By Deborah Kotob, ABOM

Release Date: December 1, 2019

Expiration Date: January 1, 2021

Learning Objectives:

Upon completion of this program, the participant should be able to:

  1. Learn about the different types of glass in buildings.
  2. Learn about UV transmission levels in automobiles.
  3. Learn about the potentially deleterious effects of indoor UV radiation on textiles, furniture and our skin and eyes.

Faculty/Editorial Board:

Deborah Kotob Deborah Kotob, ABOM, is currently director of education for Jobson Medical Information LLC, has more than 20 years of experience as an optician. With over 10 years in lens manufacturing as a Sales Consultant, Trainer and LMS content developer. She lectures, trains and conducts webinars on a variety of optical and practice development topics.

Credit Statement:

This course is approved for one (1) hour of CE credit by the American Board of Opticianry (ABO). Technical Level 2 Course STWJHI011-2

Supported By:

This course is supported by an educational grant from Zeiss Vision Care

What!Do you think that you have full UV protection indoors or when driving in your car? Think again. In this course, you will learn about an unsuspected source of UV radiation... windowpanes. What!? You read this right—many windows transmit ultraviolet radiation (UVR), meaning we do not have full protection indoors or when driving.

At this point, you might ask the same question that I asked when I first read about UV coming through windows. How much, and are the levels high enough to harm my skin and eyes? Surprisingly the UV streaming through window glass has the potential to contribute to UV damage to skin and eyes due to the cumulative irreversible nature of the injury. Sunlight is ubiquitous and permeates our lives, outdoors, in our homes, when we drive and when we sit looking out the window of our favorite coffee shop or cafe. I for one seek out the table closest to the window and face the outdoors. The sun's warmth and glow draw us like moths to a flame. UV is, after all, essential to life on our planet. The absence of light has adverse effects on our mood and overall health, and of course, without light, there is no sight! However, just as plants develop outer layers that protect them from the harmful effects of UV damage while allowing them to reap the benefits from the sun's rays for photosynthesis, so should we protect ourselves from the adverse effects of too much cumulative UV exposure to our eyes and our skin.

For all of my UV bashing, I must acknowledge its beneficial uses: UVB, for example, activates the production of the essential vitamin D in our skin. UV radiation has germicidal properties and is used to disinfect, sterilize and purify. We use UV sterilization of food and surgical tools and equipment. We can use it to kill microbes, viruses and bacteria on surfaces, in the air and water. Although we have learned to harness this radiant energy for beneficial purposes, we cannot ignore the threat it poses to our skin and eyes.


figure 1Authors of ultraviolet radiation, DNA damage, repair and human disorders, Sung-Lim Yu and Sung-Keun Lee write: "Ultraviolet (UV) radiation is one of the most common environmental health hazards that cause highly toxic effects in most living organisms. UV irradiation leads to harmful effects including skin aging, eye damage and skin cancer because of increased production of cellular reactive oxygen species and by direct DNA damage (Fig. 1). Damaged DNA, if not properly repaired, is a source of mutation and interferes with many cellular mechanisms such as replication, transcription and the cell cycle."

Photo-aging, aka premature aging: More startling stats—The EPA states that upwards of 90 percent of the visible skin changes commonly attributed to aging are caused by the sun. With proper protection from UV radiation, most premature aging of the skin can be avoided. Statista reports: In 2018, the global anti-aging market was estimated to be worth about $50.2 billion U.S. dollars. The cumulative effects of UV exposure are a known danger to the skin, and our awareness of the harmful effects of UV on the eye, thankfully, is increasing. UV exposure to the skin can cause premature aging and can lead to life-threatening melanoma and other skin cancers and conditions. Due to the thin nature of ocular tissues, cancers of the eyes and lids metastases quickly to other parts of our bodies, including vital organs. I witnessed my neighbor go from a swelling of the eye to the removal of his eye three days later. He underwent life-saving emergency surgery to remove a cancerous eye. He is fair-skinned, blue-eyed, and since his job was clearing property for construction, he spent most of his time outdoors. He was a burly, tough sort of guy who did not worry about protecting himself from the sun. He now wears an eye patch to cover the void that once was his eyeball. Although it's an extreme example of the harm that UV can cause, it is also an important message emphasizing the need for precautionary measures to lower the risk of UV exposure and damage. UV exposure to the eye can cause permanent, irreversible damage to the layers of the eye. It is a substantial contributing factor to cataract development and other acute and chronic eye disorders. Government and health care organizations have consumer campaigns to alert us to protect our skin from the sun with hats and sunscreen. Campaigns to increase the awareness of threats to our eyes are on the rise, which is terrific! However, these campaigns are not identifying all the sources of exposure so that concerned consumers can be proactive about attenuating as much of this harmful light as possible.


