Influence of four different fix methods to rat retinal frozen sections

Background Histopathological examination is an important approach to the basic and clinical study in ophthalmology.Different fix methods of retinal samples produce a large impact.The first fixed way often is used at home,and the last fixed way is preferred abroad.The comparative study between the two ways is lack.Objective This study was to compare rat retinal frozen sections following 4 different fix methods and confirm a simpler and better way.Methods Forty eyeballs were extracted from 40 SD rats and were randomly divided into four groups using random number table,ten for each group.The eyeballs were firstly fixed in 4％ paraformaldehyde overnight,4％ paraformaldehyde for 2-3 hours,formalin-acetic acid-alcohol (FAA) mixture solution,and then OCT embedding was performed in 3 groups.However,the samples were fixed in cold acetone following first liquid nitrogen frozen,OCT embeded in the forth group.Retinal serial sections of 4 groups were examined and compared after hematoxylin and eosin staining under the optical microscope.Results Retinal tissue was loosened interlayerly,and clustering of cells in the inner nuclear layer (INL) and outer nuclear layer (ONL) were seen in the 4％ paraformaldehyde overnight fix group.The arrangement of interlayer and cells was improved in the 4％ paraformaldehyde for 2-3 hours group compared with 4％ paraformaldehyde overnight fix group.The retinal structure was closer among the layers in the FAA fixed group.In the later cold acetone fixed group,retinal morphology was more clear with the intact structure and regularly arranged cells in the ONL,INL and ganglion cell layer(GCL),as an living histology structure.Conclusions The first fix of retina produces a large impact on retinal morphology and structure.However,cold acetone fixation following first liquid nitrogen frozen is simpler,less time-consuming and more efficient way for the histopathological examination of retina. Key words: Histopathology;  Retina;  Frozen section;  Rat