecutive progressive keratoconus patients were randomized to receive either conventional CXL(CCXL)or accelerated CXL(ACXL;using hydroxypropyl methylcellulose-assisted riboflavin imbibition for 10 min at 9 mW/cm^2).Visual,refractive,keratometric,topographic,and aberrometric outcomes and stromal demarcation line depth(DLD)measurements were compared at the end of a 2-year follow-up.RESULTS:Thirty-two eyes from 32 patients in the CCXL and 27 eyes from 27 patients in the ACXL groups completed 2-year follow-up.At 2y post-CXL,both uncorrected and corrected visual acuities improved significantly in both groups.The improvements in keratometric readings,flattening rate(flattening of the maximum keratometry more than 1 D),3 topographic indices,and vertical coma were significantly better in the CCXL group compared to the ACXL group(P<0.05).The DLD as measured by anterior segment optical coherence tomography or in vivo confocal microscopy was better detectable and significantly deeper in the CCXL group compared to the ACXL group.The deeper DLD was found to be significantly correlated with improvements in the mean keratometry measurements.Progression was noted in 11.1%of eyes in the ACXL group,whereas progression was not observed in any patient eye in the CCXL group.CONCLUSION:In this prospective randomized study,ACXL is less effective in halting the progression of keratoconus at a 2-year follow-up compared to CCXL.

Corneal collagen crosslinking in patients treated with dextran versus isotonic hydroxypropyl methylcellulose (HPMC) riboflavin solution: a retrospective analysis

Background:Corneal collagen crosslinking(CXL)is a widely used treatment for halting the progression of keratoconus.Although initial studies of CXL were performed with a riboflavin solution containing dextran,recent protocols for CXL have indicated the use of a riboflavin solution containing isotonic hydroxypropyl methylcellulose(HPMC).This study was performed to investigate differences in visual outcomes and Scheimpflug(Pentacam)analysis in patients who have undergone epithelium-off CXL with riboflavin solution containing either 20%dextran versus 1.1%HPMC.Methods:All patients in this non-randomized,non-masked,retrospective cohort analysis were treated at Edward S.Harkness Eye Institute,Columbia University Medical Center,New York,NY,USA.Thirty-seven eyes of 33 patients were crosslinked with a dextran solution and 19 eyes of 19 patients crosslinked with an isotonic HPMC solution,both using an epithelium-off 30-min,3 mW/cm2 protocol.All patients had a diagnosis of keratoconus or postrefractive surgery ectasia.Best spectacle corrected visual acuity(BSCVA)and Pentacam parameters were compared at all follow up visits(1,6,12,and 24 months).Differences between groups treated with HPMC and dextran were compared using student’s t-test.Differences between treated eye and fellow eye were calculated and compared between HPMC and dextran groups using paired t-test.Results:Patients treated with a dextran solution had significantly greater improvement in BSCVA at 1,6,and 24 months(p<0.05)compared to the isotonic HPMC-treated group.Kmax increased in both groups at 1 month;however,HPMC-treated patients had a greater increase compared to dextran-treated patients(p=0.01).Kmax decreased in both groups at 6 and 12 months,although this finding was only significant in the HPMC-treated group at 12 months.Conclusions:Our data suggest that crosslinking with the dextran solution may result in significantly better visual outcomes(demonstrated by visual acuity)compared to the isotonic HPMC riboflavin solution.Dextran solutions may have other potential advantages intrinsic to its biochemical properties facilitating more efficient crosslinking.Further research and long-term evidence regarding the use of dextran versus HPMC riboflavin solutions in collagen crosslinking is necessary.

