A Dissertation Submitted For The Doctorate The Research Of Rabbit Ocular Growth In Different Light Environment And The Intervention Effect Of Traditional Chinese Medicine

Objective:We observed the effects of different light sources on the axial length, structure and function of the retina, dopamine content in retina and serum as well as the D2 receptor expression in retinal pigment epithelial cells of New Zealand immature rabbits. We also explored the preventive function of traditional Chinese medicine (TCM) "Rizhong Yinyang Fang"intervention proposed by Professor Wang Yuliang on eyeball development and where the sites of action was played on, and searched for the key point that traditional Chinese medicine intervened in myopia prevention.Methods:One-month-old New Zealand immature rabbits were randomly divided into six groups with both male and female rabbits in each group. Sunlight group was exposed in natural light while LED group and full spectrum group were exposed in LED and full spectrum light. Based on this, sunlight+TCM group, fluorescent+TCM group and full spectrum+TCM group were added with "Rizhong Yinyang Fang" intragastric administration based on "Theory of yin-yang clock" of Professor Xia Guicheng, respectively. The method of administration was as follows:The "Yang-fang" was administrated in 10 a.m and the "Yin-fang" was given in 22 p.m.The dose administrated to immature rabbits was calculated according to the clinical adult dosage and intragastric administration was continued for 12 weeks. Optical parameters were measured. Weight measurement and axial length measurement were performed at the beginning of the experiment, in the 4th and the 12th week during experiment. Measurement of serum and retinal dopamine levels were performed in the 4th and the 12th week. Observation of retinal histopathological tissues and immunohistochemical examination of dopamine D2 receptor (D2R) was performed in the 12th week during experimental period.Results:The LED group showed a significant increased axial length than natural light group, full spectrum group and LED+TCM group at the same period (P<0.01, P<0.05). Axial length of fluorescent+TCM group showed no significant difference when compared with sunlight+TCM group and full spectrum+TCM group. Meanwhile the weight of immature rabbits in 6 groups showed no significant difference. Light spectrum of LED distributed from 360 nm to 700 run and the peak wavelength appeared around 450 nm and 550nm, also including purple light spectrum and blue light spectrum as well as the green light which is a medium wave with high spectral energy. While the short wavelength UV light and long wavelength red light were relatively absence. Full spectrum light had a wide range of light spectrum from 380 nm to 760 nm that was close to natural light spectrum and the peak wavelength was at about 600 nm including short wavelength UV and violet, also the medium wave yellow and green light and the long wavelength red light. Natural light spectral ranged from 380 nm to 760 nm with the peak wavelength at 490 nm.. Histopathological observation showed that there was significant difference in pigment epithelium layer, photoreceptor and nerve fiber layer between fluorescent group and sunlight group, but the difference among the test groups was not significant. Lipid particles were observed in the cytoplasm of pigment epithelial cells in full spectrum group, while the number and size was less then those in LED group. Cell membrane and microvilli had minor change. Aligned photoreceptor cells with clear inner and outer structure in former group were shown. Some level of vacuolization existed in cells of nerve fiber layer, while the degree was less then LED group. Inner and outer structures in fluorescent+TCM group and full spectrum+TCM group showed a little clear and nearly neatly arranged. Outer nuclear layers were neatly arranged and the dying was clear. Cells in nerve fiber layer were more closely aligned without vacuoles. Ganglion cell nucleus in LED+ TCM group showed relatively irregular shape when compared with full spectrum+TCM group. In the 4th and 2 th week, fluorescent group was evidently lower in serum and retinal DA levels (P<0.01) among 6 groups, and there was no significant difference among sunlight+TCM group, full spectrum group, fluorescent+TCM group and full spectrum+TCM group (P> 0.05). In the 12th week, fluorescent group was evidently lower in retinal dopamine D2 receptor (P<0.05, P<0.01)among 6 groups, while there was no significant difference among sunlight +TCM group, full spectrum group, fluorescent+TCM group and full spectrum+TCM group (P>0.05). The expression of retinal D2 receptor increased in fluorescent+TCM group (P< 0.01).Conclusion:Refractive dysplasia induced by LED may be related to the lack of UV spectral spectrum of fluorescent that resulted in the axial extension of immature rabbits, which induced a structural damage to the retina, retina and serum dopamine secretion reduction and retina D2 receptor downregulation. The effect of full spectrum lights on axial growth is similar to sunlight. The traditional Chinese medicine "Rizhong Yinyang Fang" can reverse the negative effect of fluorescent on axial dysplasia through multiple action sites and protect the structure of the retina on some extent.