Purpose: This study aimed to observe changes in anterior chamber parameters and the course of intraocular pressure (IOP) after injection of 0.1 ml intravitreal triamcinolone acetonide (TA) and to determine differences between phakic and pseudophakic eyes without vitreous reflux. Methods: A prospective observational clinical trial was conducted with 89 patients who received an intravitreal injection of TA and did not display vitreous reflux. Intraocular pressure measurements were made before injection and at 3, 10, 20, 30 and 40 mins after injection. Pentacam measurements were made before injection and at 5, 15, 30 and 45 mins after injection. Results: Anterior chamber depth (ACD) and anterior chamber volume (ACV) were significantly greater in pseudophakic eyes than in phakic eyes at all measurement time-points (p < 0.001). There was a decrease in both ACD and ACV at 5 mins after injection, and a gradual increase to normal values was observed at 15, 30 and 45 mins after injection in all study eyes. Compared with pre-injection measurements, changes in ACD and ACV were statistically significant at each time-point in both phakic and pseudophakic eyes (p < 0.001). A significant increase in IOP within 3 mins of injection was observed in both groups and a more rapid decrease 10 mins after injection was observed in pseudophakic eyes. The differences in IOP between phakic and pseudophakic eyes at all measurement time-points, except baseline and 3 mins after injection, were statistically significant (p < 0.001). Intraocular pressure < 30 mmHg and < 24 mmHg was recorded in all pseudophakic eyes at 10 and 20 mins after intravitreal injection, respectively. Conclusions: Following intravitreal injection of 0.1 ml TA, without vitreous reflux, IOP decreased to safe levels more quickly in pseudophakic eyes than in phakic eyes. Although there were more pronounced changes in anterior chamber parameters in pseudophakic eyes, these changes were reversible without any residual clinical significance. © 2009 The Authors Journal compilation © 2009 Acta Ophthalmol.