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Clear corneal phaco may impair filtering bleb
Study patients showed an IOP increase and changes in bleb morphology at 12 months after phacoemulsification.
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Clear corneal phacoemulsification may compromise the function of a previously functioning glaucoma filter or impair the filtering bleb morphology, according to a recently published study.
Janine Klink, MD, and colleagues at University Eye Hospital in Wuerzburg, Germany, prospectively evaluated 30 eyes of 30 patients that underwent clear corneal phaco after successful glaucoma filtering surgery to evaluate the influence of clear corneal phaco on bleb morphology.
The researchers assessed mean IOP and filtering bleb morphology before surgery and at 3 days, 6 months and 1 year after surgery. They compared patients with previous glaucoma surgery with a control group of 36 patients with glaucoma who underwent clear corneal phaco but did not have previous filtering surgery.
At the 12-month follow-up visit, the mean IOP in patients with previous filters increased after phaco by about 2 mm Hg, from 14.28 mm Hg preoperatively to 16.33 mm Hg (P < .05).="" conversely,="" the="" control="" group="" showed="" an="" average="" iop="" decrease="" of="" 2="" mm="" hg="" at="" 12="">
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“Our results indicate that a phacoemulsification may jeopardize a previously functioning filtering bleb, resulting in IOP increase. In this respect, the cataractogenesis of glaucoma surgery may become an important issue for indication of both glaucoma and cataract surgery,” the researchers concluded.
Half the patients in the filtering group experienced an IOP increase of more than 2 mm Hg, 11 showed no change, and four patients had an IOP decrease.
The data showed that the interval between the creation of the bleb and the performance of phaco had no influence on IOP outcome, the researchers said.
The cataract surgery was performed by three surgeons using phacoemulsification through a temporal clear corneal incision.
According to the authors, only two other prospective studies have been published on this topic, with varying outcomes. This study differentiates itself by excluding eyes presenting with angle-closure glaucoma in order to avoid opposite mechanisms of IOP lowering that arise in different forms of glaucoma.
Bleb morphology
The bleb morphology was assessed by creating a 0 to 12 score of the bleb, with 12 indicating a fully functioning bleb.
The researchers evaluated vascularization, corkscrew vessels, microcysts, encapsulation and bleb elevation. They explained that the bleb elevation was calculated separately using corneal thickness equivalents.
“Elevation was not included in our bleb score because it might have favorable (good filtration) and also unfavorable aspects (prominent Tenon cyst),” the researchers wrote.
The mean bleb morphology score decreased from 9.5 points before phaco to 8.9 points 1 year after surgery.
Specifically, they said that the number of corkscrew vessels and general vascularizations significantly increased (P = .027) in the first days after cataract surgery. The tendency of encapsulation remained stable at 1-year follow-up, and the bleb elevation significantly decreased from 1.6 to 1 corneal thickness equivalents.
“Although we could not find a strong linear relation between IOP outcome and bleb score, the tendency that a higher IOP and a more ‘unfavorable’ filtering bleb are related is obvious,” they wrote.
The study is published in the May issue of British Journal of Ophthalmology.
For Your Information:Reference:
- Janine Klink, MD, can be reached at University Eye Hospital, Josef Schneider-Starsse 11, Wuerzburg 97080, Germany; e-mail: janine.klink@mail.uni-wuerzburg.de.
- Klink J, B Scmitz, et al. Filtering bleb function after clear cornea phacoemulsification: A prospective study. Br J Ophthalmol. 2005;89:597-601.
- Jared Schultz is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses geographically on Europe and the Asia-Pacific region.