• Neodymium-YAG capsulotomy for secondary cataracts can induce acute intraocular pressure rises, possibly by a blocking of the trabecular meshwork by debris. To test a hypothesis that bag-fixated intraocular lenses may act as a barrier to debris, thus reducing pressure rises after YAG capsulotomy, we conducted a study comparing pressures (at 1, 2, 3, 6, and 24 hours after YAG capsulotomy) between bag-fixated and sulcus-fixated cases. There were substantial and statistically significant intraocular pressure rises in the sulcus-fixated group starting at 1 and 2 hours after YAG capsulotomy, and peaking at 3 hours (mean rise, 7.83 mm Hg). There were no such peaks of intraocular pressure rise among bag-fixated cases (mean change, −0.32 mm Hg at 3 hours). There was a weak but significant (r = −.18) correlation between the change 1 hour after YAG capsulotomy in intraocular pressure and percent of enclosure of the intraocular lens optic among bag-fixated cases. Higher proportions (fourfold to fivefold) of cases with sulcus-fixated lenses had significant flare and particulate matter in the anterior chamber, compared with bag-fixated cases.