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1.
Biomechanical effect of ultraviolet-A-riboflavin cross-linking on simulated human corneal stroma model and its correlation with changes in corneal stromal microstructure.
Li, H, Liu, T, Mu, B, Zhao, X, Xue, C, Shen, M, Jhanji, V, Wang, Y
Experimental eye research. 2020;:108109
Abstract
In this study, we established an experimental human corneal stroma model of simulated cornea tissue composed of thin anterior cornea strips layers obtained from small incision lenticular extraction (SMILE) surgery. We investigated the biomechanical effect of ultraviolet-A- riboflavin cross-linking at different depths of corneal stroma model and correlated it with stromal microstructural changes examined by transmission electron microscopy (TEM). Corneal strips were harvested from fresh human corneal lenticules obtained after SMILE surgery. Experimental models (n = 34) were established by superimposing the corneal lenticule strips until their thickness reached close to 500 μm. Corneal cross-linking (CXL) was performed subsequently using standard or accelerated protocol. Elasticity and viscosity were quantified using stress-strain extensometer. TEM was used to visualize the collagen fiber diameter and interfibrillar spacing. The relative change in Young's modulus (rel. ΔE) decreased nonlinearly with increasing stromal depth both in the standard and accelerated groups. Compared to the sham controls, the rel. ΔE in standard and accelerated CXL groups increased significantly in the anterior 400 μm and 275 μm depth, respectively. Also, the relative change in stress (rel. ΔS) was significantly lower after standard and accelerated CXL compared to sham controls. Depth analysis showed similar results for the elastic effect. TEM images showed a small, non-significant increase in fibril diameter. The interfibrillar spacing decreased significantly after standard and accelerated CXL in the anterior-mid stromal region. We noted that the increase of corneal stiffness correlated with decrease in interfibrillar spacing after CXL. The stiffening effect was depth dependent. The effect of accelerated CXL was less in the deep corneal stromal regions compared to standard CXL.
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2.
Randomized Control Trial on the Effectiveness of Collagen Cross-linking on Bullous Keratopathy.
Choy, BNK, Ng, ALK, Zhu, MM, Liu, CC, Xu, S, Lai, JSM
Cornea. 2020;(11):1341-1347
Abstract
PURPOSE To investigate the long-term effect and safety of collagen cross-linking (CXL) on patients with bullous keratopathy (BK) in a randomized control manner. It is, to our knowledge, the first randomized control study on the effect of CXL on BK. METHODS Subjects were randomized to receive CXL as in the standard protocol for treating keratoconus or a placebo treatment. Subjects were assessed at baseline and up to 12 months after treatment. Primary outcomes were central corneal thickness (CCT) and pain scores. RESULTS Forty-two patients with BK participated in the study treatment, 26 subjects were randomized to the CXL group and 16 subjects to the control group. The reduction of CCT in the CXL group was 37.6 and 63.8 μm at 2 and 4 weeks, respectively, which were significantly higher than that in the control group. However, there was no statistical difference in CCT reduction between the 2 groups at 12 weeks and after. There were no consistent advantages in pain score, corneal clarity, and visual acuity over the controls throughout the 1-year follow-up. However, CXL was associated with more recurrent epithelial defect (12%), and 2 of the 3 subjects with epithelial defect required amniotic membrane transplant. CONCLUSIONS CXL reduced corneal thickness in the patients with BK, at least for the initial period. However, there were no improvement in pain, corneal clarity, and vision that were of more clinical relevance to the patients. Its short-term benefit was unlikely to outweigh its potential risk of recurrent epithelial defect.
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3.
Accelerated Versus Standard Corneal Cross-Linking for Progressive Keratoconus: A Meta-Analysis of Randomized Controlled Trials.
Kobashi, H, Tsubota, K
Cornea. 2020;(2):172-180
Abstract
PURPOSE To compare the clinical results of accelerated corneal collagen cross-linking (ACXL) to standard corneal collagen cross-linking (SCXL) in progressive keratoconus by summarizing randomized controlled trials using a meta-analysis. METHODS Trials meeting the selection criteria were quality appraised, and data were extracted by 2 independent authors. A comprehensive search was performed using the Cochrane methodology to evaluate the clinical outcomes of ACXL and SCXL for treating progressive keratoconus. Estimates were evaluated by weighted mean difference (WMD) and 95% confidence interval (CI) for absolute changes of the outcomes during 12-month observation periods. Postoperative demarcation line depth was also compared. RESULTS We identified 6 randomized controlled trials that met the eligibility criteria for this meta-analysis. SCXL resulted in a significantly better outcome in postoperative changes in best spectacle-corrected visual acuity (WMD = -0.02; 95% CI, -0.03 to -0.01; P < 0.0001); however, the small differences may not be clinically significant. ACXL provided a significantly better improvement of cylindrical refraction after the 1-year follow-up (WMD = 0.15; 95% CI, 0.05-0.26; P = 0.005). Demarcation line depth at 1 month after SCXL was deeper than that after ACXL (WMD = -102.25; 95% CI, -157.16 to -47.35; P = 0.0003). No differences in the changes in maximum keratometry, central corneal thickness, uncorrected visual acuity, spherical equivalent refraction, corneal biomechanical properties, and corneal endothelial cell density were found among both groups. CONCLUSIONS An ACXL shows a comparable efficacy and safety profile at the 1-year follow-up, but it has less impact on improving best spectacle-corrected visual acuity when compared with the Dresden protocol. Overall, both methods similarly stop the disease progression.
