Recently, I underwent femtosecond laser surgery, a procedure that promised to correct my vision with incredible precision. While the results were astounding, I couldn’t help but wonder — how did physicists, who typically aren’t versed in the anatomy of the eye, end up creating a technology so pivotal to ophthalmology? After all, the physics of lasers and the biology of the eye seem like worlds apart. Ophthalmologists, deeply familiar with the intricate workings of the eye, don’t typically have the leisure time to spend in a physicist’s lab studying LASER. So how did these two seemingly disparate fields merge to revolutionise vision correction in refractive errors and cataracts?
The word ‘laser’ is actually an acronym for ‘Light Amplification by Stimulated Emission of Radiation’, a phrase that encapsulates the physics underlying this transformative technology. The fundamental concept of stimulated emission was first introduced by Albert Einstein in 1917. He theorised that when an electron in an excited state drops to a lower energy level, it can release energy as a photon. If this photon interacts with another excited electron, it can stimulate the release of a second photon of identical energy, phase, and direction — a process that amplifies light.
It wasn’t until 1960, however, this theory was practically realised. Theodore Maiman, a physicist at Hughes Research Laboratories, built the first working laser using a ruby crystal as the gain medium. The ruby laser emitted light at a specific wavelength (694 nm) in the red part of the spectrum and was the first of its kind to produce a concentrated beam of light with unique properties — coherence, monochromaticity, and the ability to be focused to a very small spot.
Chirped Pulse Amplification
Another breakthrough came in the 1980s with the development of Chirped Pulse Amplification (CPA). This technique revolutionised the field of laser physics. Working at the University of Rochester, Gérard Mourou and his student Donna Strickland (the third woman to win a Nobel prize in physics) introduced CPA to amplify ultrashort laser pulses without damaging the amplifying material. Their innovation later earned them the Nobel Prize in Physics in 2018.
But here the question still remains alive: how did physicists, who likely had little knowledge of eye anatomy, create a tool that would become vital in eye surgery? The answer lies in an accidental discovery that bridged the gap between the physics lab and the operating theatre.
A research assistant in Gérard Mourou’s lab was accidentally struck by a laser beam in his eyes without wearing the goggles he was supposed to wear — a potentially dangerous situation. Seeking medical attention, the assistant visited an ophthalmologist. But instead of focusing on treatment, the doctor who saw him became intensely curious about the physical qualities of the laser that had caused the injury, hitherto not witnessed in the clinic. The ophthalmologist was intrigued by the ‘perfect’ or precise damage to the retina in his eyes. This unusual interaction sparked a deeper investigation into the laser’s potential, leading to the development of femtosecond ophthalmology.
This cross-disciplinary serendipitous accident — where a medical professional’s inquisitiveness about a physics tool met the physicist’s quest for practical applications — made room for perfect innovation. CPA allowed for the amplification of laser pulses in a previously-impossible way, opening the door to medical applications requiring extreme precision, such as in eye surgery.
Transforming ophthalmology
Today, CPA-based lasers are at the heart of femtosurgery laser procedures, like the one I underwent for refraction correction. These lasers work by emitting pulses of light that last only a few quadrillionths of a second, making them extraordinarily precise. The high-intensity, ultrashort pulses produced by CPA-based lasers allow for precise cornea reshaping with minimal damage to surrounding tissues, resulting in improved patient outcomes and faster recovery times.
This have also transformed cataract surgery, one of the most common surgical procedures worldwide. In traditional cataract surgery, a surgeon manually makes incisions in the eye and uses ultrasonic energy to break up the cloudy lens before replacing it with an artificial intraocular lens (IOL). In laser-assisted cataract surgery, a femtosecond laser is used to create precise incisions and soften the lens, reducing the need for ultrasonic energy and allowing for more accurate placement of the IOL. This technology has improved the precision and safety of cataract surgery, leading to better outcomes and faster recovery times.
A femtosecond laser is an infrared laser with a wavelength of 1053nm used in eye surgeries, especially for its precision. It creates tiny, rapid bursts that break apart the tissue without damaging surrounding areas. Compared to the Nd laser, which operates in nanoseconds (10-9 second) , the femtosecond laser’s pulse duration is much shorter — measured in femtoseconds (10-15 second). This shorter duration significantly reduces the risk of damaging nearby tissues, making the femtosecond laser much safer for delicate procedures like corneal surgery. The femtosecond laser causes a million times less collateral damage than the Nd laser, allowing for extremely precise and safe surgeries. More than 10 million femtolaser surgeries have been performed globally so far using laser technology.
Moreover, the future of high-intensity lasers holds promise in cancer therapy. Researchers are exploring using these lasers to target and destroy cancerous cells with extreme precision, minimising damage to healthy tissues. By focusing the energy of an ultrashort laser pulse onto a tiny area, it’s possible to induce a localised effect, such as generating shockwaves or heating, that can selectively destroy cancer cells. This approach is still in its experimental stages. It could one day lead to new, non-invasive treatments for cancer patients.
A bright future ahead
Reflecting on my experience with femtosurgery, I am grateful for the improved vision. From accidental discoveries to intentional innovations, the story of laser technology continues to unfold whether in the operating theatre, the physics lab, or beyond.
It’s a reminder that sometimes, the most impactful innovations come from the unlikeliest of collaborations—where the physics of light meets the biology of sight, and curiosity knows no disciplinary bounds.
(Dr. C. Aravinda is an academic and public health physician. aravindaaiimsjr10@hotmail.com)
