Difference between revisions of Vertex distance
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* <div> '''I have ''High Myopia''. How does Vertex Distance affect me?'''</div> | * <div> '''I have ''High Myopia''. How does Vertex Distance affect me?'''</div> | ||
:If you wore contact lenses before EndMyopia (EM) and continue to use contact lenses throughout your EM journey - Then vertex distance doesn't affect you. | |||
:If you wore glasses before EM and continue to wear glasses during EM then it is recommended to invest in a [[lens kit]] and choose your reduced lenses based on testing your [[visual acuity]] - Then vertex distance doesn't affect you. If you do not have access to a lens kit and you want to reduce in pre-defined diopter steps - Then vertex distance can affect you: For example, reducing from -14.0 dpt to -13.75 dpt at a vertex distance of 15mm results in an effective perceived diopter drop of only 0.17 dpt, further reducing to -13.5 dpt would result in an effective diopter drop of 0.34 dpt. | |||
:If you switch from glasses to contact lenses at high myopia or vice-versa you definitely will need to account for vertex distance before buying new corrections. | |||
* <div> '''I wear contact lenses as [[normalized]] and put [[plus lenses]] over them as my [[differentials]]. Do I need to worry about vertex distance?'''</div> | * <div> '''I wear contact lenses as [[normalized]] and put [[plus lenses]] over them as my [[differentials]]. Do I need to worry about vertex distance?'''</div> | ||
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: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>. | ||
==Calculation== | ==Calculation== | ||