After receiving an eye prescription, an optician will take your pupillary distance (PD) measurement before sending off your frames to be fitted with lenses. This is an extremely important number because it measures the distance between your eyes to ensure your pupils match up with the optical centre of lenses. If the two don’t match up, the prescription won’t be as effective and you could experience headaches and eye-strain.
Measuring Pupillary Distance
Pupillary distance is measured in millimetres and even a slight variation can cause a number of vision and eye health problems. Taking accurate PD measurements requires comprehensive knowledge and technical skill. Opticians have been specially trained in correct measurement techniques and have access to sophisticated tools that can produce an accurate measurement.
Dangers of At Home Methods
With the popularity of buying glasses online, a number of websites have come up with do-it-yourself measurements or apps that will take this measurement for you. The problem is that these are not scientifically accurate measurements and are not being performed by professionals. There is a large margin of error and you could end up with glasses that hurt your vision—not correct it.