Journal of Clinical and Aesthetic Dermatology

FEB 2018

An evidence-based, peer-reviewed journal for practicing clinicians in the field of dermatology

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Page 18 of 62

16 JCAD JOURNAL OF CLINICAL AND AESTHETIC DERMATOLOGY February 2018 • Volume 11 • Number 2 R E V I E W visible, compared to the highly visible, shorter- wavelength lasers (e.g., KTP laser), and can pose a hazard when the beam goes unnoticed. 8 Various mathematical prediction models have been created to predict the temperature distribution in laser radiation of the human eye to evaluate the risk of ocular damage by lasers. 9–12 Components of the eye injured by lasers. Various parts of the eye can be injured by lasers, and the damage can be minor to severe. Minor thermal injury to the cornea results in severe pain, as the cornea has a high density of pain receptors. 13 However, corneal injury seldom produces significant vision impairment when confined to the corneal epithelium. 14 When injured, the lens and retina are two components that can significantly impact organ function. Injury to the lens can lead to decreased vision in the affected eye through cataract formation. The retina, which is responsible for converting light stimuli into a visual image in the brain, is particularly vulnerable to lasers in the visible to near-infrared spectrum (400nm–1400nm), known as the retinal hazard region. 7 Light in this spectrum is focused by the lens onto the retina, leading to 105 times greater retinal irradiance than corneal irradiance. 15 As many of the lasers used in dermatology fall within this spectrum, caution should be undertaken when operating cosmetic lasers, especially on the upper face. Reports in the literature. As cosmetic laser procedures of the face have become more popular in the past decade, there has been an increase in the number of reported injuries to the eye. The most highly reported injury stems from laser hair removal of the periorbital areas. 3, 6,16–22 Commonly used lasers for this procedure include the 755nm alexandrite and various diode (800–983nm) lasers. All are long wavelength lasers that are capable of causing severe injury to the eye. In fact, from 1985 to 2012, one study found that laser hair removal was the most common litigated procedure in cutaneous laser surgery, with four reported claims of eye injury. 23 For other cosmetic treatments of the face, laser injury to the eye was reported during the treatment of periorbital vascular lesions, 24 laser skin resurfacing, 25 and other unspecified cosmetic procedures. 7,26,27 Eye injury from facial treatment by intense pulse light (IPL) has also been reported. 28 In the 21 case reports analyzed from the literature (PubMed), the patients experienced a variety of ocular injury, including iris atrophy, cataracts, anterior uveitis, glaucoma, visual field defects, posterior synechiae, and pupillary defects (Table 1). In all cases, ocular injuries were immediately apparent after treatment with the laser. Common immediate signs and symptoms included severe eye pain, temporary loss of vision, and conjunctival erythema. In 13 of the 21 (62%) case reports examined in this review, proper eye protection was either not provided to the patient or the patient was asked to remove the protection device during the procedure to treat areas near the eye that could not be reached over the shield. This highlights the critical need for clinicians and aestheticians to provide proper eye protection to patients when treating the face, and for them to ensure that such devices stay on the eyes for the duration of treatment. However, ocular protection devices are not fail- safe. In 33 percent of cases in which eye protection was provided, 16,25 such as metal corneal shields and wavelength-specific glasses, severe injury to the eye also occurred, including bilateral bullous keratopathy in a patient who underwent carbon dioxide laser facial resurfacing. 25 Mechanism of injury was likely due to overheating of the metal corneal shields during the long procedure and inadequate cooling between laser pulses. 25 OCULAR PROTECTION AND LASER SAFETY MECHANISMS Laser goggles and eyewear. Different safety measures ensure that the eye and other vulnerable parts of the body are protected from injury by lasers. One of the most basic eye protections is the use of wavelength-specific goggles or spectacles during procedures. In one study of 40 patients with ocular injury, only six (15%) patients were wearing protective eyewear during the use of lasers; five of the six were not wearing proper wavelength-specific eyewear. 14 Eyewear should be snugly fitting and comfortable, and should not be removed during treatment, especially during laser alignment. For treatments involving Nd:YAG lasers, it is possible for laser radiation to be reflected back from shiny mucosal surfaces into the observer's eye, potentially causing injury to the user. 29 Thus, eye protection is also essential for observers and operating personnel. Corneal eye shields. Corneal eye shields, made of various colors and materials, are designed to fit directly on the patient's eyes, just like contact lenses. When treating the areas around the eyes, laser-impenetrable metal ocular shields must be worn for the duration of treatment. The recommended corneal shields fit behind the eyelids, as they are less likely to shift during treatment. 30 There are many types of metal corneal shields available, including the Cox II shield (Oculo-Plastik; Montreal, Canada), the Stefanovsky shield (Bernsco; Seattle, Washington), and the Khan shield (Storz; St. Louis, Missouri). The Cox shield is thinner than the Stefanovsky shield, leading to higher temperature changes on laser pulses that can cause thermal injury of the cornea at higher fluences and longer wavelengths due to heat conduction on the underlying tissues. 31 This might be the mechanism of injury in reports of patients who suffered corneal thermal injury after laser treatment, despite intact and properly placed metal corneal shields. We recommend applying one pulse at a time and moving on to a different area, which will allow the treated area to cool sufficiently and prevent heat retention on the thin corneal shields. Cooling gel and ice packs should also be applied to treated areas in between pulses. Metal eye shields can also be irritating to the eye and might leave certain parts of the eye vulnerable, such as the superior conjunctival fornix. 32 To prevent injury to this part of the eye, a large metal blade can be placed between the upper eyelid and the globe, then fixed to a toothed clamp, such as the David Baker (Oculo-Plastik) and Khan-Baker (Storz) eyelid clamps, on the upper eyelid. 30 Use of these clamps might be uncomfortable to the patient and can cause mild crush injury to the upper eyelid. 30 Two studies have examined the safety of corneal eye shields in facial laser treatments. One study found that, when irradiated by a 585nm PDL, the temperature rise at the surface of the shields, whether metal or plastic, was no more than 0.2°C. 33 The authors noted that while the metal corneal shield (Stefanovsky) did not allow light transmission or have an appreciable temperature rise, the reflective potential of the metal shield posed a risk to operating personnel. In addition, the rough, sharp edges of the metal shield could potentially cause corneal abrasions in the patient. There has only been one published case of bilateral corneal abrasions from the use of metal eye shields after laser skin resurfacing. 34 In a different study, however, all plastic shields melted or caught fire when exposed to radiation by Nd:YAG and carbon dioxide lasers. 31,35 Thus, long wavelength lasers could potentially cause severe thermal injury to patients, when using plastic shields.

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