LPI in temporal iris yields less linear dysphotopsia

This prospective study found that eyes undergoing superior laser peripheral iridotomy (LPI) are three times more likely to experience dysphotopsia than those with a temporally placed LPI.

The authors compared outcomes of temporal versus superior neodymium:yttrium–aluminum–garnet LPI in 169 patients with primary angle-closure or primary angle-closure suspect.

Each patient was randomized to receive LPI temporally in one eye and superiorly in the other. Patients were masked to the location of treatment in each eye. All participants were given a dysphotopsia questionnaire before and one month after treatment. 

Temporal laser iridotomies produced significantly more pain, despite no difference in laser energy or number of shots, but had a significantly lower rate of dysphotopsia (2.4 percent vs. 10.7 percent in superiorly treated eyes). 

Interestingly, none of the eyes with superior iridotomies that were completely exposed (not partially covered or completely covered by the lid) had complaints of dysphotopsia, while 25 percent of the patients with partially covered iridotomies had dysphotopsias.

They conclude that the ideal location of an LPI is in the temporal iris for the average patient. This is supported both by theoretical optics and the results of this clinical trial. However, they also write that nasal placement would likely result in similar findings as temporal placement.

Because eyelid positions vary among ethnicities and in older versus younger patients, one must customize the position of LPI to the individual patient's anatomic features. Furthermore, care should be taken to examine the patient's eyelids before and ensure that the upper eyelid does not cover or partially cover the temporal LPI location.