Age, gender, corneal thickness linked to elevated IOP in glaucoma, OHT
Age, gender and central corneal thickness were among factors associated with elevated IOP in patients with primary open-angle glaucoma and ocular hypertension, according to a study published in British Journal of Ophthalmology.
“IOP is an important indicator in the development and progression of glaucoma, thus fully understanding risk factors of elevated IOP and IOP fluctuation is of great significance,” Yangfan Yang, PhD, of Sun Yat-Sen University Zhongshan Ophthalmic Center in China, and colleagues reported. “To our knowledge, this study is the first to report the baseline IOP, its associated factors and diurnal fluctuation of the [primary open-angle glaucoma (POAG)] and [ocular hypertension (OHT)] patients from the [Laser in Glaucoma and Ocular Hypertension (LiGHT)] China Trial.”
Yang and colleagues recruited 771 patients, aged 18 years and older, from March 2015 to January 2019 who were enrolled in the LiGHT China cohort. Of those, 622 (mean age, 49.7 years; 58.5% men) had POAG, and 149 (mean age, 38.8 years; 48.3% men) had OHT. Investigators conducted eye exams and measured IOP throughout the day, with recordings taken at 8:00 a.m., 10:00 a.m., 11:30 a.m., 2:30 p.m. and 5 p.m.
Of the 771 participants, 1,105 POAG eyes and 271 OHT eyes were enrolled in the LiGHT China (both eyes were eligible in 605 patients; only the right eye was eligible in 73 patients, and only the left eye in 93 patients). A total of 945 POAG eyes and 264 OHT eyes accepted daytime phasing IOP measurements.
According to the study, the mean baseline IOP was 20.4 mm Hg for POAG patients and 24.4 mm Hg for OHT patients. An average of 3.4 mm Hg IOP fluctuation was reported in POAG eyes and 4.4 mm Hg in OHT eyes during daytime phasing, with elevated IOP readings found mostly in early morning or late afternoon.
Further analysis revealed that younger age, male gender and thicker CCT significantly correlated with increasing IOP in POAG patients (P < 0.01), while younger age and male gender was not significant in the OHT group. Although patients with OHT had higher IOP and thicker CCT than POAG eyes (P < .001), thicker CCT correlated to higher IOP in both groups.
“The role of age and its relationship with IOP still remains controversial,” Yang and colleagues concluded. “Numerous studies have discovered a positive association between older age and higher IOP level. However, in our study, multivariate analysis showed a significant negative correlation between age and IOP in POAG patients, consistent with the results of studies conducted in Asia populations.”
Perspective
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IOP is important in the development and progression of glaucoma. What happens to IOP as we get older? Age-related structural changes in the trabecular meshwork and sclera can lead to elevated IOP. Conversely, aqueous production decreases with age, possibly resulting in lower IOP. Does IOP in POAG patients differ from OHT patients? Yang and colleagues attempt to shed some LiGHT on these issues using data from their lasers in glaucoma and OHT multicenter clinical trial.
They found that younger age, thicker cornea and male gender were correlated with IOP in POAG patients, while only corneal thickness was associated with IOP in the OHT group. The POAG group included normal tension glaucoma patients, who tend to be older. Perhaps this helps explain why IOP was associated with youth in the POAG group.
While interesting, these results won’t change my practice. IOP is the most important glaucoma risk factor, but it affects individuals differently. Our job is to determine the appropriate IOP for each patient, regardless of age, sex or glaucoma type.
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