Your OC height is measured as the vertical distance of the centre of your pupils to the bottom of your lens, specific to your chosen frames.
It is important to have both your OC height and Pupillary Distance (PD) for higher or more complex prescriptions and Multifocal lenses. We use their vertical and horizontal alignment to perfectly centre your pupils behind your new lenses.
Mutlifocal lenses are often used as a solution for presbyopia, a condition that usually develops over the age of 40 where our eyes become less able to focus on different distances. Combined with weakening muscles around the eye, this can cause vision to blur when looking at things up close.
Bifocal lenses combine two prescriptions into a single pair of glasses. The top part of the lens allows you to see in the distance, while the lower part helps you see up close.
Varifocals are multifocal lenses with a graduated change from top to bottom, allowing you to see up-close as well as in the distance, without having to switch frames. Unlike Bifocals, there is no definitive line between the top and bottom half of the lens.
As this measurement must be very accurate, we calculate your Ocular Centre height by measuring it against your Pupillary Distance. This can be done by following these steps:
1. If you have a Home Try-On, try on your chosen frames. If you have already selected your frames without using our Home Try-On service, we will need to send you your chosen frame once you've made an order so that you can take a photo and send it to us.
Take a photo straight on, no more than 1 ft (30cm) away, looking straight ahead so your pupils appear centrally through the lenses. This is usually more successful with someone else taking the photo for you.
An example of how this photo should be taken can be seen below:
2. Use the PD ruler provided to measure your Pupillary Distance, resting it centrally on the bridge of your nose. Take note of this measurement, as well as taking a photo with the ruler on, again looking straight ahead.
3. Send the photos via email to us - from here we will calculate your measurements compared with your exact frame dimensions to ensure your lenses are as precise as they can be.