Objective To observe the effect of persistent flickering stimulus on the structure and function of retina in guinea pigs during a developmentally sensitive period.Methods Twenty-four two- week-old guinea pigs were randomly divided into flicker light (FL) group and control group, with 12 guinea pigs in each group. Animals in FL group were raised under 500 Lux illumination with a duty diurnal cycle of 50% at a flash rate of 0.5 Hz. Animals in control group were reared under steady 500 Lux illumination. Light emitting diode (LED) lamps were used for lighting under a 12-hour light/12-hour dark cycle. After the collection of fundus photographs and electroretinograms recorded at week 12, eyeballs were taken out, three dimensions were measured, and histopathological changes were examined.Results Compared to control group, tessellated fundus in FL group appeared more prevalent; implicit time of ldquo;ardquo; waves were prolonged in electroretinogram; the eyeballs were increased in horizontal, vertical, axial dimensions by (0.89plusmn;0.30), (0.69plusmn;0.20) and (0.96plusmn;0.30) mm respectively, the differences between two groups were statistically significant (t=12.7,11.9,15.8;P＜0.05). The gap of sclera collagen fiber was slightly widened.The photoreceptor layer was more likely to develop a disordered outer segment, which contained deciduous disc membranes.Conclusion Persistent flickering stimulus is attended by development of excessive ocular enlargement,which could affect the retinal structure and function of photoreceptors.
Objective To evaluate the safety repeated intravitreal injection of bevacizumab (Avastin) with different dosage in rabbitsprime;eyes. Methods Fourteen chinchilla rabbits were randomly divided into 3 groups, including both eyes of 2 rabbits in the control group,the right eyes of the other 12 rabbits in the experimental group,and the left eyes of the 12 rabbits in the experimental control group. The eyes in the experimental group underwent intravitreal injection of bevacizumab with the dosage of 2.5 mg/0.1 ml and 5.0 mg/0.2 ml of bevacizumab; the eyes in the experimental control group underwent intravitreal injection of normal saline with the same dosage as in the experimental group. Injections were performed every two weeks and lasted six weeks. Clinical observation and retinal function tests were performed before and two days after every injection. The eyes were sacrificed 1 week and 4 weeks after last intravitreal injection respectively.Electron and optical microscope and TUNEL were performed.Results After intravitreal injection,no obvious anterior chamber flare, abnormal change of the ocular fundus, or vitreous opacity and hemorrhage was observed in all of the eyes.No change was found by indirect ophthalmoscope,Bultrasonic inspection, ultrasound biomicroscopy and optical coherence tomography. The number of anterior chamber flare before and after the injection with the dosage of 2.5 and 5.0 mg, the difference among the 3 groups didnprime;t differ much from each other (Pgt;0.05).Amplitude and pattern of ERG responses and flash VEP were similar between the control and experimental groups (Pgt;0.05). Some inflammatory cells were found in the some bevacizumabinjected eyes 1 week after injection, and vanished 3 weeks later. The histological configuration of the retina didnprime;t change in both experimental control and the control group. Electron microscopy showed that plasma cells were presented and vacuolelike change was observed in part of the photoreceptor cells in 5.0 mg experimental group 1 week after injections.Cellular apoptosis was observed in the photoreceptor cell layer. The number of apoptotic cells was more in 5.0 mg experimental group than that in the control and experimental control group 1 week after injections (Plt;0.01). Conclusion Multiintravitreal injection with 5.0 mg bevacizumab may have mild toxicity to the retina in the rabbits.
