How do Laser Pointers Damage your Retina?

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Lasers are devices used for many applications, for instance, in CD burning and reading, to baffle an audience in a light show or to point out details on a projector. The handheld laser or laser pointer is not given much thought, never mind that it could be seen as a dangerous object. And although the vast majority of market-available laser pointers are completely safe and even carry a warning, incidents occur. Goofing children or adults are seriously hurt due to over exposure to a laser device into their eyes, causing vision impairment that can last for life. Although your eyes provide some natural protection against intense flashes of light, such as the blinking reflex, damage can occur before this sets in. Additionally, a person can be unaware that damage is being inflicted onto the retinal region of their eyes and therefore continue looking into the laser. In some scenarios, the label on the laser does not correspond to the actual power of a laser and therefore it can be hard to know what lasers are safe and for which laser you need protective gear. In this project, we will be exploring damage caused by a visible spectrum laser to the retina of a human eye. We will investigate the thresholds of time and laser power before thermal damage to the retina is caused. To this end, we will be using a 2D axisymmetric model of the retina undergoing heating through a laser at a fixed point. We will be analyzing several factors that can determine the extent of thermal damage to the retina and will analyze different wavelengths or colors of visible spectrum laser light. Through changing parameters, we have found that wider beams are safer compared to more narrow beams as the power output of these lasers is less condensed. Furthermore, it is shown that power is linearly proportional to the heating of the retinal region. Additionally it is shown that cornea thickness, which is related to age, as elderly people tend to have thinner corneal regions, is not a significant factor in retinal damage. The visible wavelengths considered in this project did not significantly influence the heating of the fovea. The FDA has clear guidelines regarding laser power and as shown by the model in this paper these are justified as power is a clear indicator of danger and high powered lasers should be handled with caution. However, as shown in this project, the laser diameter, or waist, is also an important factor in laser safety and should be considered more carefully when designing or distributing laser devices.

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Laser, Retina, Thermocoagulation, Human Eyeball, COMSOL


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