POLAROID LENSES

 POLAROID LENSES

    Under normal lighting conditions, light waves vibrate and travel in all directions – horizontally, vertically and also everywhere in between. When direct sunlight (which is non-polarized) or artificial light hit a smooth surface at a given angle, it reflects off the smooth surface and travels in the same direction, intensifying their effect on the eyes. 

    This phenomenon produces disturbing optical noise or glare. Glare results in eyestrain, loss of clear vision, poor colour saturation, loss of depth perception, causing discomfort.

    The principle of polarized lenses can be best illustrated by observing Venetian blinds. The blinds block lights at certain angles, while allowing lights to transmit through it at certain angles. Polarization implies restricting the light waves to one direction. Polarized lenses block horizontally aligned light which causes glare, while allowing vertically aligned light to transmit.

   

APPLICATION OF POLARIZED LENSES

    Polarizing filters are created by stretching sheets of polyvinyl alcohol (PVA) so that its molecules align in long directional chains. The PVA is then passed through an iodine solution where the light absorbing iodine molecules attach to the molecular chains forming the microscopic blinds. 

    The film so prepared is sandwiched in the lens. The back surface of the lens is cast first and the precurved Polaroid film is placed on the cast part and then liquid material is injected over. Polarizing filters are aligned 90° to the angle of the polarized light.

    As spectacle lenses are designed to eliminate the polarized light in the horizontal plane, the filter is placed vertically in the eyewear or eye rim.

    This means that the filter must be properly aligned during surfacing and edging layout, otherwise filters will not work properly.

ADVANTAGES OF POLAROID LENSES

1. Filters glares

2. Enhances contrast and depth perception

3. Reduces eye strain, greater comfort

4. Improves visual acuity, provides safety

5. Eyes feel rested

6. Realistic perception

7. Reduces reflection

8. Comfortable and attractive – looking sun wear.

TINTS VS POLARIZED LENSES

    Although, darkly tinted sunglasses may reduce brightness, they do not remove glares like polarized lenses. In addition, dark sunglasses without added ultraviolet protection may cause more damage to the patients eyes than not wearing sunglasses at all. The darkness of the lens can cause the pupil to dilate, letting more ultraviolet rays into the inner parts of the eyes.

    Polarized lenses solve both problems by eliminating glares and filtering out harmful ultraviolet light because the filter reduces the polarized glare and also has UV absorbing properties

    Boaters, fishers and water sports players have used polarized sunglasses to reduce the effect of glare from water surface. In the past few years, the benefits of polarized lenses have been realized by a variety of other outdoor sports enthusiasts as well as by drivers and general use wearers. Besides them, the skiers, golfers, bikers, and joggers can also enjoy a clearer view and elimination of glare from polaroid lenses. It is also suited for patients with eye ailments like cataracts, albinism, aniridia etc.

    However, polarized lenses may react adversely with liquid crystal display (LCDs) found on the dash board of some cars or in other places such as digital screen on automatic letter machines. The problem with LCDs is that when viewed through polarized lenses from a certain angle, they can be invisible.