One of the earliest recorded descriptions of thermal energy effect on ocular tissue in general and the retina in particular is ascribed to the Greek scholar and philosopher Plato,1 who admonished of the deleterious impact of gazing directly at a solar eclipse. However, it was not until the 17th century AD that the first scientific-like description of a central scotoma resulting from solar thermal insult to the macula was produced by Swiss scholar Theophilus Bonetus.2
The advent of the telescope in the 17th century, along with the subsequent increase in astronomy and stargazing, led to several contemporaneous reports of inadvertent retinal coagulation resulting from inappropriate utilisation of this novel technology, particularly when employed for directly viewing the sun or sun-related events. With the invention of the ophthalmoscope by Hermann von Helmholtz in 1851 (although, for the sake of historical accuracy, the ophthalmoscope had been invented four years earlier by the English Charles Babbage without Von Helmholtz’s knowledge), such reported cases could be further elucidated by direct ophthalmoscopic observation and correlation of clinical manifestations to the morphological changes in the retinal tissue subjected to thermal insult.
A series of animal experimentations on the impact of focused sunlight and retinal damage was pioneered by Czerny in 1867.3 Additional work also involving artificial light (produced from carbon arc rods), was conducted by Deutschman and Widemark in the decades that followed.
The first extensive clinical study on the impact of thermal damage to the retina (‘Solar Retinopathy’) was conducted by Birch-Hirschfeld in 1912.4 Birch-Hirschfeld was the first scientist to postulate that the humanly visible portion of the solar spectrum was responsible for the retinal changes occurring from eclipse blinding. However, it was Verhoeff and Bell who in 1916 concluded5 that solar retinopathy resulted from thermal damage, rather than from photochemical effects of light on the retina.
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