MATERIALS AND METHODS: The tenon tissue was harvested from a patient undergoing strabismus surgery. The human tenon fibroblast cell culture and isolation were performed according to the standard laboratory cell culturing protocol. The cells were divided into three groups: control, treatment with irradiated and non-irradiated riboflavin. There were five different concentrations (0.00156%, 0.003125%, 0.00625%, 0.0125%, 0.025%) in each group of riboflavin. The fibroblasts were treated with riboflavin and the cellular viability was assessed at 24-hour and 48-hour post treatment with MTT 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyl tetrazolium bromide colorimetric assay. The absorbance values were analysed using Magellan microplate reader data analysis. A triplicate of readings was taken. The data were presented as mean ± standard deviation of the triplicates. Statistical analysis was performed with Statistical Package for Social Sciences (SPSS) analysis version 23.