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The effect of thin, thick, and normal corneas on Goldmann intraocular pressure measurements and correction formulae in individual eyes.
Ophthalmology 2012; 119(3):443-9O

Abstract

OBJECTIVE

To evaluate the usefulness of the central corneal thickness (CCT)-based correction formulae for stratified CCT groups, with intraocular pressure (IOP) from the Pascal dynamic contour tonometer (PDCT) as the reference standard.

DESIGN

Retrospective case series.

PARTICIPANTS

Two hundred eighty-nine patients attending a specialist glaucoma practice and a mixture of normal subjects and subjects with confirmed glaucomatous optic neuropathy.

METHODS

Intraocular pressure was measured using PDCT, Goldmann applanation tonometry (GAT), and the Ocular Response Analyzer (ORA; Reichert Corp, Buffalo, NY). The GAT readings were obtained before automated readings and were adjusted for CCT using 4 different correction formulae. Discrepancies between GAT and CCT-corrected GAT readings were evaluated after stratification into thin, intermediate, and thick CCT groups. The IOP measurements from GAT, the ORA, and CCT-adjusted IOP were compared against PDCT IOP measurements using Bland-Altman analysis.

MAIN OUTCOME MEASURES

Mean, 95% limits of agreement, and proportion of patients with IOP difference of 20% or more between PDCT IOP and each of GAT IOP, Goldmann-correlated IOP (IOPg), corneal-compensated IOP (IOPcc), and adjusted IOP using CCT-based correction formulae.

RESULTS

Average PDCT IOP values were higher than GAT, IOPg, IOPcc, and CCT-adjusted IOP. The GAT IOP readings demonstrated poor agreement with PDCT IOP (95% limits of agreement, ± 4.7 mmHg); however, IOPg, IOPcc, and adjustment of GAT IOP with CCT-based formulae resulted in even poorer agreement (range of 95% limits of agreement, ± 5.1 to 6.7 mmHg). If PDCT was used as the reference standard, there was a 26% to 39% risk of making an erroneous IOP adjustment of magnitude of 20% or more at all levels of CCT. This risk was greatest in the patients with thicker corneas (CCT, ≥568 μm).

CONCLUSIONS

Adjusting IOP using CCT-based formulae resulted in poorer agreement with PDCT IOP when compared with unadjusted G AT IOP. If PDCT is the closest measure we have to intracameral IOP, there is a risk of creating clinically significant error after adjustment of GAT IOP with CCT-based correction formulae, especially in thicker corneas. This study suggests that although CCT may be useful in population analyses, CCT-based correction formulae should not be applied to individuals.

Authors+Show Affiliations

Eye Department, Wellington Hospital, Capital and Coast District Health Board, Wellington, New Zealand. sjkpark@gmail.comNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

22035576

Citation

Park, Serena J K., et al. "The Effect of Thin, Thick, and Normal Corneas On Goldmann Intraocular Pressure Measurements and Correction Formulae in Individual Eyes." Ophthalmology, vol. 119, no. 3, 2012, pp. 443-9.
Park SJ, Ang GS, Nicholas S, et al. The effect of thin, thick, and normal corneas on Goldmann intraocular pressure measurements and correction formulae in individual eyes. Ophthalmology. 2012;119(3):443-9.
Park, S. J., Ang, G. S., Nicholas, S., & Wells, A. P. (2012). The effect of thin, thick, and normal corneas on Goldmann intraocular pressure measurements and correction formulae in individual eyes. Ophthalmology, 119(3), pp. 443-9. doi:10.1016/j.ophtha.2011.07.058.
Park SJ, et al. The Effect of Thin, Thick, and Normal Corneas On Goldmann Intraocular Pressure Measurements and Correction Formulae in Individual Eyes. Ophthalmology. 2012;119(3):443-9. PubMed PMID: 22035576.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The effect of thin, thick, and normal corneas on Goldmann intraocular pressure measurements and correction formulae in individual eyes. AU - Park,Serena J K, AU - Ang,Ghee Soon, AU - Nicholas,Simon, AU - Wells,Anthony P, Y1 - 2011/10/27/ PY - 2011/05/10/received PY - 2011/07/28/revised PY - 2011/07/29/accepted PY - 2011/11/1/entrez PY - 2011/11/1/pubmed PY - 2012/4/28/medline SP - 443 EP - 9 JF - Ophthalmology JO - Ophthalmology VL - 119 IS - 3 N2 - OBJECTIVE: To evaluate the usefulness of the central corneal thickness (CCT)-based correction formulae for stratified CCT groups, with intraocular pressure (IOP) from the Pascal dynamic contour tonometer (PDCT) as the reference standard. DESIGN: Retrospective case series. PARTICIPANTS: Two hundred eighty-nine patients attending a specialist glaucoma practice and a mixture of normal subjects and subjects with confirmed glaucomatous optic neuropathy. METHODS: Intraocular pressure was measured using PDCT, Goldmann applanation tonometry (GAT), and the Ocular Response Analyzer (ORA; Reichert Corp, Buffalo, NY). The GAT readings were obtained before automated readings and were adjusted for CCT using 4 different correction formulae. Discrepancies between GAT and CCT-corrected GAT readings were evaluated after stratification into thin, intermediate, and thick CCT groups. The IOP measurements from GAT, the ORA, and CCT-adjusted IOP were compared against PDCT IOP measurements using Bland-Altman analysis. MAIN OUTCOME MEASURES: Mean, 95% limits of agreement, and proportion of patients with IOP difference of 20% or more between PDCT IOP and each of GAT IOP, Goldmann-correlated IOP (IOPg), corneal-compensated IOP (IOPcc), and adjusted IOP using CCT-based correction formulae. RESULTS: Average PDCT IOP values were higher than GAT, IOPg, IOPcc, and CCT-adjusted IOP. The GAT IOP readings demonstrated poor agreement with PDCT IOP (95% limits of agreement, ± 4.7 mmHg); however, IOPg, IOPcc, and adjustment of GAT IOP with CCT-based formulae resulted in even poorer agreement (range of 95% limits of agreement, ± 5.1 to 6.7 mmHg). If PDCT was used as the reference standard, there was a 26% to 39% risk of making an erroneous IOP adjustment of magnitude of 20% or more at all levels of CCT. This risk was greatest in the patients with thicker corneas (CCT, ≥568 μm). CONCLUSIONS: Adjusting IOP using CCT-based formulae resulted in poorer agreement with PDCT IOP when compared with unadjusted G AT IOP. If PDCT is the closest measure we have to intracameral IOP, there is a risk of creating clinically significant error after adjustment of GAT IOP with CCT-based correction formulae, especially in thicker corneas. This study suggests that although CCT may be useful in population analyses, CCT-based correction formulae should not be applied to individuals. SN - 1549-4713 UR - https://www.unboundmedicine.com/medline/citation/22035576/The_effect_of_thin_thick_and_normal_corneas_on_Goldmann_intraocular_pressure_measurements_and_correction_formulae_in_individual_eyes_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0161-6420(11)00743-3 DB - PRIME DP - Unbound Medicine ER -