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4.
Corneal collagen cross-linking for bacterial infectious keratitis.
Davis, SA, Bovelle, R, Han, G, Kwagyan, J
The Cochrane database of systematic reviews. 2020;(6):CD013001
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Abstract
BACKGROUND Infectious keratitis is an infection of the cornea that can be caused by bacteria, viruses, fungi, protozoa, or parasites. It may be associated with ocular surgery, trauma, contact lens wear, or conditions that cause deficiency or loss of corneal sensation, or suppression of the immune system, such as diabetes, chronic use of topical steroids, or immunomodulatory therapies. Photoactivated chromophore for collagen cross-linking (PACK-CXL) of the cornea is a therapy that has been successful in treating eye conditions such as keratoconus and corneal ectasia. More recently, PACK-CXL has been explored as a treatment option for infectious keratitis. OBJECTIVES To determine the comparative effectiveness and safety of PACK-CXL with standard therapy versus standard therapy alone for the treatment of bacterial keratitis. SEARCH METHODS We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2019, Issue 7); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Science Information database (LILACS); ClinicalTrials.gov; and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not use any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 8 July 2019. SELECTION CRITERIA We included randomized controlled trials (RCTs), quasi-RCTs, and controlled clinical trials (CCTs) of PACK-CXL for bacterial keratitis. We included quasi-RCTs and CCTs as we anticipated that there would not be many RCTs eligible for inclusion. DATA COLLECTION AND ANALYSIS Two review authors working independently selected studies for inclusion in the review, assessed trials for risk of bias, and extracted data. The primary outcome was proportion of participants with complete healing at four to eight weeks. Secondary outcomes included visual acuity, morphology, adverse events, and treatment failure at four to eight weeks. MAIN RESULTS We included three trials (two RCTs and one quasi-RCT) in this review for a total of 59 participants (59 eyes) with bacterial keratitis. Trials were all single-center and were conducted in Egypt, Iran, and Thailand between 2010 and 2014. It is very uncertain whether PACK-CXL with standard antibiotic therapy is more effective than standard antibiotic therapy alone for re-epithelialization and complete healing (risk ratio (RR) 1.53, 95% confidence interval (CI) 0.88 to 2.66; participants = 15). We judged the certainty of the evidence to be very low due to the small sample size and high risk of selection and performance bias. The high risk of selection bias reflects the overall review. Masking of participants was not possible for the surgical arm. No participant had a best-corrected visual acuity of 20/100 or better at eight weeks (very low certainty evidence). There is also no evidence that use of PACK-CXL with standard therapy results in fewer instances of treatment failure than standard therapy alone (RR 0.50, 95% CI 0.05 to 4.98; participants = 32). We judged the certainty of evidence to be low due to the small sample size and high risk of selection bias. There were no adverse events reported at 14 days (low certainty evidence). Data on other outcomes, such as visual acuity and morphological characteristics, could not be compared because of variable time points and specific metrics. AUTHORS' CONCLUSIONS The current evidence on the effectiveness of PACK-CXL for bacterial keratitis is of low certainty and clinically heterogenous in regard to outcomes. There are five ongoing RCTs enrolling 1136 participants that may provide better answers in the next update of this review. Any future research should include subgroup analyses based on etiology. A core outcomes set would benefit healthcare decision-makers in comparing and understanding study data.
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Corneal refractive surgery combined with simultaneous corneal cross-linking: Indications, protocols and clinical outcomes-A review.
Ma, J, Wang, Y, Jhanji, V
Clinical & experimental ophthalmology. 2020;(1):78-88
Abstract
Corneal refractive surgery is one of the most common approaches for correction of refractive errors. Combined corneal refractive surgery and corneal cross-linking (CXL) has been proposed as a method to achieve better refractive stability and to prevent iatrogenic corneal ectasia. However, there are concerns regarding its indications, surgical safety, standardization of protocols and long-term effect on corneal tissue. This review article aims to discuss the current knowledge and recent updates on combination of CXL and refractive surgery.
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6.
Standard and accelerated corneal cross-linking long-term results: A randomized clinical trial.
