The question
What does an optical condition have in common with a psychological one?
Two kinds of strain, one design instinct
A research-grounded framework for designing with astigmatism and anxiety, held together in one study on purpose.
The finding
Nothing clinically. But interfaces make the same mistake with both: they add strain, and strain compounds.
The output
Four behaviours that serve both an eye and a nervous system, and a checklist a design review can use.
00Why pair these
An optical condition and a psychological one, mishandled by the same instinct
Astigmatism is a shape problem in the eye. Anxiety is a state of heightened threat-perception in the mind. Nothing about their biology overlaps. What overlaps is what a badly made interface does to each.
A screen that’s slightly too low-contrast is fine for a minute and exhausting after twenty. A flow that’s slightly too ambiguous is fine once and corrosive on the tenth repeat. Neither condition announces itself in analytics. Both are more common than most product teams budget for.
Share of population, on one 0–50% axis
Astigmatism · 28–47%. A range across two population studies, by age group and diagnostic threshold.
Anxiety · about 4%. WHO estimate of the global population, 2019.
0%10%20%30%40%50%
These are not the same kind of number. One is a refractive measurement, the other a diagnostic estimate. The point is that “the average user” is a fiction: any product with a real user base already has both groups in it.
01Astigmatism · optical strain
A shape problem in the eye, made worse by shape decisions on screen
The cornea or lens is shaped more like the back of a spoon than a ball. Light bends unevenly across it and never resolves to one sharp point. The result is two images competing for the same spot, at every distance, and an eye that keeps refocusing to compensate.
Halation: bright text on a dark field scatters
High-contrast dark mode is often recommended as an accessibility default. For astigmatism, the research is more mixed. Bright text on a very dark background can scatter inside an eye that already bends light unevenly, producing a perceived glow around letterforms.
Order confirmed for Thu, Oct 2#FFFFFF on #000000 · 21:1 · max contrast, max scatter
The glow is a simulated illustration. Halation happens inside the eye, not on the screen. Preferences are mixed even among people with astigmatism, so the response is to make it adjustable and default to a softened version.
Enough contrast, not maximum contrast
WCAG 1.4.3 sets a 4.5:1 minimum for normal text. It’s a floor, not a ceiling, and the ceiling (pure white on pure black, 21:1) is the combination most likely to produce halation.
Letters that already overlap need room
Below the minimum
Astigmatism means light entering the eye focuses at two points instead of one, so every letterform already arrives slightly doubled.
line-height 1.15 · spacing normalMeets SC 1.4.12
Astigmatism means light entering the eye focuses at two points instead of one, so every letterform already arrives slightly doubled.
line-height ≥1.5 · letter ≥0.12em · word ≥0.16emWCAG 1.4.12 doesn’t mandate loose spacing by default. It requires that a layout keeps working when a reader applies these minimums themselves.
Typefaces drawn to stay legible when they blur
Characters that collide
Il1 O0
In many sans-serifs, capital I, lowercase l and the digit 1 are near-identical strokes.
What to look for
A face such as Atkinson Hyperlegible, from the Braille Institute, adds a tail on the lowercase l, a curved base on the 1 and a narrower 0, so each character stays distinct under blur or doubled focus.
02Anxiety · cognitive strain
A nervous system that can’t tell your interface from a real threat
The body’s threat-detection system responds to uncertainty the same way whatever the stakes. A missing status, a ticking clock, an action with no visible undo: each is something to keep tracking. One ambiguous moment is nothing. A flow built out of them adds up to vigilance, which never shows up as an error.
Five small moments in a cancel-subscription flow
| Step | What raises strain | What flattens it |
|---|---|---|
| Find the cancel option | Buried three levels into settings | Listed directly on the account page |
| “Offer expires in 4:59” | Countdown and scarcity messaging | “No rush. You can restart anytime.” |
| “Are you sure?” | No explanation of what’s kept or lost | States what happens to your data and lets you review |
| Processing… | No status label, no time estimate | Labelled progress |
| It’s done (maybe?) | No confirmation | Explicit confirmation and what happens next |
A hypothetical flow, illustrating how small unresolved moments compound. UXmatters calls these “micro-anxieties”.
Twelve facts, or four ideas
Working memory comfortably holds roughly seven items. A flat list forces the reader to build their own structure in real time, which is itself a small unresolved task.
