• Four main concerns: blindness, fire hazards, cutaneous burns, and inhalation of biohazardous plume

• Blindness

■ Up to 7% of emitted laser light is reflected by the stratum corneum ➔ reflected light can cause eye damage/blindness (may occur if even 1% of the beam is reflected into eye)

■ Blindness is rapid and painless

■ Any laser/light source in UV range ➔ lens damage, cataracts

○ Example: excimer laser (308 nm)

■ Any laser/light source that targets melanin or hemoglobin (visible light and near-infrared wavelengths) ➔ retinal damage (retina is highly pigmented); also damages uvea and iris

○ Examples: KTP (532 nm), PDL (585–600 nm), ruby (694 nm), IPL (various wavelengths), alexandrite (755 nm), diode (800 nm), and Nd:YAG (532 nm and 1064 nm)

○ Highest risk = near infrared and Q-switched lasers

■ Any laser/light source that targets water (mid and far-infrared wavelengths) ➔ corneal/scleral damage

○ Examples: Nd:YAG (1320 nm), Erbium:glass (1550 nm), Erbium:YAG (2940 nm), and CO₂ (10 600 nm)

• Fire hazard

■ Greatest fire risk with CO₂ and Erbium:YAG ablative and fractionated lasers

■ Risks: drapes, clothing, dry hair, and plastic tubes (endotracheal tubes, especially if oxygen is being administered)

■ Prevention: moisten hair near treatment field, ensure that any alcohol/acetone skin cleanser has fully dried before using laser, and reduce intraoperative O₂ concentration <40%

• Cutaneous burns: may occur with any laser or nonlaser energy source (IPL and RF); as a result of operator error

• Inhalation of biohazardous plume

■ HPV viral particles have been detected in laser plumes ➔ cases of laser-surgeons developing HPV-16-induced oral SCC related to inhalation

■ Prevention: ventilation and/or smoke evacuator; also recommend N95 mask

• Commonly treated vascular lesions: blood vessels as a result of photoaging, redness associated with (a/w) rosacea, spider angiomas, Poikiloderma of Civatte, hemangiomas, vascular malformations, redness in striae, redness in scars, verruca vulgaris, and Kaposi sarcoma (less common)

• Utilize selective photothermolysis to damage blood vessels via coagulation of vessel contents ➔ vessel collapse or destruction

• Target: hemoglobins (oxyhemoglobin > deoxyhemoglobin > methemoglobin)

■ Absorption peaks = 418, 542, and 577 nm

• Main SE = purpura (primarily PDL)

■ Other SEs dyschromia (↑risk in darker skinned patients), blistering (↑risk with shorter pulse widths, higher fluences, and skin of color)

• Skin cooling via precooling is critical ➔ prevents epidermal damage

■ Also allows for greater patient comfort and allows physician to treat at higher, more efficacious fluences

• General anesthesia is recommended for larger pediatric lesions

• Site of eye damage: retina

• Consider HSV prophylaxis for perioral lesions, or larger facial malformations

• Desired treatment endpoints:

■ PDL – purpura (as a result of cavitation and vessel rupture)

○ Nonpurpuric regimens utilize pulse durations of 20 ms or higher ➔ do not get cavitation or vessel rupture ➔ do not get immediate purpura (but frequently get delayed purpura days later)

■ KTP, Nd:YAG – immediate disappearance of vessel

• Complex vascular lesions typically require several treatments

• Boards fodder:

■ PDL (585–600 nm) is the treatment of choice for most vascular lesions (PWS, telangiectasias, erythematous scars, and hemangiomas)

■ IPL is the TOC for Poikiloderma of Civatte (treats both the vessels and dyschromia)

○ If IPL is not an option on the examination, PDL would be second best choice

■ Long-pulsed Nd:YAG (1064 nm) is the laser of choice for most vascular ectasias on the lower leg (venulectasias, telangiectasias, and reticular veins), because it penetrates deeper than other vascular lasers

○ Diode (800 nm) would be the second best choice

■ IPL or long-pulsed PDL (nonpurpuric) are the treatments of choice for erythematotelangiectatic rosacea

• Common laser hair reduction uses: removal of unwanted hair, pseudofolliculitis barbae, hidradenitis suppurativa, and pilonidal cyst disease

• Laser hair reduction is based upon the principle of selective photothermolysis

• Target: melanin within hair shaft, ORS, and matrix

■ Absorption peaks: broad range (~300–1000 nm)

