8.1 Laser surgery and therapy

Laser surgery and therapy harness the power of focused light to perform precise medical procedures. From ophthalmology to dermatology, lasers enable minimally invasive treatments with reduced side effects and faster recovery times.

Understanding laser-tissue interactions is crucial for effective use. Different laser types and techniques target specific tissues and conditions, revolutionizing fields like refractive surgery, tattoo removal, and dental care. Safety considerations and ongoing research continue to expand laser applications in medicine.

Fundamentals of laser surgery

• Laser surgery utilizes the unique properties of laser light to perform precise surgical procedures
• Understanding the fundamentals of laser-tissue interactions is crucial for safe and effective laser surgery
• Different types of lasers are used for various surgical applications based on their wavelength and tissue interaction properties

Laser-tissue interactions

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• Laser light can be absorbed, reflected, scattered, or transmitted by tissue depending on the wavelength and tissue properties
• Absorption of laser energy by tissue components (water, hemoglobin, melanin) leads to specific effects
• Penetration depth of laser light varies with wavelength, allowing for selective targeting of tissue layers
• Thermal effects, photochemical effects, and plasma-mediated ablation are the main mechanisms of laser-tissue interaction

Thermal effects on tissue

• Absorption of laser energy leads to localized heating of tissue
• Thermal effects can cause coagulation (60-100°C), vaporization (100-300°C), or carbonization (>300°C) of tissue
• Coagulation is used for hemostasis and tissue welding
• Vaporization allows for precise tissue removal with minimal collateral damage
• Carbonization should be avoided as it can lead to tissue damage and delayed healing

Photochemical effects

• Some lasers (e.g., UV lasers) can induce photochemical reactions in tissue without significant heating
• Photochemical effects are used in photodynamic therapy (PDT) for cancer treatment
  • Involves the activation of a photosensitizer drug by specific wavelengths of light
• Photochemical effects can also be used for tissue crosslinking and corneal reshaping in ophthalmology

Plasma-mediated ablation

• High-intensity laser pulses can generate a plasma (ionized gas) at the tissue surface
• Plasma-mediated ablation allows for precise tissue removal with minimal thermal damage
• Commonly used in ophthalmology for refractive surgery (LASIK, PRK)
• Plasma formation depends on laser pulse duration, intensity, and tissue properties

Types of surgical lasers

• Different types of lasers are used in surgery based on their wavelength, tissue interaction properties, and clinical applications
• The choice of laser depends on the specific surgical procedure and target tissue

CO2 lasers

• Emit infrared light at 10,600 nm wavelength
• Strongly absorbed by water in tissue, leading to efficient vaporization and ablation
• Used for precise cutting, ablation, and coagulation of soft tissues
• Applications include skin resurfacing, tumor removal, and gynecological surgery

Erbium:YAG lasers

• Emit infrared light at 2,940 nm wavelength
• Absorbed by water more efficiently than CO2 lasers, allowing for more precise tissue removal with less thermal damage
• Used for skin resurfacing, dental hard tissue procedures, and bone cutting

Nd:YAG lasers

• Emit infrared light at 1,064 nm wavelength
• Penetrate deeper into tissue than CO2 and erbium:YAG lasers
• Used for coagulation, tissue welding, and treatment of vascular lesions
• Applications include endovenous laser therapy (EVLT) for varicose veins and laser lipolysis

Diode lasers

• Semiconductor lasers that emit near-infrared light (800-980 nm)
• Compact, efficient, and cost-effective compared to other surgical lasers
• Used for soft tissue surgery, dental procedures, and hair removal
• Can be used in contact mode or with fiber optic delivery systems

Excimer lasers

• Emit ultraviolet light (193-351 nm) generated by a combination of a noble gas and a halogen
• Precise tissue removal with minimal thermal damage due to high energy photons
• Used in ophthalmology for refractive surgery (LASIK, PRK) and treatment of corneal disorders

Laser surgery techniques

• Various laser surgery techniques are employed depending on the desired tissue effect and clinical application
• Proper selection and execution of the appropriate technique are essential for optimal surgical outcomes

Incision vs ablation

• Incision involves using a focused laser beam to create a precise cut in tissue
  • Commonly used with CO2 and erbium:YAG lasers for skin incisions and soft tissue surgery
• Ablation refers to the removal of tissue through vaporization or plasma-mediated processes
  • Used for precise tissue removal in ophthalmology, dermatology, and other specialties

Coagulation and hemostasis

• Laser energy can be used to coagulate blood vessels and control bleeding during surgery
• Coagulation occurs through thermal denaturation of tissue proteins and contraction of blood vessels
• Nd:YAG and diode lasers are commonly used for coagulation and hemostasis
• Technique involves defocusing the laser beam or using a larger spot size to distribute energy over a larger area

Tissue welding and soldering

• Laser energy can be used to join tissue edges together, reducing the need for sutures or staples
• Tissue welding involves using laser energy to denature tissue proteins, creating a bond between tissue surfaces
• Soldering uses a protein solder (e.g., albumin) to enhance the strength of the tissue bond
• CO2 and diode lasers are commonly used for tissue welding and soldering

