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LPI in temporal iris yields less linear dysphotopsia than in superior iris
Laser peripheral iridotomy performed in the temporal iris resulted in less linear dysphotopsia than in the superior iris, according to a study.
The prospective, randomized clinical trial included 338 eyes of 169 patients with primary angle-closure glaucoma or suspected primary-angle closure glaucoma who underwent laser peripheral iridotomy (LPI) temporally in one eye and superiorly in the fellow eye.
Investigators evaluated the occurrence on new-onset linear dysphotopsia. They used a questionnaire to assess other visual disturbances preoperatively and 1 month postoperatively. Secondary outcome measures were eyelid position, laser settings and intraoperative complications.
Mean laser energy used, number of shots and total energy were similar in the temporal LPI and superior LPI groups.
Eighteen eyes (10.7%) in the superior surgery group and four eyes (2.4%) in the temporal surgery group showed signs of new-onset dysphotopsia. The difference was statistically significant (P = .002).
Linear dysphotopsia was reported in 11 eyes (6.5%) in the superior surgery group despite complete eyelid coverage of the iridotomy.
Subjective pain scores were 2.8 in the temporal LPI group and 2.1 in the superior LPI group. The between-group difference was statistically significant (P < .001).
Intraoperative hemorrhage rates were 8.9% in the temporal LPI group and 10.1% in the superior LPI group; the difference was insignificant.
Disclosure: The authors have no relevant financial disclosures.
Perspective
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The report by Vera and co-authors confirms what some others have thought, specifically, performing laser iridotomies in areas other than under the lid is a satisfactory procedure. In fact, it is probably better to change how we have practiced and to stop performing iridotomies routinely underneath the lid despite what seems like an intuitive, obvious assumption that they would be less symptomatic if covered by the lid.
Several important messages can be learned from this paper: 1) It is often dangerous to make assumptions; 2) when one assumes something to be true and somebody challenges it, it is wise to listen carefully, especially if the person is a sharp and intelligent observer; and 3) when an assumption appears to be incorrect, it is wise to examine it carefully and study it scientifically, if possible, to conclude whether the assumption is valid or invalid, and then act on the basis of that new decision.
Perhaps 10 years ago, I examined a patient of Marlene Moster. Dr. Moster had performed a laser iridotomy temporally. I was appalled! I spoke to her, and she mentioned that she frequently performed them there. We decided to study the issue. As a result, a paper was published: the effects of iridotomy size and position on symptoms following laser peripheral iridotomy. It showed that “ghost images” were less likely to occur when the peripheral iridotomies were completely exposed than when partially covered.
There are assumptions in the article by Vera and colleagues. Their explanation for why images are rarer when the iridotomies are performed temporally is not totally convincing. Additionally, there are difficulties with performing laser iridotomies temporally; they tend to bleed more, and they can be obscured by ciliary processes.
It is probably best to consider each case separately and decide where is the best place to perform a laser peripheral iridotomy on that particular patient.