The Hirschberg test (also known as the corneal light reflex test) is a quick and simple way to check ocular alignment. This assessment is particularly useful for testing for strabismus (misalignment of the eyes) in newborns, young children, patients with poor vision, patients that are not able to fixate or track well – or in any situation where a full motility evaluation is not feasible. The Hirschberg test is based on the premise that 1 mm of decentration of the corneal light reflection corresp

Your PD, or pupillary distance, is the measurement between the centre of your pupils. It’s measured in mm and very important if you have a strong prescription or are ordering varifocal lenses, so that the optical centre of the lenses can match the wearer's PD for best vision.⁣ In this episode of our "Ask the Optician" series, David Hutchfield, Head of Professional Services and Qualified Optician, explains how we obtain your PD from selfies and what's the best way for you to send them. bit.ly/3q4