Anisometropia and Associated Phoria

Man... its hard keeping up with all these updates. I think I'll just post the most interesting ones from now on.

Today was a followup exam with no clear instructions from the previous intern. Based on the file, it seemed like her IOPs were slightly high, but not abnormal. Her IOPs are being monitored, so I thought today is probably just an IOP check, to make sure they're normal.

But when the patient arrived, it seemed she was unhappy about her glasses, and said that she wanted to get her Rx rechecked and sorted out. She claimed to have had 0.5 BU OD slab-off lenses, and were very happy with them. However, when they updated her Rx with an add, they told her they can only make slab-offs starting at a minimum of 2pd.

I believe she was given the 2pd, and she said it was too strong and refunded the lenses.

So she's back today to get her Rx fixed.

Looking at her Rx, it was clear she was anisometropic. She complained of asthenopia and "pulling" at near while trying to read her recipes.

The best thing about partial/follow up exams is being able to tackle problems using problem specific testing strategies.

So I started off with VAs to see if she can see at near. Then CT/von grafe phoria/maddox to see if phorias are within limit.

Her lateral phorias were normal, but I ended up finding a 3BU OD on maddox rod at near which is what I expected for someone with anisometropia.

I go seek out my supervisor to tell him what I've found. He came and investigated her history again... apparently "pulling" meant there is a convergence problem! I was confused because her CT and von grafe values were normal... On further questioning from my supervisor, she tells us that she had never been able to cross her eyes :O... I guess I should've tested PFV and NFV as well.

So we break out the mallet box (yes, seriously) and test her ASSOCIATED PHORIA at near.

Recall: Px uses polarized glasses to look at the O X O target surrounded by texts to obtain fusion lock - but above and below the O X O target are nonius lines each seen by only one eye. In her case, she needed a 4BO to line up the nonius lines.

So, a patient who I thought is coming for an IOP checkup actually needed 3 BU OD. And on further testing also needed 4 BO.

We ended up prescribing 3 BU OD and 4 BO on top of her current Rx.

How on earth did she ever survive with just a 0.5 BU OD slab-off?