July 2008

CATARACT/ IOL

BSS Plus linked to free radical protection


by Rich Daly EyeWorld Contributing Editor

Recent research adds to data on protective effect of the irrigating solution during phacoemulsification

Source: Steven Aust, Ph.D.

An effort to quantitate hydroxyl radicals produced during phacoemulsification under different conditions also provided the best measure yet of a saline solutions beneficial role.

The first attempt to quantify the extent to which BSS (balanced salt solution, Alcon, Fort Worth, Texas) could reduce free radicals was presented at the 2008 annual ASCRS Symposium and Congress by Steven Aust, Ph.D., professor, Department of Chemistry and Biochemistry, Utah State University, Logan. He was building on his previous research published seven years earlier.

We had identified the hydroxyl radical as the primary free radical produced by sonication, Dr. Aust said, about his earlier research published in the March 2001 issue of the Journal of Cataract and Refractive Surgery.

That research found that the hydroxyl radical was formed when phacoemulsification was performed in the presence of solutions containing spin trap in double de-ionized water or BSS. However, it found that the production of the hydroxyl radical was not observed when phacoemulsification was performed with anaerobic solutions, indicating a requirement for oxygen in radical production. Additionally, the concentration of trapped hydroxyl radical was reduced in the presence of BSS Plus (Alcon), which included balanced salt solution with bicarbonate, dextrose, and glutathione.

The amount of hydroxyl radical detected was directly proportional to phacoemulsification time and was reduced in the presence of BSS Plus, according to the study, led by Michael Cameron, Ph.D., associate director, Drug Metabolism and Pharmokinetics, Scripps Research Institute, Jupiter, Fla.

Upon phacoemulsification, both salicylate and thiocyanate underwent hydroxylation when included in the irrigating solution, confirming the generation of the hydroxyl radical. The researchers did not detect other reactive oxygen species such as superoxide, hydrogen peroxide, and ozone during phacoemulsification.

The latest research on BSS and free radicals, which has been submitted for publication, sought to advance those findings.

Better defining free radical role

Dr. Austs recent study also builds on the research of others, such as Hiroshi Takahashi, M.D., who attempted to quantitatively assess stress on the corneal endothelium during phacoemulsification. In research published in the January 2005 issue of the Journal of the Nippon Medical School, Dr. Takahashi examined how ultrasound in aqueous solution induces cavitation, which directly causes water molecule disintegration and results in the formation of hydroxyl radicalsthe most potent of the reactive oxygen species.

Dr. Aust sought more specific results by attempting to quantitate the extent to which hydroxyl radicals are produced during phacoemulsification with various devices and modalities, as well as the impact of BSS, which was used throughout the testing. The research quantitated the hydroxyl radicals produced during commonly used phaco settings using the deoxyribose method.

It concluded that the amount of free radicals produced during phacoemulsification was dependent on the power level, modality, type of phaco tip and the irrigation solution. The oxidative stress on the eye during phacoemulsification, Dr. Aust concluded, may be minimized by using modalities and tips that produce fewer free radicals and by using irrigation solutions that contain organic molecules that can compete for reaction with hydroxyl radical.

The additions to the basic salt solution [BSS] reduced the chance that those free radicals will react with biomolecules in the eye, he said.

Dr. Aust said further research is needed, including an assay to detect radicals at lower levels with improved sensitivity, accuracy and precision, which would allow for an investigation of additional parameters during the procedure. Also needed is research that can correlate free radical production with tissue damage.

More scrutiny of irrigating solutions

The research comes as saline solutions have come under increased scrutiny following recent TASS outbreaks that were linked to Endosol (Cytosol Laboratories, Lenoir, N.C.). Although outbreaks have not been traced back to other irrigating solutions, the findings highlighted the potential impact of a previously low-profile surgical ingredient.

Henry Edelhauser, Ph.D., professor of ophthalmology, Emory University, Atlanta, and a nationally recognized TASS expert who helped develop BSS Plus, said the outbreak remains the most attention-grabbing aspect of irrigating solutions today. He noted that the dominant solutions in the ophthalmic market, BSS and BSS Plus, are very similar to Endosol but that they have never been implicated in any TASS cases. He cited tighter manufacturing controls for the lack of balanced salt solution-related infections.

The safety and reliability of BSS Plus have made that drug the standard irrigating solution used for routine phacoemulsification and vitreoretinal surgery.

It is the closest thing to aqueous and vitreous humor so it is a natural constituent of what is in the eye, Dr. Edelhauser said.

The key differences between BSS and BSS Plus are the ingredients. The buffer system in BSS it is acetate citrate, while BSS Plus uses bicarbonatea natural buffer inside the eye. In addition, BSS Plus contains glutathione, which serves as an antioxidant, and glucose, which serves as an energy source.

It is the most complete irrigating solution to use, Dr. Edelhauser said. h

Editors note: Dr. Aust and Dr. Edelhauser have financial interests with Alcon (Fort Worth, Texas).

Contact information

Aust: 435-797-2730, sdaust@cc.usu.edu
Edelhauser: 404-778-5853, OPHthfe@emory.edu

BSS Plus linked to free radical protection BSS Plus linked to free radical protection
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