October 2008

 

CATARACT/ IOL

 

Maintaining incision integrity


by Matt Young EyeWorld Contributing Editor

 

 
Vitreous with active endophthalmitis showing vitreous abscess; fluid ingress with flora during cataract surgery could cause endophthalmitis Source: Thomas A. Hanscom, M.D.

Small incisions clearly are desirable in cataract surgery, but it’s important to maintain the integrity of these small incisions during surgery as well. Nonetheless, different phacoemulsification techniques impact wound integrity differently. A new study reveals just how differently.

Researchers applied trypan blue dye to the conjunctival surface during cataract surgery of three groups: those undergoing microcoaxial surgery, standard coaxial, and bimanual. They assessed the amount of ingress that occurred; research pointed to the bimanual group as causing the most ingress, but other groups also experienced the problem. As a result, the researchers, including study co-author Abhay R. Vasavada, F.R.C.S., Iladevi Cataract & IOL Research Centre, Raghudeep Eye Clinic, Gujarat, India, have “concern about ocular surface fluid ingress into the anterior chamber and its potential implications with reference to endophthalmitis rates.” The study was published in the June 2008 issue of the Journal of Cataract & Refractive Surgery.

Dripping blue

Researchers looked at 180 consecutive patients who underwent microcoaxial, standard coaxial, or bimanual phacoemulsification. After trypan blue was poured over the conjunctival surface, ingress was assessed after the nucleus was removed (time point 1) and at the conclusion of surgery after IOL insertion and stromal hydration (time point 2). “At time point 1, a statistically significant difference was observed in the ingress of trypan blue in the aqueous aspirate,” Dr. Vasavada reported. “The bimanual group had the highest ingress and the microcoaxial group, the lowest. The amount of ingress in the standard coaxial group fell between the other 2 groups. At time point 2, there was no statistically significant difference between the microcoaxial group and the standard coaxial group; however, in the bimanual group, trypan blue ingress was statistically significantly higher than in the other 2 groups.”

Analysis of variance was employed during statistical analysis to compare the ingress of trypan blue. Suffice it to say, the dilution factor of trypan blue was converted into log values to make calculation easier. The log of the denominator was 2.47 +/– 0.32 in the bimanual group, 3.39 +/– 0.23 in the standard coaxial group, and 3.58 +/– 0.12 in the microcoaxial group. “The lower values observed indicate higher trypan blue content in the solution and therefore a higher level of ingress into the anterior chamber originating from the ocular surface,” Dr. Vasavada wrote.

After IOL implantation, the log of the denominator was 1.96 +/– 0.32 for bimanual, 3.18 +/– 0.28 for standard coaxial, and 3.24 +/– 0.20 for microcoaxial.

Noting imperfections

Trypan blue ingress was observable in all three groups and likely was due to the fact that clear corneal incisions do not perfectly self seal. Dr. Vasavada attributed the larger amounts of ingress with standard coaxial as compared to microcoaxial to the fact that incisions are larger with the standard technique. “We further speculate that in the bimanual group, the increased ingress of trypan blue could be due to wound distortion resulting from tight geometry of the incision,” Dr. Vasavada reported. “We believe this could be due to the tightness of the incision, which may have resulted in oar-locking. Moreover, the absence of the shielding effect of the sleeve may have adversely affected the integrity of the incision, thereby accelerating increased trypan blue ingress.”

He also suggested there are specific challenges related to IOL placement with the bimanual technique which relate to ingress. “With bimanual phacoemulsification, we hypothesize that the increased ingress could be due to the subsequent enlargement of the 1.2 mm incision with a 2.2 mm keratome for implantation of the IOL,” Dr. Vasavada reported. “We further think that this enlargement can produce an uneven surface within the incision tunnel, which may compromise the competence and integrity of the primary incision when compared with performing a single-stroke incision, as in the standard coaxial and microcoaxial procedures.”

Nonetheless, William Trattler, M.D., director, Cornea, Center for Excellence in Eye Care, Miami, questioned the study methodology. “One of my concerns with this type of study is it might depend on a variety of settings,” Dr. Trattler said. “Every time you put an instrument in the eye you might be carrying some trypan blue with you. In bimanual, there’s also a tendency to switch hands. You might tend to move the instruments more so the ingress might be seen more.”

Dr. Trattler did see this as an interesting study, however, because ingress certainly could impact infection rates. “No matter how good we are at trying to sterilize the ocular surface, there still is some normal flora present,” he said. These flora could reach the anterior chamber through ingress and result in infection. “There is some relevance to this,” he said. Other factors could be involved in trypan blue ingress, though, he said. “Inflow has to occur when the anterior chamber is depressurized,” he said. “That probably has nothing to do with the bimanual or coaxial technique.”

Editors’ note: Dr. Vasavada did not indicate any financial interests related to this study. Dr. Trattler has no financial interests related to his comments.

Contact Information

Trattler: 305-598-2020, wtrattler@earthlink.net

Vasavada: icirc@abhayvasavada.com

Maintaining incision integrity Maintaining incision integrity
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