HOW TO TEST A SUNGLASS WITH OUT UV METER

HOW TO TEST A SUNGLASS WITH OUT UV METER.

Sunglass is not just about how they look, their function is to protect your eyes from harmful UV rays from sun which can lead to everything for dark circles under eye, cataract or skin cancer of the eyelid.

Most of the eye stores don’t have UV meters to test sun glasses to see how much UV protection it provides. So is there a way to safely do sun glass test in home ??

Yes. , but it wont tell you if it is filtering all of it or just some of it, but atleast you can test if they are actually doing something or not and it wont cost you a cent to try.

Sun glasses from street vendors, stores, and from expensive establishments, all claim to have their glasses excellent UV Protection. Unfortunatlely there are more than a few opticians who don’t actually know to explain to a customer a whole lot about UV protection, lens quality etc .Others may but still want the larger profit margin that comes from selling an expensive brand. All this leaves you with less than perfect advice on buying a sunglass.

Expensive sunglasses may have better name, better lens, better product physically, but when it comes to UV protection, they may be exactly the same as low priced ones.

Polarized lens have nothing to do with UV protection . It just allows vertical component of light and eliminates horizontal component and gives better vision. Even if your lens is not polarized but 100% UV protected, it prevents eye from harmful UV  . But simply Polarized lens donot protect your eyes from harmful UV.

Method of Testing Sunglass in home :

Go in to a dark room with UV flash light, Sunglass and 500 Rupees Indian Currency. Turn on UV light and beam it BACK of 500 Rupees currency. You should notice a WHITE LINE. You normally wouldn’t see in ordinary light. These are the water marks used by banks and government official to detect counterfeit money- this WHITE LINE on the back of 500 Ruppees Indian currency will be noticeable in UVlight only. Don’t worry , you are not doing anything illegal.

Now take the sunglass you wish to test and beam the UV light through one of its lenses and on the back of the 500 Rupees. If you still see the white line in the 500 Rs, your glasses donot provide 100% UV protection ( the lenses are letting through the UV light and revealing the white line). If you don’t see the white line, your glasses have passed the UV test and do provide 100% UV protection-the lens blocks the UV, hence you cant see the white line.

I have donr this test many time for my sunglasses and discovered that many inexpensive ones provided 100% UV protection. Granted, many expensive branded ones also provided 100% UV protection. But as far as UV protection is considered both are exactly the same. SO don’t let price be your guide.

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The amount of UV protection sun glass provide is unrelated to the color or darkness of the lens. A crystal clear lens can also provide 100% UV protection.

Kids need sun glasses more than adults. Because their lens in eyes is clearer than an adults lens, so more UV light penetrate deep in to the eye. Also kids spend more time outdoors.

Look for Sun glass that Block 100% UV and HEV rays( High energy visible radiation also called Blue light). Blue light waves are what makes the sky or any object appear blue. They have short wavelengths and scatter easily and create glare.

Regarding lens material, the highest optical quality is for Glass. No scratching risk. But the problem is weight, and risk of injury if the lens shatters.

CR 39 is a plastic lens. This has less optical quality than Glass. But only half the weight for glass and low shatter risk.

Polycarbonate lenses are very safe and thinner than CR 39.Very low shatter risk, but prone to scratching. They provide 100% UV protection with out the need of any additional UV coating. They are good choice for rimless eyewear design where the lenses are attached to the frame component with drill mountings ( they are less likely to get fracture).

Trivex lenses are lighter than poly carbonate and better optical clarity but are heavier than poly-carbonate.

Photchromic lenses( also known as day and night glasses) are also a good choice to prevent ill effect of UV rays. They darken automatically when exposed to sunlight and fade back when return to indoors. The molecules responsible for causing photochromic lenses to darken are activated by Suns UV radition. Although each molecule changes by only a fraction of a nanometre, when many molecules respond in a same way the effect is dramatic as more and more light is progressively blocked out.