India being hot and sunny most of the times in a year, sunglasses is the most preferred choice for travelers outdoors.
All Sunglasses need to 100% UV protective, else can cause more damage to the eye. On usage of sunglasses our pupils dilate, and if UV protection is absent it transmits more UV to the eye causing damage to the crystalline lens and the retina. UV light causes early cataract and retinal burns when exposed to sunlight.
Many sunglasses too cut down glare, these are due to the presence of a Polaroid film that cuts down light in the horizontal meridian, reducing light penetration.
Polaroid lenses are suitable for driving, for beach goers especially for the sea and general purpose outdoor use. However Polaroid lenses are not advisable for pilots as they cause colored fringes on the windscreen of the aircraft, hampering their vision.
It is always advisable to wear only branded sunglasses, else the effect would be devastating to the eye.