Intraocular pressure in children: Effect of repeat measurements, topical anesthetic, and positioning, as assessed with Icare compared to Goldmann applanation and Tonopen

Abstract

Tonometry is critical in evaluation/management of children with known/suspected glaucoma, but cooperation often precludes Goldmann applanation(GAT). Tonopen tonometry offers portability in upright/supine positions, but requires anesthetic. Both Icare- and Icare-PRO-rebound tonometry circumvent anesthetic, the latter allowing supine intraocular pressure (IOP) measurement. This study addresses several relevant questions regarding tonometry in children: (1) Does IOP change with repeated Icare measurements? (2) Does IOP change before/after topical-anesthetic? (3) Does position(sitting-supine) alter IOP? Ongoing, prospective study of children’s eyes (normal, suspected+known glaucoma). In arm #1(Reproducibility/Anesthetic), eight sequential pre-topical-anesthetic Icare-IOPs were followed by three post-topical-anesthetic Icare IOPs, then masked GAT. In arm #2 (sitting/supine), two post-topical-anesthetic Icare-PRO(Icare FinlandOy, Helinski, Finland, not FDA-approved) vs Tonopen(MedtronicsOphthalmics,Florida) IOPs were taken in random order, followed by masked GAT (all sitting); after 5-minutes supine positioning, Icare-PRO- vs Tonopen-IOPs were repeated. Arm #1 (Reproducibility/Anesthetic) has enrolled 10 children(20eyes), median age = 11 years (6-15). Mean (range) initial IOP (mm Hg) by Icare exceeded GAT [18.7(9-42) vs 16.7 (8-32), respectively, P < 0.001]. IOP(Icare, 1st-8th) was 0.1 mm Hg, P = NS), with coefficient-of-variation = 8.4%; IOP (Icare, pre- vs post-topical-anesthetic was 0.0 (P = NS). Arm #1 was powered(>90%) to find IOP = 1.6 mm Hg. Arm #2 (sitting/supine) has enrolled 17 children (34 eyes), median age = 12 years (8-17). Mean sitting IOP (mm Hg) for GAT, Icare-PRO, and Tonopen was 16.4 ± 3.0, 17.7 ± 2.5, and 18.2 ± 3.5, respectively. Mean supine IOP (mm Hg) for Icare-PRO vs Tonopen was 18.2 ± 2.6 vs 18.8 ± 3.8, respectively. Compared with GAT (sitting), IOP (mm Hg) was 1.4 (Icare-PRO-sitting,P < 0.001), 1.8 (Icare-PRO-supine, P = 0.002); 1.9 (Tonopen-sitting, P < 0.001), and 2.5 (Tonopen-supine, P = 0.002). The study was powered (90%) to find IOP (supine vs sitting) = 2 mm Hg). Neither repeated measurement, nor topical-anesthetic significantly alters Icare-IOPs in children. Both Tonopen- and Icare-measured IOPs exceed GAT, but position-related IIOP is small. Icare tonometry may be used following topical anesthetic after attempted Tonopen/GAT. The Icare-PRO may prove useful in measuring IOP sitting and supine.