The Role of Riboflavin Concentration and Oxygen in the Efficacy and Depth of Corneal Crosslinking

Lin, Jenn-Wei

doi:10.1167/iovs.18-24437

Cited by 14 publications

(16 citation statements)

References 7 publications

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“…Therefore, the crosslink efficacy, defined by Eff=1-exp(-S), is also an increasing function of C0. This feature has been clinically reported by O'Brart et al in corneal crosslinking [30], where the PS is riboflavin solution initiated by a UVA light at 365 nm. The role of PS concentration was also shown by Table 1 of Holmes et al [31], where (for LAP) increasing the PS concentration from 0.1% to 0.5% (w/v) in the thiol-ene mixture resulted in a 15-fold increase in the storage modulus.…”

Section: Analysis Of Experimentssupporting

confidence: 60%

“…The photopolymerization dynamics may be defined by the availability of oxygen, where both type-I and -II coexist until the oxygen is depleted. The roles of light dose and PS concentration on the efficacy should be governed a new concept of a volume efficacy (Ve), first introduced by Lin [30], defined by the product of the crosslink (or gelation) depth (CD) and local…”

Section: Resultsmentioning

confidence: 99%

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Modeling the Dynamic Concentration Profiles and Efficacy of Type-I and Type-II Photopolymerization

J¹,

Cheng²,

Chen³

et al. 2018

Preprint

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The kinetics and efficacy profiles of photoinitiated polymerization are theoretically presented. For the same dose, lower light intensity achieves a higher steady-state-efficacy (SSE) in type-I; in contrast, type-II has an equal SSE. Higher light intensity has a faster rising efficacy, due to faster depletion of photoinitiator (PS) concentration. However, type-II process is also affected by the available oxygen. Higher light intensity produces more efficient singlet oxygen, resulting a higher transient efficacy, in which all intensities reach the same SSE when oxygen is completely depleted. With external oxygen, type-II efficacy increases with time, otherwise, it is governed only by the light dose, i.e., same dose achieves same efficacy. Moreover, type-II has an efficacy follows Bunsen Roscoe law (BRL), whereas type-I follows non-BRL. The measured type-I efficacy and gelation profile are analyzed by our analytic formulas. Schematics of the photocrosslinking stage defined by the availability of oxygen is developed, where both type-I and –II coexist until the oxygen is depleted. The overall efficacy may be enhanced by resupply of PS or oxygen during the light exposure. The roles of light dose and PS concentration on the efficacy of photoinitiated polymerization should be are governed a new concept of a volume efficacy (Ve), defined by the product of the crosslink (or gelation) depth (CD) and local [efficacy].

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Section: Analysis Of Experimentssupporting

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Modeling the Dynamic Concentration Profiles and Efficacy of Type-I and Type-II Photopolymerization

J¹,

Cheng²,

Chen³

et al. 2018

Preprint

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“…Extension of exposure time (or dose) in AXL may increase the crosslink depth (z) and improve the efficacy governed a crosslinked stroma volume 7 ¼ depth • strength. Higher Rf concentration (C 0 ) achieves higher efficacy, predicted by c-Ceff formula, 7 was also clinically reported by O'Brart et al 11 Therefore, new clinical studies of DL-depth for a wider range of C 0 ¼ 0.1% to 0.3%, and under the CCM protocol might lead to a breakthrough of the AXL efficacy and justify the accuracy of CCM for optimal efficacy.…”

Section: In Contrast To the Conventional Belief (By Hafezi Andmentioning

confidence: 63%

“…Epi-on is less efficient than epi-off due to limited diffusion depth (D) and the extra absorption of the epithelium; and epi-on CXL with iontophoresis has a larger z* due to improved diffusion depth (D), comparing data 1 and data 2 of Figure 1. This feature is also shown in Lin's efficacy-formula, 7 where higher D has higher value of F(z) ¼ F(z) ¼ 1 -0.5z/D and leads to higher efficacy. Figure 2 represents the conventional protocol having resupply the Rf drops every 4 minutes.…”

mentioning

confidence: 69%

Influencing Factors Relating the Demarcation Line Depth and Efficacy of Corneal Crosslinking

Lin¹

2018

Invest. Ophthalmol. Vis. Sci.

