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Techniques

Small peripheral anterior continuous curvilinear capsulohexis

Tahi, Hassan MDa,*; Fantes, Francisco MDa; Hamaoui, Mariea; Parel, Jean-Marie PhDb

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Journal of Cataract & Refractive Surgery: June 1999 - Volume 25 - Issue 6 - p 744-747
doi: 10.1016/S0886-3350(99)00041-3
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Abstract

Anterior continuous curvilinear capsulorhexis (CCC) is a routine cataract surgery procedure. Specialized instrumentation and devices1–7 were developed when CCCs were introduced because surgeons found the technique difficult. Over time, anterior CCCs have become easier to perform; however, they can still be challenging, as in eyes with mature cataract and in pediatric capsulotomy.

Manually constructed anterior CCCs are more tear resistant.8–14 Compared with other capsulorhexis techniques, anterior CCCs have better mechanical properties.15 Large CCCs are often successfully performed in senile cataract surgery. However, the execution of a small (less than 1.5 mm in diameter) CCC is still challenging.

We describe a procedure for a small capsulorhexis developed for Phaco-Ersatz, a cataract technique designed to restore accommodation by removing the cataractous lens while leaving the capsular bag intact. Polymeric material is then inserted into the empty lens capsule directly16 or after encapsulation in an artificial bag.17 Phaco-Ersatz surgery requires that the anterior CCC be on the periphery and less than 1.5 mm in diameter. The anterior CCC was developed to accommodate the special demands of Phaco-Ersatz.1,2 This procedure, with slight adaptation, may also be useful for overcoming difficulties of CCCs in pediatric surgeries because children and rabbit capsules have similar elastic and tearing properties.18 The feasibility of the small peripheral anterior CCC technique was tested in 1 rabbit; however, the procedure has subsequently been successfully performed in several rabbits.

Surgical Technique

Adhering to the Association for Research in Vision and Ophthalmology Statement for Use of Animals in Ophthalmic and Vision Research, a 3-month-old New Zealand white rabbit was used. As many anterior CCCs as possible were made in the lens capsule of this rabbit in deference to using as few animals as possible. The eye was prepared for surgery by dilating the pupil using a phenylephrine hydrochloride 10%, tropicamide 1% (Mydriacyl®), and atropine sulfate (Atropisol®) solution. The animal was anesthetized using ketamine hydrochloride (14 mg/kg) and xylazine (7 mg/kg) in a 2:1 mixture.

After a 2.0 mm self-sealing corneal incision was made, highly viscous sodium hyaluronate (Corneal Plus®) was injected into the anterior chamber. By puncturing the capsule with a 30 gauge needle on the side and directing it toward the center, a capsular tear was initiated at the periphery of the planned capsulorhexis (Figure 1, A). The flap was gently pulled centripetally with the same needle until half the capsulorhexis was completed (Figure 1, B). The procedure should always be performed with a very slow, steady motion to allow the capsule time to tear toward the center. This is fundamental to the success of a small capsulorhexis. A Utrata capsulorhexis forceps (Storz Inc.) was then used to pull the flap in 3 steps. First, the flap was grasped at 1 of its 2 edges. The tear was continued by pulling the capsule tangentially and inward (to the right for the left edge and to the left for the right edge) (Figure 1, C, D). Then, a thin shred remained attached to the inner side of the capsulorhexis. This fragment was again grasped with a forceps and gently pulled toward the center until it was torn off, completing the CCC (Figure 1, E, F).

Figure 1.
Figure 1.:
(Tahi) The capsulorhexis is initiated with a puncture, made with a 30 gauge needle, in the anterior capsule (A, B). A Utrata forceps is used to grasp the tear and direct the capsulorhexis. The tear is continued toward the 12 o'clock position (C through E). The remaining fragment is removed with a Utrata forceps and gently pulled toward the 6 o'clock position until completely torn off, completing the capsulorhexis (E, F).

Results

Up to 9 capsulorhexes were successfully completed in the rabbit eye's capsule (Figure 2, A). Capsular tearing did not occur during any procedure. The diameters of the openings from outside the eye on top of the cornea, measured with a micro ruler, ranged from 0.7 to 1.7 mm, with a mean of 1.1 mm ± 0.3 (SD) (Figure 2, B).

Figure 2.
Figure 2.:
(Tahi) Photograph (A) and diagram (B) of the rabbit's anterior lens capsule with 9 small-sized capsulorhexes.

To successfully perform a small anterior CCC, it is necessary to begin at the peripheral part of the capsulorhexis, followed by even pulling of the flap toward the center. Attempting another direction could result in uncontrollable tearing, producing an enlarged capsulorhexis or a radial tear at the periphery.

Discussion

Manual construction of an anterior CCC creates the strongest and most uniform capsulotomy.14,15,19,20 Manual anterior CCCs are ideally suited for lens refilling procedures such as Phaco-Ersatz because of their superior tear resistance. In Phaco-Ersatz, the removal of the crystalline lens material and insertion of silicone or other polymeric materials result in severe stress on the capsular bag; if performed on a capsulorhexis with a discontinuous edge, a capsular tear could result.

Because of the refractive powers of the cornea and the viscoelastic material in the anterior chamber, a slight overestimation of the measurements of the openings occurred since the measurements were made from outside the eye. To obtain the actual size of the opening, measurements should be made from within the eye at the anterior surface of the lens capsule.

An adaptation of this technique could also be used to perform a regular-sized anterior capsulotomy during pediatric cataract surgery. When beginning a pediatric CCC, 2 to 3 different starting points on the periphery of the capsule (Figure 3, A) should be made. Each tear is directed toward the center of the capsule using the same technique as described but with larger openings. The rule is to avoid crossing the center of the capsule (Figure 3, B). The CCC should always be performed from the periphery to the center of the capsule, not opposite or parallel to the capsule's periphery.

Figure 3.
Figure 3.:
(Tahi) Two capsular tears are initiated and developed toward the center of the capsule. The tears should always be directed toward the center and away from the periphery, never directly transversing the center (A, B).

This technique has been easily and successfully applied in senile donor eyes; however, as the capsule in these eyes is more fragile, emptying the capsular bag required more care and more time than in the rabbit eye.

Conclusion

This technique developed for lens refilling procedures is feasible when performing small-sized anterior CCCs. The procedure provides the benefits associated with a manual capsulorhexis and is better controlled. Capsulotomies performed with this procedure may maintain the integrity of the capsule when put under severe stress, as in Phaco-Ersatz procedures. This technique has the potential for the safe performance of anterior CCCs in pediatric surgery.

References

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© 1999 by Lippincott Williams & Wilkins, Inc.