Introduction:

Drooped nucleus and retained lens fragment is a complication not so rare in clinical practice. In the era where cataract surgery is being performed for visual enhancement rather than visual rehabilitation, the management of a dropped nucleus saves the patient from unnecessary anxiety and hastens visual recovery. In this chapter risk factors, the timing of surgery, various approaches for removal of the lens will be discussed.

Incidence:

Dropped nucleus and cortical remnants occur more frequently in phacoemulsification than other techniques of cataract surgery 1,2 . Surveys in developed nations like U.S and U.K have reported incidences of 0.3 % 1 and 1.1 % respectively. In India, few studies have quoted its incidence to be around 0.8 %. [3]

Risk Factors:

The exact cause for the posterior displacement of the nucleus is difficult to determine but certain conditions predispose for complication4

• Pseudoexfoliation syndrome
• Traumatic cataract
• Fellow eye of complicated cataract surgery
• Eyes with transillumination defects in iris
• Previously vitrectomized eyes
• Eyes with phacodonesis
• Dense brunescent cataracts
• Hypermature cataracts
• Very aged patient
• Intraoperative floppy iris syndrome
• High ammetropia
• Posterior Polar Cataract
• Posterior Sub Capsular Cataract

Preventive Steps in High risk cases:

• Adequate Pupillary dilation
• Gentle Hydro dissection

Primary Management by the Anterior Segment Surgeon:

The first step in management is to recognize the posterior capsular (PC) tear early. Early recognition reduces the chances of vitreous loss and dropped fragment. Signs of Posterior Capsular rupture: [5]

1. Sudden deepening of the anterior chamber, with slight dilation of the pupil.
2. The sudden, transitory appearance of a red reflex peripherally.
3. Newly apparent inability to rotate a previously mobile nucleus.
4. Excessive lateral mobility or displacement of the nucleus.
5. Excessive tipping of one pole of the nucleus.
6. Partial descent of the nucleus into a more posterior position.

The next step comprises of judging the situation and deciding on further courses of surgery.

1. If the retained nucleus is small and no vitreous prolapse with adequate capsular support, then continuing with the phacoemulsification depends upon surgeons’ choice and comfort. Few points to remember:
a) The primary objective is the retrieval of retained nucleus fragments without aspirating vitreous.
b) Retained fragments can be brought in an Anterior chamber by the use of Ophthalmic Viscoelastic Device (OVD).
c) Bottle height should be lowered and vacuum reduced.
d) Avoiding sculpting and rotating the nucleus. Avoid using aspiration near the PC tear.
e) Sheet’s glide can be used over the PC rent to complete the phacoemulsification.

2. If the vitreous loss has occurred then it is best to convert it to conventional EECE incision and try to remove as much nucleus as possible with the help of OVD by displacing the retained fragment in the AC.

3. In the case of posterior displacement of the fragment, in certain cases where it is at anterior hyaloid phase, PAL (Posterior assisted Levitation) devised by Kelman and modified by Packard can be utilized.5 In this technique, the fragments are approached from Pars plana route and a Dispersive Viscoelastic is injected behind it. Now manually with the tip of injecting cannula, the retained fragments are maneuvered into AC.

In case of vitreous loss we could utilize VISCO Trap technique proposed by Chang to trap the retained fragments, epinucleus and cortex in AC by the use of dispersive viscoelastic and then perform the bimanual vitrectomy along with supplementation of OVD to remove the vitreous and retained fragments.5

If the amount of retained nucleus is small where it will not require further intervention then placing of Anterior/ Posterior Chamber IOL is recommended. If management requires Vitrectomy then IOL placement should have differed.

Complications:

Depending on the size of retained lens fragments, Patients present with varying degrees of inflammation. Clinical signs may include corneal edema, glaucoma, uveitis, and vitreous opacities causing profound visual loss. Frequently, however, signs are mild, especially in the immediate postoperative interval. 6

Timing of removal:

If VR back up is available at the hospital it is best to remove the fragments/ lens in the same sitting. The reasons are:
1) Prevents the patient from undergoing two surgeries.
2) The chance of a post-op rise in pressure and inflammation is reduced.
3) Saves the patient from unnecessary anxiety.

