The Efficacy of Corneal Cross-Linking Shows a Sudden Decrease with Very High Intensity UV Light and Short Treatment Time

Pulsed vs continuous light accelerated corneal collagen crosslinking: in vivo qualitative investigation by confocal microscopy and corneal OCT

“…8,9 Conventional epithelium-off crosslinking (CXL) demonstrated its safety and long-term efficacy in stabilizing progressive keratoconus and secondary ectasias in different clinical trials. [10][11][12][13][14] On the other hand, the procedure is time consuming, lasting from 40 min to 1 h. 15 The Bunsen-Roscoe's law of reciprocity [16][17][18] theoretically demonstrated that the photochemical process behind crosslinking depends on the absorbed UV-A energy and its biological effect is proportional to the total energy dose delivered in the tissue. [16][17][18] According to this concept, it is theoretically possible to deliver the same energy dose ensuring a proportional biological effect by setting different UV-A powers and exposure times in order to accelerate and shorten the crosslinking procedure in accelerated crosslinking (ACXL) modality.…”

“…[10][11][12][13][14] On the other hand, the procedure is time consuming, lasting from 40 min to 1 h. 15 The Bunsen-Roscoe's law of reciprocity [16][17][18] theoretically demonstrated that the photochemical process behind crosslinking depends on the absorbed UV-A energy and its biological effect is proportional to the total energy dose delivered in the tissue. [16][17][18] According to this concept, it is theoretically possible to deliver the same energy dose ensuring a proportional biological effect by setting different UV-A powers and exposure times in order to accelerate and shorten the crosslinking procedure in accelerated crosslinking (ACXL) modality. [17][18][19] According to photochemical crosslinking studies based on kinetics model 7 the UV-A illumination caused a rapid depletion of oxygen in a riboflavin-soaked cornea and turning the UV light off led to replenishment of the oxygen to its original level within 3 to 4 min.…”

“…[16][17][18] According to this concept, it is theoretically possible to deliver the same energy dose ensuring a proportional biological effect by setting different UV-A powers and exposure times in order to accelerate and shorten the crosslinking procedure in accelerated crosslinking (ACXL) modality. [17][18][19] According to photochemical crosslinking studies based on kinetics model 7 the UV-A illumination caused a rapid depletion of oxygen in a riboflavin-soaked cornea and turning the UV light off led to replenishment of the oxygen to its original level within 3 to 4 min. 7 Krueger et al 20 and Herekar 21 have also observed a rapid oxygen depletion during corneal crosslinking with riboflavin and concluded that the ROS and, specifically, singlet oxygen are the predominant CXL reaction drivers.…”

Ultraviolet Corneal Crosslinking

“…J. Wernli и соавт., исследовав биоме-ханику свиной роговицы, обработанной УФ-излучением по методу ускоренного сшивания в диапазоне от 3 до 90 мВт/см 2 и от 30 до 1 мин, соответственно, сделали за-ключение о различиях в эффективности кросслинкинга в пользу стандартного способа [74]. По данным атомно-силовой микроскопии, свиные роговицы, обработанные по Дрезденскому протоколу, в сравнении с ускоренным CXL (3 мин, 30 мВт/см 2 ), обладают более высокой корнеальной жесткостью, демонстрируя существенное увеличение модуля Юнга, главным образом в передней области стромы роговицы [45].…”

Is accelerated corneal collagen cross-linking for keratoconus the way forward? Yes

“…In accordance with this, animal studies found that an equivalent corneal stiffness increase to conventional CXL can be achieved with illumination intensity of up to 40-45 mW/cm 2 , corresponding to illumination times of B2 min. 5 Although the Bunden-Roscoe reciprocity law may be valid for a certain dose range and therefore a true linear relationship between dose and time is unlikely to exist, the radicals that generate the cross-links are formed in a shorter period of time when the radiation intensity is increased from 3 to 10 mW/cm 2 . 6 Initial studies, performed on porcine eyes, showed that accelerated CXL performed at 10 mW/cm 2 for 9 min was equivalent to conventional CXL in biomechanical stiffness.…”