Calculations: Lens thickness and sags

In this month's look at calculations in practice, Janet Carlton describes how best to calculate what is all imoprtant to most patients - lens thickness

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Sometimes a patient may enquire about the different lens options and how thick they may be. This is especially for a myope interested in paying more for higher index materials.

The myopic patient needs to know how much thinner the lens will be and be able to relate this to the cost of the lens. Hyperopes tend to be less bothered by the 'value' for the thickness of their lens, and base their thinking on how thick they 'feel' the lens is. Telling a hyperope that the lens is actually 0.5mm thinner may be meaningless, if the lens still appears thick.