If white text on a black background looks doubled, ghosted, or as if each letter has a faint glowing twin, you are not imagining it and your screen is probably fine. The effect has a specific, well-understood optical cause — and a few settings changes usually eliminate it in seconds.
The short answer
The doubling is almost always the combination of two things: halation (bright shapes scattering on the retina) and astigmatism (a slightly irregular curvature of the eye’s cornea or lens). Dark backgrounds amplify both. Light backgrounds suppress both. That is why the same person who sees ghosting on a black terminal reads a paperback perfectly.
Why a dark background makes it worse
In a dark environment the pupil opens wide to gather light. A wide pupil exposes a larger area of the lens — and if that lens has even mild astigmatism, incoming light from a single point focuses at slightly different depths along different axes. The result is a smear in one direction: horizontal strokes duplicate vertically, or vice versa, depending on the axis of the astigmatism. Bright letterforms on black are the worst possible case, because the smear is a glowing shape against nothing. On a light background the pupil constricts, less of the lens is used, the irregularity contributes far less, and the doubling collapses back into a single sharp edge.
Astigmatism is common — estimates run around one in three adults — and mild cases frequently go uncorrected because they only show up in exactly this scenario: high-contrast light-on-dark viewing.
How to tell if this is what you are seeing
- Switch the same content to light modeIf the ghosting vanishes instantly, it is optical, not a display or software issue.
- Try it in a brighter roomTurn on the lights with the dark screen unchanged. Improvement means pupil size is the driver.
- Look at street lights at nightRays, starbursts or doubled points of light are the everyday signature of astigmatism.
- Cover one eye at a timeAstigmatism is often stronger in one eye; the doubling will change or disappear.
Fixes that work
Read long text in light mode
The single most effective change. A constricted pupil masks mild astigmatism almost entirely.
If you keep dark mode, drop pure white
Off-white text (#E0E0E0 to #E8E8E8) on dark grey (#16181D) sharply reduces the glow that creates ghosts. Details in white text on dark backgrounds.
Bigger, slightly heavier text
Thicker strokes survive smearing better than thin ones. Avoid light weights on dark entirely.
Raise ambient light
A lit room constricts pupils even when the screen stays dark.
Reduce screen brightness at night
The problem is the brightness gap between text and surroundings, not brightness alone.
Get your eyes checked
If you also see ghosting in daily life — headlights, subtitles, signage — an optometrist visit is worthwhile. Mild astigmatism is highly correctable with glasses or contacts.
What it is probably not
People often blame the monitor, the font or “chromatic aberration”. Real display ghosting affects all colors and all backgrounds, not specifically white-on-black. Font rendering issues produce fuzz, not clean directional doubles. If the effect is strongest with bright text on dark and disappears on light, the eye is the explanation.
Test any color pair yourself with our free contrast checker — live WCAG ratios as you pick.
Frequently asked questions
Why do I see double when reading white text on black?
Most likely mild astigmatism made visible by a dilated pupil and halation. Light-mode reading or softened dark-mode colors usually resolve it.
Is this a sign of an eye problem?
Usually it is just uncorrected mild astigmatism, which is common and easily fixed. Sudden new double vision that also appears with dark text on light should be checked promptly.
Does screen type matter?
OLED’s true black slightly increases the pupil swing versus an LCD’s dark grey, so ghosting can be marginally worse on OLED. Softened background colors help on both.
Broader context: white text on black — the full readability breakdown.