FAQ 7
Medical Applications
Based on the suggestions of large number of students and laser scientists, this section is being renamed as FAQ. The questions being addressed are of very general nature and are being forwarded to us by readers from different parts of India. This section provides an opportunity for interaction where one can ask their clarification either about the articles on web or any other question related to lasers. The reply will be sent to them after discussing with either the authors of a particular article or the experts in that field. Any comments / suggestions to improve the site are welcome.
  1. What are the main applications of lasers in Medical science?
  2. What are the various mechanisms responsible for Lasers - Tissue interaction?
  3. What are applications of Lasers in Urology?
  4. What are the lasers - tissue interaction effects in Urology?
  5. What are various lasers being used for Urology?
  6. What are the main applications of Lasers in Ophthalmology?
  7. What are the lasers - tissue interaction effects in Ophthalmology?
  8. What are various lasers being used for Ophthalmology?
  9. What are various applications of Lasers in Dermatology?
  10. What are various lasers being used for Dermatology?
  11. Are there any disadvantages of using lasers for Dermatology?
  12. What are the applications of lasers in Cardiology?
  13. What are the lasers being used for Cardiology applications?
  14. What are the applications of lasers in Dentistry?
  15. What are various lasers being used for Dentistry applications?
  16. What are the lasers being used for cancer treatment?
  17. How does Low Level Laser Therapy works?
  18. Summarize the applications of Lasers for various medical applications?


  1. What are the main applications of lasers in Medical science?
  2. Presently lasers are being widely used for numerous medical applications. These include surgery, ophthalmology, dermatology, angioplasty, cancer treatment, urology, and cosmetic applications such as laser hair removal, tattoo removal and liposuction, Low Level Laser Therapy (LLTP) etc.


  3. What are the various mechanisms responsible for Lasers - Tissue interaction?
  4. Laser light interacts with the tissue and transfers the energy of photons to tissues because of absorption. Laser heating of tissues above 50°C but below 100°C induces disordering of proteins and other bio-molecules. This process is known as photocoagulation. When lasers are used for photocoagulation during surgery, the tissues shrink in mass because water is expelled at these temperatures. The heated region changes its colour and loses its mechanical integrity. Cells in the photocoagulated region die and the tissue is a dead one and can be pulled or removed. The process of laser-induced photocoagulation can be used to destroy tumors, to treat various eye conditions like retinal disorders caused by diabetes, bloodless incision or excision in laser surgery. When very high laser power densities are used, lasers quickly heats the tissues beyond 100°C resulting in boiling and evaporation of water in the tissues. Since 70% of the body tissue is water, the boiling change the tissue into a gas. This phenomenon is called photo-vaporization. Photo - vaporization results in complete removal of the tissue thus making the process suitable for skin rejuvenation, resurfacing and of course bloodless incision or excision in laser surgery. For Photo - vaporization, the tissues must be heated quickly to more than 100°C thus requiring high power density in a pulsed mode. In general power density upto 10W/cm2 results in heating of tissues, whereas laser power in the range of 10 - 100W/cm2 results in photocoagulation. Power density greater than 100W/cm2 is required for photo - vaporization. It is worth mentioning that a given laser can be used for photo-vaporization in the focused mode, whereas same laser can also be used for photocoagulation in the defocused mode. High power lasers like excimer lasers in the ultraviolet range, can break the chemical bonds without even heating the tissues locally thus resulting in photochemical ablation. The photochemical ablation results in clean-cut incision. The thermal component is relatively small and the zone of thermal interaction is limited in the incision wall.


  5. What are applications of Lasers in Urology?
    • Urolithiasis
    • Condylomata
    • Benign Prostatic Hyperplasia
    • Prostrate Cancer
    • Vasovasostomy
    • Suture removal


  6. What are the lasers - tissue interaction effects in Urology?
    • Thermal effects
    • Mechanical effects
    • Tissue welding effects
    • Photochemical effects


