| Objective: To discuss factors to influence silicone oil emulsification andto observe pathology and ultrastructure changes in emulsified siliconeoil-filled human eyes, and to further explore their pathogenesis.Methods: Gas chromatography coupled mass spectroscopy(GC/MS) wasused to detect compounds in silicone oil samples explanted from patients' eyesfrom 2004 June to 2006 February in the 2nd hospital of Jilin University. Thereare 22 samples including 11 emulsified silicone oil ,10 nonemulsified siliconeoil and 1 standard silicone oil. The pathology and ultrastructure observe wereperformed in 4 specimens including 2 eyeballs and 2 ocular contents.Result: 1. 11 samples of nonemulsified silicone oil and one sample ofstandard silicone oil were not different in their content measured by GC-MS.In10 explanted samples of emulsified silicone oil volatile substances could bedetected, which do not exist or are at the detection limit in native silicone oilfor ophthalmic use. The majority of contaminants are low moleculealkyl .Some of them also contain fluorin atom. 2. We can see cornealendothelium cell loss, retrocorneal membranes , vascularization in lightmicroscope. When silicone oil has been filled for a short time, in lightmicroscopy retinal structure stratification remains unchanged, but celldecrease and vacuole degeneration can be seen in ganglion cell layer .In 2samples with silicone oil for more than 48 months ,retinas were most replacedby fibril membranes .Silicone oil vacuoles also can be seen in retina , iris,optic nerve and fibril membrane. These changes were more serious intransmission electron microscope (TEM) and karyolysis, Karyorrhexis can beseen in fibrocyte of corneal stroma.Discussion: Study on factors contributing to silicone oil emulsificationand ocular tissue damage from emulsified silicone oil is important foroperators to take measures avoiding these factors and take silicone oil out ofeyes timely after operation.1.factors on silicone oil emulsification. There aremany factors involving in silicone oil emulsification. First of all,physicochemical characters of silicone oil ,such as viscosity, purity ,lowmolecular weight components(LMWC) ,and chemical stability etc ,are themajor reason. It was reported earlier that silicone oil with higher viscosity( 5000mPa.s),higher purity and having no LMWC does not tend to emulsify.In addition , some authors reported that disintegration and chemicalmodification of silicone oil are the main cause of emulsification. Moreover,environment contacted with silicone oil contributes to emulsification. It wasreported that a lot of components in plasm, such as fibrinogen, blood serum,erythrocyte etc, may accelerate emulsification in vivo experiment.Overexercise of the eyeball and remnants of silicone oil and detergents canpersist and trigger emulsification of silicone oil. In our study, gaschromatogram and mass spectrum was used to detect and characterizeemulsified silicone oil and unemulsified silicone oil. No low molecular weightsilicone oil was detected in all samples, which proved that silicone oil did notbreak down in emulsification. In addition , some volatile substances could bedetected in all explanted samples of emulsified silicone oil , which do not existor are at the detection limit in native silicone oil for ophthalmic use. Themajority of contaminants are low molecule alkyl .Some of them also containfluorin atom., which may contribute to silicone oil emulsification. Therefore,the contact of silicone oil with all types of substances should be reduced to aminimum. Reuse of tubing sets must be avoided. Direct exchange betweenheavy liquids and silicone oil should be avoided and residual of heavy liquidsshould be minimized. If all these precautions are obeyed, the risk ofemulsification of silicone oil used as an ocular endotamponade can besignificantly reduced, down to the influence of individual patients' conditions.2. Impairment of emulsified silicone oil on ocular tissue. Vitreum will becomeopacity in emulsified silicone oil-filled eyes, which can cause visual acuitydescent in some extent and be difficult in fundus examination and furthertreatment. Emulsified silicone oil can also diffuse in ocular tissue and cause alot of complication in eyes. In our study, silicone oil drops may entranceanterior chamber and cause corneal tissue damage by contacting with cornealendothelium and affecting corneal nutritional accommodation. Whenemulsification happened , emulsified silicone oil entrancing anterior chamberincreased and damages would be more serve. Silicone oil as a vitreoussubstitute couldn't exchange nutrient with retina and caused retina tissuenutrient disturbance. This can be demonstrated by the fact that damages inganglion cell layer which close contacted with silicone oil was most serious inour study. Emulsified silicone oil's diffusion in ocular tissue may alsocontribute to these damages ,which can damage the normal tissue structure andfunction or influence on tissue nutritional supply. In our study ,we also findthat chronic inflammatory reaction and fibrous hyperplasia around emulsifiedsilicone oil, which were a kind of rejection of eye tissue. These rejection tosilicone oil may make damages more serious.Conclusion: Silicone has a pretty chemical stability filled in theeye ,emulsified silicone oil did not break into low molecular weight compond.Some volatile substances such as heavy liquids may contribute to silicone oilemulsification. Therefore, direct exchanging silicone with heavy liquidsshould be avoided in the vitreous surgery and heavy liquids should beremoved completely when the operation is finished. Although silicone oilfilled in the eyes didn't cause acute inflammatory reaction, it could lead todystrophy of ocular normal tissue and damage the normal tissue structure andfunction by causing nutritional supply abnormity, rejection and diffusion inocular tissue if silicone oil emulsification happened. Therefore, factorscontributing to silicone oil emulsification should be avoided in operation andsilicone oil should be removed at the early moment just after the retinalreattachment stabilized and can't be used as a long term intraoculartamponade. |
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