Action of laser on tissues Presented by- Dr. Md Nazrul Islam. Assistant Registrar, Orthopedic and traumatology Department, Shaheed Suhrawardy Hospital, Dhaka. “ Laser in Orthopedic Surgery ” (Part-2)
“ Red light aids in the production of ATP in cells, which increases cellular health and energy. The radiation (energy) in normal cells stimulates adjacent cells to divide in the normal process of regeneration and healing. Laser light stimulates abnormal tissue to activate normal inter-cellular radiation, thus stimulating the normal healing process to start again. The photons produced by laser light normalize tissue by activating enzymes within cells.
Once activated, enzymes within a cell trigger a chemical reaction in which more enzymes are activated in a domino-type effect. Low Level Laser Therapy has no effect on normal tissue. Photons will only be absorbed by cells that need them.”
The IR( Infra red) region of the spectra, water molecules are dominant absorbers.
• In the UV (Ultraviolet) and visible spectra, absorption by macromolecules like melanin and hemoglobin is more pronounced.
Electromagnetic Spectrum: Wavelength: It is the distance between repeating units of a propagating wave of a given frequency. Frequency: It is the number of occurrences of a repeating event per unit time.
Basic steps of laser action on biologic tissues:
2. This procedure is for patients presenting with refraction problems.
a. Myopia b. Hypermetropia, c. keratitis
d. keratinisation, e. keratoplasty .
The photoablative effect offers no practical advantage for making incisions or for ablating vascular tissues because they will bleed in the same way as with a scalpel. It can only be used on tissues which will not bleed.
4. The photodynamic effect Photodynamic therapy (PDT) is based on photoactive drugs that produce excited singlet-state oxygen molecules from local (ground-state) oxygen molecules under illumination with visible light.1 The singlet oxygen produces reactive oxygen species, primarily free radicals such as ·OH. These free radicals attack DNA and other vital biomolecules in the cell, leading to cell death.. Due to the limited tissue penetration of visible light, PDT has mostly been utilized for skin cancers. Applications : Cancer Psoriasis Macular degeneration
Photodynamic therapy works by the patient receiving a photosensitizing agent or photosensitizer which is a drug that exposes cancerous cells to the laser light which kills these cells. The photosensitizer has the ability to differentiate between good body cells & cancerous cells, and will not diffuse in the good cells, leaving to expose only cancerous cells.