Outcomes of different lines of keratoconus management in a tertiary eye center in north China

AIM: To evaluate the treatment selections and outcomes of keratoconus and discuss the grading treatment of keratoconus.METHODS: Medical records of 1162 patients(1863 eyes) with keratoconus treated with rigid gas permeable(RGP), corneal collagen crosslinking, and keratoplasty were reviewed. The patients were grouped according to the CLEK Study. The advanced group was further divided into a <60 D group and >60 D group. The best-corrected visual acuity(BCVA) and topographic data before and after treatment were recorded.RESULTS: In the 761 eyes with steep K<52 D, nonsurgical management accounted for 83.4%, while in the 735 eyes with steep K>60 D, surgical management accounted for 90.6%. A total of 618 eyes had improved BCVA at the final fol ow-up point(>18 mo, P<0.001). When steep K was <52 D, the BCVA in the RGP group was better than those with lamellar keratoplasty(LKP;P=0.028). When steep K was >52 D, the BCVA and topographic astigmatism outcomes showed no differences among the treatment groups. When steep K was >60 D, the BCVA in eyes treated with LKP was worse than those with steep K<60 D(P=0.025). The incidence of steep K progression in the RGP group was higher in advanced group(20.0% vs 10.8%, P=0.019). The probability of future keratoplasty in RGP was higher in advanced group(14.8% vs 7.0%, P=0.027). The incidence of steep K progression in the corneal collagen crosslinking(CXL) group was higher in advanced group(32.3% vs 8.5%, P=0.007). Multivariate logistic regression revealed the following related factors for treatment options: steep K [odds ratio(OR)=1.208, 95%CI: 1.052-1.387], TA(OR=1.171, 95%CI: 1.079-1.270), and TCT(OR=0.978, 95%CI: 0.971-0.984). The level of steep K, TA, and TCT all relates to the treatment choices of both keratoplasty and non-keratoplasty, while steep K provided the highest diagnostic accuracy(AUC=0.947, P<0.001).CONCLUSION: Steep K is an important grading treatment indicator. When steep K is <52 D, RGP lenses should be recommended. It is the best time for LKP when the steep K ranges from 52 to 60 D.

Protein expression changes in cornea after collagen crosslinking

Riboflavin/UV-mediated corneal collagen cross-linking can increase the mechanical strength of the cornea and prevent or delay corneal expansion and keratoconus progression.We performed quantitative analysis of protein iTRAQ in rabbit eye white matter after cross-linking to explore the changes of protein expression in cornea at different times after cross-linking and to understand the process of corneal stroma remodeling after cross-linking.The screening conditions are fold Change
1.2 and P-value<0.05,we identified 713 and 38 differentially expressed proteins in cornea at 1 week and 1 month after cross-linking.There were 16 differentially expressed proteins at two time points after corneal cross-linking.By annotating the functions of these proteins,we identified some proteins that affect the mechanical properties of the cornea,and these proteins are involved in cell growth,oxidative stress response,and signal transduction in the cornea.It has a guiding role in studying the corneal stroma remodeling process after collagen crosslinking.

Identifying more reliable parameters for the detection of change during the follow-up of mild to moderate keratoconus patients

Background:Reaching a consensus on which parameters are most reliable at detecting progressive keratoconus patients with serial topography imaging is not evident.The aim of the study was to isolate the parameters best positioned to detect keratoconus progression using the Pentacam HR^(®)measures based on the respective limits of repeatability and range of measurement.Method:Using the Pentacam HR^(®),a tolerance index was calculated on anterior segment parameters in healthy and keratoconic eyes.The tolerance index provides a scale from least to most affected parameters in terms of measurement noise relative to that observed in healthy eyes.Then,based on the“number of increments”from no disease to advanced disease,a relative utility(RU)score was also calculated.RU values close to 1 indicate parameters best positioned to detect a change in keratoconic eyes.Results:The tolerance index values indicated that 36%of ocular parameters for keratoconic eyes had repeatability limits which were wider than normative limits(worse),but 28%of the ocular parameters were narrower than normative limits(better).Considering only those parameters with a RU greater than 0.95,a small number of parameters were within this range,such as corneal curvature and asphericity indices.Conclusions:This study demonstrates that measurement error in keratoconic eyes is significantly greater than healthy eyes.Indices implemented here provide guidance on the levels of expected precision in keratoconic eyes relative to healthy eyes to aid clinicians in distinguishing real change from noise.Importantly maximal keratometry(Kmax),central corneal thickness(CCT)and thinnest corneal thickness(TCT)were highlighted as problematic indices for the follow-up of keratoconus in terms of repeatability.