Soft cataracts are usually seen in pediatric or young adult patients. We encounter them more frequently nowadays due to the increasing patient awareness and evolving lifestyle requirements which bring the patients earlier to the clinic. Another important reason behind the increasing number of soft cataracts in our surgical practice is the fact that the number of pars plana vitrectomies is increasing and we tend to perform combined cataract surgery with pars plana vitrectomy in patients with early cataract. Soft cataract phaco can be quite challenging especially in situations where the pupil starts coming down in the face of an uncooperative patient and positive posterior pressure during surgery. It is no surprise that soft cataract has been termed as “Neither Here-Nor-There” cataract! We will be offering 10 pearls on how to successfully manage such cases with good outcomes.
Pearl 1: Need for precise IOL calculations:
Most soft cataracts encountered in younger visually active patients call for precise IOL calculations since many of them are refractive lens exchange (RLE) or presbyopic lens exchange (PLE) patients who opt for Advance Technology IOLs (AT-IOLs). Hence, we ensure that they go through an extended and more involved preoperative work-up process and receive meticulous counselling regarding premium IOL selection issues.
Pearl 2: Understand the surgical challenges:
The soft cataract is too soft to lend itself to standard procedures of nuclear disassembly. A brisk hydrodissection may result in nucleus prolapse into the anterior chamber which may be difficult to relocate back into the capsular bag. It may be a challenge to rotate the nucleus since the dialling instruments tend to pass through them without exerting any rotational torque. For the same reason, it is difficult to chop or even crack the lens matter due to the cheese-wiring effect. The lens matter tends to be sticky and there is difficulty in separating it from the capsular bag if there is significant epinucleus. Sculpting increases the risk of early capsular tear during groove creation as there is a risk of the phaco tip going rapidly through the soft lens material and the posterior capsule. Soft nuclei lack rigid cleavage planes and do not crack or chop. Using a higher vacuum to impale the nucleus for chopping results in the soft lens material getting aspirated into the phaco tip with resultant loss of holding power. Trying to impale and extract each quadrant can result in repeated loss of lens holding, ultimately creating a bowl of nuclear material. Further attempts can convert this bowl into a plate which further increases the difficulty in its removal.
Pearl 3: Preoperative preparation- Identifying a soft cataract
Good preoperative awareness and planning is half the battle. Anticipate a soft lens if the patient is young. Perform a careful slit-lamp grading of nuclear opalescence and colour using the lens opacity classification system (LOCS III)-grades 1 to 2. Evaluate the maximum pupillary mydriasis because a small pupil and a soft cataract can be a recipe for intraoperative complications. The Dysfunctional Lens Index (DLI) score comes in handy while managing many soft cataract situations. Another key point is to look for a posterior polar element in these cases since the management strategy will be different from routine in posterior polar cataracts. It is also prudent to look for lenticonus in soft cataracts and if present, delineate its extent.
Pearl 4: Machine parameter settings
Smooth and successful performance of the surgery depends on the judicious selection of phaco parameter settings. In soft cataract situations, we would opt for lower settings in terms of power, AFR, and vacuum. Few surgeons prefer to employ the Epinucleus mode for these softer cataracts. This setting allows for less phaco energy (0-20% power), with a fair amount of vacuum (150-200 mmHg) and aspiration flow rate (22-25 ml/min). The nuclear material stays at the tip and there is less chance of surge or rupture of the posterior capsule. The parameters need to be actively titrated intraoperatively depending upon the performance and smooth progress of the given soft cataract case.
Pearl 5: Choice of Anaesthesia
It is pleasantly surprising to see many young patients cooperate for surgery under topical anaesthesia under monitored anaesthetic care. But the choice of anaesthesia depends not only on the patient’s ability to cooperate but also on surgeon’s experience and accompanying ocular comorbidities like small pupil, corneal clarity, presence of posterior polar component etc. General anaesthesia becomes the anaesthesia of choice in paediatric age group.
Pearl 6: Capsulorhexis Issues
Capsulorhexis in a young patient may be challenging due to the highly elastic nature of the anterior capsule and may require microforceps to create a ripping centrifugal force on the pull. Because of the elasticity factor, we prefer to stain the anterior capsule with trypan blue (0.06%) dye which is known to render the capsule more friable and easier to tear. The use of sodium hyaluronate (1%, 1.4%, 2.3%) may simplify many difficult rhexis situations. In patients with anterior lenticonus, the capsule is extremely fragile and tends to slip under the forceps. The tearing occurs in a cogwheel pattern due to the ultrastructural thinning and periodic dehiscence in the anterior capsule.
It is ideal to aim for a rhexis 5-5.5 mm in diameter that just overlaps the intraocular lens (IOL) optic all around. This allows safe removal of the lens matter in most of the situations. Yet another advantage is it is still large enough to a) allow hydroprolapse (if the surgeon so desires for nucleus removal.) and b) allow optic capture in case of inadvertent posterior capsular rupture. A small rhexis (≤ 4 mm) can cause difficulty in hydro prolapsing a soft nucleus and may render soft lens removal challenging.
