CATARACT/ IOL |
Maintaining incision integrity by Matt Young EyeWorld Contributing Editor |
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 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
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