Cataract surgery cuts glaucoma risk in eyes with pseudoexfoliation

Cataract surgery appears to reduce the risk of glaucoma in eyes with pseudoexfoliation (PEX) syndrome, researchers said. 

“The present study indicates that there should be a rather low threshold for performing cataract extraction in PEX eyes with regard to the risk of developing glaucoma,” wrote Olav Kristianslund, MD, MPh, resident in ophthalmology, PhD-student, and colleagues from Oslo University Hospital and the University of Oslo, Norway.

They published their findings in Acta Ophthalmologica.

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Pseudoexfoliative material apparently clogs the trabecular meshwork, Schlemm’s canal, and collector channels, elevating IOP and making PEX syndrome the greatest risk factor for glaucoma.

Several studies have shown that cataract surgery lowers IOP in eyes with or without PEX syndrome, the authors reported, but they were unable to find any research comparing glaucoma development after cataract surgery under these two conditions.

To fill this gap, they analyzed data from patients recruited for previous studies who had cataract surgery between June 2001 and December 2002 at Oslo University Hospital. From 1,193 patients, they found 51 with PEX syndrome who were still living in the Oslo area in 2008 and able to participate. They compared these with 102 controls.

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Patients in both groups had a mean age of 82.4 years at the time of re-examination and a majority, 72.5%, were female. The mean time from cataract surgery to re-examination was 76 months.

At baseline, 16 (31%) of the patients with PEX had glaucoma, compared with 10 (19%) of the patients without glaucoma. The mean IOP at baseline was 16.5 mm Hg in the PEX group and 15.7 mm Hg in the control group.

 In each case, surgery consisted of a sutureless small limbal incision, a capsulorrhexis, hydrodissection, and phacoemulsification, followed by the insertion of a foldable IOL using forceps.

Surgeons placed the IOL in the capsular bag in almost all these patients, except two in the PEX group and 10 in the control group who had the lens placed in the ciliary sulcus.

Re-examination

At re-examination, one additional patient in each group had glaucoma, bringing the total to 17 (33.3%) in the PEX group and 11 in the control group (10.8%). This corresponds to an incidence of 0.47 cases per 100 person-years in the PEX group, versus 0.17 in the control group.

The authors compared these rates with those in a population-based study (Acta Ophthalmologica Scandinavica 2007, 85: 832-837) of 2.1 per 100 person-years for patients with PEX and 0.5 for patients without the syndrome. Only 21% of patients had cataract surgery during the follow-up time. Other population studies in patients of this age have found similar results.

Both groups in the present study experienced a significant decrease of IOP, reaching 14.0 mm Hg in the PEX group and 13.9 mm Hg in the control group at re-examination.

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Spikes in IOP were significantly more frequent in the PEX group than in the control group, as well as in the patients with glaucoma compared with those without.

A possible explanation for the pressure-lowering effect of cataract surgery is that the removal of the biological lens and the central anterior capsule reduces the release of pseudoexfoliative material and pigment, Dr. Kristianslund and his colleagues wrote. In addition, this material is washed out during the surgery.

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The researchers acknowledged some limitations to their study.

First, the baseline data was extracted retrospectively.

Secondly, they did not verify known glaucoma cases or search for new ones using objective glaucoma measurements, although all the study participants underwent extensive examinations.

Finally, the population of the study was small for calculating incidence rates.

Still, the authors argued that their findings have significant implications.

“Our results indicate that phacoemulsification cataract extraction is protective against the development of glaucoma in the longer term, especially in PEX eyes,” they concluded.