Jui-Teng Lin

Purpose: To update the accommodation mechanisms and propose a dual-wavelength, dual-function laser system for presbyopia and glaucoma treatments. Study Design: Laser sclera softening (LSS) for increased accommodation of presbyopic eyes. Place and Duration of Study: New Taipei City, Taiwan, between Jan., 2023 and Feb., 2023. Methodology: Accommodation gain (AG) can be improved by: (i) thermal shrinkage of the scleral stroma and ciliary body, or (ii) softening of the scleral stroma (with temperature range of 70⁰C to 90⁰C), such that the the lens front and back curvature change (or lens thickening), leading to the thickening of ciliary body and its apex, and the increase of the space of ciliary body and lens equation (SCL), and the length of the posterior vitreal zonules (PVZ) increases. Results: A novel dual-color laser system having wavelength A and B, acting on the front-zone and back-zone of the sclera, respectively, where laser-A has a deep thermal penetration the sclera and ciliary body (CB) (0.5 to 1.0 mm); and laser-B has a shallow penetration depth in the sclera (0.3 to 0.5 mm), based on the optical property of the sclera. Laser-A (having a wavelength about0.8 to 0.98 um) leads to thermal shrinkage of the ciliary body such that the CLS is increased for accommodation gain which is much more effective than the prior art. Conclusion: The increase of AG can be achieved by scleral softening and ciliary body shrinkage which increase the SCL. A proposed novel dual-color laser system acting on the front-zone and back-zone of the sclera, respectively, could provide higher AG than that of single wavelength, or prior arts using scleral ablation. However, further clinical studies are required to justified the proposed novel system with predicted advantages and efficacy based on the optical properties of sclera.

The kinetics and the conversion features of two 3-component systems (A/B/N), based on the proposed new kinetic schemes of Mokbel and Mau et al, in which a visible LED is used to excite a copper complex to its excited triplet state (G*). The coupling of G* with iodonium salt and ethyl 4-(dimethylamino)benzoate (EDB) produces both free radical polymerization (FRP) of acrylates and the free radical promoted cationic polymerization (CP) of epoxides using various new copper complex as the initiator. Higher FRP and CP conversion can be achieved by co-additive of [B] and N, via the dual function of (i) regeneration [A], and (ii) generation of extra radicals. The interpenetrated polymer network (IPN) capable of initiating both FRP and CP in a blend of TMPTA and EPOX. The synergic effects due to CP include: (i) CP can increase viscosity limiting the diffusional oxygen replenishment; (ii) the cation also acts as a diluting agent for the IPN network, and (iii) the exothermic property of the CP. The catalytic cycle, synergic effects, and the oxygen inhibition are theoretically confirmed to support the experimental hypothesis. The measured results of Mokbel and Mau et al are well analyzed and matching the predicted features of our modeling.

Purpose: To derive and provide, for the first time, comprehensive analytic formulas for scleral softening volume efficacy (SVE) for accommodative gain (AG) via the increased space between ciliary body and lens (SCL) and mobility of the posterior vitreous zonules (PVZ). Study Design: To increase the AG of presbyopic eye by a new procedure, laser scleral softening (LSS). Place and Duration of Study: New Taipei City, Taiwan, between June 2022 and July 2022. Methodology: The SVE is calculated based on the time and spatial integral of the scleral temperature profiles, T(z,t), solutions of a heat diffusion equation. Analytic formulas for SVE is derived based on the covered area given by a triangle area. The SVE of a 3-D model is governed by the "volume" covered by the laser beam, or its spot size area, the effective penetration depth (z"), which is an increasing function of laser dose, but a decreasing function of the absorption coefficient (A), due to the Beer's law of laser intensity, I(z)=I₀exp(-Az). The efficacy depth-range (dZ) and time-ranges (dT) are defined for efficient softening with T(z,t)>T*, where T* is the scleral softening threshold temperature. Results: The accommodative gain is proportional to the 3-D SVE given by: SEV(3D) = SEV(1D) x laser beam spot (2-D area) x total number of spots (N) acting on the sclera, which is proportional to the efficacy ranges dZ and dT, in which dZ is an increasing of laser irradiation time, whereas dT is a decreasing function of depth. Softening of the scleral tissue after a thermal laser leading to the increase of PVZ mobility and SCL. However, the actual relation of SVE and the PVZ and SCL changes require measured data. Conclusion: Safety and efficacy of scleral softening for presbyopia treatment depend upon the laser parameters (intensity, dose, spot size, wavelength) and the effective depths. The SVE is proportional to the efficacy depth-range (dZ) and time-range (dT), in which dZ is an increasing of laser irradiation time and dT is a decreasing function of depth. The AG is proportional to the SVE(in 3-D).

