Korean J Ophthalmol.  2017 Feb;31(1):44-51. 10.3341/kjo.2017.31.1.44.

Validity of Tono-pachymetry for Measuring Corrected Intraocular Pressure in Non-surgical and Post-photorefractive Keratectomy Eyes

• Hahn IK
• Kim JY
• Kim MJ
• Tchah H
• Moon CH

• KMID: 2368678
• DOI: http://doi.org/10.3341/kjo.2017.31.1.44

Abstract

PURPOSE
To assess the validity of central corneal thickness (CCT) and corrected intraocular pressure (IOP) values obtained by tono-pachymetry in non-surgical and post-photorefractive keratectomy (PRK) eyes.
METHODS
For the study, 108 young healthy participants and 108 patients who had PRK were enrolled. Measurements were randomly performed by tono-pachymetry, ultrasonic (US) pachymetry, and Goldmann applanation tonometry (GAT). CCT measurement by tono-pachymetry was compared to that of US pachymetry. The corrected IOP value obtained by tono-pachymetry was compared to that obtained by US pachymetry and GAT. The corrected IOP from US pachymetry and GAT was calculated using the identical compensation formula built into the tono-pachymetry. Bland-Altman plot and paired t-test were conducted to evaluate the between-method agreements.
RESULTS
The mean CCT measurement using tono-pachymetry was significantly greater by 7.3 µm in non-surgical eyes (p < 0.001) and 17.8 µm in post-PRK eyes (p < 0.001) compared with US pachymetry. Differences were significant in both Bland-Altman plotand paired t-test. The mean difference of corrected IOP values obtained by tono-pachymetry and calculated from measurements by US pachymetry and GAT was 0.33 ± 0.87 mmHg in non-surgical eyes and 0.57 ± 1.08 mmHg in post-PRK eyes. The differences in the Bland-Altman plot were not significant.
CONCLUSIONS
The CCT measurement determined using tono-pachymetrywas significantly thicker than that of US pachymetry. The difference in CCT was greater in post-PRK eyes than in non-surgical eyes. However, the corrected IOP value obtained by tono-pachymetry showed reasonable agreement with that calculated from US pachymetry and GAT measurements.

Keyword

Corneal pachymetry; Intraocular pressure; Photorefractive keratectomy

MeSH Terms

Compensation and Redress
Corneal Pachymetry
Healthy Volunteers
Humans
Intraocular Pressure*
Manometry
Photorefractive Keratectomy
Ultrasonics

Figure

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  Fig. 1 Bland-Altman plots of central corneal thickness in non-surgical eyes (A) and post-photorefractive keratectomy eyes (B). SD = standard deviation.

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  Fig. 2 Bland-Altman plots of intraocular pressure in non-surgical eyes (A) and post-photorefractive keratectomy eyes (B). SD = standard deviation.

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  Fig. 3 Bland-Altman plots of corrected intraocular pressure in non-surgical eyes (A) and post-photorefractive keratectomy eyes (B). SD = standard deviation.

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  Fig. 4 Scatter diagram and regression line of correlation analyses between refractive error and the differences in corrected intraocular pressure between the two devices in non-surgical eyes (A) and post-photorefractive keratectomy eyes (B). D = diopter.

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  Fig. 5 Merged Bland-Altman plot and regression equation of central corneal thickness of non-surgical eyes and post-photorefractive keratectomy eyes. SD = standard deviation.

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