The word amblyopia derives from the Greek words ‘ambly’ which means dull and ‘ops’ that means vision, hence ‘amblyopia’, or in translation the ‘dullness of vision’.
Ancient times and the Middle ages
The first mention of ‘amblyopia’ dates back to the fifth century BC to the old Greek civilization. Back then Hippocrates used the word amblyopia to name conditions that resulted in decreased visual acuity in seemingly healthy eyes. Old Greeks also defined ‘strabismus’ as a disorder of eye movements and position. By today’s standards, they proposed sort of bizarre treatment options but at least it meant a start in amblyopia treatment. More than a thousand years later though, in the Byzantine empire, in the year around 900 AD, there was the first mention of occlusion for the treatment of strabismus in history. In the 13th century, the first-ever eye hospital was established in France and in the 16th century a German physician designed special hoods to put them over one’s head to treat strabismus.
The start of ophthalmology and early surgical attempts
The actual start of ophthalmology as such is believed to have occurred in 1765 in Paris, France when the first chair of ophthalmology was established. Approximately 50 years earlier, in the year 1722, a French ophthalmologist Charles de Saint-Yves wrote in his book that by covering non-strabismic eye the strabismic eye will immediately look straight ahead – something that we now know as a cover test. He also proposed that the non-strabismic eye should be covered in order to restore the correct eye position in the strabismic eye. A few years later, in 1743, George Comte de Buffon, another French physician described that the weak eye regains all its strength by occluding the good eye, which is why he is considered as a beginner of the occlusion therapy in amblyopia. The first idea of treating strabismus (and amblyopia) surgically came in the 18th century by John Taylor, although his surgical techniques on eye muscles were later recognized as a fraud. Roughly a hundred years later though, Germans Stromeyer and Dieffenbach and Belgian Cunier were the first to have performed a proper surgery for treating strabismus. Later it was also noted by Ludwig Boehm that the surgery to correct strabismus also improves amblyopia.
The beginning of modern ophthalmology
The modern ophthalmology then started in 1850 with the discovery of an ophthalmoscope by Ferdinand von Helmholtz. It was only then that ophthalmologists were able to visualize the retina and describe the amblyopic eye as functionally healthy, without any detectable abnormalities. The extensive research of eye disorders then started by ophthalmologists and Donders and Von Graefe started discussing extensively whether strabismus causes amblyopia or vice versa. The discussion then continued for almost a hundred years until the mid-20th century.
Occlusion and fusion exercises
Whilst first attempts for the treatment of amblyopia and strabismus were mostly occlusion, in the 18th and 19th century quite a few doctors came up with somewhat novel fusion exercises. Erasmus Darwin in England prescribed some sort of fusion exercises by which he separated the two visual fields, aiming to better vision. Later Louis Emile Javal, who was a strong opponent of the surgical treatment, came up with certain orthoptic exercises and occlusion for re-establishment of binocular vision. Later still Claud Worth used the occlusion and introduced the use of atropine – what we now know as penalization – as an alternative to occlusion. He also invented the active training stimulation device known as ‘amblyoscope’. Ernest Edmund Maddox later invented all sorts of different orthoptic devices and devoted his and his daughter’s career to orthoptic training, including the use of fore, mentioned Worth amblyoscope. His daughter Mary later established the first orthoptic clinic which was situated in London, UK.
Modern occlusion is (re)introduced
Later, at the beginning of the 20th century, occlusion therapy was re-introduced extensively into clinical practice in amblyopia. Sattler started to use an eye patch as we know today, although he suggested the occlusion for at least several days continually – contrary to what is known today. What he was completely correct about, though, was the fact that occlusion is the most effective in children up to the age of 6-8. At roughly the same time Weckert proposed the use of spectacle occluder instead of an eyepatch, and this technique was generally more accepted by children than Sattler’s eyepatch. In the coming decades, an extensive debate about the benefits and duration of occlusion was being gone on and the top-notch professionals back then could still not have agreed completely whether amblyopia is caused by strabismus or vice versa. They also started to recognize the potential side effects of prolonging occlusion (occlusion amblyopia, increased strabismus and the loss of binocularity) and therefore started to experiment with patching only a few hours per day.
During the 20th century, the occlusion therapy became ever more sophisticated especially in terms of the most effective duration of occlusion times. Perhaps even more importantly, the ophthalmologists also came to the agreement that robust refractive correction is at least as important as the occlusion itself, especially in anisometropic etiology of amblyopia. The improved surgical techniques made strabismus correction more effective and also much safer. An alternative to the occlusion, called ‘penalization’ was introduced into clinical practice and it represents an alluring alternative to date, particularly in those who cannot cooperate with conventional occlusion. Finally, the ever more powerful computers and continuing digitalization enabled the development of all sorts of new active treatment approaches, including, but not limited to, pleoptic training, perceptual learning and binocular dichoptic training which are more extensively discussed here.
For two and a half millennia we already know that amblyopia exists and for the same period we are trying to treat it. Throughout history many bizarre and ineffective, possibly even dangerous ways of amblyopia treatment were proposed but none of them seem to bring the results as effective as the simplest of them all – the occlusion. Combined with refractive correction, surgical intervention in certain instances and additional active treatment option we are, as of today, better equipped for amblyopia treatment than ever. Nonetheless, this does not mean that we can rest on our laurels and we must all strive to invent ever more effective and patient-friendly ways of treatments!
Loudon S. E. and Simonsz H. J. (2005). The history of the treatment of amblyopia. Strabismus 13, 93-106.
Papageorgiou E., Asproudis I., Maconachie G., Tsironi EE. and Gottlob I. (2019). The treatment of amblyopia: current practice and emerging trends. Graefes Arch Clin Exp Ophthalmol 257(6), 1061-1078.