Hashemi, H, Mohebbi, M, Asgari, S
European journal of ophthalmology. 2020;(4):650-657
Abstract
PURPOSE To compare long-term results between accelerated and standard corneal cross-linking protocols in the treatment of progressive keratoconus and compare their effectiveness between central (cone in the central 3 mm) and peripheral (cone beyond 3 mm) cases. METHODS In this randomized clinical trial, we compared 31 eyes treated with accelerated corneal cross-linking (18 mW/cm2, 5 min) and 31 eyes treated with standard corneal cross-linking (3 mW/cm2, 30 min), 16 central and 11 peripheral keratoconus in each group. In this report, 4-year changes in vision, refraction, topography, corneal biomechanics, and corneal cell count were evaluated. RESULTS Uncorrected distance visual acuity improvement was better with standard corneal cross-linking (0.19 ± 0.30 logMAR) than accelerated corneal cross-linking (0.08 ± 0.35 logMAR), but the intergroup difference was not statistically significant (p = 0.283). Cylinder and spherical equivalent significantly increased similarly in both groups. Among topographic indices, anterior Kmax-3 mm showed more reduction in standard corneal cross-linking than accelerated corneal cross-linking (1.35 ± 1.39 vs 0.36 ± 1.10 D, p = 0.011). Anterior Kmax-8 mm reduced by 1.50 ± 1.82 and 0.37 ± 1.58 D in the standard corneal cross-linking and accelerated corneal cross-linking groups, respectively (p = 0.029). Compared to 18-month results, none of the indices at 4 years showed any significant intergroup difference (all p > 0.05). In cases with peripheral keratoconus, changes in anterior Kmax-3 mm (+0.03 ± 0.66 vs -1.17 ± 1.15 D, p = 0.012) and anterior Kmax-8 mm (+0.43 ± 1.09 vs -1.57 ± 1.40 D, p = 0.003) were greater with standard corneal cross-linking. In central cases, no significant intergroup difference was observed. CONCLUSION At 4 years after the procedure, standard corneal cross-linking offered better anterior corneal flattening in the center and periphery. These differences concerned cases of peripheral keratoconus, and the two protocols were similarly effective in central cases. Beyond the 18th month, the two protocols appeared to be similarly effective.
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Association Between One-carbon Metabolism-related Vitamins and Risk of Breast Cancer: A Systematic Review and Meta-analysis of Prospective Studies.
Zeng, J, Gu, Y, Fu, H, Liu, C, Zou, Y, Chang, H
Clinical breast cancer. 2020;(4):e469-e480
Abstract
Epidemiologic studies focusing on the association between 1-carbon metabolism-related vitamins (ie, folate, vitamin B6, vitamin B2, vitamin B12) and breast cancer risk have reported inconsistent findings. We conducted a systematic search of the reported data and performed a meta-analysis of prospective case-control and cohort studies to derive a more precise evaluation. The PubMed and EMBASE databases were searched to identify eligible studies. A total of 27 studies involving 49,707 cases and 1,274,060 individuals were included in the meta-analysis. The results indicated that a high intake of folate, vitamin B6, and vitamin B2 might decrease the risk of breast cancer. The corresponding pooled relative risks (RRs) for the highest intake compared with the lowest were 0.93 (95% confidence interval [CI], 0.88-0.99; P = .018), 0.94 (95% CI, 0.89-1.00; P = .037) and 0.90 (95% CI, 0.82-0.99; P = .026). No significant association between vitamin B12 and breast cancer risk was found (RR, 0.99; 95% CI, 0.94-1.04; P = .604). Further study showed that folate and vitamin B6 might decrease the risk of estrogen receptor-negative (ER-)/progesterone receptor-negative (PR-) breast cancer but not ER+/PR+ breast cancer. The dose-response meta-analysis indicated a significant linearity relationship between folate intake and a reduced risk of ER-/PR- breast cancer. An increment of folate intake (100 μg/d) corresponded to a 7% deceased risk of ER-/PR- breast cancer (RR, 0.93; 95% CI, 0.89-0.98; P = .007). In conclusion, a high intake of 1-carbon metabolism-related vitamins might contribute to the prevention of breast cancer, especially ER-/PR- breast cancer.
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Impact of the MTHFR C677T polymorphism on one-carbon metabolites: Evidence from a randomised trial of riboflavin supplementation.