• Destruction of bulge and bulbar stem cells ➔ improved hair removal

• Dark, thick terminal anagen hairs respond best

■ Thinner, lighter hair is hard to remove

■ White hair is impossible to remove (lacks target chromophore) ➔ other epilation techniques recommended

• Adverse effects:

■ PIH (↑ in skin of color)

○ Recommendation: treat test spot and follow up in 1 to 2 weeks

■ Leukotrichia

■ Blistering/burning (↑risk in skin of color) may ➔ scarring

• Site of eye damage: retina

• Requires multiple treatment sessions, spaced 4 to 6 weeks apart; treatments often not permanent ➔ goal is “reduction, rather than removal”

• Recommend shaving before treatment in order to shorten hairs ➔ ↓skin burns from hairs on skin surface

• Do NOT fully remove hair shafts by chemicals, waxing, plucking, or threading for at least 6 weeks before treatment (eliminates target chromophore)

• Desired treatment endpoint = transient perifollicular edema

• Use wavelength-specific eyewear to protect retina

• Use parallel cooling to protect the epidermis during treatment

• Boards fodder:

■ Diode is most efficacious; usually safe in skin of color (but not as safe as Nd:YAG)

■ Nd:YAG (1064 nm) = safest hair removal laser in skin of color, but slightly less effective (Table 9-3)

• Common indications: rhytids, photoaging and actinic damage, acne scars, keloid, hypertrophic and burn scars, postsurgical scars, benign skin lesions (SKs/warts/syringomas), striae, and rhinophyma

• Target: water

■ Absorption peaks: 1450, 1950, and 3000 nm

• May be ablative or nonablative

■ Ablative lasers function by removing skin via vaporization of target tissue

■ Nonablative lasers work via subtle thermal effects on dermis ➔ stimulates a wound healing response

• May be fractionated or nonfractionated

■ Fractionated: creates thousands of microscopic thermal zones of injury (MTZ) ➔ stimulates turnover/remodeling of epidermis and dermis

○ Advantages: ↓downtime and ↓duration of erythema compared with nonfractionated resurfacing

○ Disadvantages: less efficacious; requires more treatment sessions

• Site of eye damage: cornea, sclera (burns)

• Consider HSV/fungal/bacterial prophylaxis

• Adverse effects:

■ Erythema (often persists for months)

■ Hyperpigmentation

■ Relative hypopigmentation (↑risk if deeper injury; may arise months after treatment)

■ Milia

■ Secondary infections

○ HSV: highest risk in first week

○ Bacteria (S. aureus, Pseudomonas)

■ Scarring

• Tattoo pigments are very small in diameter ➔ very short TRT (nanoseconds) ➔ QS-lasers are required

• Immediate tattoo whitening (desired endpoint) is a result of cavitation

• Amateur tattoos and black tattoos are the most responsive to treatment (usually <5 treatment sessions)

• Professional tattoos and multicolored tattoos most difficult to treat (>10 treatment sessions)

• Boards fodder:

■ Mnemonic: “The 3 B’s (black, brown blue tattoos) RAN away when they saw the 3 lasers” ➔ all 3 colors are treated with Ruby, Alexandrite, or Nd:YAG

■ Mnemonic: “If you have a Yellow, White, Red, or Violet tattoo, You Will Return Visit for 2 or more treatments with frequency-(2)doubled Nd:YAG”

■ Only ruby and alexandrite treat green tattoos

■ Red tattoos (cinnabar [mercuric sulfide]) ➔ most likely to cause allergic reactions

■ Laser treatment in patient allergic to tattoo dye ➔ possible anaphylaxis

■ White tattoos may undergo immediate paradoxical darkening (turns black or blue) with laser because of reduction of Ti⁴⁺➔Ti³⁺

■ Pink, flesh-toned, or light red tattoos (classically, permanent lip liner) may undergo immediate paradoxical darkening (turns brown-black) with laser because of reduction of ferric oxide (Fe³⁺) ➔ ferrous oxide (Fe²⁺)

■ Traumatic tattoos from gunpowder/fireworks ➔ may explode with laser

■ Pigmented lesions (lentigines, ephelides, or nevus of Ota) are treated with the same lasers as black tattoos (“RAN” lasers)

○ Ruby is classically the laser of choice for nevus of Ota/Ito

■ Minocycline hyperpigmentation ➔ treated with the same lasers as black tattoos (“RAN” lasers)