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Editors Selection IGR 14-2

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Clement Tham

Comment by Clement Tham on:

50418 Reduction in Intraocular Pressure after Cataract Extraction: The Ocular Hypertension Treatment Study, Mansberger SL; Gordon MO; Jampel H et al., Ophthalmology, 2012; 119: 1826-1831

See also comment(s) by Keith BartonPaul HealeyFabian LernerKuldev SinghSteve Mansberger


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A recent series of studies on primary angle-closure glaucoma (PACG) has also demonstrated significant IOP-lowering effects of lens extraction in eyes with co-existing cataract,1,2 and those without.3 In medically- treated, iridotomized PACG eyes with uncontrolled IOP, lens extraction could reduce IOP by an average of 34%,2,3 and reduce the mean requirement for IOP-lowering drugs by 52%2 to 60%,3 over a follow-up duration of two years.

While emerging data from studies such as those above confirm the effect of lens extraction on reducing measured IOP, we have to remain very cautious in extrapolating such information to daily clinical practice. These data raise more questions than they provide answers. Just as an example, how much of that measured IOP reduction is a genuine reduction in IOP? Would the corneal incision wounds, as well as the possible increase in mechanical tension in the zonules and other biomechanical changes in the anterior segment anatomy from cataract surgery, result in an error in our IOP measurements? Furthermore, even if the IOP reduction is accurate, it has yet to be shown whether the lens extraction has significant clinical benefits other than its optical effects, such as preventing progression to primary open angle glaucoma (POAG) in the study by Mansberger et al., or preventing glaucomatous progression in the PACG studies above.

References

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  1. Tham CC, Kwong YY, Leung DY, et al. Phacoemulsification versus combined phacotrabeculectomy in medically controlled chronic angle closure glaucoma with cataract. Ophthalmology 2008; 115: 2167-2173.
  2. Tham CC, Kwong YY, Leung DY, et al. Phacoemulsification versus combined phacotrabeculectomy in medically uncontrolled chronic angle closure glaucoma with cataracts. Ophthalmology 2009; 116: 725-731.
  3. Tham CC, Kwong YY, Baig N, et al. Phacoemulsification versus Trabeculectomy in Medically Uncontrolled Chronic Angle-Closure Glaucoma without Cataract. Ophthalmology 2012.


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