-opia

A visual disorder.

Greek ōps, ōp‑, eye, face.

Examples include myopia (Greek muein, to shut), short-sightedness, whose opposite is hypermetropia (Greek huper, over, above, plus metron, measure) or hyperopia, long-sightedness; presbyopia (Greek presbus, old man) is long-sightedness caused by loss of elasticity of the lens of the eye, occurring typically in middle and old age; diplopia is the technical term for double vision. Several examples refer specifically to impairment of colour vision, as in protanopia Greek prōtos, first), insensitivity to red light; deuteranopia (Greek deuteros, second), insensitivity to green; tritanopia (Greek tritos, third), insensitivity to blue; these are named on the basis that red, green, and blue are respectively the first, second, and third primary colours.