Clinical Analyses Of Causing Factors And The Time From Onset To Laser Photocoagulation Of Branch Retinal Vein Occlusion

The prevalence of branch retinal vein occlusion (BRVO)is high in the fundus vascular diseases. It causescomplications as for cystoid macular edema , vitreoushemorrhage ,neovascular glaucoma etal, which seriouslyreduce visual acuity. Recently,many people have studied thefeature of retinal crossing site of BRVO. At thearteriovenous crossing site , artery and vein share thecommon vascular sheath. Hypertension and arteriosclerosis ,which cause hypertrophy of the media layer of the arterialwall , result in tube cavity narrow for the compression ofthe vein. Thrombosis form easily at the site, so BRVO occurs.Someone has found that the shorter the distance betweenthe first arteriovenous crossing site and optic disc is ,theeasier BRVO occurs. Super-temporal BRVO is more than otherquadrants, which related to the near distance between thedisc and the first crossing in the supertemporally. Thereason is unkown.This article had the same results by themeasurement of the distance and inferred the possiblereasons . Laser photocoagulation is the main and prevalenttreatment to BRVO all the years. It is universallyconsidered that laser photocoagulation for non-perfusionareas should be early conducted to avoid secondarycomplications by many clinical surveys and summaries.Clinically , we should master the time of non-perfusionareas from the onset of BRVO. This article reviewed retrospectively 188 cases withBRVO who accepted FFA, and measured the distance betweenthe first arteriovenous crossing site and optic disc of 25cases of infer-temporal BRVO and 30 cases of super-temporalBRVO.This article summarized 83 cases about the time fromonset of BRVO to the apprearance of non-perfusion areas. Of 188 eyes ,the most one was affected atsupertemporally,followed by infertemporally, macularbranch,supernasally , infernasally. Except 5 eyes oftemporal BRVO and 3 eyes of nasal BRVO with the obscureocclusion site and 11 eyes of macular BRVO, of 169 eyes(onlytemporally), 127 eyes occlude at arteriovenous crossing.The artery lay anterior to the vein with 121 eyes.Fromabove ,we can see BRVO frequently occurs at arteriovenouscrossing with artery laying anterior to the vein. Chooserandomly 30 eyes at super-temporal and 25 eyes atinfer-temporal BRVO and measure the distance between thedisc and the first crossing site .The outcomes showed thedistance between disc and the crossing site insuper-temporal BRVO group was shorter than any other quartsand shorter than supertemporally in infer-temporal BRVOgroup.The distance of infertemporally is shorter ininfer-temporal BRVO group than that in super-temporal BRVOgroup. From above ,we can see that the shorter the distanceis , the easier BRVO occurs, which is a factor of affection.The distance between optic disc and the crossing site ofsupertemporally in super-temporal BRVO group is shortest,which suggested why super-temporal BRVO be more than otherquadrants BRVO. According to the hemodynamics and thevessals distribution , the possible causes maybe asfollows(1)At the arteriovenous crossing site ,up-streamforms turbulence and causes endothelialcelldamage ,thrombus forms ,and vein is occluded–a hemodynamicchange.On the optic disc ,optic nerve and central retinalartery and vein commonly pass the lamina cribrosa, witharteriosclerosis,the vein will be compressed ,where alsohave a hemodynamic change. The nearer the distance betweenarteriovenous crossing site and optic disc is,the greaterthe hemodynamic changes influnce each other, which maybehave an overlapping effect, so that at the arteriovenouscrossing site thrombus easily forms.(2)The nearer thedistance is, the bigger venous drainage area is ,whichaffect the blood stream at the arteriovenous crossingsite.(3)The thicker the density of optic nerve fibers is ,the nearer the distance to optic disc is, and the morecrowded the relation to companied vessels is, witharteriosclerosis, the vein near to optic disc will bepressed easily, BRVO is affected addition to the feature ofthe arteriovenous crossing site. This article summarized that the time from onset ofBRVO to laser photocoagulation and concluded that theproportion of 1-3 months is most.This suggested clinicallywe should advise the patients of early-stage BRVO toreexamine FFA once a month to find non-perfusion areas andgive laser photocoagulation to this areas in time. Retinalhemorrhage resolved after 3-6 months, we should advise thepatients reexamine FFA every 6 months to find secondarynon-perfusion areas and conduct laser photocoagulationtimely to avoid complications. In conclusion,The valid analyses for FFA of BRVO mayshow some affecting factors of incidence. More studies`on pathogensis should be done at the animal models and in...