简介:胆脂瘤是由一种能产生角蛋白的鳞状上皮聚集于中耳、上鼓室、乳突、岩尖而形成的,在中耳表现为独立生长、代替中耳黏膜、吸收骨质的三维上皮结构。它不是一种肿瘤,但对患者有潜在的危险。1829年,法国Cruveilhier首先描述多中心的白色“tumeursperlees”(瘤株),1838年,Miiller第一个使用“cholesteatoma”(胆脂瘤)这一术语来描述颅内角化物的堆积。1922年,Cushing提出先天性胆脂瘤的可能起源,1953年,House报道了经典的鼓膜完整的中耳胆脂瘤。事实上,胆脂瘤是一种良性的角化上皮细胞囊,由3种成分组成:囊内容、基质、基质外层。
简介:AIM:Todescribethecharacteristicsofmodulationtransferfunction(MTF)ofanteriorcornealsurface,andobtainthethenormalreferencerangeofMTFatdifferentspatialfrequenciesandopticalzonesoftheanteriorcornealsurfaceinmyopes.·METHODS:Fourhundredeyesfrom200patientswereexaminedunderSIRIUScornealtopographysystem.PhoenisanalysissoftwarewasappliedtosimulatetheMTFcurvesofanteriorcornealsurfaceatverticalandhorizontalmeridiansatthe3,4,5,6,7mmopticalzonesofcornea.TheMTFvaluesatspatialfrequenciesof5,10,15,20,25,30,35,40,45,50,55and60cycles/degree(c/d)wereselected.·RESULTS:TheMTFcurveofanteriorcornealsurfacedecreasedrapidlyfromlowtointermediatefrequency(0-15cpd)atvariousopticalzonesofcornea,thevaluedecreasedto0slowlyathigherfrequency(>15cpd).Withtheincreaseoftheopticalzonesofcornea,MTFcurvedecreasedgradually.3)Intherangeof3mm-6mmopticalzonesofthecornea,theMTFvaluesmeasuredathorizontalmeridianweregreaterthanthecorrespondingvaluesathorizontalmeridianofeachspatialfrequency,thedifferencewasstatisticallysignificant(P<0.05).At7mmopticalzonesofcornea,theMTFvaluesmeasuredathorizontalmeridianwerelessthanthecorrespondingvaluesatverticalmeridianat10-60spatialfrequencies(cpd),andthedifferencewasstatisticallysignificantin25,30,35,40,45,50cpd(P<0.05).·CONCLUSION:MTFcanbeusedtodescribetheimagingqualityofopticalsystemsatanteriorcornealsurfaceobjectivelyindetail.