# Effect of Chromostereoscopic Stimulus on Accommodative Response and Subjective Perception

## TL;DR

This study shows that blue text on a black background causes the most focusing errors and discomfort, while red text is easiest for the eyes to focus on.

## Contribution

The study provides new physiological evidence on how different colored text affects accommodation and user comfort in dark-themed interfaces.

## Key findings

- Blue text induced the greatest accommodative lag, while red text had the smallest.
- Blue text was perceived as most distant and hardest to read, while red was perceived as closest.
- Yellow text was rated as the easiest to read by participants.

## Abstract

The phenomenon of chromostereopsis, where colours are perceived at different depths due to the eye’s optics, creates a potential conflict during accommodation. This prospective, cross-sectional study aimed to investigate the effect of different chromostereoscopic stimuli on the objective accommodative response and subjective user comfort.

Thirty young, healthy adults (mean age 19.83 ± 1.18 years) read text passages presented on an iPad at a 50 cm viewing distance. Stimuli included red, green, blue, yellow, and mixed-colour text on a black background, compared to a standard black-on-white baseline. Accommodative lag was measured objectively using an open-field autorefractor, while subjective ratings of perceived depth and screen readability were collected via questionnaire.

A significant main effect of stimulus colour on accommodative lag was found (p < .001). The short-wavelength (blue) stimulus induced the greatest mean accommodative lag (0.61 D). Conversely, the long-wavelength (red) stimulus produced the smallest lag (0.18 D), indicating the most accurate accommodative focus. Subjective data strongly corroborated these findings, with blue being perceived as most distant and most difficult to read (76.67% and 73.33% of participants, respectively), while red was perceived as closest and yellow was perceived as the easiest to read (53.33%).

Colour is a critical factor in visual ergonomics for dark-themed interfaces. A pure blue stimulus on a black background acts as a poor driver for accommodation, leading to significant focusing errors and a diminished perceptual experience. These findings provide a physiological basis for user interface design guidelines, suggesting that the use of short-wavelength, saturated text for reading tasks should be avoided to optimize visual comfort and performance.