Bimanual vs coaxial MICS: who wins?

Bimanual microincision cataract surgery (MICS) and microaxial phacolemulsification provide optically better incisions but bimanual MICS respects more corneal prolateness than microaxial phaco, Mr Jorge Alio, told delegates. "MICS is associated with less corneal oedema in the short term and less inducation of corneal aberrations in the long term," he said.

His comments came during a debate on controversies in cataract and refractive surgery, under the heading 'bimanual vs coaxial phaco'.

Dr Graham Barrett, defending coaxial phaco, disagreed, stating that equipment he developed enabled a technique he called coaxial MICS, which he termed C-MICS. He said that bimanual phaco suffered from compromised fluidics. Moreover, he said that astigmatism didn't differ significantly between bimanual MICS and his C-MICS technique.

Surgeons could accomplish sufficiently small incisions using C-MICS, so bimanual MICS was not necessary, and bimanual MICS was a difficult techniqe. Finally, he said that stability was better using C-MICS.

Dr Alio opened his talk by defining the perfect cataract surgery for the 21st century. He said it must be minimally invasive, ideally a puncture. It must be safe and effective in all types of cataract cases and correct all types of defocus, including astigmatism. "It must not induce eye aberrations, it will restore accomodation and it will use adaptive optics to improve vision quality," he said.

He briefly summarized current technique emphasizing the incision, 3.1 mm to 3.4 mm in standard coaxial phacoemulsification, 2.2 mm to 2.5 mm in microaxial, sub 2 mm in bimanual MICS and and sub 1 mm in micro-MICS.

He was then asked whether the quality of the incision was worse in biaxial MICS, before responding with a study he performed on 50 eyes in 34 patients. He split the patients into two groups, with 25 eyes bimanual MICS and 25 using microaxial phaco.

Summarizing the results, he said there was excellent incision quality in both groups with no statistically significant differences. Bimanual MICS showed less corenal oedema, but only on day one. At month one, Q values, corneal RMS astigmatism and HOA were slightly better in the bimanual MICS group, but all other outcome parameters including topographic corneal and ocular aberrometric vairables did not differ significantly.

He subsequently tested corneal topography and aberrometry, using the CSO topographer, and aberrations were calculated through Seidel abberration coefficients, while total ocular aberrometry was measured one month after surgery. Only UCVA at one week and one month postoperatively was within the limit of statistical significance, while bimanual MICS was slightly better in corneal RMS and HOA.

"So if the results are fairly similar, why bimanual MICS? Microaxial has no further evolution, real sub 1 mm surgery is feasbible and it is the ony way to keep pace with the progress of cataract surgery," he said, looking ahead at cavitation and femtosecond cataract surgery. He concluded that the leading edge of the cataract surgery 'new wave' was 0.7 mm bimanual MICS. "Catch the wave!" he told gathered surgeons.

Dr Barrett, responding, said that with bimanual surgery the amount of infusion is compromised and there is significantly more leakage when compared to coaxial phacoemulification. "It is very difficult to obtain an adequate seal around a rigid instrument, such as an irrigating cannula."

He said he designed the Microflow 2.2 mm phaco needle to respond to these problems. "The label should not be labeled 2.2 mm as I use three different sleeves with the phaco needle." It was possible to reduce the incision to as low as 1.6 mm to 1.8 mm. He said even with a 1.6 mm incision, infusion was similar to standard coaxial phaco, but there was a better seal.

Astigmatism was not a significant issue with either technique.

"But equally important as astigmatism is wound strength analysis. I have compared the wound strength in different types of incision. The difference in wound strength is dramatic."

He said sceleral incisions are much more resistant to wound leakage than corneal incisions. He said the fact that these incisions are covered by conjuncitiva as well as the greater resistance to leakage may explain the increased incidence of endophthalmitis that has been reported with clear corneal incisions.

C-MICS, therefore is better than bimanual MICS for fluidics and wound strength. Comparing the debate between bimanual MICS and C-MICS to a football match he said it was clearly a 2-0 score for C-MICS; a clear win.

In a show of hands, the audience agreed with Barrett.