In this course, we want to increase awareness of the UV transmitting through the windowpanes of our home, public interior spaces and car windows. UVR exposure is not limited to the outdoor environment.

figure 2This ubiquitous high-energy electromagnetic radiation is also streaming through window glass. While people may not think about the indoor risk, UVR can still be present in enclosed environments that most of us assumed are safe from UV exposure, such as homes, offices or cars— anywhere there is glass. The level of UVR transmitting through window glass varies. Some glass materials are excellent at filtering out the majority of UV rays, while other glass materials have a window of exposure, pun intended.


The glass industry has developed various coatings to make windows more energy efficient, helping control the heat that is entering and leaving buildings. These coatings provide a higher degree of UV protection than uncoated glass. But, and this is an important "but," they don't offer complete UVR protection. Take for example, low-emissivity glass; it still allows around 20 percent of UVA rays to leak through. The American Cancer Society states: "...both UVA and UVB rays can damage skin and cause skin cancer. There are no safe UV rays." When comparing the UVA properties of various glass types, researchers learned that smooth annealed and tempered glass allowed more than 70 percent of UVA rays to transmit through. Textured annealed glass allowed 40 percent through, and laminated glass blocked all UVA.

Although at lower levels and less intense, the amount of UVR passing through windows warrants concern due to the cumulative compounding nature of UV damage to our skin and eyes. Arming your patients with this information provides them with the opportunity to take simple precautions to reduce the absorption of UVR by their skin and eyes from these harmful rays streaming through windowpanes. Even small daily doses can be problematic because UVR exposure is cumulative, and regular exposure over time can contribute to eye and skin damage. It is not just the UVR streaming through the windows in our homes; it is also UV exposure in the public space interiors we frequent (Fig. 2). It does not occur to us that UVR is transmitting through windows as we settle in with a book or our smartphone to enjoy the view, the light and people watching through the windows. I know that I have always assumed that the window was blocking UVR. Sadly, the sun streaming through windows is not benign. Windows are a dominant feature of contemporary architecture. Walls of windows are now commonplace in businesses, schools and public buildings. Even our homes are designed to flood interior spaces with natural light, which it turns out is a problem for our skin and eyes, as well as interior furniture and flooring (Fig. 3). Have you noticed that the pillow that receives the most direct light through the window fades? How about the wood floor stain under the rug versus exposed to light? That is due to UV damage. Museums are a perfect example of buildings designed to protect priceless pieces of art from the destructive effects of UV light. When roaming the halls of art and history museums, most of the hallways, corridors and rooms are windowless, and the lighting is kept low. Light, especially UV light, causes irreparable damage to priceless art. Donia Conn from the NDCC Northeast Document Conservation Center states that, "All light is energy, and the energy that light provides fuels destructive chemical reactions that contribute to the deterioration of collections in libraries, archives and museums. Light also damages bindings, photographic emulsions and other media, including the inks, dyes and pigments used in many libraries and archival materials. She goes on to say, "When making the decision about time on exhibit and light levels, be aware that low light levels for extended periods cause as much damage as high light levels for short periods. When considering how much and how often an item is to be on display, always keep in mind that light damage is cumulative and irreversible." The same applies to the skin and eyes. Light energy can cause chemical damage that is both cumulative and irreversible, whether at low levels over extended periods or short-duration intense exposure levels. UV is actinic light that results in phototoxic chemical reactions that cause oxidative damage to both the skin and the eyes.


When driving, the left side of our bodies is exposed to six times more UV than the right side. Over time, the difference becomes visible as more UV aging and damage effects begin to appear more on the left than the right side of our faces and forearms.

