Abstract
Purpose: :
To quantitatively evaluate the iris parameters for various primary angle closure mechanisms by means of anterior segment coherence tomography (AS-OCT).
Methods: :
A total of 148 subjects with primary angle closure from pupillary block (n=51), plateau iris (n=23), peripheral iris roll (n=21) and lens induced mechanism (n=53) underwent AS-OCT under dark conditions. Customized software was used on horizontal AS-OCT scans to measure iris area (500µm and 750µm from scleral spur), thickness (500µm, 750µm, 1000µm and 2000µm from scleral spur), iris length and iris tilt.
Results: :
Iris thickness at 500µm, 750µm and 1000µm from the scleral spur was significantly different for the various angle closure mechanisms (p<0.001 for all). Eyes with pupil block had the thinnest iris at the above measured sites, followed by those with lens induced mechanism and plateau iris, while eyes with peripheral iris roll had the thickest iris measurements. There was significant difference in iris area at 750 µm from the scleral spur among various angle closure eyes (p=0.003) but not at 500µm. The iris length also varied considerably (p=0.002), where eyes with peripheral iris roll had the smallest mean iris lengths (3.41mm). Finally, there was significant difference in iris tilt (p<0.001) among the eyes of different angle closure mechanisms.
Conclusions: :
Quantitative analysis of iris parameters is a helpful tool in differentiating the various mechanisms of angle closure.
Keywords: iris • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • anterior segment