Resolution limit of the eye

This repository contains data and MATLAB scripts for the project: 'Resolution limit of the eye: how many pixels can we see?'

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System Requirements

• Software: MATLAB R2021b or later
• Dependencies: No external toolboxes required
• OS tested on: Windows 11, Ubuntu 22.04
• Hardware: No special hardware required; runs on standard desktop/laptop

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Installation Guide

No installation is required.

1. Clone or download the repository as a .zip file.
2. Open MATLAB and add the matlab folder (and utils/ subfolder) to the MATLAB path:

   addpath(genpath('path_to_repository/matlab'))
   

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Data Files

• data/resolution_limit_data.csv - Observer-level results from the main resolution limit experiment. Each row corresponds to a single threshold measurement. Observer identifiers have been anonymized. The description of the variables is as follows:

Variable	Description
observer	Anonymized observer ID (e.g., Obs001, Obs002, ...)
luminance_cd_m2	Stimulus luminance in candela per square meter
eccentricity_deg	Eccentricity of the stimulus in visual degrees
color_direction	Categorical variable indicating chromatic direction (1: achromatic, 2: red-green, 3: yellow-violet)
stimulus_size_deg	Size of the stimulus in degrees of visual angle
stimulus_shape	Shape type of the stimulus encoded as categorical variable (1: square-wave grating modulated with a Gaussian envelope)
num_trials	Number of trials included in the threshold estimation
threshold	Estimated resolution threshold in units of cube-root spatial frequency
threshold_ci_low	Lower bound of the confidence interval for the threshold estimate
threshold_ci_high	Upper bound of the confidence interval for the threshold estimate
threshold_ppd	Resolution threshold in pixels per degree (ppd)
threshold_ppd_ci_low	Lower bound of ppd-based threshold confidence interval
threshold_ppd_ci_high	Upper bound of ppd-based threshold confidence interval
contrast_sensitivity	Inverse of the grating contrast used (cone contrast units)

• data/resolution_limit_median_data.csv - Summarised median threshold results across participants, used to generate predicted heatmaps.

• data/text_resolution_limit_data.csv - Resolution limit data from the text stimuli experiment. The description of the variables is the same as in the main experiment data.

Code Files

MATLAB scripts to generate the figures in the paper are provided in the directory matlab.

• plot_res_limit.m - Generates Figure 1a: Violin plots showing resolution limit (in pixels per degree) across eccentricities and chromatic directions from the data in data/resolution_limit_data.csv.
• plot_heatmap_prediction_interval.m - Generates Figure 1b: A heatmap representation of the modelled spatial resolution limits across eccentricity. Confidence intervals and predicted contours are drawn using model fits based on Watson (2018).