There are different types of automobile glass. There is laminated glass used in windshields. Laminated glass, designed to protect the driver and passengers from cuts and serious wounds from glass shards in the event of an accident, also provides excellent UVA and UVB protection. The same is not true for sunroofs, back or side windows in cars. Researchers state that sunroofs and side windows transmit almost 80 percent of UVA (Fig. 4). One study found that windshields block 96 percent of UVA while side windows only block 71 percent. A study of European luxury cars found that the windshields block UVA up to 375 to 385 nm, leaving a gap in UVA protection. We learned in the "Closing the UV Protection Gap" course that the UVA range from 380 to 400 nm represents 40 percent of UV exposure at sea level. This same study found that rear and side windows only blocked up to 335 nm!

figure 4American drivers develop more left-sided cancers: A St. Louis study found that men particularly are at increased risk of melanoma on the left side of their heads and neck, while another study concludes that melanoma and Merkel cell are prevalent on the left side in the U.S.

Carcinoma: "...both Merkel cell carcinoma and malignant melanoma are significantly more likely to present on the left side than the right in the United States. Automobile UV exposure is a well-characterized source of asymmetrical UV exposure and likely contributes to the observed excess of melanoma and MCC presenting on the left arm. These excess left-sided cancers represent 1 out of every 20 upper limb melanomas and a striking 1 out of every 10 upper limb Merkel cell carcinomas. Therefore, it may be prudent to recommend sunscreen application or other UV protective measures in skin cancer-prone individuals who spend significant time driving automobiles or trucks." (Fig. 5)


figure 5The suns' rays, whether from direct exposure outdoors or indirect exposure indoors, are not the only potential source of UV exposure. Indoors fluorescent light bulbs (Fig. 6) including energy-efficient compact fluorescents (CFL) emit UVR. Fluorescent lighting damaged skin cells in lab experiments in a study conducted by Mironava T et al. at the Department of Materials Science and Engineering, State University of New York at Stony Brook, Stony Brook, N.Y. Despite availability of UVR blocking glass, many commercial and residential buildings continue to provide incomplete protection for students, workers and residents.


figure 6With all of its beauty and benefits, we need to be mindful of the sun, and we need to take precautions to lower our risk of outdoor and indoor UV exposure. Simple measures can reduce exposure and decrease our lifetime accumulation of damage, potentially lowering our risk of UV linked ocular disorders and diseases such as cataracts and age-related macular degeneration. Wearing lenses indoors and outdoors with full UV 400 nm protection is the first and best line of defense for the eyes. A word of caution: tint color and darkness have nothing to do with filtering UV radiation. This invisible insidious threat to our eyes can only be blocked when UV blocking additives are incorporated into the monomer or coating. In fact, a tinted lens that does not provide 100 percent UV400 nm protection is exposing the eye to higher levels of UV. The reason is that our pupils enlarge behind a tinted lens in an attempt to collect enough light to see. In this enlarged state, the high level of UV in these inferior lenses is penetrating deeper into the eye and potentially causing irreversible harm to our retina. Precautions for the skin include the many moisturizing creams today that come with broad spectrum high SPF UV protection built in. When applied daily, it will provide increased protection for the skin, both indoors and outdoors.


There have been many UV revelations of late. In the CE course "Closing the UV Protection Gap," we learned that 7 out of 10 clear ophthalmic lenses don't provide full UV protection up to 400 nm, and we learned that children are particularly vulnerable to UV damage. In another course "UV Before Blue," we learned about the need to prioritize light protection and rethink our race to prevent blue light from screens while ignoring the proven threat of UVR sun exposure. In the course "Making the Invisible Visible," we learned that the invisible sunglass level protection up to 400 nm in lenses is evident with an award-winning demonstration tablet; alternatively this tool makes apparent the gap in protection from UVA by many lenses on the market today. This UV education campaign is to raise our awareness of the UV hazard and all of the sources that expose us to this threat. To reduce the risk of eye and eyelid exposure to indoor and outdoor to UVA and UVB all day, every day, recommend lenses with UV400 nm protection built into the lens. See the courses mentioned above to learn more about lenses in all materials that are designed to provide UV400 nm level protection.