The dropped nucleus, one of the most feared complications of modern cataract surgery, became an issue only after the advent of phacoemulsification. Prior to this, dropped nuclei rarely occurred because the entire lens was expressed through a large corneal wound, without intralenticular manipulations, in a technique called extracapsular cataract extraction (ECCE). Increased pressure in the posterior segment inevitably directed the lens forward and through the incision. Although vitreous loss was a complication of ECCE, the constant posterior-to-anterior pressure gradient ensured that the nucleus was delivered externally and did not drop into the vitreous.
In modern phaco surgery, by comparison, the surgical wound is essentially sealed during the operation, with fluid infusion administered to maintain anterior chamber pressure. A dropped nucleus can occur in two ways. First, if the zonules are weak, an anterior-to-posterior pressure gradient can push the nucleus posteriorly. Second, a dropped nucleus can be a result of the procedure, as the capsule is at risk of damage from manipulations of intralenticular instrumentation during phacoemulsification. The posterior capsule separates the vitreous from the active operation, but the capsule may be breached. In these cases, the dense nucleus or nuclear fragments are free to sink into the less-dense vitreous body and are simultaneously restricted from escaping anteriorly by the capsulorrhexis barrier and the pressure gradient in the eye.
PRACTICAL MANAGEMENT USING A DETAILED PLAN
Published studies reassure us that the incidence of dropped nucleus is low,1-3 and the multiple benefits of phaco surgery, compared with older techniques, more than compensate for the risk. However, any cataract surgeon who has a reasonable case volume and who operates on a spectrum of case complexity will at some point experience a dropped nucleus. Therefore, anyone performing cataract surgery must have a detailed plan to deal with this complication.
Practical management of a dropped nucleus is best divided under five headings: (1) preoperative risk management, including learning how to communicate to high-risk patients; (2) mandatory preparations, including devising an emergency plan of action; (3) intraoperative course, including enacting the emergency plan and making sure the surgeon and staff react appropriately in a dynamic and stressful situation; (4) postoperative management, including managing potential postoperative problems, communicating with the patient, and referring to the local retinal surgeon; and (5) reflection and learning, including learning how to prevent or better manage a similar case in the future.
PREOPERATIVE RISK MANAGEMENT
Risk factors. The published incidence of posterior lens dislocation ranges from 0.3% to 1.1%.4,5 Ocular risk factors include small pupil size, pseudoexofoliation, deep-set eyes, traumatic cataract, hard nucleus, and intraoperative floppy iris syndrome. Patient-specific factors include confused patients, claustrophobia, and age greater than 90 years.
Plan ahead. Advanced planning for individual risk factors is warranted to ensure efficient, safe, and stress-free surgery. Take small pupils as an example. First, presence of a small pupil should be identified during preoperative assessment. Second, the records system must reliably warn the operating surgeon of the condition in advance of the operation. Third, the surgeon must be familiar with a variety of techniques to manage this condition. Last, communication with the surgical team should clearly identify the at-risk patient on the operating list, and the surgical team should ensure that appropriate equipment is available.
The exact details of what procedure to perform, what equipment to use, and how communications are relayed should be reviewed at the local level; however, an important stipulation is that these types of communications are proven to work. Policies should be in place for the risk factors listed above. Some warrant specific measures, but others, such as patient age greater than 90 years, are difficult to modify. This does not mean that the outcome cannot be optimized.
Is it safe to proceed with surgery? Risk factors tend to summate. In extremely high-risk cases, it is important that surgery be justified. Be warned, the confused 90-yearold patient with a dense pseudoexfoliative lens in his or her one good eye, 6/9 vision with mild cataract, and agerelated macular degeneration has a high potential risk for a dropped nucleus—among other complications.
Always ask: Is it safe to proceed with surgery? In other words, if a dropped nucleus occurred, could you honestly tell the patient and his or her family that the operation was planned in the patient’s best interest? Additionally, remember that some of the factors that make cataract surgery difficult make vitreoretinal surgical management of the dropped nucleus similarly difficult.
Communicate with the patient. A patient is often keen to proceed with surgery even after he or she has been informed of the high risk for complications. The object is not to deter the patient from having surgery but to ensure proper understanding of the risks. The discussion should be recorded and included in the consent process. This is not just defensive medicine, as surgical complications are potentially stressful to the surgeon.
Keep a cool head. Good outcomes require a cool head. Therefore, during the operation is not the time to be worrying about if the patient was appropriately informed and consent was attained. Save unnecessary stress by avoiding surgery in high-risk cases just before a public holiday or other times that retinal coverage may be limited.
Ask the appropriate questions. Every profession has a unique set of mandatory preparations. For instance, before every flight, airline staff members instruct passengers what to do in case of a plane crash, and as part of their training pilots practice crash landings in a flight simulator. However, neither the pilot nor the crew expects to crash. Eye surgeons and the surgical team should learn from this. Is the operating room (OR) staff rehearsed in setting up the anterior vitrector? Is the surgeon familiar with machine settings? Is there a plan in place for using the vitrector? Can the surgeon manage a posterior capsular tear and rescue a difficult situation before a dropped nucleus develops? If the answers are unclear, arrange staff training and invite a company representative to demonstrate vitrectomy with the proper equipment. Additionally, have the OR staff rehearse the dropped nucleus scenario.
Liaise with a retinal service. It is a good suggestion to liaise with a local retinal service and establish a protocol for referring a patient with a dropped nucleus, as services differ with regard to how soon they intervene, whether they prefer a lens to be placed in the eye, and what minimum information should accompany the patient’s file. It is always easier if the first time speaking with a retinal service is not to ask for help in a disaster case.
