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Influence of central corneal thickness on measured intraocular pressure differentials: Nidek RKT ‐7700, Topcon CT ‐80 NCT s and Goldmann Tonometer
Author(s) -
Ogbuehi Kelechi C,
Mucke Sven,
Osuagwu Uchechukwu L
Publication year - 2012
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1111/j.1475-1313.2012.00945.x
Subject(s) - ophthalmology , intraocular pressure , medicine , reproducibility , repeatability , chemistry , chromatography
Purpose We sought to compare the intraocular pressure ( IOP ) measured by RKT ‐7700 and CT ‐80 noncontact tonometers ( NCT s) with that measured by G oldmann applanation tonometry ( GAT ). We also examined the influence of central corneal thickness ( CCT ) on the agreement between both NCT s and GAT in a sub‐population of healthy, young normals. Methods Triplicate IOP and CCT measurements were obtained twice from one randomized eye of 49 subjects (28 males and 21 females) aged 22.2 ± 1.3 (mean ± S.D.) years. Goldmann tonometry was performed subsequent to assessment with the RKT ‐7700 and CT ‐80, to negate the ‘ocular massage effect’, followed by ultrasound pachymetry. The results from each method were compared and assessed for repeatability and between‐observer reproducibility. Analysis was performed to determine the correlation between the differences in IOP measurements and corneal thicknesses. Results The mean differences (±S.D.) in sessions 1 and 2 respectively between RKT ‐7700 and GAT (2.6 ± 2.0 and 2.7 ± 1.4 mmHg), between CT ‐80 and GAT (2.8 ± 2.0 and 3.2 ± 1.3 mmHg) were statistically significant ( p < 0.0001). The repeatability coefficients in sessions 1 and 2 respectively were; ±1.2 and ±1.0 mmHg ( GAT ), ±1.3 and ±1.6 mmHg ( CT ‐80), ±2.3 and ±1.7 mmHg ( RKT ‐7700) and inter‐observer reproducibility was; ±1.9 ( RKT ‐7700), ±2.3 ( GAT ) and ±2.6 mmHg ( CT ‐80). Between the corneal thickness and the differences in GAT ‐measured and NCT ‐measured IOP s, there was a significant negative correlation and a trend for a larger difference in thicker corneas. Conclusion Neither the RKT ‐7700 nor the CT ‐80 can be used interchangeably with the G oldmann tonometer, although all three tonometers give repeatable measurements of IOP , in this sub‐population. IOP differences between GAT and the NCT s significantly correlated with CCT , with the possibility of even greater differences in thicker corneas.