To measure this, mark the second lens at the ordered centration distance, place them back onto the focimeter with this mark centred and read the power
* For vertical imbalance, any inaccuracy of less than 1mm between ordered lens positions or in distance between the two focimeter dots or that does not exceed 0.50A will pass.
* Ask the patient if they have any other spectacles in addition to the pair about to be checked (eg, reading spectacles, sunglasses, a spare pair, or a newer pair they can't wear) and be sure to focimeter
all of these.
This year, the charity needs handheld focimeters
, i-care tonometers, Sussex Vision test charts and small cases of trial lenses.
are handy and easy to use, although measuring lenses with high prisms can be challenging so it may be necessary to obtain sight test results from the previous practitioner with the patient's consent in these cases.