Exposure to sunlight and UV rays can harm the eyes, potentially leading to severe eye conditions. Specifically, UVB and UVA rays can cause disorders affecting the cornea, retina, lens, and eyelids. 

Sunglasses offer a solution to this problem, shielding the eyes from harmful rays and preventing discomfort caused by wind, dust, and sand.

The Criterion of UV Absorption

Protective eyewear lenses primarily aim to reduce light and selectively filter the sun’s rays. They allow visible light for clear vision while blocking harmful ultraviolet (UV) rays. UV absorption indicates the level of protection lenses offer against UVA and UVB radiation. It is determined by the ratio of light reaching the lens versus the light passing through to the eye.

UV absorption ratings range from zero to four: Normal sunglasses typically have a rating between 2 and 3, while a rating of 4 is suitable for highly bright areas like glaciers.

Different Types of Lenses

Melanin Lenses:

  • Melanin lenses mimic the natural pigment in the skin and eyes, protecting against UV and high-energy visible (HEV) radiation.
  • Advantages include maintaining natural color perception, enhancing image sharpness, reducing glare, and slowing skin aging around the eyes.
  • Melanin lenses are lightweight and made of polycarbonate, offering excellent filtration of harmful radiation. They work well for individuals seeking strong color contrast, such as brown and yellow tones.

Polarized Lenses:

  • Polarized lenses selectively filter the vertical beam of light, reducing eye discomfort caused by glare from reflective surfaces like asphalt, seawater, and snow.
  • Benefits include preserving natural color appearance, reducing eye fatigue, and complete protection against UVA and UVB rays.
  • Recommended for outdoor sports enthusiasts, active individuals, those sensitive to glare (e.g., car headlights), and individuals who want a clear, natural view of colors (particularly beneficial after cataract surgery).

Photochromic Lenses:

  • Photochromic lenses adjust their tint intensity based on exposure to UV rays. They darken when outdoors and lighten when indoors. However, they do not darken inside a car due to the UV-blocking effect of car windows.
  • These lenses combine the benefits of tinted sunglasses with transparent prescription glasses, making them suitable for various lighting conditions.
  • Photochromic lenses offer UV protection while allowing vision correction.

CPF Lenses:

  • CPF lenses have a special treatment that filters out blue light from sunlight and artificial sources like LED devices, digital screens, and energy-efficient lamps.
  • They reduce glare, improve image contrast, and are recommended for individuals with specific eye conditions such as retinitis pigmentosa, macular degeneration, albinism, and photophobia.
  • CPF lenses may not be suitable for low-light situations or nighttime use.

Mirror Lenses:

  • Mirror lenses undergo treatment to create a reflective or “mirror” effect. The intensity of the mirror effect can vary.
  • Advantages include increased light absorption compared to regular sunglass lenses, making them popular among individuals participating in outdoor sports like surfing, mountaineering, and motorcycling.

Selecting sunglasses involves considering the level of UV absorption and the specific lens types available. Understanding the benefits and applications of different lenses helps you choose sunglasses that provide optimal eye protection. 

Remember to consult an eye care professional for personalized advice and recommendations.