Intraocular Pressure in Children: The Effect of Body Position as Assessed by Icare and Tono-Pen Tonometers

Purpose To explore the effect of body position (sitting vs supine) on intraocular pressure (IOP) in children, as assessed by the Icare PRO and the Tono-Pen. Design Prospective clinical study. Methods Children with known or suspected glaucoma and those without glaucoma were recruited from the Duke Eye Center pediatric clinic. Subjects underwent tonometry in both eyes while upright (sitting), after instillation of topical anesthetic, with either the Icare PRO or the Tono-Pen first, and then the second instrument (order randomized). Goldmann applanation tonometry (GAT) was then performed by a clinician masked to the previous measurements. The subjects were then placed in the supine position for 5 minutes, and tonometry using the Icare PRO and the Tono-Pen was obtained, in the same order used when they were the sitting position. Results Enrolled were 47 children (94 eyes). Mean seated IOP for GAT, Icare PRO and Tono-Pen were 16.4 ± 4.2, 17.5 ± 3.5, and 18.0 ± 3.9 mm Hg, respectively. The mean supine IOP for the Icare PRO and Tono-Pen were 18.4 ± 4.5 and 18.8 ± 4.2 mm Hg, respectively. This rise was +0.9 ± 2.3 mm Hg for Icare PRO ( P = 0.01) and +0.7 ± 1.8 mm Hg for Tono-Pen ( P = 0.009), respectively. Conclusion In children, Icare PRO tonometry correlates well with GAT in the sitting position, and with the Tono-Pen in both the sitting and supine positions. IOP rises when a child changes position from sitting to supine when measured by the Icare PRO or the Tono-Pen. However, the increase, which is less than 1 mm Hg, seems clinically insignificant and is unlikely to alter glaucoma management in children.