Elsevier

Ophthalmology

Volume 105, Issue 6, 1 June 1998, Pages 969-973
Ophthalmology

Central corneal thickness and intraocular pressure in a Mongolian population1,

Presented in part at The XVI Congress of the Asia-Pacific Academy of Ophthalmology, Kathmandu, Nepal, March 1997.
https://doi.org/10.1016/S0161-6420(98)96021-3Get rights and content

Abstract

Objective

The purpose of the study was to quantify the variation of central corneal thickness (CCT) in an east Asian population and to examine its relationship to estimates of intraocular pressure (IOP) made with an applanation tonometer.

Design

The study design was a cross-sectional, population-based survey.

Participants

One thousand two-hundred forty-two residents of Hövsgöl Province, Mongolia, 10 to 87 years of age participated.

Main outcome measures

The CCT was measured using an optical pachymeter in all subjects. The IOP was measured using a Goldmann-type applanation tonometer in subjects 40 years of age and older.

Results

There was a highly significant decrease in CCT with age: 5 μm/decade in men and 6 μm/decade in women (both, P < 0.0001). A highly significant positive correlation was identified between IOP and CCT. Linear regression analysis suggests that between the ages of 40 and 80 years, an increase in CCT of 10 μm is associated with an increase in IOP measurements of 0.18 mmHg in right eyes (95% confidence interval, 0.12–0.25) and 0.24 mmHg in left eyes (95% confidence interval, 0.17–0.31). The authors calculate that interindividual differences in CCT may produce a difference in measured IOP of between 2.3 and 3.1 mmHg.

Conclusions

Variation in CCT is a significant source of variation in IOP measurements between individuals. The authors suggest that measurement of corneal thickness should be considered when assessing IOP as a risk factor for glaucoma in east Asians.

Section snippets

Materials and methods

A representative population-based sample was selected for examination in Hövsgöl Province, Northern Mongolia, between May and August 1995. The selection strategy and demographics of these subjects are described in detail elsewhere.19, 21 In brief, the subjects were selected from one urban and three rural locations. Four hundred subjects 40 years of age and older were chosen by simple random selection from the population of the provincial capital (the urban site). Three rural locations were

Results

Corneal thickness was measured in both eyes of all 300 subjects (100%) aged 10 to 39 years. Among the 1000 subjects aged 40 years and older, 942 attended for examination. The CCT was measured in the right eyes of 927 subjects and the left eyes of 929 subjects. Because an alternative endpoint was used for measurement of CCT in the first 100 subjects aged 40 years and older, CCT data are presented for 1129 consecutive individuals (86.8% of the 1300 subjects selected for examination). Intraocular

Discussion

The indirect measurement of a physiologic variable, such as IOP, by extrapolation from the measurement of another (force required to flatten the central cornea) inevitably will be subject to error as a consequence of the necessary assumptions made about the relationship between the two parameters. The thickness of the cornea and the mechanical properties of its constituent tissues clearly will affect the force required to flatten its center. This was recognized when the modern applanation

Acknowledgements

The technical assistance of Pak Sang Lee is acknowledged.

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  • Cited by (0)

    Supported by the British Council for Prevention of Blindness, with additional support from Danida, Copenhagen; the International Glaucoma Association, London; and The Danish Association for the Blind, Copenhagen. Analysis and writing were facilitated by grant NMRC 1994/0044 from The National Medical Research Council, Republic of Singapore, and the Singapore National Eye Centre.

    1

    The authors have no proprietary interests in the materials mentioned in this study.

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