Light in Medicine Applications

Light in Medicine

• Light exhibits properties vital in medicine, acting as both a wave and a particle.
• Light's speed changes traversing different materials; the refractive index quantifies this change.
• Light absorption often results in heat generation; this fundamental principle underpins medical applications like using infrared light to heat tissues or laser beams welding detached retinas/coagulating blood vessels.
• Fluorescence occurs when light absorption results in lower-energy light emission.
• Light reflection takes place from all surfaces, distinguishing between specular (smooth surfaces like mirrors) and diffuse (rough surfaces distributing light).
• Light is measured in units like microns (μ = 10⁻⁶m), angstroms (Å= 10⁻¹⁰m), and nanometers (nm = 10⁻⁹m).
• Wavelength delineates various types of light, including ultraviolet (UV), and infrared (IR). These further classify into different spectrums based on wavelength/frequency.

Applications of Visible Light in Medicine

• Endoscopy utilizes light to view internal body cavities (e.g., cystoscopes for the bladder, proctoscopes for the rectum).
• Ophthalmoscopes and otoscopes are used to examine the eyes and ears, respectively.
• Other types of endoscopes examine the small intestine (enteroscopy), large intestine (colonoscopy), and uterus (hysteroscopy).
• Bronchoscopes examine the air passages of the lungs.
• Various endoscopes use light sources and optical components to illuminate structures needing examination, providing magnification and image transmission.
• Flexible endoscopes offer versatility, allowing access to areas inaccessible using rigid endoscopes and enabling tissue biopsies for microscopic evaluation.

Applications of UV and IR Light in Medicine

• UV light, due to its high energy, effectively sterilizes medical instruments.
• UV has beneficial effects like converting molecules in the skin to vitamin D and harmful effects associated with damage to the skin DNA.
• IR penetrates deeper into tissue than visible light, making it suitable for deeper tissue heating.
• Specific forms of IR photography depict patterns in veins or body temperature (thermography).

Transillumination

• Transillumination involves transmitting light through tissues, helpful in procedures like hydrocephalus detection for infants.
• Pneumothorax (collapsed lung) detection in infants involves measuring light penetration differences.

Laser in Medicine

• Lasers employ stimulated emission of photons where one photon triggers two identical photons.
• Lasers emit light of a single wavelength, offering precise surgical precision.
• Their concentrated beams, when appropriately focused, produce significant power intensities, useful for many medical conditions.
• Tissue heating and destruction is a result of laser application to certain tissues.
• Examples include photocoagulation (for retinal detachment) and various dermatological procedures.
• Laser applications focus on specific wavelengths for optimal treatment effect in different conditions, such as eye diseases or skin conditions.

Specific Wavelengths and Applications

• Ophthalmologists use minimal reactive dose (MRD) of laser for eye treatment, varying per individual patient and spot size.
• Dermatological procedures such as treatment of skin conditions utilize different laser types based on the specific conditions/desired outcomes.