Abstract
Purpose: :
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.
Methods: :
This was a prospective case-control study of 98 subjects with angle closure (consisting of 32 primary angle closure suspects [PACS], 34 primary angle closure [PAC] and 32 subjects with primary angle closure glaucoma [PACG]) along with 21 normal control subjects. PAC/PACG subjects were enrolled after laser peripheral iridotomy but before commencement of any medical treatment. Ophthalmic examination including dynamic gonioscopy and automated perimetry were performed, and diurnal IOP measurements were made using non-contact airpuff tonometry at hourly intervals between 8 am-5 pm. Mean IOP, peak 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: disc ratio and pattern standard deviation (PSD) on automated perimetry.
Results: :
The majority of subjects were Chinese (89.1%) and female (61.3%). IOP fluctuation was significantly higher in PACG (5.4 + 2.4 mm Hg) and PAC (4.5 + 2.3 mm Hg) subjects compared to PACS (3.7 + 1.2 mm Hg) and normal controls (3.8 + 1.1 mm Hg) (p=0.005), with highest IOP found in the early morning. Combined PACG/PAC group had more than twice the risk (OR2.38, 95%CI =1.1-5.1, p=0.025) of having IOP fluctuation >3 mm Hg compared to PACS/normal groups. Extent of PAS (R=0.37; p =0.0001) and visual field PSD (R= 0.34; p=0.0002) were found to be risk factors for greater IOP fluctuation.
Conclusions: :
PACG and PAC eyes showed diurnal IOP fluctuation of 4-5 mm Hg, and this fluctuation was higher than in PACS and normal controls. The degree of PAS and visual field loss were risk factors for IOP fluctuation in PAC/PACG eyes.
Keywords: intraocular pressure • clinical (human) or epidemiologic studies: risk factor assessment • anterior segment