How many days' worth of eye measurement results do I use to decide what prescription to order?

Hello everyone! I’ve taken a long time to get my first differentials because I wanted to see if I could find the answer to my question on the blog or forum first, and I was a bit busy to do so. I have now looked and can’t find the answer anywhere, so I apologize if I missed it.

I understand that one finds the average of your measurements to figure out your prescription. My question is, how many days’/weeks’ worth of results do I take into account?

To start with take measurements in the morning, during the day and at the end of the day. Take measurements in good lights (natural good daylight) and not so good lights (evening artificial indoors). Take measurements when you are feeling fresh and energised but also when you are tired or exhausted. After a week you will see how much the cms differ depending on the time of the day, level of tiredness and lights. Also you will learn what influences your eyesight most - sensitivity or change in cms is slightly different for everyone. You can then spend another week further observing the nuances but 2 weeks should be enough. If the numbers don’t change too much, 1 week is OK, too. Then you can make a decision on differentials and jump on board! :relaxed:

Thank you, @BiancaK! I have been measuring my eyes three or four times a day since the end of November, so I have a lot of results.

I would day you have plenty of data then. Measure your distance to your computer (that is what most people need their diffs for most) And take into account your measurements in those lighting circumstances. Then get those diffs! They are such an important step and the only good way to get moving forward. If your aren’t certain order your best two guesses (online glasses are cost effective enough). The first pair of diffs and normz are no more than an educated guess anyways, unless you spring for a test lens kit, so they might not be perfect. You can always order something else if they aren’t. The most important things in this process is being willing to learn and willing to backtrack :smiley:
If you haven’t seen this yet, I imagine it will help: Guide:Reducing differentials - EndMyopia Wiki

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Thank you, @Lloydmom! I must say I hadn’t considered taking measurements at my computer. I probably would have ended up with differentials that were too week (although, as I fortunately don’t need an astigmatism correction for close-up, I would definately have been able to use them later).

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