A brief history of amblyopia: defining it, detecting it & treating it
Have you ever wondered when amblyopia was first identified? Or when vision screening began? I have. I’m not a historian, but the topic interests me, and I wanted to learn more to help put the work we’re doing today in context. Amblyopia isn’t a new condition. Early evidence is seen in a statue of Djoser, an Egyptian pharaoh, that dates to 2723 BC. The statue depicts a significant strabismus which mostly likely means he developed amblyopia.
Fast forward to 400 BC and Hippocrates, the father of medicine. He described amblyopia in the following way: when the doctor sees nothing and the patient sees nothing, the diagnosis is amblyopia. This is considered the first definition of amblyopia, which comes from the Greek “ambly,” meaning dull or lazy, and “ops,” for the eye.
Ancient treatments build a foundation for modern practices
Over a millennium later, an Egyptian named Paulus de Aegina was the first to treat strabismus. He developed a face mask with perforations to force people to look in specific directions. Masks continued to be used to correct strabismus, even as late as 1600 when German physician Georg Bartsch developed elaborate masks, one for endoscopia and another for exotropia.
Surprisingly, the first use of an eye patch was proposed by Turkish physician Thābit ibn Qurrah al-Ḥarrānī in 800 AD. It’s surprising because patching a child’s eye is still the most effective amblyopia treatment.
Early ophthalmology tools are still used today
Screening and diagnostic tools developed more than 170 years ago are similar to what we use today. The first visual acuity wall chart was created in 1843 by German ophthalmologist Heinrich Kuechler. These paper charts were developed before hyperopia was defined. The medical community knew about amblyopia but didn't understand its risk factors. Amblyopia that developed due to hyperopia or myopia was often attributed to strabismus.
A few years later, another German ophthalmologist, Hermann von Helmholtz, invented the ophthalmoscope which allowed for a first look inside the patient’s eye at the lens, retina and optic nerve. He is known as the father of modern ophthalmology. Thanks to von Helmholtz's ophthalmoscope, another prominent ophthalmologist, Frans Cornelis Donders of the Netherlands, was the first to describe hyperopia in 1859.
This predecessor to photo refraction was challenging, and lenses needed to be added to see the retina clearly. Today, primary care physicians use an updated version of the ophthalmoscope during pediatric and adult exams when they want to look at the fundus. It’s also a tool used to compare the color, brightness and symmetry of the ‘light reflex’ obtained from both eyes (often called Bruckner test or ‘Red reflex test’). The lack of any of these variables might be due to the presence of amblyogenic risk factors, that makes the ophthalmoscope a useful tool in the Pediatric office.
Making the connection between vision screening and child development
A Connecticut school screening program launched in the late 1800s is the first evidence of vision screening. Unfortunately, the process wasn’t standardized, which made evaluating the outcomes difficult.
Dr. Albert Sloan, a Massachusetts ophthalmologist, used an early Snellen chart to develop a set of vision screening tools for schools in 1938 that was used widely in the 1940s and 1950s. Other Snellen charts and tests were used during this same period for school screening, and the American Medical Association approved this more formal approach. At the time, the medical community recognized the consequences of amblyopia on child development. This movement led to the development of new tools for screening. But photo refraction was still another decade away.
Early photo refraction equipment developed in the 1960s used isotropic photo refraction in which the light source was coaxial to the camera's sensor. The weakness of this system was that it required robust calibration every time.
In a 1970s Harvard Medical School lab, David Hubel and Torsten Wiesel made a breakthrough in amblyopia research. Their experiments demonstrated the physiological reasons why myopia needs to be treated before ten years old. They received the Nobel Prize for that work in 1981, and their work led to a significant increase in amblyopia research.
The first photoscreening system was commercially available in the 1990s. It was a Polaroid camera that had pictures attached to attract a child’s attention. In 2002, the American Academy of Pediatrics recommended photoscreening for the first time.
Photoscreening ushers in the next chapter
Modern photoscreening devices detect amblyogenic risk factors that might lead to amblyopia, including myopia, , hyperopia, astigmatism anisometropia and strabismus. Pediatricians tell us they love these tools because they work like automatic ophthalmoscopes. Because of the adjustment ophthalmoscopes need, they’re hard to use with an adult who will sit still, let alone a child.
It's been interesting to learn more about the evolution of ophthalmology innovations over thousands of years. Each is built on the previous breakthrough. The work GoCheck Kids is doing now with photoscreening and visual acuity testing on a smartphone makes us part of this story, this history. And that’s pretty cool.
