Problems reading white on black text

There are a few threads in the legacy section that cover this subject, but none were conclusive to me so I’m opening a new one here.

The issue I’m experiencing is that I get intense blur with white text on a black background when viewed on a screen. For black on white text under the exact same conditions (same screen, same lighting, moments apart) I can get a comfortable 45 cm to blur. But with the white on black text from the forum on dark mode, I have about 15cm to blur! This is ridiculous because that would equate to -6.5 diopters and optometrists only ever prescribed -3.25 at my worst point.

I would like to use dark mode more because I generally find it less tiring to my eyes, and it is meant to inhibit myopia progression, but the blur is quite intense.

Would appreciate any input on the subject as to why this is happening and what could be done.

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Vision is generally worse in dark conditions. The pupil widens, and focus has to be a lot better to still work through the larger aperture.

How does adjusting the room light around the screen affect you? Try a desk lamp beside the monitor?

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Screen brightness and contrast could make things worse as well.

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The nature of blur means that more light bleeds into lesser light. Thus light letters on dark backgrounds will bleed the white onto the dark parts. Dark letters on light backgrounds do the same, but the letters still seem dark because they are juxtaposed against the majority-light background. If you switched to your full prescription (for that distance), the dark letters will get much more contrasty and darker. It’s the nature of blur.

However, there’s another factor that occurs, and is the reason we can still see letters despite too-weak glasses. The eye has Spherical Aberration, what that means is that different parts of the cornea/lens focus to different distances. The central part focuses further than the outer part for example.

The way this manifests itself is that when the central part is finally in focus but the rest of the eye lens isn’t, part of the view is sharp (with blur smearing it all). We can see that sharp part. In the example of the light letters on dark background, the letter can appear sharp, but have halos and smears all around it. This means that part of your cornea/lens is finally “there” can can see the letters sharp, but the rest isn’t.

When things get dark (e.g. dusk), our pupils open up. This means that more and more of the light you use to see come from the outer areas of the cornea/lens. Since they focus closer than the center, eyesight appears to deteriorate. But if you look carefully, and have a prescription that (just barely) lets you see sharp lettering in bright sunlight, you will see that those letters are still faintly sharp, just with smearing outside. Again, the nature of our eyes :slight_smile:

One of the things that contributes to lens-induced myopia is the fact optometrists tend to prescribe for that low-light (e.g. dusk) situation, thus giving you a prescription for our outer lens/cornea to make that sharp. But that’s too strong (by 0.25-0.5 diopters or more) for the central area that you use in bright daylight. This leads to greater accommodation requirements in good light leading to more myopia progression. But without that overprescribed glasses, you can’t see that well in lower light situations (e.g. driving at dusk/night) that can cause problems (like car accidents).

Thus why I have several “normals” :slight_smile: I have higher prescriptions for driving at dusk/night to stay safe, while retaining the blur challenge in good lighting with a (slightly) weaker prescription.


When everyone says that a certain food is healthy but it causes you an allergic reaction, it is no longer considered healthy for you. If dark mode causes you to strain and lean closer, it is no longer beneficial for myopia progression.

Do you have astigmatism in some form or the other? I am asking because it doesn’t sound likely that your edge of myopic blur could change so dramatically only because of colouring. I am personally only functional in light modes because I get severe ghosting in dark mode at 20ish cm even though my myopic edge of blur is over 1m. My solution so far has been to not use dark mode (as it causes me unnecessary discomfort and strain) until I am able to.


My astigmatism app I discuss incessantly has a white on dark mode which, when I first started using it, was disconcerting in its intensity. After a few months of practicing on that app, almost all of the intensity and bleed is gone.

It may be something like astigmatism that’s intensifying the appearance of the white letters on black. Something to think about. Do keep us posted on your responses and progress.


Oh I only just logged in again, thanks to everyone for the great responses!

All of the proposed factors make sense to me. This “bleed” of the white letters into the dark background does indeed seem to happen less when there is more light, either from my surroundings or from the screen itself. It is also more noticeable the higher the contrast between the letters and the background is. I do have a bit of astigmatism in one eye, but only -0.25, so it probably plays into the mix but isn’t bad enough to explain it fully.

With practice I have been able to will the blur to clear up momentarily, similar to black on white text, so I’ll keep working on this and see if it will improve.

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We call that Active Focus around these parts :slight_smile:

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