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Blood Filtration System a Novel Approach to Treating Age-Related Macular Degeneration: Presented at AAO

By Earl R Nichols

CHICAGO, IL -- October 21, 2005 -- A promising therapy that filters the body's blood and removes heavy protein particles might improve vision in patients with dry age-related macular degeneration.

It is also possible that the procedure might prevent the dry form of the disease from morphing into wet AMD, which can lead to neochoroidal vascularization and much greater risk of blindness.

The results of a study carried out in Canada and Germany involving the procedure were presented here October 14^th at the annual meeting of the American Academy of Ophthalmology (AAO).

The study is designed to enroll 185 patients in both countries with the disease. Preliminary results looked at data from 28 patients who underwent the treatment compared with 15 who underwent a sham therapy.

Rheopharesis involves the removal of specific, high molecular weight plasma protein and lipoprotein fractions from the blood, in a procedure that is similar to kidney dialysis. The body's total volume of blood is removed and filtered in eight sessions over a 10-week period. Each 3-hour session cleans approximately 12% of the body's blood supply. The main macromolecules that are filtered out of the blood are fibrinogen, cholesterol and immunoglobulin A (IgA)

The immediate effect of the procedure is to reduce the plasma viscosity by 15% to 18%, explained Dr. Ronald Danis, Professor, Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison Medical School, Madison, Wisconsin, United States. It is also believed to remove serum oxidative species that could accumulate in the Bruch's membrane and cause progressive damage to the neurons and retinal pigmented epithelium..

At 12 months of follow-up, the study findings revealed a 1.7-line difference between the treated group and the sham group. The benefit was seen after as little as 3 months of follow-up and lasted throughout the next 9 months.

Ophthalmologists who were masked to the treatment and who studied patients' fundus photographs reported that there appeared to be reduced drusen in the treatment group. There was also some suggestion that patients with the worse visual acuity at enrollment fared better from the procedure, Dr. Danis said.

The long-term outcomes of the procedure are not known, and the trial continues, Dr. Danis said. Final results should be available in early 2006.

Adverse events associated with the procedure are generally mild, and required withdrawal from treatment in 1.49% of cases, mainly due to problems with accessing the blood vessels to facilitate the filtration tubes.

The procedure is invasive and expensive, Dr. Danis said, costing around $19,000 per patient, but the rationale as to why it works is reasonable.

"If this proves efficacious at preserving vision in short-term trials, these results will then stimulate other investigations into the mechanisms and treatment of AMD," Dr. Danis concluded.


[Session title: Retina Sub-specialty Day.]

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