On devices for creating a continuous curvilinear capsulorhexis
Powers and Kahook1 reported a series of experiments designed to provide a new device for creating a continuous curvilinear capsulorhexis (CCC). The 5 phases of the device iteration illustrated the logic and thought applied to the problem and the trial and error that accompanies innovations. The most successful device was a flexible, medical-grade silicone ring that was inserted and stabilized using an ophthalmic viscosurgical device (OVD) in the anterior chamber. We have been using a similar device in our institution for over 10 years and first published our experience with it in 2006.2
The poly(methyl methacrylate) (PMMA) ring we use is half as thick (0.25 mm) as the silicone ring and has an outer diameter slightly larger (5.5 mm) than the inner 5.0 mm diameter. It can be inserted into incisions as small as 1.2 mm. Internal diameters of 4.5 mm and 6.0 mm are also available. The ring was designed to assist in centration and sizing, but when OVD is injected into the anterior chamber, the ring becomes apposed to the capsule and remains stable. It allows sufficient mobility for slight adjustments by the surgeon for optimal centration along the visual axis of the eye and the optical axis of the microscope. It is therefore unclear how much of the additional stability provided by the silicone grooved micropattern on the undersurface of the ring is beyond that provided by OVD alone and whether these useful slight adjustments are still possible.
The issue of centering the ring should also be addressed. The images that accompanied the report showed an on-center ring (Figure 7, A) followed by the CCC performed in an off-center ring (Figure 7, B). It is not stated whether this was from intentional decentration or a loss of adhesion between positioning and commencement of the CCC. We judge centration using a customized Eyecage device that we position over the cornea using the limbus as a surface marker (Figure 1). This could be used for the silicone ring. It is also important to consider combining the silicone ring with a Malyugin ring in the case of small pupils. We use a 7.0 mm Malyugin ring, and this accommodates the PMMA ring adequately. The silicone design may be difficult to manipulate with the 6.25 mm Malyugin ring and may also require a 7.0 mm ring.
There is certainly a need for devices to assist in providing well-centered consistent CCCs in both the developed and developing world. Femtosecond laser CCC techniques are not applicable to all cataracts, limited by factors including cost, access, cataract severity, and pupil size. The performance of a manual CCC is therefore likely to remain a core surgical skill for some time.
1. Powers M, Kahook MY. New device for creating a continuous curvilinear capsulorhexis. J Cataract Refract Surg
© 2014 by Lippincott Williams & Wilkins, Inc.
2. Tassignon M-J, Rozema JJ, Gobin L. Ring-shaped caliper for better anterior capsulorhexis sizing and centration. J Cataract Refract Surg