Anterior capsule-supported intraocular lens. A new lens for small-incision surgery and for sealing the capsular opening

Capsular bag refilling using a new accommodating intraocular lens

PURPOSE

To describe a capsular bag refilling procedure using an accommodating intraocular lens (IOL).

SETTING

Jinshikai Medical Foundation Nishi Eye Hospital, Osaka, Japan.

METHODS

A disk-shaped anterior foldable silicone accommodating IOL that serves as an optical device and as a mechanical device to prevent leakage of the injected silicone polymers was developed. The IOL optic is 6.0 mm and the overall diameter, 9.0 mm. After a 3.5 to 4.0 mm continuous curvilinear capsulorhexis (PCCC) is created, phacoemulsification and aspiration are performed in the usual manner. Then, a posteriorly placed accommodating IOL with sharp edges is implanted in the capsular bag to prevent posterior capsule opacification (PCO) and leakage of the injected silicone polymer. A PCCC is an option at this point. Then, an anterior accommodating IOL is piggybacked over the existing IOL and silicone polymers are injected between the 2 IOLs.

RESULTS

Experiments in numerous pig cadaver eyes and in 10 rabbit eyes showed minimal to no silicone leakage. In cases in which a PCCC was not created, 2 eyes had no PCO and 3 showed slight to moderate PCO. None of the 5 eyes with a PCCC had no PCO 5 to 8 weeks after surgery within the PCCC.

CONCLUSION

The procedure in rabbit eyes overcame 2 problems of lens-refilling techniques: leakage of the injectable silicone polymer and capsule opacification.

Accommodating intraocular lenses: a critical review of present and future concepts

BACKGROUND

Significant efforts have been made to develop lens implants or refilling procedures that restore accommodation. Even with monofocal implants, apparent or pseudoaccommodation may provide the patient with substantial though varying spectacle independence. True pseudophakic accommodation with a change of overall refractive power of the eye may be induced either by an anterior shift or a change in curvature of the lens optic.

MATERIALS AND METHODS

Passive-shift lenses were designed to move forward under ciliary muscle contraction. This is the only accommodative lens type currently marketed (43E/S by Morcher; 1CU by HumanOptics; AT-45 by Eyeonics). The working principle relies on various hypothetical assumptions regarding the mechanism of natural accommodation. Dual-optic lenses were designed to increase the dioptric impact of optic shift. They consist of a mobile front optic and a stationary rear optic which are interconnected with spring-type haptics. With active-shift lens systems the driving force is provided by repulsing mini-magnets. Lens refilling procedures replace the lens content by an elastic material and provide accommodation by an increase of surface curvature.

RESULTS

Findings with passive-shift lenses have been contradictory. While uncorrected reading vision results were initially reported to be favorable with the 1CU, and excellent with the AT-45 lens, distant-corrected near vision did not exceed that with standard monofocal lenses in later studies. Mean axial shift from laser interferometric measurements under stimulation with pilocarpine showed a moderate anterior shift with the 1CU, while the AT-45 paradoxically exhibited a small posterior shift. With the 1CU, the shift-induced accommodative effect was calculated to be less than +0.5 D in most cases, while +1 D was achieved in a single case only. Ranges and standard deviations were very large in relation to the mean values. Under physiological near-point stimulation, however, no shift was seen at all. Prevention of capsule fibrosis by extensive capsule polishing did not enhance the functional performance. Dual optic lenses are under clinical investigation and are reported to provide a significant amount of accommodation. However, possible long-term formation of interlenticular opacifications remains to be excluded. Regarding magnet-driven active-shift lens systems, initial clinical experience has been promising. Prevention of fibrotic capsular contraction is crucial, and it has been effectively counteracted with a special capsular tension ring, or lens fixation technique, together with capsule polishing. Lens refilling has been extensively studied in the laboratory and in primates. Though it offers great potential for fully restoring accommodation, a variety of problems must be solved, such as achieving emmetropia in the relaxed state, adequate response to ciliary muscle contraction, satisfying image quality over the entire range of accommodation and sustained functioning. The key problem, however, is again after-cataract prevention.

CONCLUSIONS

As opposed to psychophysical evaluation techniques, laser interferometry measures what shift lenses are designed to provide: axial shift on accommodative effort. While under pilocarpine some movement was recorded, no movement at all was found under near-point stimulation with any of the lenses currently marketed. In contrast, magnetic-driven active-shift lens systems carry the potential of sufficiently topping up apparent accommodation to provide for clinically useful accommodation while using conventional lens designs with proven after-cataract performance. Dual optic implants significantly increase the impact of axial optic shift. The main potential problem, however, is delayed formation of interlenticular regenerates. Lens refilling procedures offer the potential of fully restoring accommodation due to the great impact of increase in surface curvature on refractive lens power. However, various problems remain to be solved before clinical use can be envisaged, above all, again, after-cataract prevention. The concept of passive single-optic shift lenses has failed. Concomitant poor capsular bag performance makes these lenses an unacceptable trade-off. Magnet-assisted systems potentially combine clinically useful accommodation with satisfactory after-cataract performance. Dual optic lenses theoretically offer substantial accommodative potential but may allow for interlenticular after-cataract formation. Lens refilling procedures have the greatest potential for fully restoring natural accommodation, but will again require years of extensive laboratory and animal investigations before they may function in the human eye.

Postoperative complications of capsulorhexis

Capsulorhexis has become the preferred method of anterior capsulotomy, and untoward effects have not been frequently noted. Nevertheless, distinct complications of continuous tear anterior capsulotomy are now recognized. These include capsular bag hyperdistention, shrinkage of the anterior capsule opening with visual loss and/or intraocular lens decentration, and lens epithelial cell hyperproliferation on the posterior lens capsule. The latter has not been reported and may be associated wit reduction or closure of laser posterior capsulotomies in the form of a "string of pearls" around the capsule opening. Current styles of capsular surgery and intraocular lens implantation in which the anterior capsule edge overlaps the lens may be responsible for these phenomena. Although altering the surgical methods may obscure these complications, eliminating the anterior subcapsular and equatorial lens epithelial cells is necessary to prevent capsule contraction and lens epithelial cell hyperproliferation.