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When an object is brought close to a person's eyes, the pupils will naturally move inwards in response to a stimuli, mimicking that of esotropia.

However, what could be a reason in which the pupils shows no response to such a stimulus while behaving normal otherwise?

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  • You are talking about the optical reflex (seeing an object approach) or the corneal effect (stimulated by sensation of something on the eye), right? Both will lead to closing the eye lid, and one can train both to disappear (contact lenses, goalkeeper etc.). The pupils can’t move inward, they are not mobile. They can only narrow and widen.
    – Narusan
    Commented Jan 31, 2019 at 17:45
  • @Narusan I believe OP is referring to the direction of gaze, not actual movement of the pupils.
    – Carey Gregory ♦
    Commented Jan 31, 2019 at 18:50
  • @CareyGregory True. But then again, it doesn't really make much sense as a reflex. It does absolutely nothing to prevent damage to the eye, and there are other reflexes. Maybe the people follow the object with their gaze, and when you brink it closer to the center of the person, obviously the angle of the gaze of both eyes will increase and they will look further inwards.
    – Narusan
    Commented Jan 31, 2019 at 18:53

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I think you are mistaking accomodation (pupil movement) for convergence (eyeball movement). Pupils can constrict and dilate by motion of ciliary muscles, but any other movement is movement of the entire eyeball.

This is from Medscape on Extraocular Muscle Actions.

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Vergence includes convergence and divergence, and is the movement of both eyes together in response to proximity of objects desired to keep in focus. Although it is part of the accomodation-convergence reflex, different muscles innervate it than the pupil.

It is impossible to give a complete differential diagnosis based on the information given, and we do not give personal medical advice so any added clinical correlate would likely cause this question to be closed.

A lesion affecting Cranial Nerve III, which innervates the medial rectus, could cause paralysis of the medial rectus muscle; however, it also innervates "skeletal muscle of the levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique muscles.(innervates all the extrinsic muscles except superior oblique and lateral rectus.)" (Reference: Wikipedia)

A lesion of CNII would result in visual defects, but could also influence the perception of objects' distance and thereby impact convergence.

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