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Quantitative evaluation of iris convexity in primary angle closure.
Atsushi Nonaka1, Takuji Iwawaki, Masashi Kikuchi
1Department of Ophthalmology, Kobe City General Hospital, Chuo-ku, Kobe, Japan. a-nonaka@pb3.so-net.ne.jp <a-nonaka@pb3.so-net.ne.jp>
American Journal of Ophthalmology
|March 28, 2007
Summary
In primary angle closure (PAC) patients, ultrasound biomicroscopy revealed that increased forward iris bowing is linked to older age and shallower anterior chamber depth (ACD). This finding helps understand the mechanisms behind pupillary block in PAC.
Area of Science:
- Ophthalmology
- Anatomic studies
- Biomicroscopy
Background:
- Primary angle closure (PAC) is a significant cause of glaucoma.
- Understanding iris dynamics is crucial for managing PAC.
Purpose of the Study:
- To quantitatively assess anterior iris bowing in eyes with primary angle closure (PAC).
- To investigate the relationship between iris bowing and ocular parameters using ultrasound biomicroscopy (UBM).
Main Methods:
- A retrospective analysis of 203 phakic eyes with untreated PAC.
- Ultrasound biomicroscopy (UBM) was used to measure anterior chamber depth (ACD) and iris convexity (IC).
- Iris convexity (IC) was defined as the maximum distance from the iris's posterior surface to a plane defined by the pupillary margin and iris root.
Main Results:
- The average iris convexity (IC) was 0.22 ± 0.1 mm, with significant individual variability.
- IC showed a weak but significant positive correlation with age (r = 0.22, P < .01).
- IC demonstrated a strong negative correlation with anterior chamber depth (ACD) (r = -0.57, P < .0001).
Conclusions:
- Older age and shallower anterior chamber depth (ACD) are key factors contributing to increased forward iris bowing in PAC.
- This forward bowing is associated with pupillary block, a mechanism implicated in PAC.
- UBM provides a valuable quantitative method for evaluating iris morphology in PAC.
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