This is a demonstration that shows how the thickness of a spectacle lens is affected by using lens materials that have a different refractive index. Hi-Index lenses are useful in reducing the thickness of lenses with a high prescription, thus allowing the wearer to enjoy slimmmer and more fashionable looking eyewear.
Using the Power drop-down, select the closest lens prescription. The other lens values can be left at their 'default' settings. Then select different index values at the bottom of each image and compare the results!