Cataract Surgery and Glaucoma

Abstract

We read with great interest Nonaka et al’s recent report.1Nonaka A. Kondo T. Kikuchi M. et al.Angle widening and alteration of ciliary process configuration after cataract surgery for primary angle closure.Ophthalmology. 2006; 113: 437-441Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar In this study, the effect of cataract surgery was evaluated in 31 eyes with anatomically narrow angles (21 of them with no laser iridotomy). The authors reported that cataract surgery widened the iridocorneal angle and attenuated the anterior positioning of the ciliary processes. These results may be clinically relevant, as they suggest that lens extraction may be effective in treating plateau iris syndrome. Ultrasound biomicroscopy (UBM) has enhanced the morphologic assessment of the anterior segment, particularly the structures behind the iris. However, as UBM images represent frozen radial sections of the drainage angle, the morphology and position of the ciliary processes and the relationship between these structures and the posterior iris may vary in different radial scans (in an extreme example: through a typical ciliary process or the valley between ciliary processes).2Pavlin C.J. Harasiewicz K. Foster F.S. Ultrasound biomicroscopy of anterior segment structures in normal and glaucomatous eyes.Am J Ophthalmol. 1992; 113: 381-389Abstract Full Text PDF PubMed Scopus (464) Google Scholar Slight differences in the acquisition location of radial scans before and after cataract surgery may generate UBM images of different ciliary processes, possibly differing in morphological aspects and relative position in the anterior segment of the eye. Thus, differences in the trabecular–ciliary process distance before and after surgery may have been influenced by measuring this parameter in different radial sections of the eye. The potential lack of reproducibility in acquiring radial scans at the same location represents an inherent limitation of UBM. For an appropriate interpretation of the results, it would be interesting to know how the authors deal with this matter. Do trabecular–ciliary process distance changes consistently occur in both superior and inferior quadrants (particularly in those eyes where the trabecular–ciliary process distance changed by >0.4 mm)? Along the same line, eyes with isolated peripheral anterior synechiae may have a similar confounding effect in comparing the angle-opening distance at 500 μm from the scleral spur before and after surgery. A radial scan though a peripheral anterior synechia would show a closed angle, whereas a radial scan obtained just next to it (with no peripheral anterior synechiae) could show a wider angle—independent of if there had been eye surgery. Furthermore, the authors reported that eyes with clear lenses but poor intraocular pressure (IOP) control were submitted to lens extraction surgery. It would be interesting to know if all these eyes had had a previous iridotomy and if the presence of iridotomy was associated significantly with the main outcomes of the study. Recently, several researchers involved in studies conducted in Asian populations reported that non–pupil block mechanisms are much more common than previously expected, particularly plateau iris mechanism (up to 62% of eyes with anatomically narrow angles).3Wang N. Wu H. Fan Z. Primary angle closure glaucoma in Chinese and Western populations.Chin Med J (Engl). 2002; 115: 1706-1715PubMed Google Scholar However, although complete plateau iris syndrome is a well-defined clinical condition, there is no evidence-based definition of how narrow the angle has to be or how anteriorly positioned the ciliary processes must be before the diagnosis of plateau iris mechanism is made4Pavlin C.J. Mandell M.A. Weisbrod D.J. Simpson E.R. Anterior chamber depth in plateau iris syndrome and pupillary block as measured by ultrasound biomicroscopy.Am J Ophthalmol. 2004; 137 ([letter]): 1169-1170Abstract Full Text Full Text PDF PubMed Google Scholar—with plateau iris mechanism defined as a non–pupil block mechanism that would lead to further peripheral anterior synechiae formation and/or loss of IOP control after iridotomy. We believe that addressing this crucial limitation would be quite relevant as (1) lens extraction surgery in angle-closure eyes carries potential complications5Tan G.S. Hoh S.T. Husain R. et al.Visual acuity after acute primary angle closure and considerations for primary lens extraction.Br J Ophthalmol. 2006; 90: 14-16Crossref PubMed Scopus (27) Google Scholar and (2) it would alert the readers that the indications to perform clear lens extraction surgery to prevent an angle-closure process after iridotomy are not well defined. Author replyOphthalmologyVol. 114Issue 1PreviewWe thank Sakata et al for their comments regarding our article. Indeed, examination using ultrasound biomicroscopy (UBM) has several limitations, because it is impossible repeatedly to scan precisely the same location of ciliary process or peripheral anterior synechiae with the current commercially available UBM. In taking UBM images, however, we paid great attention to taking as clear and large images of ciliary processes as possible. Accordingly, the valley between ciliary processes was not scanned in our study. Full-Text PDF