  7. What are various lasers being used for Urology?
    • Lasers for condylomata - CO2 laser induced vaporization of small lesions, whereas Nd: YAG coagulates and is used for larger lesions.
    • Pulsed dye laser (504 nm), Argon (755 nm) for urolithiasis for controlled fragmentation
    • Nd:YAG, Alexandrite and Ho:YAG for stone fragmentation, for causing stone vaporization and formation of cavitation bubble
    • CO2 and Nd:YAG for Vasovasostomy
    • Nd:YAG for prostatic Ca
    • Holmium: YAG, Nd:YAG, for ablation of the prostate and for removal of the prostate
    • CO2 and Nd:YAG for Penile Ca - low stage disease.
    • CO2 and Nd:YAG for Bladder haemangioma
    • Suture removal -Nd:YAG and Ho:YAG, Argon, Nd:YAG, Ho:YAG, Potassium Titanyl Phosphate (KTP - 532 nm)
    • Semiconductor Laser (850 nm) for Interstitial prostate coagulation, tissue welding

  8. What are the main applications of Lasers in Ophthalmology?
  9. Glaucoma, Cataract, Diabetic retinopathy and Photorefractive keratectomy (PRK) and Laser-Assisted -in- situ Keratectomy (LASIK)


  10. What are the lasers - tissue interaction effects in Ophthalmology?
  11. Laser-tissue interactions in ophthalmology can occur in several ways, depending on the power, pulse-duration and wavelength. These interactions can have photothermal, photochemical and photoionizing effects.


  12. What are various lasers being used for Ophthalmology?
    • Argon, Krypton and Nd: YAG lasers for Glaucoma
    • Nd:YAG for Cataract
    • Argon, dye laser, Nd:YAG, Krypton and optically pumped solid-state lasers (OPSL) for diabetic retinopathy
    • Excimer laser ArF (193 nm), Nd: YAG / Glass based Femtosecond (FS) laser for PRK / LASIK

  13. What are various applications of Lasers in Dermatology?
    • Cosmetic dermatology
    • Skin resurfacing
    • Pigmented lesions:
    • Tattoos
    • Hair removal

  14. What are various lasers being used for Dermatology?
  15. Nowadays, a number of lasers are used in dermatological applications. They are argon laser (488nm & 514nm), tunable dye lasers (585 to595nm), doubled Nd:YAG (532nm), krypton laser (568nm), alexandrite laser (755nm), Nd:YAG (1064nm), Er:YAG (2940nm), CO2 laser (10600nm) etc. The pulse width of these laser systems vary from milliseconds to nanoseconds (pulsed) or the laser may be of continuous nature (CW).


  16. Are there any disadvantages of using lasers for Dermatology?
  17. It would be not out of place to mention that there are certain adverse effects of laser treatments, as these are basically burns. These include:
    • Pain, bruises, blisters, redness may occur as temporary effects
    • Possibility of infection
    • Permanent pigment changes
    • Rare occurrence of scarring

  18. What are the applications of lasers in Cardiology?
    • Angioplasty, the procedure of mechanically widening narrowed or obstructed arteries
    • Laser thrombolysis, a means for clearing blood clots present in occluded arteries as a result of myocardial infarction. Myocardial infarction occurs when blood stops flowing properly to a part of the heart, and the heart muscle is injured because it is not receiving enough oxygen.
    • Transmyocardial laser revascularization (TMLR), a procedure, which is used on patients where the problems related to coronary artery, still exists even after most of the conventional therapies have been exhausted. Typically, these patients continue to have chest pain while on maximal medical therapy, and most are at an extraordinary risk for surgical intervention. Transmyocardial laser revascularization (TMLR) is based on the use of a high-powered carbon dioxide or other laser that interjects a strong energy pulse into the left ventricle, (one of two large chambers that collect and expel blood) vaporizing the ventricular muscle and creating a transmural channel with a 1-mm diameter.

  19. What are the lasers being used for Cardiology applications?
  20. Three types of lasers are being used in these procedures: the carbon dioxide (CO2), the holmium:yttrium-argon-garnet (Ho:YAG), and the excimer lasers. Of these, the Food and Drug Administration (FDA) has approved only the CO2 and Ho:YAG lasers for use in TMR. CO2 (10.6 micron) and the Ho:YAG ( 2.1 micron) lasers rely on thermal energy to create channels, whereas the excimer laser (308 nm) ablates tissue by dissociating molecular bonds. The CO2 laser is transmitted through a series of mirrors and lenses. Whereas, the Ho:YAG and the excimer lasers allow the laser beam to be transmitted by an optical fiber. Usually high-energy pulses of 40 - 60 J with pulse width of few tens of milliseconds of CO2 lasers are required for these procedures. Ho:YAG lasers used for these applications are generally with a peak power of around 10W and pulse width of 200 - 400 microseconds. Excimer lasers employed for these applications are usually 30 - 100 nanosecond pulses with energies in the range of few tens of milijoules per pulse.


