EBM review: ANGLE CLOSURE GLAUCOMA: A MECHANISTIC REVIEW MONISHA E. NONGPIURA, JUDY Y.F. KUA AND TIN AUNGA,B CURRENT OPINION IN OPHTHALMOLOGY 2011,22:96–101. 2011/3/17 R4 雷小蕾 /VS 張雪麗. Risk factors for angle closure: recent findings. (1) Anatomical factors:
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EBM review:ANGLE CLOSURE GLAUCOMA: A MECHANISTIC REVIEWMONISHA E. NONGPIURA, JUDY Y.F. KUA AND TIN AUNGA,BCURRENT OPINION IN OPHTHALMOLOGY 2011,22:96–101
2011/3/17 R4 雷小蕾/VS張雪麗
(1) Anatomical factors:
(a) Anterior chamber – width, area and volume.
(b) Iris – thickness, area, and curvature.
(c) Lens – lens vault.
(2)Altered physiology/ dynamic factors:
(a) Iris – changes in volume with dilation.
(b) Choroid – choroidal expansion/effusion
Iris volume changes with dilation
dynamic physiological factors
also play a significant role in
the pathogenesis of angle closure
AS-OCT: pupil diameter greater
in dark (a)
Iris cross-sectional area decreases with pupil dilation and its dynamic behavior is a risk factor in angle closure. Glaucoma 2009; 18:173–179.
evaluated changes in iris cross-sectional area measured with AS-OCT in 65 glaucoma patients, including both open angle and angle closure, during physiological and pharmacological mydriasis.
4% loss in calculated iris volume per 1mm increase in pupil size, with peak loss complete in 5 s.
Glaucoma 2009; 18:173–179.
Anatomical risk factors such as axial length, refraction,gonioscopy and corneal curvature were notdeterminants of iris cross-sectional area or change in iris cross-sectional area with pupil dilation
=> this dynamic behaviour is due to movements of extracellular fluid between the iris stroma and the anterior chamber.
Figure 2. Examples of 8 cross-sectional images of the iris at 0-, 45-, 90-,
135-, 180-, 225-, 270-, and 315-degree meridians under illumination and
after pupil dilation (1% tropicamide) in (A, B) open-angle eyes and (C) fellow eyes. Iris volume changes from (A) 45.99 to 35.73 mm3 (23.3%), (B) 44.34 to 37.43 mm3 (16.6%), and (C) 44.39 to 50.19 mm3 (9.1%).
Note that pupil dilation seems to be comparable in the 3 eyes; by contrast,
the iris seems to be thicker in the fellow eye.
Ophthalmology 2010; 117:3–10.
biometric risk factors did not change significantly during mydriasis (P>0.1).
=>This dynamic iris behaviour may be a physiological adaptation to dilation to avoid blockage of the drainage angle.
Thus this inherent tendency to lose less or even gain volume during dilation, in eyes at risk of APAC, is possibly a contributing factor in the development of angle closure and may provide an alternative explanation for the higher incidence of angle closure among certain populations.
thickness regulated by various parameters
Possible mechanisms of primary angle- closure and malignant glaucoma. J Glaucoma 2003; 12:167–180.
and even precipitate APAC.
vitreous has a limited capacity to transmit fluid: anterior movement of the compressed vitreous, iris and lens when trans-vitreous flow is restricted
Within the acute PAC group though, there were no differences in the demographics and management profile between those with and without choroidal effusion.
Confirmation of uveal effusion in eyes with primary angle closure glaucoma: an ultrasound biomicroscopy study. Arch Ophthalmol 2008; 126:1647–1651.
The level of effusion : milder among PACG (all grade 1 effusion) vs APAC (grade 2 or 3).
grade 1:slitlike(supraciliary space less than half the ciliary body thickness)
grade 2: bandlike (supraciliary space greater than half the ciliary body thickness)
grade 3: obvious (supraciliary space greater than the ciliary body thickness).
Confirmation of uveal effusion in eyes withprimary angle closure glaucoma: an ultrasound biomicroscopy study. Arch
Ophthalmol 2008; 126:1647–1651.
The presence of choroidal effusion in untreated eyes raises the question of whether it is a cause or effect of PACG/APAC.
other investigators have failed to demonstrate significant changes in biometry (ACD, lens position, RLP) before and 2 weeks after LPI=> challenges the theory of anterior lens movement secondary to choroidal expansion as a possible mechanism for APAC.
Br J Ophthalmol 2005; 89:288–290.
early detection by effective screening and appropriate prophylaxis, angle closure glaucoma is a potentially preventable disease.