Influence Of Visual Electrophysiology Function In Guinea Pig Exposed To Laser

BackgroundBecause of the advantages of good direction, high brightness andconcentrated energy in time and space, laser is used more widely in military,aerospace, industry, medicine, etc. Especially, the semiconductor laser is moreuseful, due to its characteristic of easy operation, high efficiency ofphotoelectric conversion. It can cause serious threat to personnel andphotoelectric sensor equipment for the rapid development and application oflaser weapons in military. Eyes are the only optical system of our body and canbe easily damaged and glared while radiated by laser. Glare is a visual stateresulted from brightness distributed unevenly or too strongly in eyes and dividedinto discomfort glare and disability glare. Pilots often encounter all sorts of glarewhich can cause visual function decline associated with flight safety. There aremore reports about eyes injured by laser with different waves, frequencies andenergy. However, the glare influence of the laser is relatively few because it can not be easily detected.Visual evoked potential （VEP） is a bunch of electrophysiology sign ofcerebral cortex evoked by visual stimulus, recording on scalp by EEG, and isoften divided into flash VEP （fVEP） and pattern VEP （PVEP）. PVEP is usedmore often in clinical and experiments because it has stable wave and is closelyrelated with the function of retina recognizes image and human visual acuity.Objective1. Measuring laser energy density threshold leading to glare blind in guinea pigusing pattern VEP2. The influence of visual electrophysiology function in guinea pig radiated bylaser pointerMethods and materialsPart1Detecting the laser energy density threshold leading to glare blindin guinea pig using pattern visual evoked potentialTwenty-seven guinea pigs were transplanted in stainless steel bolts （length:5mm, diameter:1.2mm）6mm before bregma and10mm after bregma on skullas reference electrode and recording electrode respectively under anesthesia.These guinea pigs were randomly divided into three groups that each one had9（18eyes） by the different wave length of laser beams （635nm,660nm,690nm）.The9guinea pigs in each group were randomly divided into three subgroupsthat each one had3（6eyes）, because they would be radiated at differentstimulating current. Laser equipments were supplied from the Chinese academyof sciences institute of semiconductor. Firstly giving different constant current（I）,the power meters display different corresponding power（P）. We recorded thesecurrent and its responding power and designed the P-I curve for each laser beam. Then we made regression analysis of the P-I curves of the three laser beams andgot the corresponding power-current equation. The PVEP of guinea pigsexposed to635nm,660nm and690nm for30s was recorded by the RETI-portvisual electrophysiology system. When the tipical wave could not be recorded atone current, the current was considered as the threshold current of the laserbeam leading to glare blind. Then based on the P-I curves, we calculated thethreshold power of each laser beam. The energy density threshold leading toglare blind of each laser beam was calculated later.Part2Influence of visual electrophysiology function in guinea pig radiatedby laser pointerEighteen healthy adult guinea pigs were randomly divided into two groups,ERG group and P-VEP group, and each group had nine animals. Then wemeasured the normal ERG and PVEP of both eyes of guinea pigs in the twogroups respectively as the normal value for each group. Then the two groupswere randomly divided into three subgroups that each one had three animals（sixeyes） respectively. The ERG were recorded when animals in the three subgroupsof ERG group radiated by the laser pointer for1min,3min and5min. The PVEPwas recorded in a similar way. The results were compared with the normalvalue.ResultsPart1635nm group: The latency and amplitude of P wave recorded on guineapigs exposed to730mA current compared with the normal value didn’t showsignificant difference (P_latency=0.306,P_amplitude=0.901). While exposed to760mAcurrent, the latency didn’t showed significant difference （P=0.939）, but the amplitude showed significant difference （P=0.001）. Exposed to780mA current,there was no normal wave.660nm group: The latency and amplitude of P wave recorded on guineapigs exposed to720mA current compared with the normal value didn’t showsignificant difference (P_latency=0.844,P_amplitude=0.856). While exposed to760mAcurrent, the latency didn’t showed significant difference （P=0.436）, but theamplitude showed significant difference （P=0.000）. Exposed to740mA current,there was no normal wave.690nm group: The latency and amplitude of P wave recorded on guineapigs exposed to710mA current compared with the normal value didn’t showsignificant difference (P_latency=0.938,P_amplitude=0.349). While exposed to760mAcurrent, the latency didn’t showed significant difference （P=0.402）, but theamplitude showed significant difference （P=0.000）. Exposed to740mA current,there was no normal wave.The energy density thresholds of the three laser beams（635nm,660nm,690nm） we calculated were356.36×10-9J/cm²,349.58×10-9J/cm²and343.93×10-9J/cm2. The latencies of P wave recorded on the guinea pigs glareblinded two days later, compared with the control values of the three groups ofdifferent laser waves, didn’t show significant difference （t=-0.356, P=0.729;t=0.492, P=0.633; t=-0.445, P=0.666）, while the amplitudes showed significantdifference （t=11.01, P=0.000; t=5.223, P=0.000; t=5.702, P=0.000）. Thelatencies and amplitudes of P wave recorded on the guinea pigs glare blindedfour days later, compared with the control values of the three groups of differentlaser waves, both didn’t showed significant difference （latency: t=1.329,P=0.213; t=2.040, P=0.069; t=-0.894, P=0.392; amplitude: t=-3.030, P=0.768;t=0.194, P=0.850; t=-0.948, P=0.365）. Part2ERG group: The standard five terms of ERG were recorded in the threesubgroups radiated by laser pointer for1min,3min and5min. The resultscompared with the normal value didn’t show significant difference （P＞0.05）.And the PVEP results of the three PVEP subgroups didn’t show significantdifference（P＞0.05）, compared with the normal value.Conclusion1. The energy density thresholds leading to glare blind of laser beam are about350×10^-9J/cm². PVEP examination is a harmless and objective method tomeasure the energy density threshold of laser beam leading to glare blind.2. The visual electrogram function of guinea pigs will not change after radiatedby laser pointer for short time. But whether it causes damage to local retina anddiscomfort glare to eyes of guinea, still need further research.