LASER stands for Light Amplification by Stimulated Emission of Radiation. It owes its origins to the discovery, made in early twentieth century, of two principles of quantum physics. Laser production is based on these principles.

Laser is a highly concentrated beam of light able to generate high temperatures. Its ability to burn through materials soon led to the realization of its potential in medicine. The non-invasive nature of laser was an additional attraction. Laser became a truly valuable tool in medicine when it was adapted to the operating microscope and when the instrument, endoscope, facilitated its extensive use.

Laser and clinical treatments

Understanding of laser- tissue interactions is important, since it determines laser selection. Laser emits light at various wavelengths, which are absorbed, reflected or transmitted by the body tissues in various proportions. For a surgeon, the desired properties of a laser light are absorption and scattering. For tissue removal, lasers that are well absorbed by the tissues should be used. If coagulation is the goal, then the tissue should be able to scatter the laser. Scattering reduces the laser power and allows for coagulation rather than cutting. Precision surgery is made feasible by manipulating the balance between coagulation and cutting.

The laser heats up the tissue. This heat can be conducted to nearby untargeted tissues and produce adverse effects. Conduction is, therefore, an issue, which becomes significant when delicate tissues are involved. Heat generated by the laser should be sufficient to destroy the target without causing damage to adjacent tissues.

Laser selection also depends on the depth of the targeted tissues. Tissues, deep inside the skin surface, need deep penetrating long wavelength lasers while those at shallower depths would need radiations of short wave lengths to reach them.

Vascular laser treatments

Vascular lesions are enlarged blood vessels. Vascular laser treatments are a common procedure, based on the principle of selective photothermolysis. Despite limitations, it remains the preferred treatment. Lasers are used to selectively destroy abnormal blood vessels by targeting the chromaphore hemoglobin. Laser choice is determined by vessel depth and diameter, laser wavelength, pulse width to match the thermal relaxation time and to a limited extent spot size. Parameters like, fluences are based on patient’s threshold levels for tolerance, in order to minimize the chances of adverse effects.

Eye care laser treatments

There are presently three procedures for laser eye treatments. Photorefractive keratectomy or PRK- the first to be used for correcting myopia, laser assisted in situ keratomileusis or LASIK- an improvement over PRK and LASEK or laser assisted subepithelial keratomileusis.

All three procedures are effective in near or far sightedness, with or without low to moderate astigmatism. Discomfort is less and recoveries faster with LASIK, but chances of complications are higher. Regression is higher with PRK. Complications occur with all procedures. These include visual disturbances and at night, multiple images. For myopia of 6 to 10 dioptres, LASIK may be a better option. LASIK is not an option in cases of inadequate corneal thickness and moderately dry eyes.

All these procedures require intensive pre-operative screening. Typically, patients have to be above 21 years of age.

Skin care laser treatments

Lasers are today used to treat a huge and increasing numbers of skin lesions. Treatments include removal of pigmented lesions, skin resurfacing, scar removal, tattoo removal and low energy laser therapies.

CO2 laser is used in a majority of these lesions. Water is the targeted chromaphore. Water superficially absorbs the laser energy, which limits the penetration depth and makes CO2 laser effective in superficial skin lesions.

The 585nm pulsed dye laser targets the chromaphore hemoglobin. This high-energy short-pulsed laser very selectively destroys targets with minimal collateral damage, resulting in low incidence of scarring.

The argon laser targets hemoglobin and melanin. Because it is continuous, risk of scarring is high. Another limitation is its low penetration.

The 1064nm Nd: YAG is effective in opaque darker tissues. The pulsed-dye pigmented and the Q-switched Ruby lasers are effective in seborrheic keratoses.

Skin disease laser treatments

Skin diseases treated by laser include certain cancerous conditions, actinic keratoses, acne, psoriasis, vitilligo and hair removal. Distinguishing feature of these treatments is the use of laser with photodynamic therapy or PDT

While in a few cases, PDT with laser has been proposed as treatment of choice, overall, its role in treating some cancerous conditions is not clear. Also, the treatment of psoriasis and vitilligo has seen the introduction of 308nm excimer laser, which represents the latest advance in the concept of selective photo therapy.

Conclusion

Laser treatment as a non-invasive procedure represents a major advance in medical treatment, despite its limitations. In the coming years, the rising tides of an evolving technology will surely raise the boat of laser treatment to a position of pre-eminence in medical therapy.