Rabbit Retinal And Corneal Injury Induced By Supercontinuum(SC) Source

Background and Objective:The supercontinuum（SC）source is a new light source of broad spectrum,high brightness,and good directionality.It has been applied in many fields such as broadband fiber communication,spectral analysis,optical coherence tomography（OCT）and fluorescence lifetime imaging.The most mature and commercial SC source spectrum in the current technology mainly includes visible and near-infrared（NIR）light,which are easy to cause eye damage.However,research on eye damage has not been reported,and no relevant safety standard been conducted.For this reason,the visible-infrared SC source with ultra-wide-spectrum（420²500nm）and ultra-high-brightness was used to study the retinal and corneal damange effects,conduct the damage thresholds,analize the dependence of threshold on exposure duration and clarify the pathological features and the repair process.A typical laser was involved for comparison.It can provide a biological effect basis for SC source safety standard.Methods:1.Study on SC source and 532nm laser retinal damage threshold and damage repair:Under the condition of 3mm corneal spot diameter and parallel incident beam,the chinchilla grey rabbit eyes were exposed to 420⁷50nm SC source at different dose levels.The infrared cmponent of the SC source was filtered out to avoid the chromatic dispersion effect.The exposure duration was 0.1s,1s,10s for SC source and 0.1s for532nm laser.The lesions were examined with an ophthalmoscope at immediately and1day after exposure.Then the corneal irradiation dose corresponding to the injury of50%incidence rate,that is the damage threshold(ED₅₀),were calculated with the probit analysis method at 1day.The lesion repair process of SC source and 532nm laser under0.1s irradiation were histologically evaluated with the ophthalmoscope and H-E staining at 4h,1,3,7 and 14 days after exposure.2.Study on SC source corneal injury threshold and damage repair:Under 560μm corneal spot diameter conditions,the New Zealand white rabbit eyes were exposed to770²500nm SC source that was filtered out visible component at 2s and 10s exposure duration.The lesions were measured with slit lamp microscope at 1 h and 1day after the irradiation.The ED₅₀s were calculated with the probit analysis method at 1h after exposure.The repair process of corneal damage induced by SC source under 10 s condition were observed with the slit lamp at 1 h,2,4 and 6 days.Corneal injury caused by SC source at 10s was observed by H-E staining at 1 day after-exposure.Results:1.SC light source and 532nm laser retinal damage threshold and damage repair process.（1）Under 3mm corneal spot diameter condition,wavelength 420⁷50nm SC source at 0.1s,1s and 10s,chinchilla grey rabbit retinal damage threshold power were 15.7mW,12.1mW and 8.6mW.For exposure duration from 0.1s to 10s,the retinal damage threshold(ED₅₀)were correlated with exposure duration by ED₅₀=0.17t^0.87（J/cm²）.The 532 nm laser at 0.1s irradiation duration,the ED₅₀0 power was 13.9mW.（2）Pathological observation of the retina for 420⁷50nm SC source and 532 nm laser at0.1s exposure duration.Under the ophthalmoscope,the retinal damage characteristics of the SC source and 532 nm laser at threshold level were similar.For exposure duration from immediately to 1 day,the lesions were gradually clear and needle-like gray spots.After 3-14 day,the hyperplastic pigment granules caused the damage spot connected into a line.H-E staining,4h after irradiation,the outer nuclear layer of the two sources were condensed and deeply stained,and the photoreceptor outer segments were adhered to the retinal pigment epithelium（RPE）layer.1 day after the irradiation,the RPE layer hyperpigmented and the damaged outer nuclear layer cells lost,the damage progressively worsened.3-14 days after the irradiation,the pigment cells began to migrate to the outer nuclear layer and the inner nuclear layer,and the glial cells filled the damaged area for repair.2.SC source corneal damage threshold and damage repair process.（1）Under 560μm corneal spot diameter condition,wavelength 770²500nm SC source at 2s and 10s irradiation duration,New Zealand white rabbit corneal damage threshold power were1.14W and 0.82W.The change relationship of the corneal damage threshold(ED₅₀)with irradiation duration from 2s to 10s was ED₅₀=533t^0.79（J/cm²）.（2）Corneal pathological repair of 770²500nm SC source for 10s.The slit lamp was used 1 h after the irradiation,the lesions were light white small round spots.The damaged cornea showed several uniform circular micro-pits,and the cornea scattered light in the damaged area was enhanced.After 2-4 days,the lesion reduced or disappeared,the cornea was smooth and flat.6 days after the irradiation,the lesions disappeared and the scattered light in the corneal lesion was weakened.H-E staining at 1 day showed that the corneal epithelium was disorderly thickened,nucleus pyknosis rounded,and some stromal cells stained deeper at the threshold level.The 1.5 times threshold resulted in the disappearance of corneal stromal cells nuclei,loss of endothelial exfoliation,a hump or detachement of the epithelium layer and disordered vacuolation of the surrounding cells.Conclusions:1.Wavelength 420⁷50nm SC source under the condition of 0.1s,1s and10s and 3mm corneal spot diameter,chinchilla grey rabbit retinal damage threshold power were 15.7mW,12.1mW and 8.6mW.The retinal damage threshold(ED₅₀)were correlated with exposure duration by ED₅₀=0.17t^0.87（J/cm²）.The 532 nm laser at 0.1s irradiation duration,the ED₅₀0 power was 13.9mW.2.Wavelength 770²500nm SC source,2s and 10s irradiation duration,560μm corneal spot diameter,New Zealand white rabbit corneal damage threshold power were 1.14W and 0.82W.The change relationship of the corneal damage threshold(ED₅₀)with irradiation duration from 2s to 10s was ED₅₀=533t^0.79（J/cm²）.3.Under the same conditions,the characteristics of retinal damage induced by the visible light of SC source and 532 nm laser were similar.In the threshold level,retinal damage of SC source was light gray small round spot.Immediately after the irradiation,it was an acute reaction period,mainly affecting the outer nuclear layer and the pigment epithelial layer,and then the lesion area was enlarged;3 days after the irradiation,it was the repairing stage,the pigment cells and glial cells filled in the damaged area.4.The cornea was irradiated by infrared light of SC source at 10s with threshold level to form the light white spot.The results showed that the corneal epithelium was thickened and the stroma nuclei were pyknosis and hyperchromatic.The slightly higher threshold level not only damaged the epithelium and stroma,but also caused the loss of endothelium cell.