Expert perspectives on the evolution of retina practice, procedures, technologies and instrumentation.
Charles M.T. DeBoer, MD, PhD; Stephen J. Smith, MD; Mark S. Blumenkranz, MD
Laser (light amplification by stimulated emission of radiation) technology has had a tremendous impact on the world, underpinning many of the key technologies that we use daily. Retina photocoagulation was the first medical application of laser, and the laser has revolutionized retinal therapeutics, imaging, and diagnostics.[1,2] Its use is ubiquitous in retinal practice, and it continues to be a foundational tool in the fight against blindness. This very brief overview of the history and significance of this technology attempts to summarize a few of the key moments for our field.
Einstein first proposed the concept of stimulated radiation emission in 1917, providing the theoretical foundation for a technology that was not reduced to practice until 1960.[1,2] The concept of therapeutic ocular photocoagulation was first introduced prior to the invention of the laser by Professor Gerhard Meyer-Schwickerath in Germany, who demonstrated that photic burns could be used in patients with retinal detachment. The earliest ocular experiments harnessed sunlight, with attention then shifting to carbon and xenon arc photocoagulators. These early systems were limited by significant collateral tissue damage and difficult ergonomics for the physician, a problem that laser was uniquely equipped to solve.
Laser is optically amplified light, and is coherent (emitting photons of the same phase), monochromatic (narrow wavelength), and collimated (minimal divergence of light rays). These properties opened a new frontier in retina - sophisticated, precise energy delivery targeting specific tissue layers. The eye is optimized for light transmission and conversion of light into neural signals.2 Laser represents a perfect marriage of high technology in a biological system uniquely designed to harness that technology to address clinical needs. Ophthalmologists immediately recognized its clinical value, with the first studies of its use in the eye by Zaret and colleagues published 1 year after the first laser was built.
The red ruby laser[5,6] was the first commercialized system, and it was supplemented by the introduction of the blue-green argon laser in 1964. Utilizing different wavelengths of light enabled greater target specificity, and the red Krypton laser improved laser penetration through blood and cataracts. As use of laser increased, slit-lamp based laser systems were introduced with an eye toward improved visualization, precision of spot size, location, and ergonomics. The surgical endolaser was introduced in 1980, and in 1981, binocular indirect photocoagulators enabled another method in addition to the slit lamp system and contact lenses, to treat peripheral pathology in the clinical setting.[9,10] As we moved into the 21st century, photodynamic approaches with verteporfin, scanning galvanometers, digital angiographic capture systems, eye tracking systems, and software modules have enabled the creation of sophisticated instrumentation including micropulsing and reduced fluence pattern laser delivery that improve delivery speed while offering greater precision and safety.
Over the last half a century, laser has played a central role in the management of retinal tears, retinal and choroidal tumors, proliferative diabetic retinopathy[15,16], macular edema, and age-related macular degeneration. The advent of anti-VEGF therapy reduced the role of laser in the treatment of exudative macular degeneration and macular edema, but it continues to play an important role in the management of retinal tears, tumors, and vasogenic retinal and choroidal diseases including diabetic retinopathy, vascular tumors, selected forms of retinal venous occlusive disease and central serous choroidopathy amongst others.
Over 6 decades have passed since the first laser was built and applied to the retina, yet it remains a foundational therapeutic, diagnostic, and imaging modality in our clinics. Its use as a treatment for proliferative diabetic retinopathy alone has preserved vision in tens of thousands of patients. The development of laser in our field serves as a testament to the ingenuity of ophthalmologists, whose identification of this key innovation in the broader scientific community helped pave the way for the use of laser in medicine as a whole. Preventing blindness and restoring vision is the hallmark of our specialty, and laser therapy is one of our greatest success stories.
(Milestone essay published 2021)