Histo spot: A small circular punched-out spot in the retina at a site where spores of the fungus histoplasma (histo) seeded in the eye. Histo spots may be multiple, found in both eyes, and scattered throughout the retina. Histo spots in the macula are significant since they may stimulate the growth of abnormal new blood vessels located under the retina. These new blood vessels may suddenly bleed, causing permanent macular scarring and impairing central vision. If the process is detected at an early stage, it may be successfully treated with focal retinal laser.