# 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.

## Related

- https://eyedoctorphoenixaz.com/eyeglasses-and-eyewear/prescription-lenses
- https://eyedoctorphoenixaz.com/eyeglasses-and-eyewear/frame-selection-and-fitting
- https://eyedoctorphoenixaz.com/eyeglasses-and-eyewear/designer-frames

---## About this practice
Arizona's Vision Eye Care Center, 15215 S 48th St Ste 180, Phoenix, AZ 85044.
Phone (480) 706-3937. Monday to Thursday 9:00 AM to 6:00 PM, Friday 8:00 AM to 5:00 PM. Closed Saturday and Sunday.
Independent optometry practice, founded 1994. One location. Does not perform refractive or cataract surgery.
This site publishes no star rating and no review count, because the figures across the practice's own properties contradict one another and cannot be verified.
This page is general information, not medical advice.