Yong Zhang1, Kuan-Chen Wang2, Chao-Kai Chang3, Jui-Teng Lin4. 1. Department of Ophthalmology, Shandong Provincial Hospital, Shandong University, Jinan 250021, Shandong Province, China. 2. Department of Electronic Engineering, Taiwan University, Taipei, Taiwan 101, China. 3. Nobel Eye Institute, Taipei, Taiwan 101, China. 4. New Vision Inc., Taipei, Taiwan 103 and Gong-Rui Medical Technology Corp, Xiamen, Fujian Province, China.
Abstract
AIM: To analyze the efficacy of ultraviolet (UV) light initiating corneal cross-linking (CXL). METHODS: The time-dependent absorption of UV light due to the depletion of the initiator (riboflavin) was calculated. The effective dose of CXL with corneal surface covered by a thin layer of riboflavin was derived analytically. The cross linking time was calculated by the depletion level of the riboflavin concentration. A comprehensive method was used to derive analytic formulas. RESULTS: The effective dose of CXL was reduced by a factor (R) which was proportional to the thickness (d) and concentrations (C0) of the riboflavin surface layer. Our calculations showed that the conventional dose of 5.4 J/cm(2) had a reduced effective dose of 4.3 and 3.45 J/cm(2), for d was 100 and 200 µm, respectively, and C0=0.1%. The surface cross linking time was calculated to be T*=10.75s, for a depletion level of 0.135 and UV initial intensity of 30 mW/cm(2). The volume T* was exponentially increasing and proportional to exp (bdC0), with b being the steady state absorption coefficient. CONCLUSION: The effective dose of CXL is reduced by a factor proportional to the thickness and concentrations of the riboflavin surface layer. The wasted dose should be avoided by washing out the extra riboflavin surface layer prior to the UV light exposure.
AIM: To analyze the efficacy of ultraviolet (UV) light initiating corneal cross-linking (CXL). METHODS: The time-dependent absorption of UV light due to the depletion of the initiator (riboflavin) was calculated. The effective dose of CXL with corneal surface covered by a thin layer of riboflavin was derived analytically. The cross linking time was calculated by the depletion level of the riboflavin concentration. A comprehensive method was used to derive analytic formulas. RESULTS: The effective dose of CXL was reduced by a factor (R) which was proportional to the thickness (d) and concentrations (C0) of the riboflavin surface layer. Our calculations showed that the conventional dose of 5.4 J/cm(2) had a reduced effective dose of 4.3 and 3.45 J/cm(2), for d was 100 and 200 µm, respectively, and C0=0.1%. The surface cross linking time was calculated to be T*=10.75s, for a depletion level of 0.135 and UV initial intensity of 30 mW/cm(2). The volume T* was exponentially increasing and proportional to exp (bdC0), with b being the steady state absorption coefficient. CONCLUSION: The effective dose of CXL is reduced by a factor proportional to the thickness and concentrations of the riboflavin surface layer. The wasted dose should be avoided by washing out the extra riboflavin surface layer prior to the UV light exposure.
Authors: Silvia Schumacher; Michael Mrochen; Jeremy Wernli; Michael Bueeler; Theo Seiler Journal: Invest Ophthalmol Vis Sci Date: 2012-02-16 Impact factor: 4.799
Authors: Janna C Nawroth; Lisa L Scudder; Ryan T Halvorson; Jason Tresback; John P Ferrier; Sean P Sheehy; Alex Cho; Suraj Kannan; Ilona Sunyovszki; Josue A Goss; Patrick H Campbell; Kevin Kit Parker Journal: Biofabrication Date: 2018-01-16 Impact factor: 9.954