If the patient is being referred to a VR surgeon then a thorough preoperative assessment should be done before deciding upon the timing of surgery. If another cornea is clear then it should be done within 1-2 weeks. [8]

Pre Operative assessment:

Before taking up the patient for surgery a complete ophthalmological assessment should be performed, comprising of :

• BCVA
• Slit-lamp Biomicroscopy (pre and post-dilation)
• Degree of corneal edema
• Uveitis
• Cortex at pupil
• Assess extent of posterior capsular rupture and
• The integrity of the capsular zonular apparatus
• Applanation Tonometry
• Fundus examination/ B Scan USG
• In patients with severe corneal edema, uveitis retained lens material at the pupil or associated vitreous hemorrhage precluding visualization into the vitreous cavity, a preoperative B Scan Ultrasonography is essential. Associated pathologies like retinal detachment, choroidal detachment,

Vitreous hemorrhage can also be picked up.

The clinical findings and options of treatment should be discussed in detail with the patient.
Written consent in this regard should be taken.

Management Option:

Small lens fragment <2mm can be safely observed without any active intervention for 1-2 weeks depending upon clinical situation further decision can be made.[9]

Uveitis ranging from moderate and severe is one of the most common indications for surgery.[9]

Raised intraocular pressure (IOP) is another cause of surgical treatment. IOP should be managed medically and if not being controlled then prompt surgical treatment should be contemplated.[10]

Associated Retinal detachment, retinal tears, endophthalmitis are other indication for urgent treatment

Surgical Treatment:

Numerous techniques for removal of nucleus have been described in literature. Ideal technique depends upon availability of instrumentation, size and hardness of nucleus and surgeon preference.
Principally it comprises of following step: [11]

• Complete 3 port pars plana vitrectomy .
• Removal/ emulsification of nucleus from vitreous cavity
• Peripheral retina evaluation for and breaks/ tears.
• Placement of Intraocular lens.

STEP 1: Pars plana Vitrectomy

Key Points :
1. Remove all the vitreous from Anterior Chamber/ primary cataract wound (if present)
2. Intra vitreal Triamicilone could be utilized for better visualization of vitreous.
3. All the vitreous attachment to the nucleus should be removed.
4. If fragmatome is being used then induction of PVD is must and vitreous base should be trimmed to the extent possible.

STEP 2: REMOVAL OF NUCLEUS

It depends upon the type of nucleus:

a) Soft nucleus:

Most of the times it can be removed by cutter itself.

Key Points :
1) Cut rate should be low near 600-800 cuts per minute with suction on the higher side.
2) Few drops of PFCL can be used as a cushion to prevent the nucleus pieces falling directly over the macula and causing damage to it.
3) Light pipe can be used to crush the nucleus against the cutter probe for easy cutting.

b) Hard Nucleus:

1) Using Fragmatome/ Phaco Tip without Sleeve:

Key Points :

• Perform adequate vitrectomy prior to use of an ultrasonic fragmatome to avoid vitreous fibrils being sucked into the fragmatome hand piece, causing vitreous traction. Using triamcinolone acetonide to stain the vitreous ensures easy visualization.
• Reducing fragmentation power to only 5 -10 % facilities nuclear extraction by continuous occlusion of the suction port and avoidance of projectile fragments.[12]
• Using a small bubble of PFCL for protecting retina from projectile nuclear fragments.

2) Delivering Nucleus via limbal route:

• Elevating it with using Active suction with the hard tip flute cannula and bringing it to the anterior chamber.
• Using a pick/MVR blade to elevate it in the anterior chamber. The major disadvantage being it may cause damage to underlying retina.

• Using PFCL to float it upto pupillary plane and then delivering the nucleus via limbal route. The major advantage being all the nuclear fragments floats above the bubble and can be removed, it can be also utilized with accompanying retinal detachment. The caution has to be taken as nuclear fragments tend to slip over the meniscus to the periphery, hence meticulous examination of periphery also helps in the visualization and removal of these fragments. [13]

STEP 3:

Peripheral Examination by indentation helps us to locate any pre-existing breaks or localize any unknown breaks caused during the surgery and manage them by barraging them with laser intraoperatively thus reducing the chances of postoperative retinal detachment.[14]

STEP 4:IOL choice:

Depending upon the presence of adequate capsular support an in the bag or sulcus placement of IOL can be attempted. For sulcus fixation, a 3 piece IOL or PMMA IOL is preferred over a single piece lens. [15]
In case adequate support is not available then sclera fixated/ glued IOL can be placed or 3 pieces open looped anterior chamber IOL can also be placed.

Conclusion:

The current instrumentation and surgical technique have rendered the management of dislocated nucleus very successful with very low complication rates, correct patient selection and discussion of the pros and cons of surgery forms an important part of management. Correct treatment at the appropriate time is one of the most important keys in the management of the posterior dislocated nucleus.

Bibliography: