When developing mobile apps / charts for assessing visual acuities using Snellen’s / LogMAR notation, there is a need to estimate the size of letters for a given working distance for assessing a specific cutoff.
Under normal vision, for a visual acuity of 6/6, the whole letter subtends an angle of 5 minutes of arc at the eye.
In a Tumbling E scenario, the height and width of are equal and each subtends 5 minutes of arc. Each of the the strokes of the letter subtends one minute of arc (one fifths).
Google Sheet
https://docs.google.com/spreadsheets/d/1D1Kiyf9wF1jcy3RfwNGyK8b4LW4AVqKcfDXqBv1-ukQ/edit?usp=sharing
References
