Extended-wear, soft, contact lenses produce hyperopia in young monkeys

To investigate the effects of experimentally induced defocus on eye growth and refractive development, one eye of four infant rhesus monkeys was fit with either a +3.0 D (N = 2) or -3.0 D (N = 2) extended-wear, soft, contact lens, and the other eye was fit with a zero-powered, control lens. The lens rearing regimen was started between 12 and 22 days of age and continued for 24 to 64 days. Hyperopic shifts in refractive error were found in all eyes, including the eyes treated with plano lenses. In addition to these absolute hyperopic shifts, 1.5 to 3.25 D of axial anisometropia were produced in all four monkeys, with the eyes wearing the powered lenses becoming relatively more hyperopic than the control eyes wearing the plano lenses. The induced hyperopia and anisometropia decreased rapidly after lens removal. The reapplication of the lenses at later ages in two animals produced smaller, but similar, changes. It appears that in very young primates extended-wear, soft, contact lenses can alter eye growth and refractive development through both visual and nonvisual mechanisms.