Effect of Prone Positioning on Intraocular Pressure in Patients With Acute Respiratory Distress Syndrome, Objectives: To evaluate the effect of prolonged duration of prone position (with head laterally rotated) on intraocular pressure in acute respiratory distress syndrome patients. Design: Prospective observational study. Setting: University hospital ICU. Patients: Twenty-five acute respiratory distress syndrome patients, age 60 years (51–67 yr), Sequential Organ Failure Assessment score 10 (10–12), PaO2/FIO2 ratio of 90 (65–120), and all in septic shock. Interventions: None. Measurements and Main Results: Intraocular pressure (in mm Hg) measured by hand-held applanation tonometer, at different time points. Before prone (in both eyes): at 30–45° head-end elevation position (THE pre-prone), in supine position just before turning prone (Tsupine pre-prone); during prone (in nondependent eye): at 10 minutes (T10 prone), 30 minutes (T30 prone), and at just before end of prone session (Tend-prone). After end of prone session (both eyes): at 5 minutes (T5 supine post-prone), 10 minutes (T10 HE post-prone), 15 minutes (T15 HE post-prone), and 30 minutes (T30 HE post-prone). Median duration of prone position was 14 hours (12–18 hr). Median intraocular pressure increased significantly (p ≤ 0.001) in both eyes. In dependent eye, from 15 (12–19) at THE pre-prone to 24, 21, 19, and 16 at T5 supine post-prone, T10 HE post-prone, T15 HE post-prone, and T30 HE post-prone respectively, whereas in nondependent eye from 14 (12–18.5) at THE pre-prone to 23, 25, 32, 25, 22, 20, and 17 at T10 prone, T30 prone, Tend-prone, T5 supine post-prone, T10 HE post-prone, T15 HE post-prone, and T30 HE post-prone respectively. Bland-Altman plot analysis showed significant linear relationship (r = 0.789; p ≤ 0.001) with good agreement between rise in mean intraocular pressure of the both eyes (dependent eye and nondependent eye) with their paired differences after the end of different duration of prone session (T5 supine post-prone). Conclusions: There is significant increase in intraocular pressure due to prone positioning among acute respiratory distress syndrome patients. Intraocular pressure increases as early as 10 minutes after proning, with increasing trend during prone position, which persisted even at 30 minutes after the end of post prone session although with decreasing trend. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website (http://journals.lww.com/ccmjournal). Presented, in part, as an abstract at the ESICM LIVES (September 27, 2017, Vienna, Austria) and ISCCM CRITICARE (March 8, 2018, Varanasi, India) meetings. Dr. Gurjar received funding from Intramural and Extramural Research Grant (unrelated to submitted work), and he received funding from Jaypee Medical Publishers, New Delhi, India (royalties). The remaining authors have disclosed that they do not have any potential conflicts of interest. For information regarding this article, E-mail: m.gurjar@rediffmail.com Copyright © by 2019 by the Society of Critical Care Medicine and Wolters Kluwer Health, Inc. All Rights Reserved.