Objective To observe the retinal toxicity of intravitreal injection of Bevacizumab (Avastin) in albino rabbit eyes at different doses. Methods Sixteen New Zealand albino rabbits，thirty-two eyes were divided into four groups at random. Three groups were prepared for Avastin experiment, named A, B, C. Each group received intravitreal injection of Avastin at dose 1.25 mg/0.05ml，2.5 mg/0.1ml and 6.25 mg/0.25 ml respectively. The other group named D served as a control, and accepted intravitreal injection of 0.9% normal saline 0.1 ml. Then test it by electroretinagram (ERG) after 1, 2 and 4 weeks. In addition, each group was removing two rabbitprime;s eyes to observe the retinal morphology and ultra structure by light microscope and transmission electron microscopy after intravitreal injection avastin 1, 2 and 4 weeks. Results The ERG pattern and amplitude of each group were normal after intravitreal injection Avastin 1, 2 and 4 weeks. （P＞0.05）Between study and control groups, there was no significant difference in retinal morphology which was observed by light microscope at any stage of the study. By electron microscopic observation, retinal ultramicrostructure was no evident retinal toxicity being tested both at group A and B (1.25 mg/0.05 ml and 2.5 mg/0.1 ml). But at group C (6.25 mg/0.25 ml), significant mitochondrial swelling and hydropic changes were seen in the inner segments of photoreceptors. And there was no improvement of the pathological changes in four weeks. Conclusion It is safe that intravitreal injection of Avastin in rabbitprime;s eyes at dose 1.25 mg or 2.5 mg at single time. （Chin J Ocul Fundus Dis，2008，24：193-196）
Objective To observe the effects of structure and function of cornea, chamber angle and retina of varying doses of Bevacizumab which was injected intravitreally in rabbits. Methods Twenty-four New Zealand albino rabbits were divided into three groups randomly, the right eyes in three groups received int ravitreal injection Avastin at dose 1.25 mg，2.5 mg and 5 mg respectively as experimental eye, the left eyes accepted intravitreal injection 0.9% normal saline at the same volume as a control eye. The anterior segment of eye and ocular fundus were examined and intraocular pressure was measured by slit-lamp microscope and direct ophthalmoscope before and after injection. It was tested by Electroretino gram (ERG) before and after injection 1, 4, 8 weeks. At the 8th week, it carried out corneal endothelium counting; then enucleated eyes to observe by the light microscope and transmission electron microscope. Results No statistically significant difference regard to IOP,corneal endothelium counting, a-and b-waves of ERG at any stage of study in every group（P＞0.05）. No obvious change at cornea, chamber angle, retinal structure and retinal ultrastructure in every group under light microscope. Conclusion This study indicated that there is no obvio us toxicity of intravitreal injection with Avastin 1.25~5.0 mg in normal rabbit eyes. （Chin J Ocul Fundus Dis，2008，24：189-192）
Objective lt;brgt;To inspect the rate of success of anastomosis and tissue damage with different power levels of photocoagulation in the treatment of experimental branch retinal vein occlusion (BRVO) by laser induced chorioretinal venous anastomosis. lt;brgt;Methods lt;brgt;Forty pigmented rabbits (80 eyes) were divided into four groups in random, and 10 (20 eyes) in each. Chroioretinal venous anastomosis was attempted to create using the krypton red laser with 4 different power levels (group A: 400 mW,group B: 600 mW,group C: 800 mW,group D: 1000 mW) in these animals in which BRVO had previously been created photodynamically. Fundus photography and fundus fluorescein angiography were performed at various times after the treatment and histological examination was taken at the end of the study. lt;brgt;Results lt;brgt;The model of BRVO was successfully set up. At the lowest power of 400 mW there was an absence of anastomosis formation and the damage to the retina and choroid was mild, Bruch′s membrane showed no evidence of rupture. At the power levels of 600 mW and 800 mW an anastomosis formed in 15% and 55% respectively and the damage was medium in degree. At the highest power level of 1 000 mW a 80% rate of success was obtained, however, the damage to the retina and choroid tended to be severe.The difference of the rate of success of anastomosis between different groups was highly significant (P=0.001), the difference between group B and group C was also highly significant (PBC=0.008), and the difference between group A and group B, group C and group D was not significant (PAB=0.072、PCD=0.091). lt;brgt; lt;brgt;Conclusion lt;brgt;The optimal power level of krypton red laser induced chorioretinal venous anastomosis is 800 mW, 0.1 s, 50 μm in our study. lt;brgt; lt;brgt;(Chin J Ocul Fundus Dis,2002,18:13-16)
