The use of facial masks, covering our nose and mouth, is now part of our life in many circumstances: indoor public spaces, such as public transports, supermarkets, stores, among others. The use of a mask is not very pleasant, but for those who wear glasses, there is an additional problem: it can make the glasses fog up . So, suddenly, we can really stop seeing. Why the glasses became fogged up? This problem is not specific to masks and glasses. It happens whenever the air contacts a cooler surface that makes it cool. The cooling of the air causes it to change from a gaseous state to a liquid state, a phenomenon called condensation. The fogging of the glasses when wearing a mask is due to the condensation of the hot air that we exhale that escapes through the upper area of the mask directly to the cooler lenses of the glasses. Small droplets of water then form, which accumulate. These droplets do not tend to disperse due to a property that holds their molecules together, called surface tension . And how do we solve the problem of fogged glasses? Adjusting the mask well is the main action to take To prevent the glasses from fogging up, the air we exhale must be prevented from contact with the glasses lenses . For this, the upper edge of the mask must be very well adjusted to the nose and laterally to the nose to prevent the passage of air. Thus, the air will be forced to escape through the sides, bottom, or through the mask, and not towards the glasses. Some masks have a moldable structure along their upper edge, like a piece of wire, which facilitates adjustment. The glasses themselves can help to make this adjustment, placed over the top of the mask: the mask can be pulled a little higher up over the nose, as long as the other areas to be protected are not exposed. Wearing the glasses a little lower, more on the tip of the nose, always over the mask, also helps. A piece of adhesive, suitable for use on the skin, can also help to adjust the mask. There are specific adhesives for use on more sensitive skin. There are also tapes with two adhesive sides that can be suitable. Depending on the shape of the mask and how it should be attached (for example, behind the ears or behind the head), there may be some variations. However, the idea is always the same: preventing the air we exhale from contacting the lenses of the glasses. Water and soap. Why? Another method that can help is to wash the lenses with soap and water , shake off the excess wash and let it air dry or wipe gently with a soft cloth before using the glasses and mask. This wash leaves a thin film on the lens. The soap in this film acts as a surfactant, that is, it will decrease the surface tension of the droplets caused by the condensation (fogged up) and they spread evenly forming a transparent layer. And the lenses are not fogged! Other products, but with due care Many other forms, from homemade ideas to commercial products, are referred to or are available for cleaning and with properties that prevent fogging due to condensation. There are for eye glasses, car glasses, window glass and shop windows, mirrors, among others, based on globally on the same principles. But, about your eye glasses, keep in mind: Eyeglass lenses may have some treatment that is incompatible with washing with water and soap or other products. Always follow the lens cleaning and maintenance instructions. Do not use any products outside their own indications, either because they can damage your glasses or because they may not be suitable for eye glasses because they cannot be close to the eyes. Sources: A simple method to prevent spectacle lenses misting up on wearing a face mask. Ann R Coll Surg Engl 2011;93:168 How to keep your glasses from fogging up while wearing a mask. Cleveland Clinic Click here for more information and advice of Hospital da Luz about COVID-19 pandemic caused by the novel coronavírus SARS-CoV-2 . The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
