Thus, although inessence, cell replacement therapy may hold great promise for the treatmentof ABCA4-associated retinopathy, there are many variablesthat still need to be optimized, including selection of the optimal originof stem cells, whether or not to differentiate cells exvivo prior to transplantation and if so, until what stage,whether to deliver individual cells or cell sheets, and how to surgicallydeliver these cells. The gene discussed is ABCA4; the disease is retinal disorder.