Did you remember to apply sunscreen today? As skin is the largest organ of the human body, it is hard to ignore the effects of damaging sunlight. However, have you considered the sun’s effects on your eyes? Like the skin, the human eye is exposed to ultraviolet radiation (UVR) from the sun each day. Commonly, individuals believe standard UVR-blocking sunglasses are adequate protection against harmful radiation. However, because these lenses can reduce one’s innate behavioral aversion to bright sunlight and the squint mechanism, they can lead to an increase in a person’s dosage of UVR and result in a “sunburn” effect on the ectoderm tissue of the eye. Some frame styles, though effective at protecting the frontal optical axis, can leave one susceptible to harmful rays that affect the lateral surfaces of the eye. Dr. Jan Bergmanson, professor of optometry in the University of Houston College of Optometry (UHCO) and founding director of the Texas Eye Research and Technology Center (TERTC), has been working with Essilor International, one of the largest lens manufacturers in the world, to improve the eye’s protection against ultraviolet radiation through a rating system for protective lenses.
What are your goals for the current research?
We have a long-standing interest in ultraviolet radiation. You cannot see UVR. Therefore, you have to measure it with a sensor. Typically, what has been done is that the manufacturer held a lens and then placed a light source perpendicular it. Then, the amount of light coming through the lens was measured. Now, we are concerned about the amount of UVR that is transmitted to the eye from the sides and reflected on the back surface of the lens.
Sunlight comes from everywhere. You can protect your eyes from ultraviolet radiation with goggles, spectacles, sunglasses, contact lenses and intraocular lenses. However, effectiveness of a protective device will be dependent on where it is placed relative to the eyes and if light can get in from the back or from the side. Currently, there is no way of calculating the effectiveness of an ocular device meant for UVR protection. As a result, it is hard for consumers to evaluate the protective capability of a device through the stickers placed on the frame. In this research, we are going to try to establish a number that tells the individual how much protection they can get from a certain device or protective option. We will measure different devices to develop a scientific methodology to come up with that number, called a protection factor. We are also developing a sensor that can measure the amount of light transmitted in each direction.
Would prescription sunglasses rated by your proposed protection factor be more effective than a pair of sunglasses that were purchased from a store and rated, for example, UV 400?
Our proposed factors would tell you more about how the device can perform. Most of the UVR we have is coming from the sun. When you put an average pair of spectacles on, any light can hit the eye. We have become aware that some pathologies are best explained by light hitting the eye from the side – ocular malignancy, corneal and/or retinal pathologies, solar keratitis, spheroid degeneration, pinguecula, pterygium, climatic droplet keratopathy and/or cataracts. Clinically, we know that radiation that comes from the side is important. Fifty percent of the UVR comes directly from the sun, and 50 percent will come from anywhere else, like reflections off surfaces. We are going to try to use scientific methodology to arrive at an eye protection factor. We hope to provide a number that consumers can use to identify whether the sunglasses or contact lenses they are purchasing have the appropriate amount of UVR protection for their needs.
Do traditional contact lenses have UVR protection?
Some contacts have UVR blocking capabilities but, as it turns out, the contact lens is a less capable blocker than a spectacle. The contact lenses are only .06 millimeters thick, and a compound in the plastic causes the blocking effect. It is not able to match the protection achieved through spectacle lenses, which are made thicker. However, there is always a space between a spectacle lens and the eye. The contact lens, as its name implies, avoids this opening for harmful rays to enter. From this perspective, the contact lens provides the better protection. When a coating is placed on the spectacle lens, only that coating is UVR absorbent. Transmittance, the portion of light that passes through the lens, is factored in by what is mixed in the plastic. The thicker the lens, the more UVR is absorbed. Therefore, thickness is a factor.
Does the protection vary for soft contacts versus hard or for larger versus smaller spectacles?
Potentially, there could be a difference between hard and soft lenses. However, hard contact lenses, also known as gas permeable, which are placed on the cornea, do not cover the entire cornea and thus could increase one’s susceptibility. Currently, we fit people with scleral lenses that cover the entire cornea, though those lenses are used with individuals who have compromised eyes. Hypothetically, with scleral lenses, you could begin to get more effective UVR protection.
There is no such thing as one device that takes care of everything. No light can pass by the side of traditional contact lenses, which is a good feature, but it is not as good a filter as a spectacle lens. A spectacle is a better filter, but light can get in from the side. When considering a spectacle, the wrap-around frames provide better protection from light that comes from the side.
What is the significance of this study for the field of optometry?
The eye is affected by UVR that is reflected off flat surfaces such as beaches, bodies of water and the snow, and the retina is particularly vulnerable to UVR exposure. Through my clinical work, I have seen optometrists and ophthalmologists not providing protection to their patients in need of adequate UVR protection, which means they do not understand the transmittance scope completely. Therefore, this protection factor will give doctors a number that will help them counsel patients. What we have measured on our roof is that on nine days out of ten during the summer we have excessive ultraviolet radiation. That is more irradiation than what is considered good for your body. By developing this protection factor, we are providing a clinical tool that is easier for patients who have been counseled on the dangers of UV radiation to choose protection that is adequate for their needs, whether it is for recreational use or indicated as the result of increased susceptibility due to eye surgery.
In addition to Essilor International, Bergmanson is working with physicist Dr. James Walsh, Director of Pre-University Studies at MAHSA University.