Solanki Lala, B. Optometry

Fellow Optometrist (Specialization in Low Vision), Dr. Shroff Charity Eye Hospital, Delhi.

 

Pigmented dye incorporated in lenses are called tinted lenses. These type of tints reduce the light intensity by absorbing light entering the eyes, allowing partial light to pass through the lens.

Gleams of Sunshine

For adequate sun protection, brown or amber tinted lenses are prescribed as it blocks entire UV rays. Survey showed amber coloured lenses block blue light and can regulate the mood of those suffering from bipolar disorder, insomnia, and sleep deprivation.(1) Evidence on circadian rhythm in humans suggest that total darkness may be achievable by blocking wavelengths of blue light. The lenses block these wavelengths from reaching the eyes and keep nocturnal melatonin levels normal in a light environment which suppresses the making of melatonin otherwise. Circadian rhythms in humans might not be able to be impacted by wearing amber tinted lenses.(2)

Yellow: Research says visual performance of yellow tint commensurate spectrally neutral filter. (3) Yellow lenses are used in shooting as sportsmen believe their shooting ability improves. Research concluded “the benefit of yellow lenses depends entirely upon the individual; some may be helped while others may be hindered”. (4)

Yellow lenses are suggested for driving in fog & haze. But it is seen that any lens that absorbs light in the blue end of the spectrum can help in reducing  glare from the light scattered by atmosphere. In contrast to the atmospheric gases, fog is not as selective in the wavelength of light it scatters. (4)

Green: The human eye is most sensitive to green wavelength of lights hence green lenses act as good absorptive glass in IR and UV region. (5)

Pink: Attractive tint, soothing to eyes. It shows uniform transmission across the visible spectrum (6) causing no colour distortion for the user.

Gray: The superiority of Gray is its even transmission through the whole visible spectrum. This allows colours to be seen in their innate state relative to one another. (5)

G-15: G- Green & 15 refers to the amount of light pass through the lens and remaining 85% of lights get blocked.

Night Owl: Night Vision Goggles is an optoelectronic device that allows images to be produced in levels of light process towards total darkness. Military are familiar with NVGs.

Panoramic NVGs double the user’s field of view.(9)  NVG enhances the night vision with image intensification. (9, 10)

Blue: These lenses filter blue light by blocking the transmission of a specific segment or range of wavelengths. The lenses are patterned to help reduce the occurrence of digital eye strain and avoid circadian rhythm cycle disruption.(7)

Some experts from AAO believe blue tinted glasses are not necessary because no evidence found saying blue light causes digital eye strain nor light emitted by devices cause eye damage. Digital eye strain & negative effects of blue light on our eyes are two separate concerns. (8)

Gradient tint: Lens with darker tint at top fading gradually to little or no tint at bottom of the lens. This provides additional protection of light coming from above without blocking repleteness of light coming from ahead or below. (5)

Tinted glasses are greatest of all time, not only suiting the summer threads but also protecting us from UV radiation, reducing glare issues, enhancing contrast and hence patient should be prescribed according to need in daily practice.

 

References

  1. Jim Phelps, M.D from Corvallis, Oregon, Dark Therapy for Bipolar Disorder Using Amber Lenses for Blue Light Blockade.
  2. Mental Health Benefits of Amber Colored Lenses
  3. Bradley A, Colored filters and vision care, part 1, Indian J Optom 6(1):13-17, 2003
  4. Luckiesh M, Moss E, The science of seeing, New York, 1937, D Van Nostrand Co.
  5. Clifford W. Brooks , Irvin M. Borish , System for Ophthalmic Dispensing
  6.  St Cloud, Mine, Spectral transmission of common ophthalmic lens material,Vision-Ease,1984.
  7. Dr. Sheri Rowen ,MD, FACS, Eyesafe Vision Health Advisory Board
  8. Rahul Khurana, ophthalmologist and clinical spokesperson, American Academy of Ophthalmology
  9. “Main Login”. Military.com. Retrieved 16 March 2018
  10. “Defense Tech: Army Optic Combines Heat, Light for Better Sight”. defencetech.org .Retrieved 16 March2018.