Diurnal intraocular pressure fluctuation and associated risk factors in eyes with angle closure.

OBJECTIVE

To investigate diurnal intraocular pressure (IOP) fluctuation in eyes with angle closure in comparison with normal subjects and to look for associated risk factors for IOP fluctuation.

DESIGN

Prospective, cross-sectional study.

PARTICIPANTS

Ninety-eight eyes of 98 Asian subjects with angle closure (consisting of 32 primary angle-closure suspects [PACS], 34 subjects with primary angle closure [PAC], and 32 subjects with primary angle-closure glaucoma [PACG]) and 21 eyes of 21 normal control subjects.

METHODS

All angle-closure subjects were enrolled after laser peripheral iridotomy but before commencement of any medical or surgical treatment. Ophthalmic examination, including dynamic gonioscopy and automated perimetry, were performed, and diurnal IOP measurements were obtained using noncontact air-puff tonometry at hourly intervals between 8:00 am and 5:00 pm. Mean diurnal IOP, peak diurnal IOP, trough IOP, and IOP fluctuation (peak IOP-trough IOP) were compared between groups. Multiple linear regression analysis was performed to study the association of IOP fluctuation with clinical variables such as age, extent of peripheral anterior synechiae (PAS), central corneal thickness, vertical cup-to-disc ratio, and pattern standard deviation (PSD) on automated perimetry.

MAIN OUTCOME MEASURES

Mean diurnal IOP, peak IOP, and IOP fluctuation.

RESULTS

Most subjects were Chinese (89.1%) and female (61.3%). Intraocular pressure fluctuation was significantly higher in PACG (5.4+/-2.4 mmHg) and PAC (4.5+/-2.3 mmHg) subjects compared with PACS subjects (3.7+/-1.2 mmHg) and normal controls (3.8+/-1.1 mmHg; P = 0.005), with highest IOP found in the early morning. The combined PACG and PAC group had more than twice the risk (odds ratio, 2.38; 95% confidence interval, 1.1-5.1; P = 0.025) of having IOP fluctuation of more than 3 mmHg compared with the combined PACS and normal group. Extent of PAS (Pearson's correlation coefficient, r = 0.37; P = 0.0001) and visual field PSD (r = 0.34; P = 0.0002) were found to be associated with greater IOP fluctuation.

CONCLUSIONS

The PACG and PAC eyes showed diurnal IOP fluctuation of 4 to 5 mmHg, and this fluctuation was higher than in PACS subjects and normal controls. The degree of PAS and visual field loss were associated with IOP fluctuation in PAC and PACG eyes.