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The recent article of Spadea et al. 1,2 and Toker et al. 3 evaluated the efficacy of accelerated corneal crosslinking (AXL) under different treatment protocols, and the relationship between CXL efficacy and the demarcation line (DL) depth based on available measured data. 1,2 The sudden-drop of DL depth at high intensity (>45 mW/cm 2) has the similar feature as the AXL efficacy reported by Wernli et al. 4 However, it is clinically unclear whether DL depth is proportional to the crosslink depth or the CXL efficacy. 1-3 Moreover, controversial results of AXL efficacy were reported due to inconsistent protocols which were not optimized. To improve the efficacy of AXL, Lin proposed a new protocol called riboflavin (Rf) concentration-controlled method (CCM), 5 in which extra Rf drops are applied to the cornea, at every crosslink time (T*), during the UV exposure, having a frequency defined as Fdrop ¼ N-1, with N ¼ 0.365 [I 0 /C 0 ] 0.5. This formula provides the optimal protocol that higher intensity (I 0) and/or lower Rf concentration (C 0) requires larger Fdrop to compensate its faster Rf depletion, and lower steady-state efficacy, comparing to the low-intensity Dresden protocol. This correspondence intends to further analyze the clinically measured DL depth via the key influencing factors of CXL, including Rf concentration profile (pre-and intraoperatively), 6 Rf initial diffusion depth, UV light effective dose, epithelial absorption (for epi-on case), and most importantly, the administration protocols of Rf during CXL, governed by Fdrop and the waiting period after each Rf drop. 5 The measured DLdepth of various protocols will be analyzed and compared to a combined-efficacy formula. 5,7 The measured DL depth may be compared to a combined type-I CXL efficacy given by 5-7 c-Ceff ¼ 1-exp (-4R), with R ¼ (62/t') [C 0 F(z)/I 0 3 ] 0.5 , where F(z) ¼ 1-0.5z/D, is the Rf initial concentration profile defined by a diffusion depth (D); and the resupply Rf drops every t'minutes. R is the efficacy ratio between the noncontrolled Dresden protocol and the optimal protocol (via CCM) having R ¼ 1.0, and c-Ceff ¼ 0.98, for all range of UV intensity I 0 ¼ 3 to 60 mW/ cm 2 .

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“…In addition, recent investigations performed on the kinetic behaviors of TBAB and CO 2 gas hydrates under various temperature conditions have revealed that high concentrations of TBAB reduce the number of moles of consumed methane compared to pure water 29. In contrast, kinetic promoters including sodium dodecyl sulfate (SDS) enhance the gas consumption and gas storage capacity at a faster rate while the hydrate stability conditions (phase equilibrium) will not be affected 9, 30–32.…”

Section: Introductionmentioning

confidence: 99%

Effects of Graphene Oxide Nanosheets and Al₂O₃Nanoparticles on CO₂Uptake in Semi‐clathrate Hydrates

et al. 2020

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Gas hydrate/clathrate hydrate formation is an innovative method to trap CO2 into hydrate cages under appropriate thermodynamic and/or kinetic conditions. Due to their excellent surface properties, nanoparticles can be utilized as hydrate kinetic promoters. Here, the kinetics of the CO2 + tetra‐n‐butyl ammonium bromide (TBAB) semi‐clathrate hydrates system in the presence of two distinct nanofluid suspensions containing graphene oxide (GO) nanosheets and Al2O3 nanoparticles is evaluated. The results reveal that the kinetics of hydrate formation is inhibited by increasing the weight fraction of TBAB in aqueous solution. GO and Al2O3 are the most effective kinetic promoters for hydrates of (CO2 + TBAB). Furthermore, the aqueous solutions of TBAB + GO or Al2O3 noticeably increase the storage capacity compared to TBAB aqueous solution systems.

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The Role of Riboflavin Concentration and Oxygen in the Efficacy and Depth of Corneal Crosslinking

Cited by 14 publications

References 7 publications

Modeling the Dynamic Concentration Profiles and Efficacy of Type-I and Type-II Photopolymerization

Modeling the Dynamic Concentration Profiles and Efficacy of Type-I and Type-II Photopolymerization

Influencing Factors Relating the Demarcation Line Depth and Efficacy of Corneal Crosslinking

Effects of Graphene Oxide Nanosheets and Al₂O₃Nanoparticles on CO₂Uptake in Semi‐clathrate Hydrates

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The Role of Riboflavin Concentration and Oxygen in the Efficacy and Depth of Corneal Crosslinking

Cited by 14 publications

References 7 publications

Modeling the Dynamic Concentration Profiles and Efficacy of Type-I and Type-II Photopolymerization

Modeling the Dynamic Concentration Profiles and Efficacy of Type-I and Type-II Photopolymerization

Influencing Factors Relating the Demarcation Line Depth and Efficacy of Corneal Crosslinking

Effects of Graphene Oxide Nanosheets and Al2O3Nanoparticles on CO2Uptake in Semi‐clathrate Hydrates

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Product

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Effects of Graphene Oxide Nanosheets and Al₂O₃Nanoparticles on CO₂Uptake in Semi‐clathrate Hydrates