Cataract
July 2021
by Liz Hillman
Editorial Co-Director
Ronald Yeoh, MD, first coined the term pupil snap sign in 1996.1 Since then, he has been calling attention to the somewhat subtle sign to help surgeons recognize when there has been a posterior capsule rupture that puts the nucleus at risk of dropping into the vitreous.
The pupil snap sign is observed during hydrodissection. Dr. Yeoh explained that typically in a normal hydrodissection, the nucleus will lift or come forward, when it is appropriately performed. If there is resistance to the flow of injected fluid, the surgeon might inject harder, Dr. Yeoh continued.
Source (all): Ronald Yeoh, MD
“When this happens, the anterior chamber usually deepens and often the pupil dilates more; these are important observations that are a prelude to hydrorupture, and if observed, the injection should immediately be stopped and the anterior chamber vented by pressing on the wound lip,” Dr. Yeoh said.
If this action isn’t taken and vigorous hydrodissection is continued, the posterior capsule can rupture, hence hydrorupture. At this moment, the surgeon might observe the pupil snap sign, which Dr. Yeoh described as a “sudden, brisk pupillary constriction” of about 30% of the already dilated pupil.
“At the moment of hydrorupture, the abrupt sagging of the nucleus, which was previously lifted up against the back of the pupil by the fluid injected, leads to the brisk pupillary constriction as the nucleus is no longer abutting the pupil,” Dr. Yeoh said.
When the pupil snap sign occurs, Dr. Yeoh said the surgeon should observe if there is nucleus tilt. If hydrorupture is suspected, the surgeon should be prepared to elevate/support the nucleus with a 25-gauge needle through the pars plana and deliver it through a larger incision. If the surgeon proceeds with phaco, pressurization of the anterior chamber by a phaco tip could propel the nucleus into the vitreous cavity, Dr. Yeoh cautioned.
To avoid this situation on the whole, Dr. Yeoh stressed the importance of careful hydrodissection. He said to avoid hydrodissection through a sideport, which can lead to higher pressures. Hydrodissection in the setting of a large, dense nuclei or with a small capsulorhexis is another scenario that predisposes to hydrorupture of the posterior capsule.
While this complication is not very common, Dr. Yeoh said recognition of the pupil snap sign may prevent the disastrous complication of a dropped nucleus.
About the physician
Ronald Yeoh, MD
Medical Director
Eye & Retina Surgeons
Singapore
Reference
- Yeoh R. The ‘pupil snap’ sign of posterior capsule rupture with hydrodissection in phacoemulsification. Br J Ophthalmol. 1996;80:486.
Relevant disclosures
Yeoh: None
Contact
Yeoh: ersryeoh@gmail.com
