Netrometer: Measurements on the move

Knowing about a patient’s existing correction is essential to the process of refraction. Not only will it indicate the extent of any change in refraction, it also should influence the final choice of correction prescribed to ensure patient comfort. If refraction was merely the prescribing of lenses to correct the actual lower order aberrations (spherical and cylindrical on axis error), then we would have been replaced by autorefractors years ago.

Accurate lens measurement is also important when discussing what existing correction is best for any individual task, and forms an essential part of patient education – especially for those who may be confused by which of their current spectacles are for a particular purpose. This is something all those who undertake domiciliary visits will recognise. The housebound are often the very same people who may need some instruction as to what the various, and often numerous, pairs of spectacles they own are best used for. Often for similar reasons, they are also the people most likely to offer ambiguous or inconclusive responses during subjective refraction. So reliable objective measurements, both of their refractive error and of their current corrections, are essential.