When physics merged with biology to revolutionise ophthalmology

Sub: Sci

Sec: Health

Context:

Physics and Ophthalmology (study of medical conditions relating to the eye), two seemingly disparate fields came together to revolutionise vision correction through the use of LASER.

What is stimulated emission?

The 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.
The practical application of the concept was realised when Theodore Maiman in 1960 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 like coherence, monochromaticity, and the ability to be focused to a very small spot.

LASER (Light Amplification by Stimulated Emission of Radiation)

A LASER is a device that generates an intense beam of coherent monochromatic light by stimulating of photons from excited atoms or molecules.
Monochromatic light: light containing beams of same wavelength.
Lasers are used in surgery, barcode scanner, precision tools to cut diamond, Laser printing

Chirped Pulse Amplification (CPA):

Gerard Mourou and his student Donna Strickland in 1980s introduced CPA to amplify (increase the intensity) ultrashort laser pulses without damaging the amplifying material.
This technique revolutionised the field of laser physics and earned them the Nobel Prize in Physics in 2018.
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.

How CPA revolutionised eye surgery:

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.

Discovery of the effectiveness of laser beams in eye correction:

This discovery happened when a research assistant in Gérard Mourou’s lab was accidentally struck by a laser beam in his eyes without wearing the goggles.
The Doctor who treated him conducted a deeper investigation into the laser’s potential, leading to the development of femtosecond ophthalmology.

About femtosecond laser:

A femtosecond laser is a high-intensity infrared laser with a wavelength of 1053nm used in eye surgeries, especially for its precision.
Compared to the Nd laser, which operates in nanoseconds (10^-9second), the femtosecond laser’s pulse duration is much shorter and is measured in femtoseconds (10^-15second).
This shorter duration significantly reduces the risk of damaging nearby tissues, making the femtosecond laser much safer for delicate procedures like corneal surgery.

Lasers in cancer therapy:

Researchers are exploring using high-intensity 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.