The Effect Of Low Energy Laser Irradiation On Inadequate Optic Nerve Injury In Rats

ObjectiveTo investigate the effect of low energy laser irradiation on inadequate optic nerve injury in rats,we observed F-VEP(flash-visual evoked potential),RGC(retinal ganglion cell)number and the expression of CNTF(ciliary neurotrophic factor) level in retina of rats.MethodsA non-operated group served as normal group (n=5). The other 45 animals were divided evenly into 3 time subgroups.Each subgroup were randomly divided into untreated control group (n=5,with inadequate optic nerve injury only) and LELI group(n=10, treated by 660nm low energy laser irradiation,5 min,once a day postinjury). The optic nerve injury operation of rats was created by crushing optic nerve at 2 mm retrobulbarly. Electro- physiological examination(F-VEP) was performed at 1day,3days,5days,7days,10days,14days postinjury.Each time subgroup were sacrificed under anesthesia at various times post optic nerve injury:3 days,7 days and 14 days. The method of immuno- histochemistry was applied to measure the changes of RGC number and CNTF expression level in retina at different times after operation.ResultCompared with that of normal group, latency of F-VEP in optic nerve crushed rats increased after the operation,obviously on the 10th day after injury. The difference of latency in LELI group and untreated control group is not obvious (P>0.05) on the 1st and 14th day,while obvious(P<0.05) on the 3rd,5th,7th,10th day postinjury. RGC number of the injured nerve declined obviously from 7th day after operation.In immunocytochemical study, although CNTF increased both in untreated control group and LELI group after injury, the IOD value of CNTF was much more increased in LELI group than that in control group. The elevated value of CNTF reached a peak 7 days after injury.ConclusionsF-VEP latency of the injured nerve in LELI group declined prominently compared with that in control group.With the irradiation of low energy laser, the expression of CNTF level increased,while the loss of RGCs decreased obviously after optic nerve injury. The upregulation of CNTF expression might provide a supportive enviroment,which could protect the degenerarion of RGCs and increase nerve conductive velocity after the inadequate optic nerve injury.