Baltimore-Cataract surgery in eyes with posterior polar cataracts presents a special challenge, but safety may be optimized with a customized approach that recognizes that not all posterior polar cataracts are alike and employs techniques for minimizing the risk of posterior capsule rupture, said Robert S. Weinberg, MD.
"In various surgical series in the literature, rates of posterior capsule rupture for these types of cataracts have ranged as high as 26% to 40%. However, much lower incidences have also been reported. Special care can help to minimize complications, but it is still worthwhile to have vitreoretinal assistance ready on standby," said Dr. Weinberg, associate professor of ophthalmology, The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore.
Based on his review of the literature and personal experience, Dr. Weinberg discussed various elements of techniques that might be considered to improve the safety of surgery for posterior polar cataracts. One recommendation has been to alter the technique depending on the size of the opacity and degree of nuclear density.
Intracapsular cataract extraction with scleral suturing of a posterior chamber IOL was recommended if the opacity was larger than 4 mm and the nucleus was hard, Dr. Weinberg said.
"I personally would perform an intracapsular extraction if there was a dislocated lens, and it is something to think about for eyes with a large posterior polar cataract and hard nucleus. Whether that approach is always preferred for the latter eyes seems more questionable," he said.
When performing phacoemulsification to remove a posterior polar cataract, Dr. Weinberg noted there does not appear to be any consensus in the literature about method of anesthesia.
"In some series, topical anesthesia has been used, but my personal preference is for a subTenon's injection," Dr. Weinberg said.
Use of dispersive viscoelastic
One element that all authors seem to agree on is the importance of using a dispersive viscoelastic for capsulorhexis and with care to avoid overfilling so as not to cause a break in the posterior capsule. It is also recommended that the capsulorhexis should be relatively small (5 mm or smaller).
"One article suggests initiating the capsulorhexis by lifting up with a forceps rather than using a cystotome. My experience indicates that a cystotome can be used safely, although it is important to be careful not to exert downward pressure on the capsule," Dr. Weinberg said.
In order to avoid causing hydraulic rupture of the capsule, hydrodissection should not be performed, and hydrodelineation should be minimal. Avoidance of hydrodissection is extremely important in improving safety. Overall, the authors who have published on this topic advise against nucleus rotation, although I. Howard Fine, MD, has suggested nuclear rocking can be helpful. Various techniques of nucleus manipulation have been recommended with no clear consensus favoring any one in particular, and the choice may depend on nuclear hardness. However, there is agreement that phacoemulsification should be performed with the power, bottle height, vacuum, and aspiration rate all set low.
"Usually, this surgery is done in younger people with softer nuclei, so nucleus removal itself can be relatively easy. Even so, it can be rather slow with these settings that are designed to maintain chamber stability and avoid raising pressure," Dr. Weinberg said.
To avoid exerting pressure on the posterior capsule, the epinucleus should be viscodissected one quadrant at a time. Once each portion of the epinucleus has been elevated, irrigation and aspiration of the cortex is performed with low vacuum (300 mm Hg) and low bottle height.
"It is better to keep the vacuum low and take a little longer in order to avoid extra movement that could break the capsule," Dr. Weinberg said.