Two categories. In my experience, dropped nucleus cases referred for retinal surgery fall into two categories: well-managed and poorly managed. With the latter, it is likely that surgical trauma occurred and the surgeon struggled to execute an emergency procedure. Stress plays a major role in the outcomes in these cases, as it can interfere with cognitive processing. When something goes wrong during surgery, keep in mind that even good surgeons can make bad decisions. Avoid getting angry with yourself or the eye; instead, concentrate on the preparations you have in place to resolve the complication. Another good defense is taking on only appropriate cases.
Surgical objectives. Once a dropped nucleus occurs, the first rule is to accept it. Then remove all instruments from the eye, maintain composure, and plan what to do next. Remember that, at this stage, it is not having the problem that is a measure of professional competence but how the complication is managed. Going back to the airline industry analogy: Can you safely land the crippled plane?
If the nucleus has dropped into the vitreous, it will need referral for retinal surgery. Ignoring it at this point in the operation is the best course; do not give in to the temptation to fish into the vitreous cavity with the phaco tip for nucleus material. Because the patient most likely is under local anesthesia, take care to transmit a calm and professional atmosphere. Most patients figure out there is a problem, and what they want is reassurance that the problem is being addressed. An increasingly concerned and agitated patient is likely to move more often, making the surgical challenge more difficult. The OR staff must be made aware of the problem, and the team needs to focus at this stage, enacting the prepared plan quietly and efficiently.
The basic surgical objectives include these:
- Clean the anterior vitreous away from the wound and pupil with an anterior vitrector;
- If soft lens matter remains, a careful attempt at removal is appropriate, so long as traction on the vitreous is avoided. Triamcinolone injection can help to identify vitreous. If you are unacquainted with this technique, make plans to practice it before the next case. One alternative to an anterior vitrectomy approach is to use a posterior cutter and trocar system with infusion through the anterior chamber. If this equipment is unfamiliar, consider observing its use in a retinal OR;
- Ensure that the corneal wound is sealed and the pupil (if undamaged) is round; and
- Avoid unnecessary trauma or stress to the corneal endothelium and iris.
The ideal situation. What all retinal surgeons hope for in these cases is a relatively quiet eye with a clear cornea, good intraocular pressure (IOP) control, and a round pupil. If only small amounts of lens material are in the vitreous and an IOL can safely be placed in the eye without compromising outcomes, most retinal surgeons would be in favor of implantation. On the other hand, a whole dense nucleus in the vitreous presents challenges, as the fragmatome is insufficient for handling dense nuclei. In these cases, the surgeon may have to resort to floating the whole lens out of the eye and delivering it through a corneal wound. Obviously an IOL would not be helpful in this circumstance. Fortunately, very dense cataracts are rare in the developed world, but when they do appear they are more likely to drop during phacoemulsification.
Risk for complications. A case complicated by vitreous loss and dropped nucleus is at risk for postoperative complications such as raised IOP, cystoid macula edema, and uveitis. These eyes also can develop retinal detachment and, as a further complication, venous occlusive disease. If only a very small chip of nucleus is lost in the vitreous, an IOL can be placed and the eye monitored carefully postoperatively. If the eye appears to be settling without further complications, conservative treatment is appropriate. However, any sign of IOP problems or inflammation requires a vitreoretinal consult. In all other cases of dropped nucleus, urgent vitreoretinal referral is appropriate. The increasing tendency is for retinal surgeons to operate as soon as possible on dropped nucleus cases, obviously depending on workload. General agreement is that the maximum wait for retinal surgery is 1 week.
Lens material in the vitreous. An eye with lens material in the vitreous is especially vulnerable to postoperative complication. Until the retinal service can receive the patient, the duty of the operating team is to manage the eye for complications such as elevated IOP and uveitis. More specific roles and responsibilities must be established with the retinal surgery service. Exact medications vary, but common forms include frequent topical steroids and antibiotics and oral and topical IOP-lowering medications. IOP must be checked regularly and actively managed. It is debatable to admit a patient into the hospital in this period, but allowing a patient to go home is not an excuse for failing to monitor the eye. In the case of a sick patient who cannot self-medicate and who lacks social support, extra care and likely admittance to a ward until vitreoretinal surgery can be performed is advised; patients with a dropped nucleus often fall into this category. Poor management in the time before surgery can lead to poor outcomes.
Other considerations. It is difficult for any surgeon to admit to the patient and his or her family that a problem has occurred, but shirking this responsibility will only bring repercussions later. Avoid blaming other team members for the problem, as this destroys morale. If the patient was identified as high risk beforehand and consented appropriately, he or she will likely be understanding. Show concern, and allow the patient to ask questions. Be positive, and clearly set out a plan for how the problem will be managed.
REFLECTION AND LEARNING
A caring doctor and conscientious surgeon naturally feels disappointed after surgery has not gone well. It is best to use the case as a learning experience, for the benefit of future patients. Asking what went wrong and why it went wrong can provide insight for future procedures. Should you have operated on this case? Could extra measures have been taken to reduce the risk? Could you have managed the complication better? Do you need to learn new techniques? Did the team respond well in a proficient manner? Involving the team in a constructive debriefing is, in my opinion, mandatory.
Christopher Gorman, BSc (Path), MB ChB (Hons), FRCOphth, is a Consultant Ophthalmic Surgeon at Glamorgan House Spire Cardiff Hospital, Cardiff, United Kingdom. Dr. Gorman states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: firstname.lastname@example.org.
- Narendran N, Jaycock P, Johnston RL, et al. The Cataract National Dataset electronic multicentre audit of 55,567 operations: risk stratification for posterior capsule rupture and vitreous loss. Eye (Lond). 2009;23(1):31-37.
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