Objective To investigate the pathological spectrum of hypertensive retinopathy. Methods Systemic hypertension was produced experimentally in SD rats by partially constricting the right renal artery and removing the left kidney.The eyes obtained from hypertensive animals at 2 weeks,1,2,4months were examined by means of light microscopy,immunohistochemical staining,electron microscopy and histochemical electron microscopy and compared with the control group. Results 1.From 2 months after surgery,thickening of retinal capillary basement membrane(RBM)became apparent.2.From then on,RBM showed an increased staining reaction for type Ⅳcollagen and laminin,while staining reaction of RBM for fibronectin in hypertensive rats was negative at any stages.The number of anionic sites within the RBM was gradually reduced following the development of hypertension and it was definitely decreased at 4 months. 3.A few deteriorated endothelial cells were lifted focally from the RBM with subendothelial swelling in retinal vessels at 2 weeks,and the pericytes exhibited edema and deterioration at 4 months. Conclusions Detachment of the endothelial cells from the RBM,thickening of the RBM companied with the reduction of anionic sites and deterioration of pericytes may be responsible for hypertensive retinopathy. (Chin J Ocul Fundus Dis, 1999, 15: 163-166)
Purpose To evaluate the prostag landins(PG) levels and to identify the effect of dexamethasone(DXM) on PG in response to photochemical insult in rat retina. Methods The experiments were performed on 36 SD rats which were separated into two groups,control and treated groups,and the latter received daily intraperitoneal injections of DXM (1 mg/kg) for 5 consecutive days,starting 3 days before light exposure.The animals were continually exposed to green fluorescent light(510-560 nm)with an illuminance level of (1900plusmn;106.9)lx for 24 hrs.The retinal concentration of PGE 2 and 6-keto-PGF1alpha; were tested at 6hrs,1,3,7 and 14 days after light exposure. Results The PGE2 and 6-keto-PGF1alpha; levels of the control groups (37.50plusmn;2.75,48.06plusmn;4.0 4,81.90plusmn;4.89) pg/mg and (4.68plusmn;0.69,7.50plusmn;0.57,10.40plusmn;0.71) pg/mg had significantly higher values than those of the treated rats(20.60plusmn;4.28,37.36plusmn; 3.34,54.85plusmn;4.57) pg/mg and (2.50plusmn;0.59,4．68plusmn;0.81,6.87plusmn;1.10)pg/mg (Plt;0.01) after 6 hrs,1 and 3 days light exposure respectively. Conclusion By inhibition of PG synthesis,the DXM may play an ameliorative effect on retinal photochemical injury of rats. (Chin J Ocul Fundus Dis,1999,15:94-96)
Objective To observe the pathological and functional changes of retinal photochemical damages exposed to green flurescent light. Methods The Sprague Dawley rats were continually exposed to green fluorescent light with an illuminancem level of (1 900plusmn;106.9) Lx for 24 hours.The changes of retinal morphology and morphometrics and flash electroretinogram were studied before light exposure and at the 6th hour,6th day and 14th day after light exposure. Results At the 6th hours after light exposure,the outer nuclear layer(ONL)of retina becoma thinner compared with that bfore light exposure.The thickness of ONL decreased by 23.91% and the inner and outer segments appeared disorderly arranged.At the 6th day after light exposure the thickness of ONL is thinner than that at the6th hour,i.e.decreased by 46.6%. At the 14th day after light exposure the thickness of ONL decreased by 42.40%.Flash electroretinogram showed that the amplitudes of a and b wave decreased continuously at the 6th hour and 6th day and unrecovered at the 14th day after light exposure. Conclusion This model might be an ideal one for research on retinal photochemical damage. (Chin J Ocul Fundus Dis,1998,14:101-103)
Purpose To observe the pathologic changes of retinal photic injury in mice. Methods A light damaged trunk was designed by ourselves.The mice were given an intermitent light exposure for 3 days,12 hours light exposure every day and 12 hours dark adaption before every exposure.Experimental animals were sacrificed on the 1st,6th,12th,18th and 30th day after light injury,and the eyes were enucleated for light and electronic microscopy observation. Results The early pathologic changes including disc membrance swelling,disorganization in outer segments,and mitochondrial swelling,spherical change in inner segments．Then the chromatin densification,liquefaction and margination,and the shrinkage of nuclear membrance were found in the nuclear layer.Finally the outer nuclear layer became thin and disappeared.The apical microvill of RPE cell disappeared and basic fold became flat in some samples. Conclusion The photoreceptor degeneration was the pathologic characteristic of retinal photic injury in mice. (Chin J Ocul Fundus Dis,1998,14:215-218)