Difference between revisions of Vertex distance
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Ask a second person to measure the distance from your closed eye to your glasses while you wear them. Or, as a literal "rule of thumb", try placing different fingers between your closed eye and the back of your glasses, then measure the thickness of your finger - This is an estimate for your vertex distance. | Ask a second person to measure the distance from your closed eye to your glasses while you wear them. Or, as a literal "rule of thumb", try placing different fingers between your closed eye and the back of your glasses, then measure the thickness of your finger - This is an estimate for your vertex distance. | ||
* <div> '''I use the endmyopia.org Diopter Calculator App and my results differ from my manual centimeter [[ | * <div> '''I use the endmyopia.org Diopter Calculator App and my results differ from my manual centimeter [[measurement]]s, why?''' </div> | ||
The [https://play.google.com/store/apps/details?id=org.endmyopia.calc Diopter Calculator App for Android] (as for the June 2020) measures the distance from the screen to the tip of your nose. Since the distance from the nose to your eyeball is not taken into account, your focal length seems smaller (and your diopters higher) than with a manual measurement. You can however correct these values by applying the same formula as for the vertex distance, inserting the distance from the tip of your nose to your eyeball for <math>x</math>. | The [https://play.google.com/store/apps/details?id=org.endmyopia.calc Diopter Calculator App for Android] (as for the June 2020) measures the distance from the screen to the tip of your nose. Since the distance from the nose to your eyeball is not taken into account, your focal length seems smaller (and your diopters higher) than with a manual measurement. You can however correct these values by applying the same formula as for the vertex distance, inserting the distance from the tip of your nose to your eyeball for <math>x</math>. | ||