January 2009

 

CATARACT/ IOL

 

Tracking lens epithelial cells


by Matt Young EyeWorld Contributing Editor

   
Cellular PCO Source: Mostafa A. Elgohary, M.D.

Posterior capsule opacification (PCO) is understood to result from proliferating and migrating lens epithelial cells across the posterior capsule. It’s the most common cause of visual acuity reduction after cataract surgery. And yet, only recently did a researcher actually confirm the presence of lens epithelial cells in the anterior chamber after phacoemulsification. It seems odd that scientists would have waited so long to do this, given that LECs are thought to cause the most common visual problem after phacoemulsification. Nonetheless, Abhay Vasavada, M.D., Raghudeep Eye Clinic, Iladevi Cataract and IOL Research Centre, Ahmedabad, India, and colleagues claim that they have, for the first time, established such cell presence. Their research was published in Eye in June 2008.

“In the past, various speculations have been made about the presence of LECs in the anterior chamber following phacoemulsification,” Dr. Vasavada wrote. “However, to our knowledge, no study has been conducted to confirm this hypothesis. This is the first study documenting the presence of LECs in the anterior chamber after phacoemulsification.”

A long time coming

Dr. Vasavada analyzed 50 patients undergoing cataract surgery. At the conclusion of phacoemulsification, fluid was collected from their anterior chambers. Thirty samples were used to detect viability. The agents calcein AM and propidium iodide were used to do this. “The presence of lens epithelial cells was confirmed in 27 of the first 30 samples,” Dr. Vasavada reported.

That’s confirmation enough, with 64.7 cells confirmed to be present in the 27 samples. Among these, 35.5% were live cells and 64.5% were dead. All cells were present either in groups or individually. Calcein (green) indicated positive live cells, and propidium iodide (red) indicated positive dead cells. They were visualized using fluorescein and rhodamine filter sets, respectively. The leftover 20 samples were used to perform immunofluorescence detection of A-crystallin and vimentin.

“The presence of A-crystallin and vimentin confirmed that these cells were LECs,” Dr. Vasavada noted. “A-crystallin is a water-soluble chaperon protein of the undifferentiated LECs. Vimentin is an intermediate filament cytoskeleton protein of the LECs. Both A-crystallin and vimentin were earlier used as marker proteins for the LECs.”

Where did they come from?

“We believe that the observed cells in this study could have been detached from any of the three zones of the lens epithelium,” Dr. Vasavada reported. “In the present study, it was interesting to observe the presence of live cells and nucleated fibres even after a thorough clean-up of the anterior chamber. We believe that hydrodissection combined with rotation of the nucleus causes friction between the cataract and LECs, leading to the removal of the LECs.” Phacoemul-sification can cause turbulence, and also detach LECs, he noted. Dr. Vasavada suggested that, once free in the anterior chamber, these cells can attach themselves to the posterior capsule and facilitate PCO development.

“The LECs are shown to possess various adhesion molecules that help in their attachment to the lens capsule,” he reported. “Various substances like growth factors, fibronectin, and so on are released into the aqueous humour after the surgery due to the breakdown of blood aqueous humour, which facilitates the proliferation and differentiation of the adhered LECs.”

Now that Dr. Vasavada has proven once and for all that LECs are present in the anterior chamber after phacoemulsification, he has some new ideas for similar research. “It would be worthwhile to further investigate the role of these live LECs in the incidence and severity of PCO,” he concluded. More interest, however, is in migration of lens epithelial cells behind the capsule, which causes problems like posterior capsule fibrosis, said Tat-Keong Chan, F.R.C.Ophth., Singapore National Eye Centre. That results in clouding or thickening of the posterior capsule.

“If you don’t clean the case properly, some cells migrate to the back,” he said.

As for lens epithelial cells found in the anterior chamber, Dr. Chan said this is not terribly concerning, and if opacity results, it can be corrected with a YAG laser.

Editors’ note: Dr. Vasavada has no financial interests related to this study. Dr. Chan has no financial interests related to his comments.

Contact information

Chan: snecctk@pacific.net.sg
Vasavada: +91 79 27492303, icirc@abhayvasavada.com

       
Tracking lens epithelial cells Tracking lens epithelial cells
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