Study shows IOP declining with age in urban Chinese population

A majority of patients with open-angle glaucoma had normal IOP, suggesting that the optic disc should be clinically examined.

Mingguang He

IOP diminished with age in an urban Chinese population, largely because of lower body mass index and blood pressure than seen in similar European cohorts, a large study found.

Data were culled from the Liwan Eye Study, a population-based analysis conducted in southern China. The analysis included 1,405 patients from Guangzhou City, a large metropolitan area that comprises 10 administrative districts. Liwan District has a population of about 500,000 people.

“There are limited population-based data available on IOP and [central corneal thickness] in adult Chinese dwelling in China,” Mingguang He, MD, PhD, corresponding author of the study, and Dandan Wang, MD, first author, said in an email interview with Ocular Surgery News. “The decision to select this district was taken because of its stable population and a socioeconomic profile representative of Guangzhou as a whole. Therefore, we believe the study sample is representative of urban elderly population in China.”

The study was published in the American Journal of Ophthalmology.

Patients, methods, results

Patients underwent IOP, refractive error, corneal curvature, axial length, body mass index (BMI), and optical and ultrasound central corneal thickness (CCT) measurements. Patient histories of hypertension and diabetes were also analyzed.

IOP data were available for 1,348 subjects; mean patient age in this subgroup was 64.8 years. Data from right eyes were analyzed.

Data showed that CCT diminished significantly with age (P < .001) and increased appreciably with corneal curvature (P < .001) and diabetes (P = .037). There were significant positive correlations between IOP and greater CCT, BMI and hypertension (all P < .001).

IOP also declined with age (P = .003); this contrasted with many European analyses showing an increase in IOP with age, the authors said.

“There is evidence suggesting that the prevalence of diabetes/hypertension is greater in Europeans and increases greater with age in comparison to that in Chinese,” Dr. He said. “[The] inter-ethnic difference in the prevalence of systemic diseases such as obesity and hypertension is hypothesized to account for the lower IOP and its decreasing tendency with age in Chinese.”

Among 65 subjects with ocular hypertension, or IOP above the 97.5th percentile, mean CCT was 555 µm. This value was significantly higher than that of subjects with normal IOP (P = .01).

Clinical considerations

The correlation between ultrasound CCT and IOP in Chinese, Mongolian, Japanese, Latino, Singaporean, Dutch and mixed European populations suggested similar corneal biomechanics across ethnic groups, the authors said.

“A majority of open-angle glaucoma cases identified in the Chinese population have normal intraocular pressure, at least based on one-time measurement in the cross-sectional study,” Dr. He said. “This suggests that the physicians in clinics should pay attention to not only the intraocular pressure but also the clinical examination of the optic disc if they don’t want to miss the glaucoma cases.”

Physicians should take a systemic approach to assessing IOP, Dr. He said.

“In the assessment of IOP level, physicians should also consider systemic disease, such as obesity and hypertension,” he said. “A control on cardiovascular diseases and lifestyle may also benefit the glaucoma treatment, although this needs to be tested in robust clinical studies.”

CCT should also be factored into the IOP assessment equation, Dr. He said. – by Matt Hasson

Reference:

• Wang D, Huang W, Li Y, et al. Intraocular pressure, central corneal thickness and glaucoma in Chinese adults: The Liwan Eye Study. Am J Ophthalmol. 2011;152(3):454-462.

• Mingguang He, MD, PhD, can be reached at the Department of Preventive Ophthalmology, Zhongshan Ophthalmic Center, Guangzou 510060, China; email: mingguang_he@yahoo.com.
• Disclosure: Dr. He has no relevant financial disclosures.