Dispensing without the rules

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However, a sizeable proportion may be put down to measurement error. Manual measurement with a rule is familiar and, in experienced hands, assumed to be very accurate, but sometimes this very assumption can mask errors creeping in relating to parallax, patient posture, relative positions of practitioner and patient, even eye movements and how deep set the eyes are, so creating a greater distance between eyes and rule.

Increasing numbers of practitioners are becoming familiar with electronic means of assessing dispensing measurements. As personalised lenses became more popular, systems such as the original Visioffice from Essilor were introduced to allow a rapid and repeatable assessment of all the measurements required to dispense such a lens. It is also increasingly the case that a patient who is paying for a premium lens is less impressed by the old ruler, especially if they have previously been dispensed to using one of the electronic systems.