On medical examination, the optic nerve head can be visualised by an ophthalmoscope. Optic disc pallor may be apparent with an ophthalmoscope if the result is longstanding. He was an early user of the ophthalmoscope invented by Hermann von Helmholtz in 1851. After retiring Armour made a lens-free direct ophthalmoscope. At the onset of symptoms, ophthalmoscope examination can differentiate AION from PION. It gives a view comparable to a standard ophthalmoscope. Babbage also invented an ophthalmoscope, which he gave to Thomas Wharton Jones for testing.