ABSTRACT

Laser devices are widely used for medical, military, industrial and entertainment purposes. This extensive and unregulated use of lasers can cause a variety of maculopathies that can result in permanent vision loss. Uncontrolled and inappropriate use of laser instruments should be prevented with strict rules. We strongly emphasize the importance of changing the general misperception that lasers are safe to use for entertainment purposes. In this study we aim to report the clinical features of three patients with a history of maculopathy caused by exposure to laser light in an entertainment venue.

Introduction

The laser, whose name originated as an acronym for ‘Light Amplification by Stimulated Emission of Radiation’, was first developed in 1960.¹Following animal studies, laser devices became widely used in a range of fields for medical, industrial, research and entertainment purposes. As the usage of lasers became more common, the incidence of laser-related injuries also increased.²Because visible and near-infrared light are focused and concentrated on the retina, this tissue is most susceptible to laser-related injury.³Reports of retinal laser injuries include subretinal hemorrhage, retinal edema, damage to the retinal pigment epithelium, vitreous or chorioretinal hemorrhage, perifoveal pigment changes or deposits, foveal ring-shaped hypopigmented lesions and rarely, choroidal neovascularization.⁴We aimed to present two cases of foveal subhyaloid hemorrhage and one case of subfoveal intraretinal hemorrhage associated with laser burns.

Discussion

With the widespread use of lasers in various fields and the retina’s sensitivity to laser light, laser-induced ocular injuries are commonly encountered in ophthalmology practice. The American National Standards Institute defined four classes of laser device based on their potential risk.⁵In this classification system, red-orange lasers with up to 1 mW of output power and longer wavelengths are in class II; green-blue lasers with up to 5 mW output power and shorter wavelengths are Class III. Exposure to class III and IV lasers can result in injury to the eyes and skin.^2,4,5Laser-induced ocular injuries may result from ablative, thermal or photochemical mechanisms depending on factors related to both the laser and the eye, including laser power, wavelength, spot size, exposure time, pupil diameter, proximity to the fovea, and amount of retinal and choroidal pigmentation.^2,4The main laser-related determining factor in retinal damage is the wavelength of the incident light.²Visible and near-infrared incident light with wavelength between 380 and 1400 nm damages the retina. The damage increases in severity with longer exposure times. The blinking reflex and flinching in response to laser light limits laser exposure to between 0.15 and 0.25 seconds; these mechanisms serve as natural protection against laser-induced damage. Other important laser-related factors determining damage severity are pulse duration and energy level. High-energy and short pulses cause more damage to the retina.²In our cases, we could not learn specific details regarding the wavelength, power and duration of the lasers our patients were exposed to; therefore, we do not know the laser class and duration of exposure that caused their retinal injuries. However, there are many reports in the literature of macular damage caused by class IIIA and higher lasers.^6,7,8,9,10The main retinal injuries reported related to class IIIA lasers are retinal pigment epithelium alterations; subretinal, intraretinal, subhyaloid and vitreous hemorrhages; epiretinal membrane; and full-thickness macular holes. The prefoveal hemorrhage observed in two of our cases and subfoveal hemorrhage in the other suggest that the lasers were Class IIIA.

The most important eye-related determining factor in laser-induced ocular damage is its localization on the retina. The resulting functional loss increases proportionately to the proximity of the damage to the fovea. With increasing distance from the fovea, the resulting scotomas are usually asymptomatic. Another factor related to the eye is pupil size. Because pupil dilation in dark environments allows more light to reach the retina, the resulting damage is more severe than that incurred in light environments. Furthermore, in individuals with more retinal and choroidal pigmentation, melanin absorbs more laser light, which leads to more severe injuries.^2,4

Laser-induced hemorrhage may occur in different layers of the retina, and treatment options vary based on which layer is involved. In a report by Alsulaiman et al.⁹of seven cases of intraocular hemorrhage associated with high-power lasers, five patients developed subhyaloid hemorrhage and two patients sub-ILM hemorrhage. Neodymium: yttrium-aluminum-garnet (Nd:YAG) hyaloidotomy was performed in all patients with subhyaloid hemorrhage; the procedure resulted in a rapid improvement in vision in three patients, but was unsuccessful in the other two. The two patients with sub-ILM hemorrhage were followed; during follow-up their hemorrhages spontaneously regressed and visual acuity improved. Similarly, two of our cases developed subhyaloid foveal hemorrhage, but unlike the other reports we achieved anatomic and functional success in these cases with surgery including 23-G PPV, posterior hyaloid dissection and ILM peeling.

The humanized monoclonal antibody bevacizumab (Avastin; Genentech /Roche, San Francisco, CA, USA) is used in the treatment of many retinal diseases, primarily choroidal neovascularization and age-related macular degeneration. Bevacizumab selectively inhibits VEGF, prevents abnormal vasculature formation and limits vascular permeability.^11,12Considering these effects of anti-VEGF therapy, we applied a total of three intravitreal anti-VEGF injections at one-month intervals in our patient with subretinal hemorrhage, despite the lack of clear guidance on this topic. An increase in visual acuity was achieved, atrophy at the fovea and damage at the IS/OS border resulted in permanent functional loss.

Another type of laser-related retinal injury is full-thickness macular holes. In a study by Alsulaiman et al.,⁹laser-induced full-thickness macular hole was observed in four cases; anatomic and functional success was achieved in these patients with PPV, ILM peeling and silicone or gas tamponade injection.

Conclusion

Outside the medical and military fields, the use of lasers ranging from 5 to 1200 mW has become very common in entertainment centers, presentations and meetings or as toys. Our natural protective mechanisms are insufficient for lasers of this power, and extremely severe, permanent functional losses may result. Restraining the uninformed use of high-power lasers by the general public through legislation and educating the public about the harmful effects of laser light are crucial to prevent laser-related permanent retinal injuries.