Designing for Low Vision Users: Vision Accessibility

Low vision encompasses numerous conditions affecting visual perception differently: age-related macular degeneration causes central vision loss, diabetic retinopathy affects peripheral vision, cataracts reduce contrast and clarity, and numerous other conditions create varied visual barriers. Low vision users often employ multiple strategies: enlarging text through browser zoom, using screen magnification software, adjusting display contrast, using high-contrast color schemes, and adjusting lighting. Websites should support these strategies, not hinder them. Unlike blind users relying on screen readers, low vision users typically use visual interfaces. They need design practices supporting their partial vision while maintaining the visual experience.

Color contrast is fundamental to low vision accessibility. The difference in brightness (luminance) between text and background directly affects readability for users with low vision. WCAG Standards: Sufficient contrast dramatically improves readability for low vision users. A 7:1 ratio (Level AAA) provides exceptional clarity compared to minimum 4.5:1 ratio. Font size: Body text should be minimum 16px. Low vision users often increase text size through browser zoom, but starting with readable base sizes helps. Font choice: Sans-serif fonts (Arial, Helvetica, Verdana) are generally more readable than serif fonts for screen display. Clean, simple typefaces work better than decorative fonts. Line spacing: Minimum 1.6 line height for body text improves readability. Generous spacing between lines reduces visual crowding. Letter spacing: Adequate spacing between letters aids readability, particularly important for users with macular degeneration affecting letter perception. Avoid all-caps: All-capital text is harder to read than mixed case. Reserve all-caps for short labels only. Websites must support user-initiated text resizing. Users should be able to increase text size up to 200% without losing functionality or requiring horizontal scrolling. Testing approach: Zoom your website to 200% in browser DevTools. Verify: Clear visual hierarchy helps low vision users understand content organization. Use size, color, weight, and spacing to establish hierarchy. Avoid dense content blocks with poor organization. Good visual hierarchy: Headings substantially larger than body text, clear spacing between sections, consistent layout. Poor visual hierarchy: Text sizes too close together, crowded layouts, inconsistent spacing making structure unclear. Don't use color alone to convey information. For color-blind users and those with certain visual conditions, color-only information is inaccessible. Good: "Required fields are marked with an asterisk (*) and have red labels" Poor: "Required fields are shown in red" Supplement color coding with additional visual cues: patterns, icons, text labels. Dense layouts with minimal white space overwhelm low vision users. Generous white space between elements improves visual clarity and reduces cognitive load. Flashing content (more than 3 flashes per second) can trigger seizures in people with photosensitive epilepsy. Rapid animations distract and disorient users.

Form fields should have: Interactive elements should: Tables should: Images should:

Approximately 8% of men and 0.5% of women have red-green color blindness. Other color blindness types (blue-yellow, complete achromatopsia) affect smaller populations. Avoid red-green combinations: Many color-blind users cannot distinguish red from green. Avoid using these colors as the only distinction between elements. Test with simulators: Color blindness simulators (available online) show how designs appear to users with different types of color blindness. Test your palette. Use redundant coding: Combine color with patterns, icons, or text labels. If a chart line is red for "sales," also make it dashed or include a legend. High contrast palettes: Some color combinations that are indistinguishable to some color-blind users remain distinguishable with sufficient brightness contrast. Prioritize luminance (brightness) differences.

Use WebAIM Contrast Checker or similar tools to verify contrast ratios for: In browser DevTools, zoom to 200% and verify: If possible, test with actual screen magnification software (Windows Magnifier, macOS Zoom, or commercial products). These tools reveal issues that simple browser zoom doesn't catch. Use color blindness simulators to see your site as users with different types of color blindness see it. Adjust palettes if important information becomes indistinguishable. Have low vision users test your site if possible. Actual users identify issues that designers miss and provide invaluable feedback on readability and usability.

Accessible approach: Inaccessible approach: