Sunglasses

To prevent the adverse effects of ultraviolet radiation on the eyes and to protect them, suitable and standard sunglasses must be used.

∴ Guide to selecting sunglasses to protect the eyes: To evaluate a product or personal protective item against ultraviolet rays, an index called the Protection Factor against ultraviolet rays (PF) is used. This factor is used to determine the degree of protection of products such as textiles, protective creams, and sunglasses. In other words, the protection factor indicates how much a product prevents the passage of ultraviolet rays. For example, if a material's protection factor equals 20, it means that only 5 percent of ultraviolet rays will be able to penetrate it and 95 percent of ultraviolet rays are absorbed by the material in question. For proper and sufficient protection against the sun's ultraviolet rays, materials must have a protection factor higher than 15. The eyes, like the skin, are at risk from ultraviolet rays. The degree of protection of sunglasses against ultraviolet rays is determined by the EYE PROTECTION FACTOR (EPF). EPF is essentially the ratio of the dose of ultraviolet rays received by the eye without glasses to that received by the eye with glasses. The EPF scale is a numerical scale from 1 to 10, and glasses with an EPF equal to 9 or 10 allow almost no ultraviolet rays to pass through (according to standard AS/NZS 1067:2003). Usually, based on EPF, sunglass lenses are divided into several groups as shown in the table below.

∴ Sunglass lens groups:

0: mostly used for beauty and fashion and is not considered a sunglass; it provides less protection against glare and only slight protection against ultraviolet rays. 1: mostly used for beauty and fashion and is not considered a sunglass; it somewhat reduces glare and provides somewhat slight protection against ultraviolet rays. 2: sunglass - moderate glare reduction and suitable protection against ultraviolet rays 3: sunglass - high glare reduction and suitable protection against ultraviolet rays 4: special sunglass - very high glare reduction and suitable protection against ultraviolet rays

Note: The eye protection factor may not be limited only to protection against ultraviolet rays; in other words, the suitability of a pair of glasses is not affected only by protection against UVR, and other factors must also be considered, such as the degree of eye coverage by the lens and frame of the glasses (Frame Coverage), protection against ultraviolet rays (UV Protection), protection against blue light (Blue Light Protection), and protection against infrared rays. From the sum of these 4 variables, an index called FUBI is obtained, which is the numerical average of the four aforementioned items.

∴ How to determine the effectiveness of sunglasses: Before buying sunglasses, you should pay attention to a reputable brand of the glasses. The protection-factor label (9, 10, and UV400) should be kept in mind. If laboratory equipment is available, a spectrophotometer can be used to determine the protection factor based on the amount of transmission in the ultraviolet A and B ranges and to make sure the glasses are suitable. The glasses can be tested using the UV meters that opticians or optometrists use.

∴ Characteristics of suitable sunglasses: 1/ The lenses of the glasses must absorb an acceptable amount of the sun's ultraviolet rays. 2/ Reduce the intensity of visible light by 75-90 percent. 3/ Not alter the nature of light and images. 4/ The lenses should be gray, green, or brown, with gray being preferred.

• Sunglasses should also cover the entire eye area and its surroundings on the face.

• The lenses of some sunglasses are matte to improve their quality, but these matte lenses are not recommended by the American Academy of Ophthalmology.

• To tell whether a glass lens is of good quality, a simple method can be used. Hold the glasses at the correct distance from the eye and, with one eye closed, look through them at a square or rectangular object. Move the glasses slowly from one side to the other and then from top to bottom. If the lines of that object, for example the floor tiles of the room, are straight, the glasses have good lenses. If the lines become curved (especially in the center of the lens), try another pair.

• Note that the color of the lenses has absolutely no relation to their quality. Some sunglasses have mirrored lenses. Although these lenses reduce the intensity of visible light well, they are not necessarily able to fully absorb ultraviolet rays. Although ultraviolet rays are generally a harmful phenomenon, people who suffer from retinal diseases must take greater care of their eyes.

 

∴ Necessary recommendations for selecting sunglasses:

1/ People who are skiing, sunbathing, or mountaineering at high altitudes must definitely use sunglasses. For such environments, glasses that transmit only 8-12 percent of light are needed.

2/ Colored glasses tending toward green and brown are harmful because they distort the color spectrum. Of course, for people who want to drive for long periods, it is recommended to use brown glasses, because these glasses reduce the blue light of the sky and increase visual acuity; therefore, for everyday use, using this color is not recommended. 3/ If you sit behind the wheel, it is recommended not to use green sunglasses, because they impair the recognition of red and yellow light and are unsuitable in this respect. As a rule, know that the best color for sunglasses is, first, gray, and after that, brown. 4/ The lenses of sunglasses must have sufficient strength. Polycarbonate is the most resistant of all materials. 5/ The frame of the glasses should be large so that complete protection is provided in this respect. 6/ A standard pair of sunglasses is one which, when shaken in front of a patterned page, should not make the page appear wavy or blurred.

7/ If you want to know whether the darkness of your sunglasses is suitable, look in a mirror with your sunglasses on in a room with normal light; if your sunglasses are suitable, you should not be able to see your eyes. 8/ Children who play under the sun for long hours must use their own special glasses. 9/ If you are exposed to high levels of radiation at your workplace, sunglasses will not suffice; therefore, it is recommended to use different, special glasses (for example, in welding or working with devices that produce radiation, special glasses or shields are needed). 10/ People who have undergone cataract surgery, LASIK, or LASEK must use approved sunglasses when exposed to the sun. 11/ Some skin or eye medications increase the eyes' sensitivity to sunlight; if using these medications (for example, those who use eye drops or doxycycline tablets), one must definitely use sunglasses. 12/ Sunglasses with reflective lenses that have a mirrored coating are suitable for skiing or mountaineering. 13/ Given the various costs you incur daily, buying a standard pair of sunglasses is not only a correct and appropriate action but also necessary. The price of using counterfeit glasses is endangering the health of your eyes. 14/ To obtain sunglasses, it is better to consult an ophthalmologist or get help from an optometrist, and to purchase them, go to reputable opticians. By buying a good pair of glasses, you can easily use them for several years. 15/ If you have a visual impairment and use prescription glasses, if you wish, you can use special sunglasses that fit over the prescription glasses, or order photochromic or tinted lenses for your prescription glasses.