Compare Goldmann applanation tonometer (GAT) prism and correcting applanation tonometry surface (CATS) prism to intracameral intraocular pressure (IOP), in vivo and in vitro.
Pressure transducer intracameral IOP was measured on fifty-eight (58) eyes undergoing cataract surgery and the IOP was modulated manometrically to 10, 20, and 40 mmHg. Simultaneously, IOP was measured using a Perkins tonometer with a standard GAT prism and a CATS prism at each of the intracameral pressures. Statistical comparison was made between true intracameral pressures and the two prism measurements. Differences between the two prism measurements were correlated to central corneal thickness (CCT) and corneal resistance factor (CRF). Human cadaver eyes were used to assess measurement repeatability.
The CATS tonometer prism measured closer to true intracameral IOP than the GAT prism by 1.7+/−2.7 mmHg across all pressures and corneal properties. The difference in CATS and GAT measurements was greater in thin CCT corneas (2.7+/−1.9 mmHg) and low resistance (CRF) corneas (2.8+/−2.1 mmHg). The difference in prisms was negligible at high CCT and CRF values. No difference was seen in measurement repeatability between the two prisms.
A CATS prism in Goldmann tonometer armatures significantly improve the accuracy of IOP measurement compared to true intracameral pressure across a physiologic range of IOP values. The CATS prism is significantly more accurate compared to the GAT prism in thin and less rigid corneas. The in vivo intracameral study validates mathematical models and clinical findings in IOP measurement between the GAT and CATS prisms.
Susanna JR, De Moraes CG, Cioffi GA, Ritch R. Why do people (still) go blind from glaucoma? Trans Vis Sci Tech. 2015;4:1–10. CrossRef
Condon N, Broman A, Bandeen-Roche K. Central corneal thickness and corneal hysteresis associated with glaucoma damage. Am J Ophthalmol. 2006;141:868–75. CrossRef
Whitacre M, Stein R. Sources of error with use of Goldmann-type tonometers. Surv Ophthalmol. 2002;38:1–30. CrossRef
McCafferty S, Lim G, Duncan W, Enikov E, Schwiegerling J. Goldmann Tonometer error correcting prism: clinical evaluation. Clin Ophthalmology. 2017;11:835–40. CrossRef
Kass M, Heuer D, Higginbotham E, Johnson C, Keltner J, Miller J, Parrish R, Wilson M, Gordon M. The ocular hypertension treatment study: a randomized trial determines that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma. Arch Ophthalmol. 2002;120:701–13. CrossRefPubMed
McCafferty S, Lim G, Duncan W, Enikov E, Schwiegerling J. Goldmann Tonometer prism with an optimized error correcting Applanation surface. Transl Vis Sci Technol. 2016;5:1–5. CrossRef
Lam A, Wu Y, Wong L, Ho N. IOP variations from sitting to supine postures determined by rebound tonometer. J Opt. 2013;6:95–100. CrossRef
Jorge J, Marques R, Lourenco A, Silva S, Nascimento S, Queiros A, Gonzalez-Me’ijome J. IOP variations in the sitting and supine positions. J Glaucoma. 2010;19:20–31. CrossRef
A-Yong Y, Su-Fang D, Yun-E Z, Xing-Yu L, Fan L, Jianhua W, Qin-Mei W. Correlation between corneal biomechanical properties, applanation tonometry and direct intracameral tonometry. Br J Ophthalmol. 2012;96:640–4. CrossRef
- Goldmann and error correcting tonometry prisms compared to intracameral pressure
Eniko T. Enikov
- BioMed Central