The bimanual phaco technique has greatly benefited from the progress made in the field of phaco machines and related instrumentation, but unfortunately implants adapted to microincisions have been evolving more slowly. On the other hand, in view of the growing interest on the part of surgeons for this technique, IOL laboratories are expanding their research programmes in this direction. In the future, through the availability of implants capable of being introduced through micro-incisions smaller than 1.5 mm, bimanual phaco will become a standard approach to phakoexeresis.
Currently, two methods are available to perform an intraocular implant with bimanual phaco surgery.
To insert a classic soft posterior chamber implant with an injector, a third incision is performed between the two microincisions, or one of the two incisions is enlarged to 2.8 mm. Preserving the microincisions will make it possible to maintain a closed eyeball through the end of the procedure. Certain classic implants in 26% hydrophilic acrylic, with square edges, 6 mm biconvex optics and four thinner and angled haptic lenses can be injected through a 2 mm incision because of their design, which prevents the plugging effect in the injector and confers greater resistance to the compression. Others, in hydrophobic acrylic, with optics measuring 5.5 mm, can be injected through an incision enlarged to 2.2 mm with a modified injector and cartridge.
To implant an ultrathin intraocular lens appropriate for bimanual surgery, one of the two microincisions will be enlarged to between 1.5 and 1.8 mm, which does not significantly compromise leaktightness of the incision required at the end of the procedure. These ultrathin new generation implants are fusiform hydrophilic acrylic monoblocs without angles. Their optical diameter is 5.5 mm for a total diameter of 11 or 11.2 mm with full haptic lenses. They are injected through an incision measuring between 1.5 and 1.8 mm by means of an injector device. A foam tip is placed on the injector’s plugger to prevent damage to the implant while being pushed in.
Some special conditions are necessary for the implantation of this new type of intraocular lens: a capsulorhexis measuring 6 mm in width, and a bag opened wide with viscoelastic agent. When installing the implant, the injection cartridge is placed in a parallel position within the extension of the incision edges, supported on them but without penetrating into the groove. The implant is injected by means of a firm pressure on the piston in order to ensure that the implant is properly placed in the incision, along which it will slide as if in a chute. Correct positioning of the lens in the bag must be carefully monitored in intracameral deployment of haptic lenses. It should be borne in mind that there is a risk of tearing of the posterior capsule when turning over an ultrathin implant installed upside down. The optics of these lenses must be placed closely against the posterior capsule, avoiding any viscoelastic residues under the implant at the end of the procedure.
This type of microincision implant received its first clinical evaluation as applied by Kanellopoulos in 2000. The first study referenced in the Journal of Cataract and Refractive Surgery and conducted by Dogru et al was published in 2004.
For the time being, prudence and a “wait-and-see” attitude in regard to the stability of such implants in the capsular bag are still called for. With greater perspective, we will be better able to evaluate the qualities of these ultrathin implants. Their secondary capsular opacification rate seems to be greater than with classic implants and some authors are considering the possibility of applying an adjuvant treatment in the capsular bag to limit the opacification.
