Abstract
Purpose: :
To assess the relationship between intra-ocular pressure (IOP) and anterior chamber angle (ACA) width assessed by gonioscopy and anterior-segment OCT (AS-OCT, Carl Zeiss Meditec, Dublin, CA) in a Singapore population.
Methods: :
2047 subjects aged 50-years and over without ophthalmic symptoms recruited from a community polyclinic underwent gonioscopy, Goldmann applanation tonometry, and AS-OCT. On gonioscopy, a quadrant was considered to be closed if the posterior trabecular meshwork was not visible on non-indentation gonioscopy. On AS-OCT, a fellowship trained glaucoma specialist graded images obtained at the four quadrants of the eye as having an open or closed ACA (qualitative analysis). In the AS-OCT quantitative analysis, the anterior chamber depth (ACD), anterior chamber volume (ACV), angle opening distance (AOD) and trabecular-iris space area (TISA) 750 um from the scleral spur were measured using a customized computer software (Zhongshan Angle Assessment Program, Guangzhou, China). IOP values were adjusted for age, gender, diabetes, systemic hypertension, central corneal thickness, and body mass index.
Results: :
Mean IOP was 14.7 mmHg (SD±2.4) (range 8-26). IOP [mean±SE] increased according to the number of quadrants closed on gonioscopy (none-14.6±0.1, one-14.8±0.2, two-15.1±0.3, three-15.0±0.2, four-15.7±0.2mmHg), and according to the number of quadrants considered closed on AS-OCT (none-14.6±0.1, one-14.9±0.1, two-14.7±0.1, three-15.0±0.2, four- 15.9±0.2mmHg). The quantitative ACA analysis excluded 587 eyes, mostly due to inability to locate the scleral spur. The IOP was significantly higher comparing the 1st vs. 4th quartile of ACD (15.3±0.1 vs. 14.4±0.1mmHg, p<0.001), ACV (15.1±0.1 vs. 14.5±0.1mmHg, p<.001), AOD750micra (15.2±0.1 vs. 14.4±0.1mmHg, p<.001), TISA750 (15.2±0.1 vs. 14.4±0.1mmHg, p<.001).
Conclusions: :
IOP tended to increase according to the number of ACA quadrants considered closed on gonioscopy and AS-OCT. IOP also increased in eyes with narrower ACA as assessed quantitatively by AS-OCT. These data suggest that the degree of ACA opening influences IOP level.
Keywords: intraocular pressure • imaging/image analysis: clinical