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.

Visual rehabilitation in low-moderate keratoconus:intracorneal ring segment implantation followed by same-day topography-guided photorefractive keratectomy and collagen cross linking

AIMTo present the results of same-day topography-guided photorefractive keratectomy (TG-PRK) and corneal collagen crosslinking (CXL) after previous intrastromal corneal ring segment (ISCR) implantation for keratoconus.

Human eye ocular component analysis for refractive state and refractive surgery

AIM： To analyze the clinical factors influencing the human vision corrections via the changing of ocular components of human eye in various applications; and to analyze refractive state via a new effective axial length.METHODS： An effective eye model was introduced by the ocular components of human eye including refractive indexes, surface radius（r1, r2, R1, R2） and thickness（t, T） of the cornea and lens, the anterior chamber depth（S1） and the vitreous length（S2）. Gaussian optics was used to calculate the change rate of refractive error per unit amount of ocular components of a human eye（the rate function M）. A new criterion of myopia was presented via an effective axial length.RESULTS： For typical corneal and lens power of 42 and 21.9 diopters, the rate function Mj（j=1 to 6） were calculated for a 1% change of r1, r2, R1, R2, t, T（in diopters） M1=＋0.485, M2=-0.063, M3=＋0.053, M4=＋0.091, M5=＋0.012, and M6=-0.021 diopters. For 1.0 mm increase of S1 and S2, the rate functions were M7=＋1.35, and M8=-2.67 diopter/mm, respectively. These rate functions were used to analyze the clinical outcomes in various applications including laser in situ keratomileusis surgery, corneal cross linking procedure, femtosecond laser surgery and scleral ablation for accommodation.CONCLUSION： Using Gaussian optics, analytic formulas are presented for the change of refractive power due to various ocular parameter changes. These formulas provide useful clinical guidance in refractive surgery and other related procedures.

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.