Eyeglasses and Eyewear
High Index Lenses
High index lens materials refract light more efficiently than standard plastic, so the same prescription is achieved with less thickness. The result is thinner, flatter and lighter lenses, most noticeably above about three dioptres.
Lens thickness is a function of prescription strength and material. A material that bends light more efficiently needs less curvature to produce the same correction, and less curvature means a thinner lens.
That matters cosmetically, because a thick lens edge is visible from the side and magnifies or minifies the appearance of the eyes. It also matters practically: a lighter lens is more comfortable over a long day and puts less strain on the frame and on the bridge of your nose.
The benefit scales with prescription. Below about two dioptres the difference is marginal and not worth paying for. Above three or four it is substantial, and above six it transforms how the glasses look and feel.
Questions and answers
Do I need high index lenses?
It depends on your prescription. Below about two dioptres, no. Above three or four, the difference in thickness and weight is very noticeable.
Do they change how well I see?
The correction is identical. What changes is thickness, weight and how flat the lens looks. Higher index materials do have slightly more chromatic dispersion, which a small number of people notice as colour fringing at the lens edge.
Does frame choice affect thickness?
Considerably. A smaller frame means a smaller lens, and a smaller lens has less edge thickness for the same prescription. Frame choice can make more difference than material for high prescriptions.
Are they more fragile?
Not meaningfully, though very high index materials are less impact resistant than polycarbonate. For children and sport, polycarbonate remains the right choice.
Talk to someone about high index lenses
Appointments are scheduled two per hour, so there is time to answer questions properly. Call (480) 706-3937 or request a time online.