Helmholtz Ophthalmoscope

The invention of the ophthalmoscope is credited to Hermann von Helmholtz in 1851. Called an Augenspiegel (eye mirror), the device allowed physicians to view the eye, and answer the question: "why does the pupil sometimes appear dark, and sometimes light?" The instrument used an angled mirror to direct the light from a candle directly into the eye, while the physician was able to view the pupil through a magnifying lens.

Babbage Ophthalmoscope

Although the Helmholtz ophthalmoscope is recognized as the first practical device, Charles Babbage, the British mathematician, conceived of one in 1847. He built the device, but when physicians could not see an image, he abandoned the device. Unknown to Babbage, the instrument would have worked perfectly with a different lens between the observer and the mirror. Interestingly, the Babbage ophthalmoscope resembles Brunton’s device.

Lindsay Ophthalmoscope

All the earliest ophthalmoscopes required an external light source to illuminate the pupil. The easiest way to direct the light was by using a mirror. Ophthalmoscopes with fixed mirrors required the physicians to physically move themselves to capture the light source they were using - be it a candle or a lantern. In 1882, George Lindsay of London solved that problem by inventing an ophthalmoscope with a rotating mirror. The mirror could be spun, often on two axis, to capture the light in the best way possible.

Morton Ophthalmoscope

Besides a good light source, the other element needed to get a clear image with a direct ophthalmoscope is a correcting lens. The correcting lens was needed to get the best image based on the refraction of the patient’s pupil. The Helmholtz ophthalmoscope had a single lens, so correction was not possible. Andrew Stanford Morton, of University College, London, solved the problem by adding a dial with 29 additional lenses into the rotating mirror design of the George Lindsay ophthalmoscope. Once the lens was selected, it could be slid into place behind the viewing port.