The discovery of laser has changed the face of medical surgery. Compared to conventional surgeries, lasers offer a safer, more effective and predictable non-invasive surgical alternatives. Nevertheless, concerns remain, as it is not a painless procedure and produces adverse effects that need adequate post-treatment regimens.

What are lasers?

LASER is an acronym for Light Amplification by the Stimulated Emission of Radiation.

Lasers are defined and distinguished from ordinary light by three properties. They are:

• Collimated, meaning, all laser rays travel in the same direction. They remain pencil thin, retain their intensity over long distances, and are therefore able to burn through materials.
• Coherent, meaning, all laser waves have same wavelength are in phase with each other. Coherence increases the amplitude or power, increasing the radiance of a laser beam.
• Monochromatic, meaning, the laser is of one color or composed of a narrow band of colors or wavelengths. Light to be coherent must be monochromatic.

Laser development and clinical laser history

Laser production is based on two principles of quantum physics, enunciated by Bohr. The first principle says that light consists of, not continuous waves, but discrete bundles of energy or photons. The second principle says that all atoms are usually in their state of rest. But due to absorption of energy from the atmosphere, some atoms are always in their higher excited states. This excited state can be maintained for only a very short period. The atom soon returns to its state of rest, in the process spontaneously releasing photon or photons traveling in a random direction. All light in nature is spontaneously emitted.

Einstein theorized that if a photon, with the appropriate energy, were to energize an atom, an identical photon traveling in the same direction would be released. These new photons, in turn, could energize more atoms releasing more photons, setting off a multiplier effect. It was postulated that if millions of atoms in a container were simultaneously stimulated by the same source, millions of photons with identical wave lengths, in the same phase and traveling in the same direction would be spontaneously released resulting in a narrow concentrated beam of light that was later termed LASER.

Laser production needs a medium whose atoms are to be stimulated. The first laser used a synthetic ruby crystal as a medium and a flash lamp to stimulate the atoms. The ruby laser was the first to be used as a surgical tool in eye surgery. Laser systems are named after their mediums.

The He:Ne lasers, introduced in 1960, were the first continuous mode lasers. Today it is widely used in telecommunications. In surgery, He:Ne lasers are used with invisible lasers to impart visibility. The advent in 1964 of the invisible CO2 laser was an important event. Laser became a valuable surgical tool only when the CO2 laser was adapted to the microscope in 1972. CO2 lasers are the most used lasers today.

In 1964 the Nd: YAG and the argon lasers were developed. In 1981 the potassium titanium or the KTP lasers was introduced. The excimer laser and the tunable dye lasers are recent additions.

Laser treatment received a big fillip when laser laproscopic cholecystectomy was accepted as standard treatment in symptomatic biliary disease. It received a further boost when laser was adapted to the endoscope, enabling viewing of incisions by video.

Lasers and tissues

For improved clinical practice, it is important to understand laser tissue interactions. The laser properties of collimation, coherence and monochromicity are the basis for laser therapeutic applications. Monochromicity is a critical property as it allows selective chromophore absorption of single wavelengths. Wavelength also determines laser penetration. In general, long wavelengths penetrate more than short wave length. Collimation and coherence allows laser to travel long distances through optic fibers without loss of light.

In laser applications, two properties, power and energy density, also known as irradiance and fluence respectively, are critical. Irradiance is energy per area of application and is expressed as watt/sq.cm. Tissue cutting needs high irradiance and coagulation low irradiance. Fluence is the power produced at any time on unit area. It is measured as watts x time and expressed as joules/sq.cm. High wattage and shorter application time would produce rapid tissue heating and low wattage and longer time would result in gradual tissue warming.

Laser is transmitted, reflected, absorbed or scattered by tissues. In surgery, absorption and scattering are more desired outcomes. Cutting needs light that are absorbed and coagulation needs light that are scattered Scattering, reduces power intensity and allowing coagulation rather than cutting. Precision in surgery is obtained by manipulating absorption and coagulation

Lasers and legal negligence

Legal issues are causing increasing concern in cosmetic skin treatments. The standard complaint is negligence in case of unsatisfactory outcomes. Negligence can be proved only if the plaintiff is able to show the presence of all four components that comprise negligence. These are duty, breach of duty, causation and damages. In such cases, even the physician extender and an internist will be held to the standard of a physician.

The standards of care are derived from no law books and are always changing. At any time, it is an imprecisely defined concept, hewed from differences and inconsistencies between the medical profession, the legal system and the public. There are differences within the medical community regarding standards. What is the sanctity of elucidations in courts by expert witnesses if they vary from those of other equally able experts?

The field of skin laser treatment is itself beset with problems. The increasing reliance on laser technology has led to unrealistic public expectations. The physicians are always attempting innovations for which there are no standards. Surgeons have started seeing themselves also as artists.

There are no easy answers. Case by case approach may have to be taken. Therefore, some sort of universally applicable guidelines, which can be a benchmark for standards will have to be developed. That allows flexibility in defining standards, especially in some rapidly evolving areas, such as, laser technology.

Anesthesia for laser treatments

In topical treatment, cryoanesthesia-the use of cold to anesthetisize - is an old treatment. Refrigerant sprays and ice packs are cheaper alternatives.

The eutectic mixture local anesthetic cream (EMLA) is used in painful tattoo treatments. EMLA is not advised in infants for more than a month and is now restricted to adults and adolescents.

Infiltrative anesthesia like, lidocaine administered intradermally or subcutaneously, is a common anesthetizer. It acts quickly and lasts from 30 to 120 minutes. Being an amide, chances of allergic reactions are less compared with ester anesthetics.

Nerve blocks can anesthetize large skin areas with a small amount of anesthesia. Oral sedations are used mostly in children who have low pain tolerance. Intravenous sedation is given in painful laser treatments. General anesthesia may be the only option in children with vascular lesions.

Skin care post laser treatments

Almost all laser treatments need good post care regimens. Vascular lesion treatment causes purpura, erythema and edema. A topical antibiotic ointment should be applied to the irradiated areas and sun exposure should be avoided.

Tattoo and pigmented lesion treatments cause an ash-white tissue response. The treated skin is cleansed with mild soap twice daily for 1 to 2 weeks and antibiotic applied subsequently until the areas are healed.

In all treatments of lesions and scars, the skin after irradiation is very delicate and must be handled with care. Showers are allowed but not prolonged bathing. Gently dry the skin. Do not take aspirin. Use ice to prevent or reduce swelling. Avoid swimming and contact sports.

After skin laser resurfacing, the treated areas should be kept moist by healing ointments. Patients who had large areas resurfaced or patients with herpes labialis are advised a 10-day course of antiherpetic medication are.

Laser treatment side effects

All laser treatments produce virtually the same set of side effects at variable rates of occurrence. Erythema and edema occur in all cases. Hyper and hypo pigmentation occur mostly when pigmented lesions or tattoos are removed. Skin texture changes and scars are commonly due to excessive fluences. All pulse dyed treatments cause purpura and hyperpigmentation. Continuous wave systems do not cause purpura. Generally, the less selective continuous wave lasers cause more side effects than pulsed lasers.

Causes of side effects are mostly low operative skill, patient traits, skin pigmentation, pre-existing medical conditions, sun exposure or inadequate wound care. Advanced techniques like selective photothermolysis have reduced side effects. Nevertheless, errors are made.

Conclusion

Optimal laser treatment requires, besides laser irradiation, pre-treatment preparation and post-treatment care for any adverse side effects. Laser technology is continuously making strides. Laser specific anesthesia and advanced post treatment regimens are needed. Poor laser tolerance in children is still a problem.