November 2008

 

CATARACT/ IOL

 

To chill or not to chill


by Matt Young EyeWorld Contributing Editor

   

Save for improving vision, surgeons go to great lengths to minimize the impact cataract surgery has on their patients. To some extent, they have concentrated on controlling temperature—opting for modalities that create less heat. A new study suggests, however, that cooling irrigation solution has no impact on results whatsoever. Research in this area of irrigation temperature has been all over the place in terms of results. Some studies have suggested cooling helps; other research has suggested that warming refrigerated solution could be of benefit. Still other ophthalmologists opt for room-temperature solution. While the latest study won’t serve as the deciding one in this debate, its conclusion is worth understanding.

BSS vs. cold BSS

This study, published online in June 2008 in Eye, pitted 35 patients undergoing phacoemulsification with 23 degree Celsius (room-temperature) BSS Plus (Alcon, Fort Worth, Texas) against 35 patients with BSS Plus cooled to 10 degrees Celsius. The list of things that wasn’t different about these corneas after surgery was fairly extensive. There was no significant difference in percentage change of CCT from pre-op to post-op days 1, 7, and 30. There was also no significant difference in endothelial cell density loss and the coefficient of variation (CV) from the pre-op to post-op period at 1 month.

And on the first day post-op, there was no significant difference between the two groups in terms of anterior chamber flare. “The temperature of the BSS Plus solution did not affect any parameter of the study,” reported study co-author Abhay Vasavada, M.D., Raghudeep Eye Clinic, Iladevi Cataract and IOL Research Centre, Ahmedabad, India. “The use of moderately cooled BSS had no detectable effect and benefit on the outcome of the surgery.”

Some surgeons have operated with cooled BSS under the assumption that it could prevent post-op corneal swelling. If Dr. Vasavada’s results are correct, this assumption would be wrong. But there still is research out there that conflicts with Dr. Vasavada’s results, to which he alluded. “A 10°C decrease in the temperature of the ocular tissue can reduce the metabolic activity of the cornea by as much as 50%,” Dr. Vasavada noted. “A few authors have proposed that ocular hypothermia achieved with the use of a refrigerated infusion fluid might reduce ocular tissue damage during intraocular surgical procedures.”

Still other studies have found that temperature did not statistically significantly impact post-op corneal thickness or endothelial cell count. “In another in vivo experiment on rabbit eyes, it was observed that when the anterior chamber was perfused with cold irrigating solution, the swelling was more persistent than that observed in eyes exposed to irrigating solutions at room temperature,” Dr. Vasavada reported. “This indicates that refrigerated irrigation solutions should be warmed before use.”

Some research has even suggested that cooler is better for some reasons, but not others. “It was suggested that cooled irrigating solutions appear to inhibit acute blood aqueous barrier disturbance but delay and possibly prolong the inflammation when compared with irrigating solutions at room temperature,” Dr. Vasavada noted. At this point, more studies are needed to draw definitive conclusions, but if history repeats itself, then more studies may just draw opposite conclusions. Suffice it to say that Dr. Vasavada’s research was thorough and credible and should be added to the authoritative list of studies about temperature and irrigating solution. Nonetheless, surgeons internationally continue to remain true to cooling BSS solution in some cases, secure that there are benefits. “We cool BSS,” said Mohan Rajan, M.D., Rajan Eye Care Hospital, Chennai, India. “We cool viscoelastic as well.”Dr. Rajan says the cooled BSS produces an anesthetic effect. It also produces clearer corneas post-op, he said. Finally, he said, it has a “very good effect on corneal endothelium.” “The cell loss is less than 2 to 3% with a two to three year follow-up period,” he noted. That said, his clinic has not compared chilled BSS against room temperature BSS.

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

Contact information:

Rajan: rajaneye@vsnl.com
Vasavada: +91 79 27492303, icirc@abhayvasavada.com

       
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