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IOL selection with eccentric pupils
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With cataract surgery we make an assumption that the center of the visual axis, the center of the pupil and the center of the IOL will be close, and that since we're putting a round optic in a round capsular bag, that the orientation isn't critical. But what do we do in eyes with eccentric pupils?
 The eccentric pupil is nasally shifted in this eye. |
We know that the temporal cornea is farther from the pupil than the other quadrants, and that's one of the reasons why it's a good location for our cataract incisions. In an eye with a significantly decentered nasal pupil, we need to make some adjustments in order to ensure the best centration of the IOL with the visual axis. Orienting the IOL vertically, at the 12 and 6 o'clock meridian, may let us nudge the IOL nasally to improve centration. Multifocal IOLs may pose issues with proper centration of the multifocal rings within the pupil.
For the IOL calculations, the traditional K measurements are likely to be very close, but perhaps looking at the corneal power more nasally would be of some benefit. In the postoperative state, these eyes may be more prone to dysphotopsias, particularly if the IOL isn't well-aligned with the pupil.
In the majority of cases with eccentric pupils, the visual results are excellent despite the lack of perfect centration of the IOL with the visual axis. Severe pupil or iris abnormalities should be addressed, as I'll show in the next blog entry.