Progression and regression of Elschnig pearls within 1-day-intervals illustrate the dynamic behaviour of PCO

October 1, 2005

The formation of Elschnig pearls is a highly dynamic process and is detectable even over very short time intervals. Elschnig pearls can appear or disappear within one day, according to Oliver Findl, MD, from the Medical University of Vienna, Austria.

Clinically, posterior capsule opacification (PCO) has two different components: a regeneratory and a fibrotic component. Regeneratory PCO is more common and is the main reason for a decrease in visual function after implantation of an intraocular lens (IOL). Regeneratory PCO is thought to be caused by residual equatorial lens epithelium cells (LEC) that migrate and proliferate between the posterior capsule and the IOL, first forming mono-layers of cells and later Elschnig pearls, mainly responsible for decreased visual acuity and loss of contrast sensitivity.

Dr Findl and co-workers investigated the changes of Elschnig pearls in 26 pseudophakic eyes with severe PCO in a prospective study.

Between day 0 and 14, there was a strong correlation between increase and decrease in pearl size, illustrating that cases with a high progression of Elschnig pearls also show a high regression, which can be interpreted as a high turn-over of Elschnig pearls.

"Several questions still remain unanswered," said Dr Findl. "First, what are the factors influencing the dynamics of change of PCO, which vary between patients? Do these differences arise as a result of unknown patient factors, or because of differences in IOL material, for example," he questioned. "Second, what is the average life-time of a pearl? We saw pearls appear and disappear within days but, on the other hand, pearls remained unchanged over the course of weeks. These questions must be answered," insisted Findl. To address these issues, a further investigation with a larger cohort of patients is essential.

The dynamic behaviour of PCO development observed strongly implies that it may be possible to influence this development through pharmaceutical intervention. Because PCO is still the major restricting factor in lens refilling procedures in the animal setting to allow for restoration of accommodation, the possibility of impeding PCO development with pharmaceuticals would be a significant advance. Further, this would have favourable implications for PCO treatment in developing countries where Nd:YAG laser treatment is less freely available.

According to Oliver Findl, the reproducibility of the assessment in this study was found to be good, however, because of the complexity of analysis, this evaluation method is not appropriate for studies with larger numbers of images. For that purpose, semi-automated evaluation software was recently developed to enable analysis of a greater number of images in a shorter timeframe. Should the new system prove effective, Findl plans to perform interventional trials to test the efficacy of therapeutic agents on the dynamic behaviour of PCO.

Oliver Findl, MD, is Associate Professor of Ophthalmology at the Department of Ophthalmology, Medical University of Vienna, Austria. He may be reached at +43 1 40 400 7967; oliver.findl@meduniwien.ac.at