Can clear lenses protect us from UV rays?

Nowadays, there is widespread awareness of the dangers of direct exposure of our eyes to sunlight. This is why we often hear about glasses with UV protection in their lenses.

UV and Blue light protection

Nowa­days, there is wide­spread aware­ness of the dan­gers of di­rect ex­po­sure of our eyes to sun­light. This is why we of­ten hear about glass­es with UV pro­tec­tion in their lens­es.

When we are ex­posed to sun­light for ex­tend­ed pe­ri­ods of time, we risk dam­age to the eyes in the form of dis­or­ders such as cataracts, mac­u­lar de­gen­er­a­tion, pinguec­u­la, ker­a­to­con­junc­tivi­tis and pho­tok­er­ati­tis, which, in the most se­vere cas­es, can lead to tem­po­rary loss of vi­sion. By de­f­i­n­i­tion, sun­glass­es are de­signed to pro­tect us from harm­ful so­lar ra­di­a­tion, but it must be said that not all types of sun­glass­es are fit­ted with lens­es that block 100% of UV ra­di­a­tion. Pro­tec­tive sun­glass­es are rec­og­niz­able by a “UV400” spec­i­fi­ca­tion, which in­di­cates that the lens­es block ul­tra­vi­o­let rays in fre­quen­cies up to 400 nanome­ters, which in­clude both UVA and UVB rays. What not every­one knows is that UV pro­tec­tion is in no way re­lat­ed to the col­or of the lens­es. In fact, you will find dark lens­es that don’t pro­vide 100% pro­tec­tion from UV rays and com­plete­ly trans­par­ent lens­es that to­tal­ly pro­tect up to 400 nanome­ters.

So how does it work?

Be­fore get­ting into the dif­fer­ences be­tween one lens and an­oth­er, we need to start from an analy­sis of the so­lar spec­trum. Light is that part of the elec­tro­mag­net­ic spec­trum that is vis­i­ble to the hu­man eye. It is an elec­tro­mag­net­ic wave emit­ted by the sun and fil­tered by the at­mos­phere be­fore reach­ing the ground. It en­com­pass­es wave­lengths, i.e. the dis­tance be­tween the peaks in a se­ries of waves, from 400 nm to 700 nm. spettro eng.jpg

Ul­tra­vi­o­let (UV) ra­di­a­tion is in the in­vis­i­ble por­tion of the elec­tro­mag­net­ic spec­trum, from 100 to 400 nm, and may be di­vid­ed into three bands (i.e. UVA, UVB and UVC) based on their bi­o­log­i­cal ef­fects. Un­til a few decades ago, we used to wor­ry main­ly about UVA rays, which are the ones re­lat­ed to tan­ning. With wave­lengths be­tween 280 nm and 400 nm, UVA rays com­plete­ly pen­e­trate the ozone lay­er in the up­per part of the at­mos­phere, pass through it, and reach the earth’s sur­face. Con­verse­ly, the ozone, to­geth­er with the wa­ter va­por, oxy­gen and car­bon diox­ide pre­sent in the at­mos­phere, block about 90% of in­com­ing UVB rays (280-315 nm) and all of the in­com­ing UVC rays (100-280 nm).

To­day, how­ev­er, due to pol­lu­tion re­lat­ed to green­house gas­es, this pro­tec­tive lay­er is in­creas­ing­ly thin­ning, so the dan­ger from UVB rays is grow­ing. Both UV-A and UV-B ra­di­a­tion can have short and long-term neg­a­tive ef­fects on our eyes and vi­sion, but UV-B rays, the high en­er­gy of which is ca­pa­ble of im­pact­ing the reti­na, are par­tic­u­lar­ly dan­ger­ous for our eyes. In ad­di­tion to ul­tra­vi­o­let rays, which have wave­lengths be­low 390 nm, dan­ger to our eyes also comes from high-en­er­gy vis­i­ble (or “HEV”) light. Known col­lo­qui­al­ly as “blue light”, HEV light is a blue-vi­o­let light with wave­lengths be­tween 400 nm and 500 nm, which, un­like the UV bands, is in­clud­ed with­in the vis­i­ble spec­trum. The short­er wave­length HEV light falls with­in the blue-vi­o­let por­tion of the spec­trum. This is light emit­ted both by the sun and by ar­ti­fi­cial light sources. Light from the LED screens of com­put­ers, phones, tablets and tele­vi­sions is one ex­am­ple. Pro­longed, un­pro­tect­ed ex­po­sure to HEV light can cause dam­age to the eyes, es­pe­cial­ly to the reti­na, and is a risk fac­tor for the on­set of age-re­lat­ed mac­u­lar de­gen­er­a­tion.

Sun­glass­es and cor­rec­tive glass­es: which lens­es of­fer the right pro­tec­tion?

SUN­GLASS­ES: To best pro­tect our eyes, we must nev­er for­get to wear sun­glass­es and should al­ways have our chil­dren wear them be­fore go­ing out­side. When marked with the ap­pro­pri­ate “UV” la­bel, sun­glass­es pro­tect against ul­tra­vi­o­let rays up to 400 nanome­ters. And what about blue light? As men­tioned above, blue light also comes from the sun and is ac­tu­al­ly up to 30 times greater than the blue light emit­ted by elec­tron­ic de­vices. This is why many col­ored lens­es now in­clude blue-light pro­tec­tion (or “blue block”), and they are be­com­ing more and more pop­u­lar.

PRE­SCRIP­TION GLASS­ES: The lens­es most in de­mand are, with­out doubt, those with blue-light fil­ters (such as our Blue Nat­ur­al lens­es), giv­en the wide­spread use of dig­i­tal de­vices and re­mote work. Lens­es with HEV fil­ters pro­tect up to 420 nanome­ters, so they com­plete­ly block all UV rays. As a re­sult, when you are wear­ing blue-block glass­es, you are 100% pro­tect­ed against HEV light. If you feel you don’t need to pro­tect against blue light, there are also trans­par­ent lens­es with UV pro­tec­tion of up to 400 nanome­ters, such as our NoUV lens­es.

Fi­nal­ly, it should be not­ed that UV and blue-light pro­tec­tion are avail­able both in the lens­es them­selves and as a lens coat­ing. What does this mean? In the first case, the ma­te­r­i­al re­spon­si­ble for ab­sorb­ing harm­ful rays is mixed di­rect­ly into the raw ma­te­r­i­al of the lens, as in the case of our NoUV or Blue Nat­ur­al lens­es.

In the sec­ond case, the pro­tec­tion is ap­plied lat­er as a lens coat­ing. There are spe­cif­ic coat­ings, such as our Chro­ma for blue light or Per­for­mance NoUV for UV rays, that can be ap­plied to the sur­face of the lens. Of course, the most durable so­lu­tion is a lens made of a pro­tec­tive ma­te­r­i­al, giv­en that coat­ings are more sub­ject to scratch­es and oth­er wear and tear over time. Nonethe­less, high-qual­i­ty coat­ings are an ex­cel­lent so­lu­tion, es­pe­cial­ly since the first type of pro­tec­tive lens­es are not avail­able in all in­dices. When choos­ing lens­es and frames, it’s best to opt for a frame de­sign that fol­lows the shape of your face as close­ly as pos­si­ble. In this way, you lim­it the amount of sun­light that reach­es your eyes from the sides and from above.