Assess experimental reliability question 1
The diagram shows a section through the human eye.
When a person looks directly at an object, light is focused on the fovea of the retina.
Scientists are developing a new treatment for AMD. The treatment involves an operation to replace the damaged cells in the fovea with new cells.
Early results show an improvement in the condition. However, the treatment has only been tested on two patients.
Suggest what else scientists need to do before the treatment is allowed to be used for all patients with AMD.