  21. What are the applications of lasers in Dentistry?
  22. Lasers have been in use in dentistry for the last more than two decades. These are being used to treat various problems such as Tooth decay, gum disease, biopsy or lesion removal and teeth whitening etc.


  23. What are various lasers being used for Dentistry applications?
    • Er:Cr:YSGG operating at 2.78 micron with pulse width of 60 - 700 microseconds and are capable of delivering energies up to 400 millijoules for tooth decay applications.
    • An argon ion laser utilizes a blue light with a wavelength in the range of 470 nm to 520 nm, diode lasers with a wavelength of 810 nm or Nd:YAG lasers with a wavelength of 1064 nm, pulsed Er:YAG laser wavelength ( 2.94 micron) for teeth whitening.
    • Nd:YAG for gum diseases
    • HeNe (660nm), Nd:YAG ( 1064 nm), Erbium:YAG ( 2940nm) and diode laser (780 nm) for treatment of lesions

  24. What are the lasers being used for cancer treatment?
  25. Lasers can be used either to shrink or destroy a tumor with heat or to activate a chemical - known as a photosensitizing agent - that kills only the cancer cells. This process is generally known as photodynamic therapy or PDT. The CO2, argon, Ho:YAG and Nd:YAG lasers are used to shrink or destroy tumors.


  26. How does Low Level Laser Therapy works?
  27. Low-level laser therapy affects cellular activity in many ways such as stimulating cell growth; increasing cell metabolism; improving cell regeneration; producing an anti-inflammatory response; producing an edema reduction; reducing fibrous tissue formation; stimulating nerve function. There are no known permanent or serious side effects from appropriately applied laser therapy.

    LLLT uses low-powered laser light in the range of 1-1000 mW, at wavelengths from 632-1064 nm helps in Neurorehabilitation by stimulating a biological response. These lasers emit no heat, sound, or vibration. Instead of generating a thermal effect, LLLT acts by inducing a photochemical reaction in the cell, a process referred to as biostimulation or photobiomodulation.


  28. Summarize the applications of Lasers for various medical applications?

  29. Laser Wavelength Power / Energy Applications
    Nd:YAG 1.064micron and 1.320 micron Upto 100 W / upto 3.5 J/pulse Urology, Tatoo removal, Ophthalmology, Neurosurgery, Gynecology, Cosmetic
    Frequency doubled Nd:YAG (Potassium-titanyl-phosphate: KTP) 0.532 micron Upto 180 W Urology, Pulmonology
    Copper Bromide / vapour 510, 578 nm Dermatology
    Ruby (Q-switched) 694 nm Dermatology
    Fiber lasers 1040 - 1045 nm Upto 20 W Ophthalmology
    Ho:YAG 2.1 micron Upto 100 W Urology, Orthopedics,
    Er:YAG 1.54 micron, 2.94 micron Upto 100 W / Upto 5 J/cm2 Dermatology, Cosmetic,
    Thulium:YAG / Thulim : silica fiber 1900 - 2000 nm 200 W Urology, Gynecology, Neurosurgery. ENT, Pulmonology
    Argon 488, 514 nm Upto few watts / upto 100 J/cm2 Urology, Tatoo removal, Ophthalmology, Photodynamic Therapy, Dermatology
    Dye lasers 577 - 680 nm Upto 120 mJ / upto 12 J/cm2 Tatoo removal, Urology,
    Alexandrite (Q-switched) 755nm Upto 100 mJ Tatoo removal, Urology
    Semiconductor laser 800 - 980 nm Upto 200 W Urology, Dentistry, Surgery, LLLT
    Ho:YAG 2.1 micron Upto 100 W / upto 3.5 J/pulse Urology, Gynecology, Neurosurgery. ENT, Pulmonology
    Excimer 190 - 350 nm Upto 400 mJ/cm2 Ophthalmology
    CO2 laser 10.6 micron Upto 50 W / 100mJ per pulse Surgery, Urology, Dermatology, ENT


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Updated: 12 October, 2018
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