Try changing the index of refraction (this would correspond to changing the material that the lens was made out of - glass, plastic, etc. If you have eyeglasses, your optometrist might have talked to you about the tradeoffs of glass vs. plastic, which are thicker/thinner - heavier/lighter ... this actually ties in well to the standard about choosing the material with the right properties (density, index of refraction) for the job. Anyway, what does a higher index of refraction do