Recently, Vock et al.1,2 published 2 interesting articles. In the first, they compared the clinical results of posterior continuous curvilinear capsulorhexis (PCCC) in eyes with 2 types of single-piece hydrophilic acrylic intraocular lenses (IOLs) with and without haptic angulation. The results showed significantly lower intensity of posterior capsule opacification (PCO) within the PCCC area than within the peripheral area of the posterior capsule with both types of IOL implantation. However, haptic deformation was found in 9 eyes (29%) with an angulated IOL and in no eye with a nonangulated IOL.
In the second article, Vock et al. compared the incidence of PCO in eyes with and without a PCCC following implantation of a single-piece hydrophilic acrylic IOL. They found that the incidence of PCO in the visual axis area was significantly lower in the PCCC eyes than in the non-PCCC eyes. During the follow-up, 40% of the non-PCCC eyes had a neodymium:YAG laser capsulotomy compared with none of the PCCC eyes. I have a few comments on the articles and the surgical technique.
Several approaches to reduce the incidence of PCO have been evaluated clinically. One approach is to perform a PCCC during cataract surgery. The advantage of this technique is that it stops lens epithelial cell (LEC) migration and proliferation on the central area of the posterior capsule by surgically removing the central area. Consequently, a PCCC should reduce the incidence of PCO. This technique was initially performed during cataract surgery in infants and children with good results.3 However, PCO still occurred and the LEC grew on an intact vitreous face or IOL optic surface. Eventually, dense PCO could form. To address this issue, Gimbel and DeBroff4,5 performed PCCC with an optic capture. This technique has been evaluated in clinical studies with favorable results.6 In the second article by Vock et al.,2 the incidence of PCO was significantly lower in the PCCC eyes than in the non-PCCC eyes. Since only 1 type of IOL was used in that study, we do not know whether the results would be the same if different IOLs were used. We do not know whether PCO could form over time in the eyes with the ruffled PCCC rim.
The disadvantage of PCCC is the difficulty of the surgical technique, which may be challenging for the average cataract surgeon. More important, PCCC significantly compromises the integrity of the posterior capsule and diminishes the physical barrier effect created by the square-edged IOL optic and intact posterior capsule. If a PCCC is too large or oval in shape, the posterior capsule may weaken and could provide less IOL support. As we know, the square-edged optic requires tension on the posterior capsule or close contact between the IOL optic and the posterior capsule to create a physical barrier and block LEC migration. When a PCCC is created, the posterior capsule has little tension and is more flexible and less supportive; the physical barrier effect may be too weak. Without a strong physical barrier, the LEC will migrate to the posterior capsule freely and proliferate to eventually form dense PCO.
Creating a PCCC may trigger capsule fibrosis and contraction and consequently induce IOL haptic deformation, optic tilt, and decentration. In the first article by Vock et al.,1 haptic deformation was reported in 9 eyes (29%) with angulated IOLs but no eye with a nonangulated IOL. It was probably caused by capsule contraction and fibrosis. Physically, the angulated haptic should deform and change shape easier than the nonangulated haptic if capsule contraction or fibrosis occurs. Of course, the haptic material and type are also important factors. Surprisingly, no haptic deformation was reported in the second article by Vock et al., even with the same IOL type.
Another interesting observation in the first article was that eyes with angulated IOLs had significantly less anterior capsule opacification than eyes with nonangulated IOLs (P = .012). A persistent anterior lenticular gap was found in 97% of eyes in the angulated IOL group compared with 29% of eyes in the nonangulated IOL group. The angulated IOL group showed a slightly higher incidence of central PCO and a higher incidence of LEC growth and proliferation. These results suggest that direct contact between the IOL optic and lens capsule may be associated with LEC growth and proliferation.
Currently, most cataract surgeons think the most effective approach to reduce PCO is to create a 360-degree physical barrier between the IOL optic and the posterior capsule immediately after IOL implantation. To create a physical barrier, a square-edged design is critical and complete cortical cleanup with removal of the lens material is important. Creating tension on the posterior capsule around the optic edge is also important. To achieve this goal, an IOL should have stronger haptics and greater haptic angulation to be able to stretch the posterior capsule.7
In summary, the Vock et al. articles provided scientific data and clinical evidence to support performing a PCCC during cataract surgery to reduce the incidence of PCO. The long-term effect on different types of IOLs and the potential drawbacks of this technique should be investigated in future studies.
1. Vock L, Menapace R, Stiffer E, et al. Clinical effects of primary posterior continuous curvilinear capsulorhexis in eyes with single-piece hydrophilic acrylic intraocular lenses with and without haptic angulation. J Cataract Refract Surg. 2007;33:258-264.
2. Vock L, Menapace R, Stiffer E, et al. Effect of primary posterior continuous curvilinear capsulorhexis on clinical performance of ACR6D SE single-piece hydrophilic acrylic intraocular lenses. J Cataract Refract Surg. 2007;33:628-634.
3. Koch DD, Kohnen T. Retrospective comparison of techniques to prevent secondary cataract formation after posterior chamber intraocular lens implantation in infants and children. J Cataract Refract Surg. 1997;23:657-663.
4. Gimbel HV, DeBroff BM. Posterior capsulohexis with optic capture: maintaining a clear visual axis after pediatric cataract surgery. J Cataract Refract Surg. 1994;20:658-664.
5. Gimbel HV, DeBroff BM. Intraocular lens optic capture. J Cataract Refract Surg. 2004;30:200-206.
6. Menapace R. Routine posterior optic buttonholing for eradication of posterior capsule opacification in adults; report of 500 consecutive cases. J Cataract Refract Surg. 2006;32:929-943. erratum, 1410.
7. Sun R., 2007. Multiple approaches to PCO prevention [letter], J Cataract Refract Surg, 33, 5-6.