Confused about light levels and measurements

Im still somehow confused about light levels (lumens) and measurments…
So i set up a decent place for measuring my distance vision. I put up a 6m snellen chart on a wall with direct white light on it (680-700 lx) so I can have stable measurments all the time. As I wrote in my previous post I started reading endmyopia with one pair of glasses weaker of about 1.25/1.50D than my current myopia and my question is:

Since I’m blur adapted I need to reset my vision cortex. Is it perfectly fine to buy lenses which brings me to 20/20 in 680-700 lx level and after some time reduce it by 0.25D or I’ll be overcorrected outside in daylight?

Acording to wikipedia daylight has between 1000-120 000 lux so i don’t how it responds to indoor measurments. Also Jake mentioned in one of his blog about measuring in poor lighitng condition and good lighing condition and setting up a base line if I remember correctly. I don’t know if my light level is good or too good and i should lower that to not be overcorrected outside in my normalised glasses…

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Its a good question and a hard to answer with one specific solution. Its good that you’re trying to get your measurements as consistent as possible with the same setup every time.

The short answer is yes, you will be overcorrected in daylight.

The longer answer is that it really depends on your situation, what glasses you feel comfortable with wearing. Some people like to just wear one pair of normalised and dont mind sometimes being overcorrected in bright light. Other people have two pairs of norms, one for indoor one for outdoor.

Also to note is that being overcorrected in bright daylight is hard to avoid at all stages of reducing. For example. Say you’ve just reduced your glasses 0.25 diopters, from 5.0 to 4.75. Your eyes are sitting at 5.0. For the first month or so you’ll get lots of blur challenge indoors and outdoors because the difference between your eyes and your glasses are 0.25. As your eyes improve and go from 5.0 → 4.9 -->4.8 etc you’ll be in more situations where you will have no blur challege or are over corrected, especially outside. Usuallly outside full sun is the first situation where you find you dont have blur challenge and then even being slightly over corrected.

Also have a look at this pole of what people experience between indoors and outdoors. Most people have quite a big difference 0.5 diopters is the most common. With this kind of difference its inevitable that you’ll be overcorrected sometimes.


My plan is to wear contact lenses only for outdoor and sometimes when it’s necessery in a house, if i’ll be doing some close up time in them i will wear reading glaasses of course. If I work longer at home in front of the computer, I will wear differentials for that,
My main thing will be spendling lots of time outside in a daylight, especially when holidays are comming. (I’m a student)
In that case what would you do if you were me? Lower light lever or do something else to have blur challange outside in daylight?
I know all eyes are different and it will be only assumption but maybe it will guide me :slightly_smiling_face:

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I think you’ve got two options.

  1. Keep it simple and have 1 set of normalised for both indoor and outoor not worry too much. (This is what I do)
  2. Have two pairs of normalised. One for indoor and one for outdoor. This will help you get more consistent blur challenge.

Thank you!
I think I will keep it simple but reducing after some time by 0.25 from 20/20 in 700 lx will be enough to move forward?

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Consistency in environment and light conditions is the most important thing. Sounds like you’re already across this. So that’s good.

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I prefer to have just one pair of normalised for all occasions and lighting conditions…kind of.

When I first reduce to a new pair of normalised I will wear that probably 90% of the time. The only time I might use my previous norms is in the first few weeks for night driving or maybe watching TV at night if the blur is driving me nuts and I just want some clarity. Usually after the first few weeks than I only use the new pair of norms until it’s time to reduce again.