EyeTools Question of the Day #360
I am an eye care specialist working in a community practice. I know that using thinner and lighter lenses can help make glasses look nicer and feel lighter but I’m not sure which refractive index to recommend for which prescription. I want to make sure I don’t use a refractive index that is unnecessarily high. Can you help?
Standard lenses have a refractive index (light bending property) of 1.50.
Thinned lenses 1.60.
Super thinned lenses 1.67.
Ultra-thinned lenses 1.74.
The higher the refractive index the thinner and lighter the lenses and the more expensive the lenses.
I have seen lots of guidance on which lens powers need which refractive index but the one I use is:
Max of +/- 2.00 power in one meridian, 1.50 index standard lenses.
Max of +/- 4.00 power in one meridian, 1.60 thinned lenses.
Max of +/- 6.00 power in one meridian, 1.67 super thinned lenses.
Max of +/- 9.00 power in one meridian, 1.74 ultra thinned lenses.
I recently came across a case where a patient with +4.00 in one meridian was prescribed 1.74 super thinned lenses. In my opinion, this was clinically unnecessary and wasted her money. I cannot think of a good reason for advising 1.74 ultra thinned lenses for low-powered lenses.
High index lenses will be less bulky, especially at the edges of the lens, and will prevent the lens edges from protruding over the edge of the frame.
Because they’re thinner, high index lenses are also lighter. This makes glasses more comfortable to wear as it reduces their overall weight.
This can reduce pressure on the patient’s nose which is very useful if they have delicate skin on and around the nose. Explain the benefits of thinner and lighter lenses to your patients and recommend them with confidence using the guidelines outlined above..
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