Abstract
Purpose:
To evaluate the five-year change in intraocular pressure (IOP) and its determinants in adults in urban southern China.
Methods:
All participants who underwent a baseline eye examination between 2003 and 2004, participated in a five-year follow up examination. IOP was measured with a handheld tonometer before pupil dilation. A handheld auto-refractorwas used to measure baseline refraction. Both optical and ultrasound pachymetry were used to evaluate central cornea thickness (CCT ), and A-mode ultrasound was used to measure axial length. Height and weight were measured using a standard calibrated scale according to a standard protocol. An interviewer-administered questionnaire was used to collect data about patients’ income, education, and medical history of systemic and eye diseases. Only data of the right eye was analyzed.
Results:
Of the 1405 subjects (aged 50 and over) participating in the baseline examination, 173 (12.3%) had died by November 2009, and 308 (25.0% of survivors) did not return for re-examination. Those who participated in the 5-year follow-up (n=924) were younger (63.4±9.0 vs.66.4±10.6 years, p<0.001), more likely to have hypertension (43.9% vs 32.2%, p=0.001) and diabetes (11.4% vs 6.64%, p=0.032), and had a poorer baseline VA level (for both the better-seeing and worse-seeing eye, p<0.001) than the non-participants. Data on IOP were available for 799 (64.9% of survivors, 86.5% of participants at 5year period with mean age of 65.3 ± 10.0 years old) after excluding subjects with history of cataract surgery and glaucoma, or had an IOP of more than 21 mm Hg or less than 10mm Hg at baseline, or a missing value of IOP data in both examination. IOP slightly decreased after 5 years (mean change -0.6+/-3.4 mmHg, p<0.05). The change in IOP was greater among younger subjects (-0.8±3.2 for those aged 50-59 years vs -0.17±3.86 for those aged 70 years or older, P =0.03). In multivariate analysis, the 5-year difference in IOP was significantly associated with thicker CCT (beta=0.01,p=0.001) and lower baseline IOP (beta=-0.69,p<0.001), whereas no associations were found for age, gender, history of hypertension, baseline BMI and baseline spherical equivalent.
Conclusions:
The five-year difference in IOP is associated with CCT and baseline IOP, and the change in IOP tends to become greater among younger subjects. These findings may have implication in explaining the change in IOP with aging.