Fig. 5. Histopathological examination of retinopathy in the eyes of rats treated with zinc oxide nanoparticles (ZnO NPs). (A) vehicle treated groups for 90 days; (B) ZnO NPs treated groups for 90 days; (C) vehicle treated groups for 90 days plus a 14-day recovery period; (D) ZnO NPs treated groups for 90 days plus a 14-day recovery period. Note the normal microscopic structure of the eye of rat from control group. However, retinal atrophy is remarkable in the eye of rat treated with ZnO NPs for 90 days. Furthermore, this is still remaining in the eye of rat from ZnO NPs treatment and 14-day recovery group. Hematoxylin & eosin staining of paraffin embedded sections from the eye from rat, Magnification, ×200.