Reading is an integrative task which primarily involves the area just to the right of fixation. Recognising faces is another significant integrative task, in which we build up a complex image by quickly saccading our fovea around the facial features, a bit like the way we build up this view of an island.

Guided saccades build up a larger detailed image
Our facial landmarks are the eyes and the mouth, with only brief excursions around the rest of the head.

Guided saccades build up an integrated image of a face
Patients with macular disease often have trouble with recognising faces. It’s partly a contrast task — after all, faces aren’t high-contrast black and white, they are shades of skin tone viewed at a variety of distances and at a variety of illumination levels. But it’s also a task that requires putting careful putting together the parts in relation to each other, which is a task that needs some field of view. Anyone with significant patchiness of their macular field will start having trouble with recognising faces.
I actually use this as a kind of VA measurement, but as a rough proxy for how patchy the patient’s macular fields are. I’m usually seated about a metre away, and I ask the patient if they are confident they would recognise me just from looking at my face. If they say yes, I move my chair right back to the door and ask again. Or if they say no, I move closer, even to as close as 30cm.
I record that as ‘recognise face at 1.5m’ or similar. It’s a useful bit of information. Patients often present some years later saying that their vision is worse, but they have almost the same VA. But if they can only recognise your face at one metre, where before they could recognise you at three metres, that’s an easy confirmation that they’ve lost significant macular field.
Recognising a face is one thing. Once you’ve established that a certain person is present, you don’t have to keep on recognising them. You can keep track of them by other cues — what they are wearing, how tall they are, and of course voice.
Recognising facial expressions is a whole different thing. Faces are dynamic, rapidly changing as an important part of any interpersonal interaction.
\Same face, dynamic facial expression.

Same face, different expressions
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