Purpose: To derive and provide analytic formulas and proposed protocol for accommodative gain of presbyopia eyes via laser scleral softening, which causes increased space between ciliary body and lens (SCL) and mobility of the posterior vitreal zonules (PVZ). Study Design: To increase the accommodation of presbyopia by laser scleral heating/softening. Place and Duration of Study: New Taipei City, Taiwan, between April 2022 and June 2022. Purpose: To analyze the safety and efficacy of presbyopia treatment via scleral softening. Methodology: The scleral softening efficacy is calculated based on the rate equation of scleral tissue with a rate coefficient given by an Arrhenius formula, Temperature spatial and temporal profiles are given by the numerical solutions of a heat diffusion equation with a volume heating source. Various effective depths including tissue damage depth, temperature penetration depth and conversion depth, governed by tissue absorption coefficient, light intensity and dose (or irradiation time), and the related threshold values, are introduced in replacing the conventional penetration depth based on a Beer's law. Results: Given the the temperature spatial and temporal profiles, scleral softening efficacy can be calculated. Scleral surface damage can be prevented by cooling window. The suggested protocol for scleral softening treatments include: a diode laser at about 1.45 to 1.5 µm or about 1.86 to1.9 µm, or about 2.0 to 2.15 µm, wavelength (with absorption coefficient about 20 to 100 cm^-1); laser power about 0.2 to 0.8 W per spot, having a total of 4 to 16 spots; and irradiation time of 100 to 600 ms. Results of corneal thermal shrinkage are demonstrated by the topography changes of pig eyes, in which the scleral softening does not affect the corneal shapes. The accommodative gain is proportional to the softening efficacy (Seff) of the scleral tissue after a thermal laser leading to the increase of PVZ mobility and SCL. However, the actual relation of Seff and the PVZ and SCL changes require measured data. Conclusion: Safety and efficacy of scleral softening for presbyopia treatment depend upon the laser parameters (intensity, dose, spot size, wavelength) and the effective depths. By choosing the laser treated areas, a dual function treatment using scleral softening for presbyopia, and cornea stromal shrinkage for hyperopia is proposed and demonstrated by topography of pig eyes.

Purpose: To analyze the safety and efficacy of corneal photovitrification (CPV) for improved visions of age-related macular degeneration (AMD) eyes. Study Design: Using CPV for improved visions of AMD eyes. Place and Duration of Study: New Taipei City, Taiwan, and Austin, TX, USA; between April, 2022 and June, 2022. Methodology: The CPV efficacy is calculated based on the rate equation given by dM/dt=-k(t) M(t), where M(t) is the PCV-treated corneal stroma; and k(t) is the rate coefficient given by an Arrhenius formula, k(t) = A₀ exp[−Ea/(RT(t,z)], where t and z are the laser irradiation time and depth of the cornea stroma; Ea  is the activation energy and R is the gas constant. The temperature spatial and temporal profiles are given by the numerical solutions of a heat diffusion equation with a volume heating source. Various effective depths including the tissue damage depth, temperature penetration depth and conversion depth, governed by the tissue absorption coefficient, light intensity and dose (or irradiation time), and the related threshold values, are introduced in replacing the conventional penetration depth based on a Beer's law. Results: The suggested protocol for CPV treatments include: a diode laser at about 2 µm wavelength (with absorption coefficient about 100 cm^-1). The laser dose is about 25 J/cm²/spot and irradiation time of 150 ms. Conclusion: The efficacy of CPV may be predicted/calculated by our modeling based on rate equation and the corneal stroma temperature rise due to laser heating. The preferred retinal locus (PRL) movement observed post-CPV is caused mainly by neuroadaptation.