Selective photothermolysis

• Principle of selectively targeting specific tissue structures while minimizing damage to surrounding tissue
• Relies on matching laser wavelength to absorption properties of target tissue and using appropriate pulse duration
• Used in dermatology for treatment of pigmented lesions, vascular lesions, and hair removal
• Requires careful selection of laser parameters based on tissue properties and clinical goals

Applications in ophthalmology

• Lasers have revolutionized the field of ophthalmology, enabling precise and minimally invasive treatments for various eye conditions
• Ophthalmology was one of the first specialties to adopt laser technology in clinical practice

Refractive surgery (LASIK, PRK)

• Laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) are used to correct refractive errors (myopia, hyperopia, astigmatism)
• Excimer lasers (193 nm) are used to reshape the cornea by removing precise amounts of tissue
• LASIK involves creating a corneal flap before laser treatment, while PRK ablates the surface of the cornea directly
• Wavefront-guided techniques use personalized measurements of the eye's optical aberrations to enhance visual outcomes

Glaucoma treatment

• Laser trabeculoplasty (SLT, ALT) is used to lower intraocular pressure in patients with open-angle glaucoma
  • Selective laser trabeculoplasty (SLT) uses a 532 nm Nd:YAG laser to target pigmented trabecular meshwork cells
  • Argon laser trabeculoplasty (ALT) uses a 488-514 nm argon laser to create thermal damage in the trabecular meshwork
• Laser iridotomy is used to create a hole in the iris to improve aqueous humor drainage in angle-closure glaucoma

Retinal photocoagulation

• Laser photocoagulation is used to treat various retinal disorders, including diabetic retinopathy, retinal vein occlusions, and retinal tears
• Thermal effects of laser energy are used to coagulate abnormal blood vessels, seal retinal tears, and stimulate tissue repair
• Common lasers used include 532 nm Nd:YAG, 577 nm yellow dye, and 810 nm diode lasers
• Micropulse laser techniques allow for more selective treatment with reduced collateral damage to the retina

Applications in dermatology

• Lasers have become an essential tool in dermatology for the treatment of various skin conditions and cosmetic concerns
• The selectivity and precision of lasers make them well-suited for targeting specific skin structures and pigments

Tattoo removal

• Q-switched lasers (Nd:YAG, alexandrite, ruby) are used to break down tattoo pigments into smaller particles that can be cleared by the immune system
• Different laser wavelengths are used to target specific tattoo colors (e.g., 532 nm for red, 1064 nm for black)
• Multiple treatment sessions are typically required for complete tattoo removal
• Picosecond lasers have shown improved efficacy and fewer side effects compared to traditional Q-switched lasers

Pigmented lesion treatment

• Lasers can be used to selectively target and remove benign pigmented lesions, such as age spots, freckles, and melasma
• Q-switched lasers (Nd:YAG, alexandrite, ruby) and intense pulsed light (IPL) systems are commonly used
• Selective photothermolysis is employed to target melanin while sparing surrounding skin
• Multiple treatments may be necessary, and post-treatment hyperpigmentation is a potential side effect

Vascular lesion treatment

• Pulsed dye lasers (PDL) and Nd:YAG lasers are used to treat vascular lesions, such as port-wine stains, hemangiomas, and telangiectasias
• Laser energy is absorbed by hemoglobin in blood vessels, leading to coagulation and vessel closure
• Cooling of the skin surface helps to minimize collateral damage and reduce side effects
• Multiple treatments are often required, and purpura (bruising) is a common temporary side effect

Hair removal

• Long-pulsed alexandrite, diode, and Nd:YAG lasers are used for permanent hair reduction
• Laser energy is absorbed by melanin in the hair follicle, causing thermal damage and inhibiting future hair growth
• Selective photothermolysis allows for targeting of hair follicles while sparing surrounding skin
• Multiple treatments are necessary for optimal results, and efficacy varies depending on hair color and skin type

Applications in dentistry

• Lasers have found numerous applications in dentistry, offering minimally invasive and precise treatment options for both hard and soft tissue procedures
• The use of lasers can reduce the need for traditional dental drills and improve patient comfort

Cavity preparation

• Er:YAG and Er,Cr:YSGG lasers are used for precise removal of dental caries and preparation of cavities
• Laser energy is absorbed by water and hydroxyapatite in tooth structure, allowing for selective removal of decayed tissue
• Advantages include reduced need for anesthesia, minimized vibration and noise, and preservation of healthy tooth structure
• Lasers can also be used for etching of enamel and dentin surfaces to enhance bonding of restorative materials

Soft tissue procedures

• Diode, CO2, and Nd:YAG lasers are used for various soft tissue procedures in dentistry
• Applications include gingivectomy, frenectomy, biopsy, and treatment of periodontal pockets
• Laser energy allows for precise cutting and coagulation of soft tissue, reducing bleeding and postoperative discomfort
• Lasers can also be used for photobiomodulation to promote healing and reduce inflammation after surgical procedures

