Rebound tonometry over an air-filled anterior chamber in the supine child after intraocular surgery

Abstract

Intracameral air is a critical component of multiple ophthalmic surgical procedures and is frequently used in pediatric intraocular surgery. Among other benefits, it helps to facilitate postoperative examination in uncooperative children by allowing quick confirmation of a formed anterior chamber. The purpose of this study was to evaluate the usefulness and accuracy of a position-independent rebound tonometer (Icare PRO) in measuring intraocular pressure (IOP) intraoperatively in pediatric eyes with intracameral air compared to a commonly used handheld applanation tonometer (Tono-Pen XL). In this prospective study of sequential children undergoing intraocular surgery, IOP was measured immediately following general anesthesia induction using both Icare PRO rebound tonometry and Tono-Pen XL tonometry, with instrument order randomized, in the supine child's eye(s). At completion of surgery after standard placement of intracameral air IOP was again measured using both instruments. A total of 42 eyes of 30 children were included. Surgeries included glaucoma (25), cataract-related (16), and both (1). Mean preoperative IOP by Tono-Pen XL was 23.52±9.76mm Hg; by Icare PRO, 20.94±10.01mm Hg (P=0.0012). Mean IOP over intracameral air at surgery conclusion by Tono-Pen XL (n=41) was 12.66±4.90; by Icare PRO (n=42), 12.96±5.10mm Hg (P=0.46). One eye had postoperative IOP unrecordable by Tono-Pen XL but 7.9mm Hg by Icare PRO. Bland-Altman analysis, which included only paired measurements, showed a preoperative mean difference in IOP (ΔIOPT-I) of 2.58mm Hg (95% CI, -6.86 to 12.02); postoperative mean ΔIOPT-I of -0.42mm Hg [95% CI, -7.57 to 6.73]. Position-independent rebound tonometry (Icare PRO) accurately measured IOP in supine children's eyes postoperatively in the presence of intracameral air.