What if the Capsulorhexis is too big?

rhexis too big

Ideally, the capsulorhexis diameter should be slightly smaller than the optic diameter so that we can achieve 360° overlap. But what if it doesn’t? Well, it turns out that it is not that big of an issue because the capsule shrink-wraps in the post-op period and it makes the capsulorhexis diameter about 10% smaller — sometimes even more. Remember that the cataract is about 4 mm thick (like an M&M candy) while the IOL is as thin as a coin (1 mm thin). This means that the capsular bag will end up shrink-wrapping quite a bit in the post-operative period.

M&M vs dime

The typical amount of capsulorhexis diameter shrinkage is about 10% but this can vary. Cases of capsular phimosis are an example of shrinking many times more than typical, with the zonular structures being too weak to oppose the shrink-wrap forces.

capsule contraction

In the case presented here, the capsulorhexis overlaps the optic in some areas, but not in others. Since the optic is 6 mm in diameter, this means that the capsulorhexis is slightly larger than 6 mm in some areas and then slightly smaller than 6 mm in others. Again, this is not a concern since the 10% shrinkage (or more) of the capsular bag will result in overlap of the optic and secure positioning for many years to come.

Click below to watch the video of a capsulorhexis that is slightly too large:

 

4 Comments

  1. YOU SEEM TO IMPALE THE NUCLEUS WITH YOUR CHOPPER TO MAKE THE FIRST CHOP, YES? WHICH CHOPPER DO YOU USE? I AM USE TO PUTTING THE CHOPPER BEHIND THE EQUATOR, AND THE CHOPPER HAS AN OLIVE TIP WHICH YOURS DOES NOT SEEM TO HAVE. THANKS

    1. Yes, you are correct. Different machines have different energy deliver amounts and even frequency. The percent that the machine shows is just a percent of maximum. It’s an odd measure if we compare it to other gauges such flow of fluid or vacuum level, which are both reported in actual units which are comparable between various platforms.

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