Rooney, M, Bottiglieri, T, Wasek-Patterson, B, McMahon, A, Hughes, CF, McCann, A, Horigan, G, Strain, JJ, McNulty, H, Ward, M
Biochimie. 2020;:91-99
Abstract
Homozygosity for the C677T polymorphism in MTHFR (TT genotype) is associated with a 24-87% increased risk of hypertension. Blood pressure (BP) lowering was previously reported in adults with the TT genotype, in response to supplementation with the MTHFR cofactor, riboflavin. Whether the BP phenotype associated with the polymorphism is related to perturbed one-carbon metabolism is unknown. This study investigated one-carbon metabolites and their responsiveness to riboflavin in adults with the TT genotype. Plasma samples from adults (n 115) screened for the MTHFR genotype, who previously participated in RCTs to lower BP, were analysed for methionine, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), betaine, choline and cystathionine by liquid chromatography tandem mass spectrometry (LC-MS/MS). The one-carbon metabolite response to riboflavin (1.6 mg/d; n 24) or placebo (n 23) for 16 weeks in adults with the TT genotype was also investigated. Plasma SAM (74.7 ± 21.0 vs 85.2 ± 22.6 nmol/L, P = 0.013) and SAM:SAH ratio (1.66 ± 0.55 vs 1.85 ± 0.51, P = 0.043) were lower and plasma homocysteine was higher (P = 0.043) in TT, compared to CC individuals. In response to riboflavin, SAM (P = 0.008) and cystathionine (P = 0.045) concentrations increased, with no responses in other one-carbon metabolites observed. These findings confirm perturbed one-carbon metabolism in individuals with the MTHFR 677TT genotype, and for the first time demonstrate that SAM, and cystathionine, increase in response to riboflavin supplementation in this genotype group. The genotype-specific, one-carbon metabolite responses to riboflavin intervention observed could offer some insight into the role of this gene-nutrient interaction in blood pressure.
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9.
Riboflavin supplementation alters global and gene-specific DNA methylation in adults with the MTHFR 677 TT genotype.
Amenyah, SD, McMahon, A, Ward, M, Deane, J, McNulty, H, Hughes, CF, Strain, JJ, Horigan, G, Purvis, J, Walsh, CP, et al
Biochimie. 2020;:17-26
Abstract
DNA methylation is important in regulating gene expression and genomic stability while aberrant DNA methylation is associated with disease. Riboflavin (FAD) is a cofactor for methylenetetrahydrofolate reductase (MTHFR), a critical enzyme in folate recycling, which generates methyl groups for homocysteine remethylation to methionine, the pre-cursor to the universal methyl donor S-adenosylmethionine (SAM). A polymorphism (C677T) in MTHFR results in decreased MTHFR activity and increased homocysteine concentration. Previous studies demonstrated that riboflavin modulates this phenotype in homozygous adults (MTHFR 677 TT genotype), however, DNA methylation was not considered. This study examined DNA methylation, globally and at key MTHFR regulatory sites, in adults stratified by MTHFR genotype and the effect of riboflavin supplementation on DNA methylation in individuals with the 677 TT genotype. Samples were accessed from participants, screened for the MTHFR C677T polymorphism, who participated in observational (n = 80) and targeted riboflavin (1.6 mg/day) RCTs (n = 80). DNA methylation at LINE-1 and key regulatory regions of the MTHFR locus were analysed by pyrosequencing in peripheral blood leukocytes. LINE-1 (+1.6%; p = 0.011) and MTHFR south shelf (+4.7%, p < 0.001) were significantly hypermethylated in individuals with the MTHFR 677 TT compared to CC genotype. Riboflavin supplementation resulted in decreased global methylation, albeit only significant at one CpG. A significant reduction in DNA methylation at the MTHFR north shore (-1.2%, p < 0.001) was also observed in TT adults following intervention with riboflavin. This provides the first RCT evidence that DNA methylation may be modulated by riboflavin in adults with the MTHFR 677 TT genotype.
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Metabolic treatments of migraine.
Lisicki, M, Schoenen, J
Expert review of neurotherapeutics. 2020;(3):295-302
Abstract
Introduction: Most preventive migraine treatments modify the brain's excitation/inhibition balance and/or serotonin metabolism, which likely accounts for their unfavorable adverse effect profile. Novel biological therapies blocking CGRP transmission are effective and better tolerated, but they are expensive and may not influence brain dysfunctions upstream in the pathophysiological cascade of migraine, including premonitory and aura symptoms. Biochemical and clinical studies suggest that there may be another complimentary treatment strategy, the one that targets the underestimated metabolic facet of migraine pathophysiology.Areas covered: After a brief description of the metabolic abnormalities found in migraine patients, we will review and discuss published data on metabolic treatments of migraine. There is evidence that riboflavin and co-enzyme Q10 are effective for the prevention of migraine and quasi devoid of adverse effects. Response rates are close to those of topiramate, propranolol, and CGRP/CGRPrec mAbs. The evidence is weaker for thioctic acid. Dietary and pharmacological strategies inducing ketosis are novel promising approaches for which preliminary trials with favorable outcomes have been published.Expert opinion: Metabolic treatments of migraine constitute an effective, well-tolerated, inexpensive, and evidence-supported therapeutic option for migraine prophylaxis, and may be considered as first treatment line in many patients, including in children and adolescents.