Agreement of intraocular pressure measurement by scleral Schiotz and Goldmann applanation tonometer

Aim & background : Intraocular pressure (IOP) measured through the sclera has some advantages over IOP measured through cornea. This study aimed to determine the agreement between IOP as estimated by scleral Schiotz (SS) tonometer and Goldmann applanation tonometer (GAT). Methods: In this cross-sectional observational study, IOP was measured by GAT on the cornea and Schiotz tonometer on the temporal sclera. Axial length and central corneal thickness (CCT) were noted. IOP was then estimated from SS IOP as eGAT using a predictive formula. Agreement of IOP corrected for CCT (cGAT) with eGAT and SS IOP were assessed. The effects of age, axial length, refraction, CCT, gender, and ocular and systemic comorbidity on measured IOP were also assessed. Results: The study included 155 patients with a mean age of 54.27 +/- 10.02 years. Mean IOP measured by GAT and scleral Schiotz were 16.58 +/- 2.76 mm Hg and 16.10 +/- 2.96 mm Hg, respectively. The mean IOP by cGAT and eGAT were 16.70 +/- 2.80 mm Hg and 17.07 +/- 3.10 mm Hg, respectively. Both eGAT & SS IOP had good agreement with cGAT on the Bland-Altmann plot (p = 0.96 & 0.51, respectively). Further, SS IOP showed good agreement even with GAT IOP (p = 0.78). Age, axial length, refraction, central corneal thickness, gender, and ocular and systemic comorbidity did not show significant correlation with IOP measurement. Conclusion: Estimated GAT IOP showed good agreement with measured GAT values. SS IOP also agreed well with GAT IOP. Clinical significance IOP measurement on the sclera using Schiotz can be used as an alternative to GAT.