I would like to comment on Kohnen's editorial about the squared, sharp-edged optic intraocular lens (IOL) design.1 It brought to my attention the possibility that a standard surgical procedure I routinely perform in cataract surgery may contribute to edge glare from the AcrySof® IOL.
After removing the nucleus via phacoemulsification and cortical cleanup, I routinely polish the posterior capsule. I then turn the irrigation/aspiration port upward and polish the undersurface of the anterior capsule with low aspiration. This is done using an aspiration setting of 5 mm Hg and vacuum of 5 mm Hg with the Alcon Legacy unit. The 3 most superior clock hours are not polished because of the difficulty of reaching this area with the 45-degree angulated tip.
The reasons for polishing the undersurface of the anterior capsule are as follows:
- Removing residual lens fibers may contribute to a quieter eye postoperatively. The lessened antigenic load presented to the eye's immune system should reduce inflammation. Nishi and Nishi2 show that residual lens epithelial cells (LECs) participate in postoperative pseudophakic inflammation. However, I could not find an article that supports or refutes the theory that removing LECs from the anterior capsule reduces postoperative inflammation.
- An opacified anterior capsule may hinder good fundus visualization for evaluation of peripheral retinal disease, photocoagulation, or vitreoretinal surgery.
- An opacified anterior capsule rim may decrease the quality of the optical image. This would be most applicable in capsular phimosis syndromes in which the anterior capsule overlapping much of the IOL optic may degrade entering images. More controversial is that a clear anterior capsule rim could increase unwanted optical images. This is now discussed further.
The sharp capsular bend of an AcrySof IOL will help reduce posterior capsule opacification (PCO) but may increase glare. Kohnen suggests that anterior capsule opacification (ACO) might decrease glare if the IOL optic edge is covered with fibrosed anterior lens capsule. Is one of the drawbacks to polishing the anterior capsule an increase in glare phenomena? If the anterior capsule covers the optic, should anterior capsule polishing be done when using the AcrySof IOL?
Nishi and coauthors3 present a Miyake-Apple view of PCO obscurring iris details in a round-edged AcrySof IOL design (Figure 3). This is compared to the same view using a sharp-edged AcrySof IOL in which no significant reduction of iris details occurs due to minimal PCO (Figure 3). Comparing these views, one notes a blurring of the round AcrySof IOL edge. Therefore, ACO may blur the optic edges in a similar fashion. This would reduce the edge-glare phenomenon.
Since some patients experience edge-related glare and some ACO may reduce this, should polishing the undersurface of the anterior capsule be abandoned? I do not believe it is clear that edge glare is reduced by anterior capsule haze. Assia and coauthors4 show no correlation between glare disability and the grading of ACO or PCO. There are other unwanted optical phenomena that can occur from the IOL, such as shimmering effects and halos around point sources of light, that opacification of the anterior capsule does not eliminate. As pointed out by Erie and coauthors,5 these include surface-related internal and external reflections and glare, which occur in patients even during the day and persist despite the use of pilocarpine. Since PCO is visually disturbing, perhaps ACO is too, even though it may reduce edge glare from the IOL.
When deciding on any surgical intervention, the potential benefits must be compared with the risks. Therefore, should anterior capsule polishing continue? I believe this needs further study. Two questions to address in any study design include whether the anterior capsule polishing really decreases postoperative inflammation and residual LECs from the equatorial region of the capsular bag will migrate anteriorly, negating the effect of polishing.
Michael Millstein MD
aCleveland, Ohio, USA
1. Kohnen T. The squared, sharp-edged optic intraocular lens design (editorial). J Cataract Refract Surg 2001; 27:485-486
2. Nishi O, Nishi K. Disruption of the blood-aqueous barrier by residual lens epithelial cells after intraocular lens implantation. Ophthalmic Surg 1992; 23:325-329
3. Nishi O, Nishi K, Akura J, Nagata T. Effect of round-edged acrylic intraocular lenses on preventing posterior capsule opacification. J Cataract Refract Surg 2001; 27:608-613
4. Assia EI, Cahane M, Blumenthal M. Effect of capsulorhexis diameter on glare disability. J Cataract Refract Surg 1996; 22:947-950
5. Erie J, Bandhauer M, McLaren J. Analysis of postoperative glare and intraocular lens design. J Cataract Refract Surg 2001; 27:614-621