The effect of thermal insult to ocular tissue was first recorded in Western literature over two millennia ago. During the early scientific period and the ensuing eras, our understanding of this phenomenon, as well as our ability to accurately deliver dose-controlled therapeutic thermal energy to retinal tissue, have improved greatly. Since their commercial introduction in 1970, ophthalmic photocoagulation laser systems have been playing a cardinal role in the treatment and/or management of various ocular pathologies, predominantly though not limited to, retinal pathologies. Seminal studies, such as the Diabetic Retinopathy Study (DRS) and Early Treatment Diabetic Retinopathy Study (ETDRS), have solidified the role of such tools in the ophthalmologist’s therapeutic armamentarium; and to this day, as either stand-alone treatment or in combination with pharmacological agents, retinal laser therapy is recognised as the ‘gold standard’ for treating diabetic macular oedema (DME) and proliferative diabetic retinopathy (PDR). The continuous elucidation of the role that the retinal pigmented epithelium (RPE) plays in the emergence of retinal pathologies has prompted researchers and clinicians to further investigate selective RPE treatments – featuring significantly reduced or altogether devoid of collateral thermal damage to inner neural retinal structures with limited regenerative capacity. The convergence of electronic dosimetry, diagnostics imaging and new therapeutic laser modalities into a singular entity may serve as the technological platform for successfully employing such therapies in the near future.
Ophthalmic lasers, history of lasers, laser technology, laser evolution, thermal damage to retina, photocoagulation, multi-wavelength lasers, Diabetic Retinopathy Study (DRS), Early Treatment Diabetic Retinopathy Study (ETDRS), scanning lasers, selective retina therapy (SRT), image-guided laser therapy
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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Kfir Azoulay and Pazit Pianka are employed by Lumenis, manufacturer of ophthalmic lasers. Anat Loewenstein is a paid consultant to Lumenis.
Kfir Azoulay, Lumenis Holland, Locatellikade 1, 1076 AZ Amsterdam, The Netherlands. E: firstname.lastname@example.org
The publication of this article was supported by Lumenis.