Experienced surgeons rarely encounter complications during cataract surgery, but when they do, it is natural for physicians to fear that the patient's outcome will be suboptimal. When the patient has preexisting pathology, surgeons can mentally prepare themselves for the battle ahead and have on hand the necessary ancillary devices such as capsular tension rings and segments. They can also warn the patient that surgery may not result in an ideal outcome. Ophthalmologists can protect and almost excuse themselves to some extent.
On the other hand, when surgeons encounter a complication in a seemingly straightforward case, it is much harder to explain to the patient and his or her family why an ideal outcome was not achieved, especially if the ophthalmologist was overly confident in his or her predictions.
Although this case happened nearly 20 years ago, it seems like only yesterday, and I remember every detail. My 65-year-old patient was scheduled for routine phacoemulsification. She had a 2+ to 3+ nuclear sclerotic cataract in her left eye, which reduced her visual acuity to 20/60. An examination did not reveal a posterior polar component to her cataract. The IOP was normal in both eyes, and a preoperative fundus examination showed no retinal pathology. I expected a straightforward phaco procedure with implantation of a foldable IOL.
As was my surgical technique then, I performed a 3.2-mm keratome incision and a 1-mm sideport incision. Next, I created a 5-mm continuous circular capsulorhexis. Hydrodissection was performed through the main incision with a flattened 25-gauge cannula. I commenced phacoemulsification, but not being able to rotate the nucleus, I decided to achieve more effective hydrodissection by doing so through the sideport incision. To my mind, because the sideport incision was smaller and more watertight than the main incision, I would be able to exert a greater and more effective cleaving force to separate the nucleus and achieve a cortical-cleaving hydrodissection.
As I injected the BSS (Alcon Laboratories, Inc.) subcapsularly, I saw the anterior chamber deepen and the pupil dilate, after which it suddenly and briskly constricted by about 30%. I had no idea what had happened. I knew, however, that the best thing to do in an unexpected situation is to stop, take stock, and review the situation, so I did just that. The patient's eye was calm, and I began to wonder whether what I had seen was a figment of my imagination. With the nucleus still in its original position, I resumed phacoemulsification after inserting my phaco tip and sideport instrument. Almost immediately, the nucleus started to tilt and fall backward. I still remember the sinking feeling I experienced, as I had never dropped a nucleus before.
Luckily, the nucleus tilted and descended very slowly. I quickly injected some viscoelastic into the anterior chamber and then enlarged the wound to 7 or 8 mm. I carefully inserted a vectis under the descending nucleus, and much to my relief, I was able to bring the nucleus forward and remove it completely. Next, I placed a few stitches and stabilized the anterior chamber, which allowed me to perform a limited anterior vitrectomy. I could clearly see a large, central, posterior capsular rupture. The anterior capsular rim was entirely intact, which made it simple to implant a three-piece IOL in the sulcus. On the first postoperative day, the patient had a visual acuity of 20/40 and ultimately achieved a good visual result.
WHAT ACTUALLY HAPPENED?
As I came to learn from analyzing the video, the initial deepening of the chamber and pupillary dilation with hydrodissection indicated an excessive buildup of pressure within the anterior chamber, owing to my enthusiastic hydrodissection through the sideport incision. After the injection of BSS, the loculation of fluid behind the nucleus lifted it, causing further pupillary dilatation (Figure 1). More injection pressure resulted in a rupture of the posterior capsule, decompression of the capsular bag, and abrupt sagging and backward movement of the nucleus, causing the sudden pupillary constriction. I dubbed this phenomenon the pupil snap sign of hydrodissection in my 1996 description (Figure 2).1
My further manipulation of the nucleus led to its dropping. Fortunately, by handling the slowly dropping nucleus gently, I was able to retrieve it before it reached the macula. I have watched videos in which surgeons' unawareness of the pupil snap sign led to immediate and violent propulsion of the nucleus to the posterior segment upon pressurizing of the anterior chamber with a phaco tip, necessitating a pars plana vitrectomy for retrieval of the nucleus.
Video recording all surgeries is useful. Through my analysis of the surgical video of this case, I learned that the pupil snap sign warns of a defect in the posterior capsule caused by overzealous hydrodissection. Upon seeing this sign, the surgeon should either convert to a manual extraction of the nucleus or proceed extremely carefully with phacoemulsification and desist as soon as the nucleus shows signs of tilting.
I also learned that hydrodissection through the sideport incision is not a good idea. Yes, it is more effective, but it is also more dangerous. Slower and safer hydrodissection through the main incision is much better.
These lessons are relevant to this day. I have observed the pupil snap sign in a patient with lens-touch cataract after an intravitreal gas injection and a rapidly developed cataract. A posterior capsular rupture was caused by hydrodissection. As the number of intravitreal injections of antivascular endothelial growth factor agents increases, the incidence of lens-touch cataracts is likely to rise. Surgeons' awareness of hydrorupture is therefore, of growing importance.
Laser cataract surgery is also becoming increasingly popular. One of the first articles published on related complications described two cases of dropped nuclei after hydrodissection.2 In response to my letter, the authors confirmed that there was indeed a pupil snap sign in eyes with about 20% pupillary constriction.3
Section Editor David F. Chang, MD, is a clinical professor at the University of California, San Francisco, and is in private practice in Los Altos, California. Dr. Chang may be reached at (650) 948-9123; firstname.lastname@example.org.
Ronald Yeoh, FRCSEd, FRCS(G), FRCOphth, is medical director, founding partner, and a senior consultant ophthalmic surgeon at Eye & Retina Surgeons, Camden Medical Centre, Singapore. He acknowledged no financial interest in the products or companies mentioned herein. Dr. Yeoh may be reached at email@example.com.
- Yeoh R. The ‘pupil snap' sign of posterior capsule rupture with hydrodissection in phacoemulsification. Br J Ophthalmol. 1996;80(5):486.
- Roberts TV, Sutton G, Lawless MA, et al. Capsular block syndrome associated with femtosecond laser-assisted cataract surgery. J Cataract Refract Surg. 2011;37:2068-2070.
- Yeoh R. Hydrorupture of posterior capsule in femtosecond laser cataract surgery. J Cataract Refract Surg. 201;38:730.