Interphase fluorescence in situ hybridisation of the X and Y chromosomes in the human eye

Aim - To determine the sex of individual cells in paraffin sections of the human eye by fluorescence in situ hybridisation (FISH) of the X and Y chromosomes. Methods - The authors developed a protocol for FISH of the X and Y chromosomes in paraffin sections of human eyes. Results - In all the specimens that had been fixed in 10% formalin and with a fixation time of up to 3 days sex determination of individual cells was achieved. The percentage of cells with clearly identifiable signals was up to 98% for corneal epithelium, keratocytes, corneal endothelium, trabecular meshwork, lens epithelium, retina, and optic nerve. Conclusions - FISH allows the determination of the sex of single cells in paraffin sections of human eyes without destruction of the tissue structure. Its main application is the histological analysis of sex mismatched corneal, RPE, or neuroretinal transplants to distinguish host and donor cells.