There are exceptions.
The causes of strabismus are complex, but there are patterns.
The strabismus we talk about is not the same thing as the "squint eyes" that ordinary people understand. Strabismus is the inability of both eyes to keep their eyes fixed on the same target at the same time. The husband and Fa Xiao drank out late, and when they got home, the daughter-in-law "squinted at him", and this kind of "squint" is not squint, it is called "sideways vision".
Overall,When "the force that separates the eyes makes the eyes focus on the same target," or "the force that sets the eyes together the same target, the resistance that separates the eyes," the two eyes are unable to focus on the same target, and squints occur.
In other words, the reason why most of us don't have esotropia is because the extraocular muscles of our eyes are in a controlled state of balance.
Myopia does predispose to exotropia.
When looking close, you need to "turn inward" to keep your eyes on a nearby target. This "inward" action is called a "set", and it is divided into three parts: the near-perceptual set, the reflex, the accommodative set, and the fusion set. It's a bit awkward, so I won't go into detail about these kinds of collections. Everyone thinks that no matter what kind of set is missing, it is equivalent to "reducing the power to keep two eyes on the same goal", and the "power" here is the collective force.
When looking close, the human eye needs to invoke more accommodations to focus on the near area, because the accommodation and the collection are "linked" (related to neural mechanisms, which will not be discussed in detail here), so the "regulatory collection" is generated to help the eyes turn inward. That is, "conditioning set" is the power to keep two eyes fixed on the same goal.
The myopic eye does not need to invoke as much adjustment when it sees near, and the "accommodative gathering force" is correspondingly reduced. When the converging force is reduced to a certain extent and the "equilibrium state" is broken, it is unable to resist the "force that separates the eyes outward", and an external deviation occurs.
Farsightedness is indeed prone to esotropia.
If the farsightedness of the hyperopia eye is not corrected with glasses, it is necessary to call adjustment to "resolve hyperopia". As the regulation increases, the "regulation set" increases. When the "force that causes the two eyes to converge and turn inward" increases to a certain level and exceeds the "separate force" that makes the eyes focus on the same target, the "equilibrium state" is broken, and an inverted slope occurs.
All of the above is analyzed from the perspective of "regulatory sets". However, there are many causes of strabismus, such as the neurological level, the muscular level, the mechanical limiting cause, the gathering and separating forces, etc., and no matter which reason prevails and breaks the "equilibrium state", the eye position will be skewed towards the direction of the "upper hand".
So,Myopia can also have esotropia, and farsightedness can also have exotropia, but this is relatively rare.