FEB 04, 2011
The authors conducted this case-control study to assess the morphologic changes in the anterior segment in eyes with nuclear or cortical opacity due to age-related cataract and to evaluate the relative merits of using anterior chamber depth (ACD) and anterior chamber volume (ACV) to determine eligibility for cataract surgery.
Using rotating Scheimpflug imaging (Pentacam), they found significant differences in lens thickness, ACD and ACV between eyes with nuclear and cortical age-related cataracts. They say that ACD decreased more in eyes with cortical cataract, suggesting that the risk for angle-closure glaucoma may be greater in cases of cortical opacity in which lens expansion is greater. They conclude that ACD should be the main indicator for cortical cataract surgery rather than visual impairment and lens opacity.
The authors enrolled in the study 269 patients (330 eyes) with nuclear or cortical age-related cataract, 30 eyes for each nuclear opalescence and cortical grade, and 19 control subjects (30 eyes). They found that in eyes with age-related cataract, lens thickness increased as cortical opacity increased, whereas ACD and ACV decreased. ACD inversely correlated with Lens Opacities Classification System III (LOCS III) grades for nuclear opalescence (r = -0.197, P = 0.004), nuclear color (r = -0.195, P = 0.005) and cortical opacity (r = -0.508, P < 0.005). They also found significant differences between nuclear and cortical cataract in lens thickness in LOCS III grade 3, ACD in grade 4 and ACV in grade 5.
Compared with nuclear cataracts, cortical cataracts showed significant changes first in lens thickness (from grade 3) and subsequently in ACD and ACV. The authors say that this finding is consistent with the fact that ACD is determined by the position and thickness of the lens. They say the study's results also suggest that nuclear cataracts may induce anterior lens positioning, although further study is needed to verify and clarify this phenomenon.
I found this to be a very interesting study. The results suggest that we should all become more aware of the benefits of cataract surgery for reducing IOP and preventing chronic angle closure even in the presence of a peripheral iridotomy. Accordingly, I have lowered my threshold for recommending surgery in patients with mild cataract and shallow ACs.