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Editors Selection IGR 7-2
Examination methods: IOP and aging
Comment by Yoshiaki Kitazawa on:
11908 Long-term physiologic changes of intraocular pressure: a 10-year longitudinal analysis in young and middle-aged Japanese men, Nakano T; Tatemichi M; Miura Y et al., Ophthalmology, 2005; 112: 609-616
A vast majority of studies on the aging effect on IOP indicate an increase of IOP with aging in different populations. Some recent studies in Japan, however, report that IOP decreases with age in the Japanese population. It should be noted that in virtually all studies the relationship between age and IOP was studied cross-sectionally and only a few longitudinal studies have been done to assess the effect of aging on IOP.
Nakano and associates (105) report on the changes of IOP determined over ten years in healthy Japanese males. The subjects underwent ocular and systemic examinations as annual, aviation physical checkups of Japanese aircraft crew members. Two thousands three hundreds and thirty subjects aged 21 to 49 years and without ocular and systemic diseases constituted the population for analyses. IOP was measured with a Goldmann applanation tonometer.For analysis of the longitudinal trend of a variable linear regression coefficient for 11 points of measurements were determined. Factors affecting the ten-year mean values and a trend of IOP were examined by multiple, linear regression analysis. IOP was found to tend to decrease with age in all three age groups. The ten-year mean values of IOP were noted to be significantly inversely correlated with spherical power, positively correlated with esophoria, systolic blood pressure, heart rate, and hematocrit. The trend of IOP was significantly positively associated with the trends of systemic factors: body mass index (BMI), systolic blood pressure, and hematocrit, but not with any ophthalmologic factors.
The study should be commended as the first study which measured IOP along with various ocular and systemic factors under control of possible confounders: the examination was conducted at the same time of day, body position, resting condition, and month of every year. Evidently the IOP decreased with age in the population studied by the authors. Care should be taken, however, when one applies the results to the general population. The subjects in this study are not general population but highly selected healthy males in their 20s to 40s of age who met specific, physical requirements of aviation occupation. Hence, examinees may well have been subject to selection bias. In spite of the obvious limitations the results of the study are in good agreement with a number of previous studies in Western countries and Japan in that the trend of IOP changes is positively associated with that of BMI, blood pressure, and hematocrit. Their findings suggest that the presence of racial difference in IOP cannot be determined until the relationship of IOP to systemic factors is elucidated by well planned longitudinal studies.
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