Convergence Prism and Accommodation.

[braheem24]

34 year old male, never been able to read for a long period of time as far as he can remember.

old rx
-1.25
-1.25

new Rx
-1.25 2BI
-1.25 2BI

My question, is it possible the convergence required to align his eyes was making him for a lack of a better word a latent hyperope and inducing plus in his vision?

Is it possible he may need less minus once he adapts to the prism?

[braheem24]

Should I just PM DRK, cause I know hes going to be the main responder to this type of question :D

[drk]

You're understanding the relationships somewhat...good for you.

Assuming that this Rx signifies what it usually does, it means this guy has an exodeviation at distance.

Assuming the prescriber does what is normally done (and that's a big if, since "normal" is pretty tough to define), 4^ correction is probably a partial (maybe 50%) correction of the exodeviation, which may well be 8^ or more.

Pick up a 8^ prism and hold it base OUT to mimic 8^ exophoria! You notice that to fuse the horizontal diplopia, you have to use "fusional vergence" and you may even start to accommodate to help fuse (since "accommodative convergence", while a separate type of vergence than fusional, is often triggered). That means that he could theoretically be in a chronic accommodative spasm, and is therefore a pseudomyope.

So yes, maybe he'll go less minus over time, as you postulate.

There's much more, but that's a start.

[braheem24]

Rx is for distance correction.

At 5BI total OU, image starts to split in the other direction when looking at objects over a mile, under a mile not really noticable so I would assume 4 is the total prism since 5 is not tolerable.

Should the patient be cyclopleged and refracted?

If so, would the inverse be true? would paralyzing the accommodation also inhibit convergence? ie: When cyclopleged an increase in BI prism may appear? or would convergence increase to further compensate for lack of accommodation?

[OHPNTZ]

I don't think the patient needs to be cyclopleged. I think a parks 3 step to rule out a nerve palsy, or a full binocular work up would be more in order...especially testing positive fusional vergences with blur/break/recovery to the expected norm.

This patient may benefit from a combination of prism and vision therapy, with a gradual reduction in the prism amount.