Flat · 12 facts
Subscription ends Aug 30Data deleted after 30 daysDownloads work until Aug 30Team loses access Aug 30Exported files stay in DriveNo refund for partial monthsRestart anytime before Aug 30Saved card removedInvoices kept for 1 yearAPI keys deactivated immediatelySupport tickets open 90 daysCustom domain releases in 7 days
Grouped · 4 chunks
Your planSubscription ends Aug 30Restart anytime before Aug 30No refund for partial months
Your dataData deleted after 30 daysExported files stay in DriveAPI keys deactivated immediately
Your team & domainTeam loses access Aug 30Custom domain releases in 7 daysDownloads work until Aug 30
Billing & supportSaved card removedInvoices kept for 1 yearSupport tickets open 90 days
03Synthesis
Four behaviours that serve both an eye and a nervous system
Both threads converge on one complaint: the interface demands repeated, involuntary effort before the person can get to what they came to do. Every principle below has to earn its place on both sides.
01
Say what’s happening, plainly
A state that’s only implied asks the reader to look again. “Look again” is never free.
Optical. Re-checking is a literal re-focus. Cognitive. An unresolved signal keeps being tracked until it’s closed.
02
Nothing moves unless the person moves it
Layout that shifts or a step that auto-advances forces a fresh read of a screen already resolved.
Optical. A shift means re-locating and re-focusing. Cognitive. Predictability and familiar conventions.
03
Every irreversible step gets a way back
A confirm dialog isn’t a review. A real review shows the consequence and leaves room to change course.
Optical. Reversibility absorbs a misread label. Cognitive. Forgiving, undo-friendly interactions.
04
Scale and pace are the reader’s to set
Text size, spacing and timing are three separate dials, not one bundled “accessibility mode”.
Optical. Room to grow without the layout breaking. Cognitive. No forced countdowns.
04Applied patterns
One settings screen, tested against all four
A speculative account-settings screen, not tied to any real product, showing the principles as actual controls.
Text size & spacing · adjust each independently− Aa +
Autosave · every change is savedSaved just now
Export your data · same spot every visitExport
Delete account · next screen states what’s removed, with 30 days to change your mindReview & delete…
05Audit checklist
Sixteen checks, five groups, each traceable to a source
Contrast & legibility
- Body text meets 4.5:1 against its background; large text meets 3:1.WCAG 1.4.3
- Colour is never the only signal for state, error or required fields.WCAG 1.4.1
- Body copy uses a face with distinct l / 1 / I and 0 / O.Braille Institute
- A softened theme exists alongside pure black-on-white or its reverse.On dark mode and halation
Spacing & layout
- Content doesn’t clip or overlap when a user increases line, paragraph, letter and word spacing.WCAG 1.4.12
- Text and controls resize to 200% without loss of content or function.WCAG 1.4.4
- Dense disclosure is grouped into three to five labelled clusters.Halo Lab, on Miller’s Law
Timing & motion
- No countdown on a decision unless functionally required; any timer is visible, pausable and extendable.WCAG 2.2.1
- Auto-advancing content can be paused, stopped or hidden.WCAG 2.2.2
- Promotional urgency never appears on a cancellation, deletion or downgrade flow.TetraLogical
Reversibility & transparency
- Every irreversible action shows a review step stating exactly what changes.TetraLogical · UXmatters
- A field requesting personal information explains why before the field.TetraLogical
- Destructive actions carry a real undo window, not only a confirmation dialog.UXmatters
Predictability & status
- The same control performs the same action, in the same place, on every screen in a flow.TetraLogical · UXmatters
- A wait state carries a plain-language label and, where possible, an honest duration.TetraLogical
- Every completed action gets an explicit, visible confirmation.TetraLogical · Halo Lab
06Sources
What this is built on
- Mayo Clinic: Astigmatism, symptoms and causes
- Characterizing Astigmatism in the United States
- UK Biobank: Frequency and Distribution of Corneal Astigmatism in Adult Life
- AstigmatismoFit: Why Dark Mode Can Make Astigmatism Worse
- Braille Institute: Atkinson Hyperlegible
- WCAG 2.1: SC 1.4.3, Contrast (Minimum)
- WCAG 2.2: SC 1.4.12, Text Spacing
- WCAG 2.2: SC 2.2.1, Timing Adjustable
- TetraLogical: Designing for People with Anxiety
- UXmatters: Designing Calm
- Halo Lab: Mental Health and Inclusive UX
- Knowledge Action Portal on NCDs: Anxiety Disorders (relaying WHO)
Keep exploring
Explore more work
Finding what breaks before users do
A heuristic evaluation of the document wallet used by 550+ million citizens.
10 findingsRead case study →
The Invisible Redesign
Two enterprise platforms, rebuilt around the habits expert users already relied on.
2023 – 2025Read case study →
UX for Conversational AI
One intent, resolved the same way across voice and chat.
2022 – 2023Read case study →