Jace, from Connecticut, is one of four children all born with severe childhood blindness who gained 'life-changing improvements' to their vision after an experimental trial of gene therapy.

A robotic device allows eye surgeons to perform high-precision procedures on the retina, the fragile lining on the back of the eye that is less than a millimeter thick.

When even the most highly trained surgeons perform procedures on the retina-one of the smallest, most delicate parts of the human body-the stakes are high.