June 2010

 

CATARACT/ IOL

 

Understanding & preventing PCO


by Matt Young EyeWorld Contributing Editor

   
Significant fibrous PCO Source: Anand Sudhalkar, M.D.

New research takes a comprehensive look at posterior capsule opacification (PCO) and emphasizes the importance of sharp optic edges in preventing cataract surgery’s most common long-term complication. While this is a well-known observation in ophthalmology, the research also eliminated various other factors as helping or hindering PCO development that are notable. “The meta-analysis of the included studies showed no significant differences between different IOL optic materials,” according to Oliver Findl, M.D., department of ophthalmology, Hanusch Hospital, Vienna, Austria. “The choice of postoperative anti-inflammatory treatment does not seem to influence PCO development; however, there are too few evidence-based studies up to now.” The report was published in the February 2010 issue of the Cochrane Database of Systematic Reviews.

Putting PCO prevention to the test

Dr. Findl and colleagues reviewed prospective, randomized, controlled trials that included a 12-month follow-up period at minimum. The research, which consisted of 66 studies, included everything from modifications in surgical technique to inhibit PCO to uses of different IOL designs. Attempts to reduce PCO could be categorized into four different groups, Dr. Findl said. First, insofar as surgery was concerned, Dr. Findl studied the polishing of the capsule to reduce the number of lens epithelial cells left over in the capsular bag post-op. “Another surgical strategy is to control the size of the capsulorhexis,” Dr. Findl reported. “A smaller capsulorhexis usually results in a complete overlap of anterior capsule and IOL optic. This sealing is thought to enhance the PCO inhibiting effect of the IOL optic.”

Second, IOL design geometry and material properties were a consideration. Third, other implants like capsular tension rings (CTRs) could help inhibit PCO. Fourth, pharmacological help to reduce PCO was analyzed. In terms of surgery, Dr. Findl found only a few studies could be combined into a meta-analysis and therefore preferred to relate individual study results rather than make sweeping conclusions. Importantly, regarding surgery, Dr. Findl found evidence suggesting small rhexis may lead to lower PCO rates. Various studies have come to different conclusions about the effectiveness of anterior capsule polishing; no recommendations were therefore made. A capsular bending ring may be useful in enhancing visual acuity and decreasing the YAG capsulotomy and PCO rate. Pharmacology analysis revealed the following: Immunotoxin MDX-A may contribute to lower YAG capsulotomy and PCO rates.

Heparin eye drops have contributed to lower—though not significantly lower—PCO rates. Other medications including dexamethasone, diclofenac, and ketorolac have had no impact on PCO rates. IOL optic design was important because, “We could provide clear evidence that sharp edge IOLs develop significantly less PCO than round edge IOLs of the same optic material,” Dr. Findl noted. Sharp edge IOLs not only improved YAG and PCO rates, but also improved BCVA itself. A laser ridge in PMMA IOLs had no clear impact on PCO development, however. IOL material, meanwhile, likely has no bearing on PCO because there seemed no significant differences between PMMA, hydrophilic acrylic, hydrophobic acrylic, and silicone lenses. Although silicone IOLs did seem to have lower PCO rates in several studies and hydrophilic acrylic had higher PCO rates, meta-analysis was complicated because several studies compared round edge IOLs with sharp edge IOLs. “In those cases, the difference in optic edge design probably had more effect on the development of PCO than the difference in optic material,” Dr. Findl noted. Despite the large body of literature on PCO prevention, there are still holes in understanding waiting to be filled. “There are still no prospective [randomized controlled trials] focusing on the effect of posterior capsule polishing, capsular tension rings and primary posterior capsulorrhexis on PCO,” Dr. Findl noted. Meanwhile, Randall E. Cole, M.D., medical director, Boozman-Hof Eye Surgery and Laser Center, Rogers, Ark., has determined what helps and what doesn’t in terms of PCO prevention from his early research on the issue as well as from practical experience. “A posterior chamber lens implant that has a square edge is key,” Dr. Cole said. “The downside to that is certain designs can give rise to dysphotopsia.” Dr. Cole also mentioned good cortical cleanup as being very important. “Being meticulous with cortical cleanup and not leaving lens remnants is critical,” Dr. Cole said.

Using an NSAID for 2 to 3 weeks after surgery helps, as do steroids. “The younger the patient, the more likely he or she is going to need a YAG laser,” Dr. Cole added. “With premium multifocal lenses especially, it doesn’t take much to cause a problem so you will likely need intervention there.” Anecdotally, Dr. Cole also related something somewhat unusual that might cut down on PCO. Posterior capsules that have a “little dusting of pigment from the back of the iris” have a strong inhibitory effect on PCO and secondary cataracts. “I don’t know why that is,” Dr. Cole acknowledged. Dr. Cole used to vacuum the back of the anterior capsule rim to prevent PCO. “Outside where you make a continuous capsulotomy, I would spend time vacuuming epithelial cells off the back of the capsule,” Dr. Cole reported. “I don’t think that was helpful.”

Editors’ note: Dr. Findl has no financial interests related to this study. Dr. Cole has no financial interests related to his comments.

Contact information

Cole: 479-246-1751, dreyerecole@aol.com
Findl: oliver@findl.at

Understanding & preventing PCO Understanding & preventing PCO
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