Allvar Gullstrand, a Swedish ophthalmologist who discovered how the eye bends light to form images, was born on this day in 1862. When Gullstrand began his work, the optics of glass lenses were already well established. But it wasn't clear how the eye's lenses functioned, especially when changing focus. Gullstrand wrote out complex mathematical models and proposed that when the eye changes focus on near and far objects, it relies on more than just the curvature of the lens: Vast numbers of tiny, transparent fibers within the lens also make adjustments.
In 1911, Gullstrand also developed two tools for inspecting the eye: the ophthalmoscope for peering at the retina and optical disk; and the slit lamp, which allows doctors to locate foreign objects or tumors in the fluid of the eye. That same year, he received the Nobel Prize in physiology or medicine for his work. Gullstrand died in 1930.
[Source: Emily McMurray, Ed., Notable Twentieth Century Scientists (Gale Research Inc., ITP, 1995).]