The synergistic features of a three-component, photoinitiating system (A/B/C) based on the measured data and proposed mechanism of Liu et al. are analyzed. The co-initiators/additives B and C have dual-functions of : (i) regeneration of photoinitiator A, and (ii) generation of extra radicals for enhanced conversion efficacy (CE). The synergistic effects led to higher CE for both free radical polymerization (FRP) and cationic polymerization (CP). The CE of FRP has 3 terms due to the direct (tyep-I) coupling of the triplet state of A with the monomer (M) and the coupling of the two radicals, R and R', with M. The CE of CP has a transient state proportional to the effective absorption constant (b), the light intensity (I) and initiator concentration (A0), but a steady state is independent of the light intensity (I). For the CE of FRP, the contribution from radical R had two cases: (i) linear dependence on T=bIA0, or (ii) nonlinear square root dependence T0.5. The synergistic effects led to higher conversion of FRP and CP, consistent with the measured results. The theoretically predicted new features include: (i) co-initiator [C] which always enhances both FRP and CP conversions, and (ii) co-initiator [B] which leads to more efficient FRP, but it also reduces CP.

This article presents, for the first time, the efficacy and curing depth analysis of photo-thermal dual polymerization in metal (Fe) polymer composites for 3D printing of a three-component (A/B/M) system based on the proposed mechanism of our group, in which the co initiators A and B are Irgacure-369 and charge–transfer complexes (CTC), respectively, and the monomer M is filled by Fe. Our formulas show the depth of curing (Zc) is an increasing function of the light intensity, but a decreasing function of the Fe and photoinitiator concentrations. Zc is enhanced by the additive [B], which produces extra thermal radical for polymerization under high temperature. The heat (or temperature) increase in the system has two components: (i) due to the light absorption of Fe filler and (ii) heat released from the exothermic photopolymerization of the monomer. The heat is transported to the additive (or co-initiator) [B] to produce extra radicals and enhance the monomer conversion function (CF). The Fe filler leads to a temperature increase but also limits the light penetration, leading to lower CF and Zc, which could be overcome by the additive initiator [B] in thick polymers. Optimal Fe for maximal CF and Zc are explored theoretically. Measured data are analyzed based on our derived formulas.

This article presents, for the first time, the efficacy and curing depth analysis of photo-thermal dual polymerization in metal (Fe) polymer composites for 3D printing of a 3-component (A/B/M) system based on the proposed mechanism of our group, in which the co initiators A and B are Irgacure-369, and charge-transfer complexes (CTC), respectively; and the monomer M is filled by Fe. Our formulas show the depth of curing (Zc) is an increasing function of the light intensity, but a decreasing function of the Fe and photoinitiator concentrations. Zc is enhanced by the additive [B] which produces extra thermal radical for polymerization under high temperature. The heat (or temperature) increase in the system has two components : (i) due to the light absorption of Fe filler, and (ii) heat released from the exothermic photopolymerization of the monomer. The heat is transported to the additive (or co-initiator) [B] to produce extra radical R' and enhance the monomer conversion function (CF). The Fe filler leads to temperature increase, but also limits the light penetration leading to lower CF and Zc, which could be overcome by the additive initiator [B] in thick polymers. Optimal Fe for maximal CF and Zc are explored theoretically.

Purpose: To analyze the factors influencing the corneal crosslinking (CXL) efficacy and comparison of epi-on and epi-off procedures. Study Design: modeling the efficacy of epi-off and epi-on CXL. Place and Duration of Study: New Taipei City, Taiwan, between November, 2021 and December, 2021. Methodology: Solving the rate equations for the CXL efficacy which includes the roles of concentration of the photosensitizer, riboflavin (RF), RF depletion effects, dynamic of light intensity, and the non-uniform distribution of RF in the stroma, or the diffusion depth of RF. Both steady-state and transient state features are explored for the efficacy, crosslink depth (CD) and the effects of epithelium layer for the epi-on situation. Results: The steady-state efficacy is proportional to the square-root of [RF-concentration] /[light-intensity], The competing factors of reduced RF, F(z), and reduced light intensity in the stroma determine the relative efficacy of epi-on and epi-off. For example, for F(z)Conclusion: For the steady-state epi-on is more efficient than epi-off, when the RF reduction factor is less than the light intensity gain factor. In contrast, in the transient state (with efficacy <0.6), the efficacy is proportional to the light dose, and therefore epi-on is always less efficient than epi-off.