The Sunshades:  Are they just for fashion?

Introduction:

In tropical climate like Nigeria, it is not very uncommon to see many adorning their faces with sunshades to complement their outlooks. To some it gives them unique look and cosmetically quite appealing; To some they offer protection against dust, wind and flying objects.

But how many of us are aware of the importance of wearing sunshade? How important are the sunshades to our eyes? Or are sunshades just for fashion?

I have asked many of my patients who are fond of using sunshades but the reasons were not quite satisfactorily. Some of the responses I received were mere indications of ignorance and I have decided to research into this topic so as to enlighten the generality of the public. That your sunshade you are wearing always may be more than just for fashion.

Origin of sunshade:

Glass making technology has its origin in some early human civilization. During this period of medieval glass making, certain metallic salt known as colorant were added to glass mix to produce solid tinted glass. The magnificent stained-glass windows of cathedrals in Europe stand as testimony to the medieval glass-maker’s mastery of this craft.

The earliest examples of solid tinted ophthalmic lenses in Europe date from the seventeenth century. Solid tinted lenses were in use until the twentieth century when Mr. Crookes began his researches on protective lenses for furnace workers. He eventually introduced tinted glasses and in use until the years between the World wars when the American Optical Company and Bausch & Lomb developed the green and the brown lenses for military aircrew members.   In mid 1950s, the US AirForce contracted Bausch & Lomb to develop the G-15 Neutral Density Lens. Today’s grays lenses seen on the civilian market resulted from the original G-15 Lens.

How are sunshades produced?

The plastic sun shades are produced by immersing plain white plastic lenses in a hot dye bath. The dye is absorbed into the plastic lens substance to a depth of 3 – 4 micrometer below the surface, where the pigment ions attach to the molecules of the lens polymers. Most of these stabilized dyes used are chemically stable and the resulting tint [sunshade] dose not change or bleach appreciably during the service life of the plastic sunshade.

Importance of sunshade to our eyes

The sun emits some dangerous ray that are quite damaging to our eyes. Some of these rays are Ultraviolet rays [UV] and Infra-red rays [IR]. These rays can cause cataract, retina burns, etc. and the eyes need protection from these harmful radiations emitted by the sun. Plastic Sunshade or Sunglasses offer this protection

Almost all plastic sunshades contain a UV radiations inhibitor or blocker that provides excellent eye protection. The wide varieties of dyes used for making sunshades have capacity to absorb UV radiations to between 380 nm and 400 nm. These dyes are called UV radiation blocking dyes.

Most sunshades contain chromophores. These chromophores are the molecules that block UV light and prevent it from entering the eyes..

Who should wear sunshade

  • Patient with macular degeneration should wear sunglasses. It is worthwhile for a macular degeneration patient who has lost some vision in one or both eyes to have special orange lenses that block blue light radiation of the sun.
  • Photophobia [light sensitivity]
  • Light coloured eyes [irises]. Especially in light stained people
  • Ocular or eye infection e.g. iritis.
  • Cataracts
  • Recently performed cataract surgery
  • Macular degeneration*
  • Retinitis Pigmentosa*
  • An outdoor occupation
  • A recreational activities that involve snow, sand, water, high altitudes
  •  Tropical Travel plans
  • If you are on photosensitizing drug. (photosensitizing drugs make people more sensitive to light)
  • Common sense! If you are in very bright sunlight [during summer] always wear sunglasses

What to look for when selecting your sunshade

Not every sunshade sold in the open market or supermarkets have filter properties or UV blocking effect. Some of them are ordinary polarized lenses. Though polarized lenses are good but they do not filter damaging light in the IR and Blue ranges.

So, when selecting your sunshade, always check for the following:

  • Check and make sure that their tint (colour) is uniform throughout. Sunglasses that have gradient colour from top to bottom are not advisable.
  • Check to be sure there is no distortion in the lenses.
  • Do not buy sunshade made of glass. Apart from the danger they pose to the eyes in accident (traumatic injury), they can bleach with time. Most glass sunshades are produced using vacuum coatings. Vacuum coatings does not provide chemically stable sunshade and it can bleach as it ages.
  • Do not buy sunshade because of how dark it is. The visual appearance of a tinted sunshade does not provide information on the UV radiation blocking capacity {i.e. transmittance of UV rays or IR]. So the darker your sunglasses, does not mean more protection from UV radiations. Buy sunshade from eye care professionals who can advise you properly on them. The transmittance and absorption power of sunglasses can only be determined by examination in the eye clinic by eye care professionals {using the spectral transmittance curve}

Avoid sunshade with rose, smoke, blue and yellow colours. These colours impair colour vision significantly and may be dangerous when worn while driving. Sunshade must permit the wearer to recognize and react to traffic signal lights.

Advantages of plastic sunshades over glass sunshades

Tinted plastic offer several advantages over glass sun lenses. These include:

  • The plastic sun shades are lighter in weight
  • They are more protective and do not shatter during accident or cause traumatic injury to the eyes
  • The plastic sunshade is uniform in tint density across the entire aperture of the lens.
  • The plastic sunshade tint does not wear off overtime as the tint in vacuum coated glass sunshade do.
  • The original tint of plastic sunshade can be removed so easily by immersing them in a bath of diluted bleach. This opportunity enable user to enjoy variety of colours. The glass sunshade does not afford this.
  • All white tint-able plastic lenses contain a UV blocker or inhibitor that provides excellent ocular protection from the short wave-length [UVR below 330 nm] without additional treatment.

Gradient tint are easily obtained with plastic sunshades. But note that gradient tint are not completely protective.

Conclusion

The first wearers of sunshade did so for protection and not for fashion. During those dark days, fashion was not in consideration. But today, manufacturers of sunshades thought of the aesthetic value. They have introduced so much cosmetic into sunshade and it can be worn to complement our looks. But while wearing sunshade for fashion let us not forget the major purpose they were made for. Use them wisely

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