We would like to thank Dr Spaeth for his kind comments and heartily agree with him that iridotrabecular angle is but one of a myriad of anatomical characteristics of the iridotrabecular recess that is likely to determine risk of contact between iris and trabecular meshwork. However, it is one with a proven association between evidence of anterior segment pathology (PAS) and glaucomatous optic neuropathy.1 Dr Spaeth's classification identifying iridotrabecular angle, iris profile, as well as the apparent and true level of iris insertion is currently unsurpassed for describing gonioscopic anatomy in cases of angle-closure.2 However, the advent of UBM and OCT imaging of anterior segment structures has helped reinforce our awareness that the relationship of iris and trabecular meshwork change on a second to second basis.3 The ultimate challenge will be to assimilate the static features that Spaeth highlights into a comprehensive, dynamic model of the determinants of iridotrabecular contact, which is validated in longitudinal studies of incident angle-closure and glaucomatous optic neuropathy.
References
Foster PJ, Nolan WP, Aung T, Machin D, Baasanhu J, Khaw PT et al. The definition of an ‘occludable’ angle: drainage angle width, peripheral anterior synechiae and glaucomatous optic neuropathy in East Asian people. Br J Ophthalmol 2004; 88: 486–490.
Spaeth GL . The normal development of the human anterior chamber angle: a new system of descriptive grading. Trans Ophthalmol Soc UK 1971; 91: 709–739.
Gazzard G, Foster PJ, Friedman DS, Khaw PT, Seah S . Light to dark physiological variation in irido-trabecular angle width. Br J Ophthalmol 2000 (Peer reviewed video report http://bjo.bmjjournals.com/cgi/content/full/88/11/DC1/1).
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He, M., Foster, P., Johnson, G. et al. Reply to Dr Spaeth. Eye 21, 100 (2007). https://doi.org/10.1038/sj.eye.6702400
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DOI: https://doi.org/10.1038/sj.eye.6702400