Any farsighted person must use accommodation to clear vision.  Your son uses
2D of accommodation to clear distance vision and 4D to 5D to clear near.  In
humans, accommodation is linked to convergence; when the eyes accommodate
they also turn in (A/CA ratio).  The usual ratio is about 4 prism dioptres
of turning in per dioptre of accommodation.  However, some people have
higher ratios, up to 8 to 10 prism dioptre convergence pre dioptre of
accommodation.  As the amount of turning in increases, the muscles that turn
the eyes out become overtaxed and the result is esotropia.  This kind is
called accomodative esotropia because it is caused by the over accommodation
and the esotropia goes away when accommodation is normal.

Also, people vary in where their eyes are pointing when at rest.  Most
people's eyes turn out slightly at distance and more at near, but some
people have a slight turning in at distance and near.  This is not a problem
as the eye uses muscles to align the eyes.  However, if your son has a
slight turning in, a high A/CA ratio and farsightedness then he could have
an alternating esotropia (fancy name for both eyes turning in, taking
turns).  If you have only the farsightedness without the high ratio, then
your eyes likely won't turn in.

The glasses solve the turning in because they remove the need to accommodate
for the distance and thus the eyes do not turn in excessively.

Well most, not all.  And most do not have the other conditions that make
eyes turn in.

No.  The best and standard treatment for esotropia due to accommodation is
glasses. .

Yes, this is expected.  He has to work his eye aligning muscles very hard to
try to maintain no eye turn and when he is tired, he will not control the
turn as well and it will be more evident.

Get the second opinion, but the first one was a good one.

The most common reason for children his age to need glasses is
farsightedness causing an eye turn.  If you do not correct the eye turn, he
will not develop good depth perception and, if the problem persists, may
eventually tend to turn only one in and then will develop a lazy eye.  He
will thank yo when he is an adult for correcting his vision now.

He likely will become less farsighted as he grows older; if that happens
then he will no longer need the glasses

Dr Judy

How often do his eyes turn in, and is it always the same eye that turns it
or does it alternate?

If they're straight 90% of the time, and it's an alternating turn, then
there could be an argument for just monitoring him closely rather than going
straight for the specs. Especially if the doctor said he hasn't got a lazy
eye. HOWEVER if they are turning in more of the time, or all of the time, OR
if it's always the same eye that turns in, then the specs are a good idea.

1. +2 is moderately far-sighted.
2. Already answered by Dr Judy
3. Most toddlers are far-sighted, but not as much as your son.
4. Not at his age. In fact at any age, glasses are the easiest and most
effective way to manage an esotropia.

Unfortunately the doctor is right when he says the eyes may become MORE
crossed without the specs, but this is better than developing a permanent
turn and/or a lazy eye, which are the alternatives you need to be concerned
about.

Dom

First of all, +2 might be the expected refractive error between birth
and one year, but not for a 3 year/old.  According to my experience,
the average refractive error at age 3 years is about +0.50.

Secondly, esotropia -- even if alternating -- is not a "normal"
condition.  If binocular vision is not developed during this sensitive
developmental period, then it may never develop.

Thirdly, amblyopia (lazy eye) is much more co-morbid with
farsightedness and esotropia.  I have seen children who eccentrically
fixate just a little, and hence do not look cross-eyed, but in fact
are.

In summary, it would appear that the risks of doing nothing exceed the
risks of doing something.

DrG