I believe kenalog is an intermediate-duration glucocorticoid, also
known as a steroid.  The effects of one steroid injection should wear
off in a matter of days or weeks, depending on where the injection is
given:  Days if injected into muscle, weeks if injected into a joint.

That said, those systemic side effects don't normally happen from one
injection.  I've had kenalog injections for bursitis and didn't
develop any side effects.   But the vision damage you have could
definitely be the cause of depression and weight gain.

One large dose of kenalog could cause some weight gain but that's
because of sodium and water retention.   The effect wears off once the
steroid is out of the system.  Edema can occur around the injection
site.

Good luck,

Kevin

Glucocorticoids can also have profound CNS effects, including euphoria,
dysphoria, or depression.  I know this because as a young man, I was
prescribed Kenacort for seasonal allergies, and I did lot's of research.  
You can probably look it up in the PDR.

DrG