A conditioning lesion of the peripheral sensory axon triggers robust central axon regeneration in mammals. We visualize the ASJ neuron of C. elegans with a cell-specific green fluorescent protein reporter driven by a thioredoxin trx-1 promoter and trigger conditioned regeneration by laser surgery or genetic disruption of sensory pathways. Utilizing calibrated fluorescent beads, we demonstrate that these neurons brighten when conditioned, suggesting that trx-1 expression indicates regenerative capacity. We show that trx-1 functionally enhances conditioned regeneration but inhibits non-conditioned regeneration. Finally, six strains isolated in a forward genetic screen for reduced fluorescence also show reduced axon outgrowth. We demonstrate a link between trx-1 expression and the conditioned state that we leverage to rapidly assess regenerative capacity.