Pseudo-Exfoliation / Small Pupil / Weak Zonules / Shallow AC (watch video below)
A sweet 80 year old patient comes to see you for cataract surgery. The best corrected vision is 20/100 and she presents with the following slit-lamp examination of the anterior segment. Look carefully at this pre-operative photograph:
There is a 3+ nuclear sclerotic cataract and the maximum dilation after three sets of mydriatic drops is about 4 mm. The anterior chamber is shallow at about 2 mm and biometry shows a slightly longer axial length of 24 mm. Using the Ladas Super Formula at www.IOLcalc.com, you determine that an IOL of +18.5 (using an A-constant of 119.2) will give an emmetropic post-op result. What do you see on the anterior lens capsule?
Zooming to higher power magnification on the slit-lamp shows a round area of deposits of pseudo-exfoliative material. At even higher detail we can see that there is a zone of clearance on the anterior lens capsule. The iris margin “wipes” the surface of the anterior capsule so that no pseudo-exfoliative material is deposited in this ring-shaped area. There are deposits in the center and periphery of the anterior lens capsule.
Pre-Operative Examination
Pseudoexfoliation is associated with glaucoma, iris abnormalities and zonular weakness, all of which can cause difficulty during phacoemulsification. Proper preparation and early intervention can make surgery easier for the surgeon and safer for the patient. Pseudoexfoliative material can be dispersed throughout the anterior segment on the anterior lens capsule in a target manner as shown above, over the zonules and ciliary processes, on the iris and in the angle of the eye (referred to as Sampaolesi’s line on gonioscopy). Any iridodonesis or phacodonesis that is noted at the slit lamp is an indication of severe zonular weakness. A pearl that I learned from Alan Crandall, MD, is to beware of a shallow anterior chamber in patients with pseudoexfoliation because it usually means that the entire lens-iris diaphragm is loose and pushing forward, thereby shallowing the anterior chamber. This patient has an AC depth of just 2 mm in the setting of a 24 mm axial length — this is a high risk for loose zonules.
This photo shows deposits of pseudo-exfoliative material on the iris at the pupil margin:
The association with glaucoma is high, and patients should be screened for optic nerve damage and treated if an elevated IOP is detected. These pseudoexfoliation patients may be more prone to inflammation, and they should receive preoperative topical nonsteroidal anti-inflammatory drugs, which will also help prevent intraoperative miosis.
Intra-Operative Techniques
For this case, we are going to use a technique of bringing the nucleus out of the capsular bag and tilting it into the iris plane so that the iris sphincter is holding it in place. This requires a capsulorrhexis of at least 5 mm in diameter, but our current pupil size is just 4 mm. Injecting viscoelastic at the pupil margin can help to push the iris and expand the pupil, a technique Robert Osher, MD, has called viscomydriasis. We can then make the capsulorrhexis right at the pupil margin or, even better, just underneath it. Most experienced surgeons, having done thousands of procedures already, can make the capsulorrhexis larger than the pupil without directly visualizing it.
Balanced salt solution is used to hydrodissect the nucleus out of the capsular bag and then tilt it into the iris plane. The iris sphincter will now hold the nucleus in place while the surgeon uses a phaco chop technique to emulsify and aspirate it. This technique brings the nucleus out of the capsular bag in order to minimize stress on the zonules. And even in cases in which there is zonular laxity, this supracapsular technique can be safer than intracapsular techniques such as divide-and-conquer.
Watch the narrated video below to learn these techniques:
