Lin^– HSCs preserve cones in retinitis pigmentosa. (A) Cross-section of a normal human eye showing vascularized retina with avascular area of central vision (macula). Inset shows enlarged detail of retina with two types of photoreceptors; rods mediate night vision and cones mediate color and central fine vision. (B) View through the pupil of a normal eye showing optic nerve, macula, and vascularized retina. (C) View through the pupil of an eye with late-stage retinitis pigmentosa showing pigmentary changes and attenuated vessels, which occur with photoreceptor loss. (D) Engraftment of Lin^– HSCs in blood vessels might prevent loss of cones and preserve macular vision as seen in E. However, there will still be loss of rods, giving rise to pigmentary changes.