Effect of a discontinuous capsule bend

Posterior capsule opacification

PURPOSE OF REVIEW

This paper assesses the factors that contribute to the formation of an effective capsular bend as a deterrent to posterior capsule opacification. Its goal is to assist the practicing ophthalmologist in separating current understanding of this process from various working models previously proposed.

RECENT FINDINGS

While a square-edge design appreciably improves resistance to posterior capsule opacification, significant factors remain under the control of the surgeon. These factors combine to form the physical and psychological barrier of a capsular bend. Innovative digital imaging has shown lens epithelial cell migration, allowing for a more rapid assessment of posterior capsule opacification resistance. A three-piece intraocular lens allows for full 360 degree capsular bend formation surrounding the optic edge; some single-piece designs may inhibit capsular bend formation. Decreasing, but not eliminating, the surviving lens epithelial cell population may diminish capsular bend strength, which may decrease resistance to posterior capsule opacification in the face of a regenerating cortex. All demographic features of clear/refractive lens exchange suggest higher rates of posterior capsule opacification than with standard cataract surgery.

SUMMARY

The quality of capsular bend formation will determine how resistant an intraocular lens will be to posterior capsule opacification as a consequence of regenerating cortex. As refractive lens exchange and new accommodating intraocular lens designs become more popular, the problems of regenerating cortex will increase in magnitude.

Influence of optic edge design, optic material, and haptic design on capsular bend configuration

PURPOSE

To assess and classify capsular bend configuration at the optic rim and its association with posterior capsule (PCO) and anterior capsule opacification (ACO) and capsulorhexis contraction with various intraocular lenses (IOLs).

SETTING

Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

METHODS

A total of 659 post-cataract surgery eyes of 370 patients from different prospective randomized studies were evaluated. All eyes had standardized phacoemulsification surgery with implantation of an IOL in the capsular bag. The IOLs had a sharp or round optic edge design and were made of silicone, acrylic, or poly(methyl methacrylate) optic materials. One year postoperatively, the configuration of the capsular bend at the optic rim was assessed at the slitlamp, and standardized slitlamp images of ACO and fibrotic PCO were taken. One week, 1 year, and 3 years postoperatively, digital retroillumination images were taken for objective quantification of regeneratory PCO and the capsulorhexis area. The outcome measures were the type of capsular bend configuration, ACO score (0% to 100%), regeneratory PCO score (0 to 10), fibrotic PCO score (0 to 3), and amount of capsulorhexis contraction (mm(2)).

RESULTS

Four main types of capsular bend configuration were classified: parallel, "Y," right angle, and wrapping. The right-angle type was observed in the most cases (52%). Eyes with a wrapping capsular bend configuration had significantly less PCO, more capsulorhexis contraction, and more ACO than eyes with the other configurations. Wrapping capsule configuration was seen most often (55%) in round-edged silicone IOLs that had a thin optic rim.

CONCLUSION

The design and material of IOLs influenced the long-term capsular bend configuration at the optic rim. The right-angle type was the most common capsular bend configuration. Intraocular lenses with silicone optic material and a thin optic rim caused a wrapping capsule configuration and resulted in more capsulorhexis contraction and ACO, but less PCO.

[Influence of intraocular lens material and design on the development of posterior capsule opacification]

Based on the literature of 1999-2005, we attempted to clarify the influence of material and design of an intraocular lens (IOL) on the development of posterior capsule opacification (PCO) and identify the future problems to be solved. The sharp edge design of an IOL has significantly reduced PCO in recent years. Histopathological studies showed that a sharp capsular bend was formed at the sharp posterior optic edge, and the migration of lens epithelial cells was obviously inhibited at the site. Experimental and clinical studies suggest that the sharper the edge is, the sharper the capsular bend, and the greater the preventive effect, regardless of IOL material. The sharp capsule bend appears to represent a physical hindrance, which may induce contact inhibition of cell movement. How material participates in the preventive effect should be clarified in a future study. Thus, at the moment, the formation of capsular bend at the posterior optic edge appears to be the decisive criterion to evaluate the influence of IOL material and design on the development of PCO. Optimization of design and material of an IOL, which facilitates capsular bend formation as sharply and quickly as possible, may reduce PCO to a clinically negligible level.

Long-term efficacy of adding a sharp posterior optic edge to a three-piece silicone intraocular lens on capsule opacification: five-year results of a randomized study

PURPOSE

To compare the intensity of capsule opacification with the sharp and the round optic edge variant of an open-loop hydrophobic silicone intraocular lens (IOL).

DESIGN

Randomized, controlled, double-blind clinical trial with intraindividual comparison.

METHODS

Fifty-one patients with bilateral age-related cataract were included (102 eyes). Each patient had had cataract surgery in both eyes and received a Microsil IOL with a sharp optic edge design (model S) in one eye and a Microsil IOL with a round optic edge design (model R) in the fellow eye. Both IOLs had an identical haptic design (nonangulated polymethylmethacrylate) and silicone optic material. The patients were examined at the slit lamp, best-corrected visual acuity was assessed, and standardized high-resolution digital retroillumination images of the posterior capsule were taken 5 years after surgery. The intensity of regeneratory posterior capsule opacification (rPCO), fibrotic PCO (fPCO), and anterior capsule opacification (ACO) was assessed subjectively at the slit lamp, and of rPCO, objectively using automated image analysis software (AQUA). The need for an Nd:YAG laser capsulotomy (Nd:YAG-LCT) was noted.

RESULTS

The mean AQUA PCO score was 1.2 for the model S and 2.4 for the model R lens (P = .001). The model S lens also led to less peripheral fPCO (P = .003). Concerning ACO, there was no significant difference between both IOL groups (P = .72). Whereas no capsulotomy was required with the model S, four cases (16%) had been performed in the model R group.

CONCLUSION

Five years postoperatively, the sharp-edged silicone IOL showed less rPCO and fPCO than the round-edged IOL. However, regarding ACO, there was no significant difference between both IOL styles.