SAN FRANCISCO Optometrists can easily diagnose postsurgical
complications in cataract patients by carefully evaluating the posterior
Here at the spring session of the San Francisco Optometric Continuing
Education Symposium, Victor Chin, MD, director of cataract and lens surgery at
Pacific Vision Institute in San Francisco, described two syndromes
capsular distention and capsular contraction that may arise after
uncomplicated cataract or refractive lens exchange surgery and prevent the
patient from achieving the optimal visual outcome.
Capsular distention syndrome
At the symposium sponsored by the Pacific Vision Institute and Pacific
Vision Institute Research Foundation, Dr. Chin explained that in capsular
distention syndrome, fluid or retained viscoelastic material is trapped between
the IOL and the posterior capsule.
The accumulated fluid may be turbid and cloud the visual axis, causing
glare and haze, he said. The distended capsular bag may also be filled with
material with an index of refraction different from the aqueous, which thereby
functions as an additional plus power lens in the optical system. This, coupled
with any anterior displacement of the IOL from posterior pressure, may result
in an unexpected myopic outcome.
Dr. Chin stated that in cases involving multifocal lenses, these
symptoms may be magnified secondary to the diffractive optics of multifocal
The leading theory that explains capsular distention syndrome suggests
that the anterior surface of the IOL becomes occluded by a capsulorrhexis
smaller in diameter than the optic of the new lens. The capsule adheres to the
IOL, creating a potential space. Oncotic pressure from trapped substances such
as viscoelastic can slowly draw fluid into this pocket, filling and distending
the capsular bag.
Dr. Chin indicated that diagnosis can be easily made by looking at the
space between the IOL and the posterior capsule. Normally, that space should be
minimal and clear; in capsular distention syndrome, the space is obvious and
The treatment, Dr. Chin stated, is Nd:YAG laser capsulotomy to release
the sequestered material. The procedure has a high success rate, reducing
refractive error and improving the quality of vision.
Capsular distention syndrome.
The first arrow indicates the corneal light reflex, the second is the light
reflecting off the IOL and the third light reflex represents the posterior
capsule. Thick, cloudy fluid is in the intervening area between the IOL and
|The ring of capsular wrinkling
in the midperiphery of the multifocal IOL may interfere with reading
Images: Chin V
The quality of the posterior capsule should be evaluated especially
carefully in patients with multifocal IOL implants, Dr. Chin added. Even small
wrinkles can hinder good reading vision, for example, if they are located in
the mid-periphery, over certain add zones. These patients may, in fact, have
excellent distance vision, but poor reading vision.
Dr. Chin pointed out that before performing LASIK or PRK monovision to
improve reading vision in patients who are not getting enough add with their
multifocal IOL, the posterior capsule needs to be evaluated. A YAG laser
capsulotomy should be performed before LASIK or PRK enhancement is performed.
Before performing a YAG laser capsulotomy, the entire posterior capsule
should be examined. If the capsulotomy is performed only centrally, it may not
result in improved near vision when capsular contraction and wrinkling is
present peripherally even in accommodating IOLs. Peripheral capsulotomy is
typically successful in improving near vision in these patients.
For cataract surgery patients with astigmatism, an individual surgical
plan must be established, reported Neil Friedman, MD, in another presentation.
This private practitioner from Palo Alto, Calif., stated that the astigmatism
can be corrected either intraoperatively or postoperatively.
During cataract surgery, options include limbal or corneal relaxing
incisions (LRIs/CRIs), astigmatic keratotomy (AK) and the use of toric IOLs.
After cataract surgery, astigmatism can be surgically corrected with laser
vision correction or one of the aforementioned incisional techniques.
Establishing a surgical plan for each patient entails obtaining
consistent measurements from multiple sources preoperatively, Dr. Friedman
said. The refraction, keratometry and corneal topography measurements should be
in agreement with respect to the magnitude and orientation of the astigmatism.
The effect of the cataract incision must also be considered. Once these
numbers have been gathered, the desired correction is calculated using various
nomograms or online calculators.
Dr. Friedman compared LRIs to the use of toric IOLs. LRIs are quick,
easy to perform, low-tech and low-cost and can be enhanced at the slit-lamp
postoperatively, he said. However, the outcomes are surgeon-dependent, with
some degree of variability and unpredictability.
Toric IOLs have the advantage of being precise and predictable and
require no new surgical skills; however, the technology is more costly. If the
IOL rotates, it can result in a 3.3% loss of effect per 1 degree of rotation
from the correct axis, Dr. Friedman said.
For more information:
- Victor Chin, MD, is the director of cataract and lens surgery at
Pacific Vision Institute, One Daniel Burnham Court, San Francisco, CA 94109;
(415) 922-9500; www.pacificvision.org.
- Neil Friedman, MD, is in private practice at Mid-Peninsula
Ophthalmology Medical Group. He can be reached at 900 Welch Road, Suite 402,
Palo Alto, CA 94304; (650) 324-0056; www.mpomg.com.