Tooth whitening

• Laser-assisted tooth whitening involves the use of a high-intensity light source to activate a bleaching agent applied to the teeth
• Common light sources include halogen, LED, and diode lasers
• Laser energy helps to accelerate the breakdown of pigments and enhance the penetration of the bleaching agent into the tooth structure
• In-office laser tooth whitening can achieve faster and more dramatic results compared to at-home bleaching techniques

Applications in otolaryngology

• Lasers have been widely adopted in otolaryngology (ENT) for the treatment of various conditions affecting the ear, nose, and throat
• The precision and versatility of lasers make them well-suited for delicate procedures in these anatomical regions

Stapedotomy

• Stapedotomy is a surgical procedure used to treat otosclerosis, a condition that causes hearing loss due to fixation of the stapes bone in the middle ear
• Argon, KTP, and CO2 lasers are used to create a small hole in the stapes footplate to allow for placement of a prosthetic device
• Laser stapedotomy offers improved precision, reduced risk of damage to surrounding structures, and faster recovery compared to traditional techniques

Laryngeal surgery

• CO2 and KTP lasers are used for various laryngeal procedures, including removal of vocal cord lesions (polyps, nodules, cysts) and treatment of recurrent respiratory papillomatosis
• Laser energy allows for precise excision of lesions while preserving surrounding healthy tissue
• Advantages include reduced bleeding, faster healing, and improved postoperative voice outcomes
• Lasers can also be used for transoral laser microsurgery (TLM) of laryngeal cancers, offering organ preservation and reduced morbidity compared to open procedures

Nasal and sinus surgery

• Diode and Ho:YAG lasers are used for various nasal and sinus procedures, including turbinate reduction, septoplasty, and treatment of nasal polyps
• Laser energy allows for precise removal of tissue and reduction of bleeding, improving visualization and reducing the need for nasal packing
• Laser-assisted functional endoscopic sinus surgery (FESS) can be performed for the treatment of chronic rhinosinusitis and other sinus disorders
• Advantages include reduced tissue trauma, faster healing, and improved postoperative patient comfort

Safety considerations

• Laser safety is of paramount importance in any medical setting to protect patients, healthcare providers, and other personnel from potential harm
• Proper training, safety protocols, and protective equipment are essential for the safe use of lasers in surgery and therapy

Eye protection

• Appropriate eye protection must be worn by all personnel in the laser treatment room to prevent eye injuries from direct or reflected laser light
• The type of eye protection required depends on the laser wavelength and power output
• Patients undergoing laser procedures near the eyes (e.g., facial treatments) must also have their eyes protected with appropriate shields or goggles

Smoke evacuation

• Laser-tissue interactions can generate smoke plume containing potentially harmful particles, gases, and biological materials
• Adequate smoke evacuation systems must be used to remove smoke plume from the surgical field and protect personnel from inhalation
• High-efficiency particulate air (HEPA) filters and ultra-low particulate air (ULPA) filters are used in smoke evacuation systems to capture fine particles

Anesthesia and sedation

• Many laser procedures require local or general anesthesia to ensure patient comfort and safety
• The choice of anesthesia depends on the type and duration of the procedure, patient factors, and physician preference
• Proper monitoring of vital signs and airway management are essential during laser procedures under anesthesia or sedation

Postoperative care

• Patients should receive clear instructions for postoperative care after laser surgery to promote healing and minimize complications
• Instructions may include wound care, pain management, activity restrictions, and follow-up appointments
• Patients should be informed about potential side effects and complications, and when to seek medical attention

Advances in laser therapy

• Ongoing research and technological advancements continue to expand the applications and improve the outcomes of laser therapy in medicine
• Novel laser systems, treatment strategies, and combination therapies are being developed to address a wide range of medical conditions

Low-level laser therapy (LLLT)

• Also known as cold laser therapy or photobiomodulation, LLLT uses low-power lasers to stimulate cellular processes and promote tissue healing
• LLLT has been studied for various applications, including wound healing, pain management, and tissue regeneration
• Proposed mechanisms of action include increased ATP production, modulation of inflammatory pathways, and stimulation of stem cell proliferation and differentiation
• While promising, further research is needed to establish optimal treatment protocols and efficacy for specific clinical applications

Photodynamic therapy (PDT)

• PDT involves the use of a photosensitizing agent that is activated by specific wavelengths of light to generate reactive oxygen species and induce cell death
• PDT is primarily used for the treatment of various cancers, including skin, lung, esophageal, and bladder cancers
• Advantages of PDT include selective targeting of tumor cells, reduced systemic toxicity, and the ability to repeat treatments as needed
• Ongoing research aims to develop new photosensitizers, improve light delivery systems, and expand the clinical applications of PDT

Nanoparticle-enhanced laser therapy

• The use of nanoparticles in combination with laser therapy has emerged as a promising strategy to enhance the specificity and efficacy of laser treatments
• Nanoparticles can be designed to absorb specific laser wavelengths, enabling targeted delivery of laser energy to desired tissues or cells
• Gold nanoparticles have been extensively studied for applications in photothermal therapy of cancer, where laser energy is converted to heat to destroy tumor cells
• Other nanoparticle systems, such as carbon nanotubes and quantum dots, are being investigated for various therapeutic and diagnostic applications in laser medicine