Establishment Of Animal Model For Myopia Induced By Long-wavelength Monochromatic Light In Guinea Pig And Investigation Of Expression Of Opsin In Its Retina

PARTâ… Establishment of animal model for myopia inducedby long-wavelength monochromatic light in guinea pig1.Objective:To study the influence of two kinds of monochromatic lights withlong-wavelengths of 530nm and short-wavelengths of 400nm, equal to the peakspectral sensitivity of two kinds of cones, on the refractive system development ofguinea pig. Establish a new myopia animal model to study the relationship betweencolor vision and myopia.2.Method:Sixty 3-day-old guinea pigs were randomized into 6 groups, exposing to greenlight (530nm), to purple light (400nm), to purple light with-1.5D spectacle forchromatic aberration compensation, to purple light with piano spectacle, to dim lightand to bright light respectively (10 guinea pigs in each group). Refraction, axiallength, and depth of vitreous cavity were measured at 2, 4, 6, 8 weeks after thetreatment.3.Result:1) At any period after treatment or at overall level, no statistic difference inrefraction was found among the groups exposed to purple light without spectacle,with-1.5D spectacle and with piano spectacle (F=2.152, P=0.1786). No statisticdifference between the group exposed to dim light and the group exposed to brightlight (F=2.606, P=0.1817). 2) Compared with that of group exposed to dim light,refraction of the group exposed to green light was obviously shifted to myopia at anyperiod after the treatment. Refraction of the group exposed to purple light showeddifference Since 6 weeks, reached the peak at 8 weeks and maintained hyperopia. 3)Compared with that of group exposed to dim light, the axial length of group exposedto green light was greatly different 4 weeks afterward. The depth of vitreous cavity ofgroup exposed to green light was different from that of the group exposed to dim lightat 2 weeks and the difference continued to expand afterward. 4.conclusionMonochromatic light with the long-wavelength of 530nm induced myopia inguinea pig, with the presence of eye elongation, increment of depth of vitreous cavity.After eliminating the effect of space limiting, form-deprived and defocus, a grand newmyopia animal model was successfully established and named as color visionimbalance myopia animal model, according to its close relation with color vision.PARTâ…¡The changes of expression of opsin for myopiainduced by long-wavelength monochromatic light inguinea pig1.Objective:To investigate the expression of opsin in myopia induced by 530nmmonochromatic light in guinea pig and the relationship between the expression ofopsin and myopia induced by 530nm monochromatic light.2.Method:Sixty 3-day-old guinea pigs were randomized into 4 groups and exposed to greenlight (530nm), purple light (400nm), dim light (2.2mmol/m~2/s) and bright light(5.6mmol/m~2/s) for 8 weeks. Retinae were dissected at 10-12 o'clock in the morningand the ultramicro-structures of the photoreceptors were observed throughelectromicroscope. The changes in quantity of cone cells were observed byfiat-mounted retina by immunocytochemisty. The level of opsin and its mRNA wereobserved through Western-blot and real-time PCR respectively.3.Result:1) Compared with those in dorsal retina of purple light group, photoreceptors indorsal retina of green light group were present with shorter outer segments, partiallyvacuolated membrane disc of outer segments, abundant chondriosomes in innersegments and bigger nucleus. While the ventral retina showed opposite feature. 2) Thedensity of L-cone in dorsal retina of green light group increased while that of purplelight group decreased. Fluorescing staining of S-cone of ventral retina showed nodifference among all the groups. The overall density of cone increased in green lightgroup while decreased in purple light group. There was still no difference between thebright light group and dim light group. 3) There was no difference in expression ofS-opsin mRNA among all the groups (F=3.61, P=0.0649). There was no difference inexpression of L-opsin mRNA between the dim light group and bright light group. Green light group expressed higher level of L-opsin mRNA than dim light group,while purple light group expressed lower level. 4) There was no difference inexpression of S-opsin among all the groups (F=3.34, P=0.0764) nor in expression ofL-opsin between dim light group and bright light group. Green light group expressedmore L-opsin than dim light group and purple light group expressed less L-opsinmRNA than dim light group.4. conclusion1) Green light (530nm) and purple light (400nm) accelerate the metabolism ofphotoreceptors in dorsal and ventral retina respectively. 2) Monochromatic light withthe long-wavelength of 530nm induces the increment of long wavelength sensitivecones in myopic guinea pig, with a rise in long-wavelength sensitive opsin expression.This might be a compensative response of the photoreceptors to the chromatic lightenvironment. 3) Opsin might play a role in the forming of 530nm monochromaticinduced guinea pig myopia.PARTâ…¢The changes of expression of opsin for myopia of form-deprivation and defocus in guinea pig1.Objective:To investigate the opsin expression in form-deprived and defocus myopia inguinea pig and study the relationship between the opsin expression and experimentalmyopia.2.Method:Twenty guinea pigs were randomized into form-deprived group and defocusgroup (n=10). Guinea pigs in form-deprived group wore a diffuser RGP on one eyesince the third day after birth. Those in defocus group wore a -4D RGP on one eye.The contralateral eyes were left as control. Refraction, axial length and depth ofvitreous cavity were measured after 2 weeks. Retinae were dissected at 10-12 o'clockin the morning. The level of opsin and its mRNA were observed through Western-blotand real-time PCR respectively.3.Result:Both groups showed an increased expression of S-opsin and L-opsin comparedto the control.4.conclusion1) Opsin expression might play an important role in the forming of experimental myopia in guinea pig. 2) Cone might be the detector receiving the signal ofform-deprivation and defocus.