Sub Navigation
The Story Behind: Retinal Screening
Leider ist diese Seite derzeit nicht in deutscher Sprache verfügbar.
A window to the brain
Ophthalmology, the treatment of eye-related illnesses, is one of the oldest medical disciplines: As early as 3,600 years ago, eye operations were performed in ancient Babylon. The local law code there stipulated that for a successful operation, the doctor should be paid 10 silver shekels; in case of failure, his hands were to be cut off.
Ophthalmology was also practised, with even greater skill, in ancient Greece and Rome. Much of that expertise, however, was lost in the Middle Ages, and it wasn't until the late 18th century when ophthalmologists gave up the rather cultish treatments that had been the norm for centuries.
The first and second half of the 19th century, finally, raised ophthalmology to one of the most exact of clinical studies. A key element of that progress is the ophthalmoscope, invented in 1850 by German scientist Hermann von Helmholtz. The ophthalmoscope allowed doctors to peer into the retina of a living person, and the technology has since been perfected and today serves as an efficient early detection tool for a range of diseases.
Helmholtz knew about the importance of the ophthalmoscope as soon as he had invented it. In a letter to his father, he wrote proudly, "Till now a whole series of most important eye-diseases, known collectively as black cataract, have been terra incognita, because the changes in the eye were practically unknown, both during life, and, generally speaking, after death. My discovery makes the minute investigation of the internal structures of the eye a possibility".
Because the retina is a part of the nervous system pushed outward during embryonic development, the ophthalmoscope also opened a window to the brain: In patients with headaches, the finding of swollen optic discs, or intracranial pressure which could be due to hydrocephalus, is a key sign of a brain tumour. Hypertensive changes of the retina closely mimic those in the brain, and they may be early warning signs of an impending stroke. In patients with diabetes, regular ophthalmoscopic eye examinations are mandatory to screen for diabetic retinopathy. If spotted early, vision loss due to diabetes can be prevented by retinal laser treatment.
Helmholtz's invention has been frequently refined to ease practitioner use. In 1915, William Noah Allyn and Francis Welch invented the world's first hand-held direct-illuminating ophthalmoscope, precursor to the device now used by clinicians around the world.
Pomerantzeff, Webb invent SLO
Ophthalmoscopy received its next major push in Boston, where in 1962, Russian-born Oleg Pomerantzeff accepted an invitation from Dr. Charles Schepens to join the Retina Foundation, now called the Schepens Eye Research Institute, an affiliate of Harvard Medical School. This move coincided with the birth and early development of the laser, a new light source in which Pomerantzeff immediately took a vivid interest.
In 1977, he realized that it should be possible to invert the optical principle of the camera and use the central portion of the anatomical pupil of the eye for illumination of the retina, and all of the pupil's surrounding area for light collection from the retina. A major motivation for his idea was the potential for reducing the intensity of the illuminating light source.
Pomerantzeff's idea was perfected by Robert H. Webb, a researcher at Harvard and the Massachusetts General Hospital. In the early 1980s, Webb built the first commercial scanning laser ophthalmoscope (SLO).
"The SLO has been one of the major developments of the century in ophthalmoscopy," says Austin Roorda, an expert in Clinical Optometric Science at the University of California, Berkeley.
Ultra-wide field imaging
While the SLO was an improvement over conventional methods, it required dilation of the pupil and to see the retina in the periphery and multiple images to build up a wider field of view.
Roughly a decade later, British engineer Douglas Anderson developed an SLO that produced high-contrast wide-field digital images and completely eliminated the need for dilation. Though not a physician, Anderson was driven by a desire to improve retinal screening after his 5-year-old son went blind in one eye because a retinal detachment was detected too late. Afterward, Anderson founded Optos and set out to develop the wide-field SLO.
While earlier eye exams took a 15- to 30-degree scan of the eye's interior, the wide-field scan Anderson developed together with two colleagues shows some 200 degrees or 82 percent of the retina. The images can be stored and later compared with other test results.
Anderson had his first ophthalmoscope out in 1999; by 2008, some 13 million patients had their eye exams taken by the wide-field scanning laser ophthalmoscope.
Read more about the inventors: Douglas Anderson, Robert Henderson, Roger Lucas (UK)