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Editors Selection IGR 16-2

Anterior Segment Imaging: Pentacam in laser iridotomy

Comment by Tin Aung on:

26287 Anterior chamber measurements taken with Pentacam: an objective tool in laser iridotomy, Antoniazzi E; Pezzotta S; Delfino A et al., European Journal of Ophthalmology, 2010; 20: 517-522

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The Pentacam is a Scheimpflug optical system that is capable of obtaining cross-sectional images of the anterior chamber in a non-contact fashion. In their paper, Antoniazzi et al. (694) prospectively evaluated the differences in anterior chamber morphology after laser peripheral iridotomy (LPI) in 20 eyes with narrow angles. Images of the nasal and temporal angles were obtained and parameters such as anterior chamber volume (ACV), central anterior chamber depth (ACD), peripheral anterior chamber depth (PACD) and the width of the chamber angle were measured before and after LPI. In eyes with narrow angles, the authors found that there were significant changes in all parameters except CACD after LPI, and the reproducibility of Pentacam measurements was very good.

The paper was interesting, as it showed the importance of documenting and measuring anterior chamber and particularly, angle parameters in a clinical setting to assess the effectiveness of treatments such as LPI. Documentation of angle findings is an often neglected area in ophthalmic practice. While most glaucoma specialists will image the optic disc and retinal nerve fiber layer thickness, angle imaging is rarely performed, making it difficult to monitor the extent and progression of angle closure over time. However, while the Pentacam is effective in measuring anterior segment parameters such as ACD and ACV, the instrument may not be appropriate for assessing the angle width, as the resolution of the angle recess is quite limited.

Documentation of angle findings is an often neglected area in ophthalmic practice

In this paper, the authors also discussed the limitations of gonioscopy such as the lack of reproducibility and variability in findings with changes in illumination or technique in holding the gonioscopy lens. However, there are also limitations to anterior segment imaging instruments such as anterior segment OCT, ultrasound biomicroscopy and Pentacam; and as stressed by the authors, none of these instruments can satisfactorily replace gonioscopy.

While this paper showed that the Pentacam is an objective instrument that may demonstrate the efficacy of LPI, more research is required to determine if the Pentacam can be a tool for detecting eyes at risk for angle closure.

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