Pearl 7: Hydro-procedures
The type of hydroprocedure adopted depends upon the integrity of the posterior capsule. With intact posterior capsule we perform cortical cleaving hydrodissection. We avoid hydrodelineation because the residual thick epinucleus layer removal requires increased surgical manipulations and surgical time and may be challenging particularly when the pupil is coming down. However, there is no harm in performing hydrodelineation if a surgeon so desires.
A single wave of fluid during cortical cleaving hydrodissection may not effectively separate the tacky lens matter (epinucleus + cortex) from capsule resulting in poor nuclear rotation. Multiple, gentle fluid waves are injected beneath the rhexis margin – Multi quadrant hydrodissection to achieve greater success in cortical separation from the capsule. A Sinskey’s hook can then be used to gently try and rotate the nucleus confirming a good hydro-dissection. As described earlier the nucleus may not rotate.
With compromised posterior capsule (like in a PPC, post-traumatic or post-vitrectomy eyes) cortical cleaving hydrodissection must be avoided. Hydro free dissection or only hydrodelineation or inside out hydrodelineation may be done in cases with a compromised posterior capsule. We would employ a non-rotational nucleus disassembly manoeuvre to deal with the lens matter. Do not attempt to rotate the nucleus in such situations when cortical cleaving hydrodissection hasn’t been performed.
Pearl 8: Nucleus management
There are multiple techniques of nucleus removal in soft cataracts and there is no “one-size-fits-all” kind of technique. Hence, we feel the surgeon should be familiar with all the techniques and apply the one that best fits the given soft cataract case or move to another if that technique doesn’t work well. We would always prefer to go in for endocapsular techniques to begin with because is always desirable to work away from the endothelium. Endocapsular techniques: Simple bimanual or coaxial irrigation- aspiration (I/A) may suffice in situations like paediatric cataracts, traumatic cataract in young adults, swollen soft cataracts in post vitrectomy eyes etc. We have used a customized aspiration cannula with a 0.5 mm diameter aspiration port which succeeds in removing many soft cataracts that otherwise would have needed the use of a phaco handpiece. However, the high bore aspiration needs a matching infusion to maintain a stable anterior chamber.
For cataracts that are not amenable to aspiration with I/A system we will fall back on the phaco handpiece. Our standard technique is to sculpt and debulk the central core of the soft nucleus converting it into a bowl. Then the distal bowl wall is held with just enough vacuum (which often times comes by trial and error) and try to pull the bowl towards the central area of the capsular bag. This manoeuvre at times may need the epinucleus to be nudged with the Sinskey. Once the entire nucleus has flipped over it is aspirated en-masse and not piece-meal. Most of the softer nuclei can be removed with full flips if they are soft or with hemiflips if there is some firmness. This technique works faster than the chip and flip method wherein the nucleus is first converted into a bowl and then sequentially nibbled converting the bowl in to a plate that is subsequently elevated into the bag centre and consumed. Other techniques include - nucleus fragmentation using the hydro-chop, visco-chop or pre-chop techniques described by various authors. Some not so soft cataract cases may be amenable to stop and chop technique. We would decrease the vacuum as the remaining pieces decrease. Use dispersive OVD to inflate the bag which acts as a buffer while emulsifying the last 2 or 3 pieces. Supracapsular techniques: The nucleus is hydroprolapsed out of the capsular bag and emulsified in the supracapsular plane. Corneal endothelium must be adequately protected with a dispersive OVD though most of the manoeuvres may be performed with zero to minimal US power. Avoid supracapsular technique in eyes with a small pupil, small rhexis or a shallow anterior chamber.
Pearl 9: Epinucleus management
If a proper cortical cleaving hydrodissection has been performed we are less likely to be left with a residual epinuclear sheet. However sometimes we do encounter a thick layer of epinucleus especially when hydrodelineation has been performed intentionally or inadvertently. We prefer to remove the epinuclear layer using the phaco probe in the Epinuclear mode. It is seized with the phaco tip and slowly carouselled out of the bag preferable in-toto and aspirated with zero power and low vacuum though at times short bursts of power may hasten things up. High vacuum settings can result in a break of occlusion and aspiration of small pieces of the epinucleus. Attempting this at various locations can convert the bowl into a plate, making further removal difficult. At this point, the epinucleus may be viscoprolapsed to the center of the bag with a gentle but continuous injection of OVD under the epinuclear bowl.
Pearl 10: Cortex removal & IOL implantation
Once the lens has been removed, it is best to spend a little extra time in cortical clean-up for the younger patient. Further hydrodissection or viscodissection is helpful if there is any resistance encountered during its removal.
Bimanual I/A facilitates cortex removal since it offers the 360 degrees approach. A surgeon accustomed to coaxial I/A may prefer I/A tip with a 45-degree bend in it to effectively remove the sub incisional cortex. Posterior capsular plaque can be removed with polishing. If it is recalcitrant, it is better to leave it intact and perform YAG capsulotomy later, rather than risk a posterior capsular rupture. Capsular plaque associated with a PPC ought to be left alone.
As young patients will continue to have a prolonged active lifestyle, it may be necessary to choose a premium IOL.
Bonus Pearl: Considerations for PCO
Early-onset PCO is frequent in younger patients with soft cataract and it tends to be quite aggressive. So, we would like to clean the capsular bag very meticulously and also polish the undersurface of the anterior capsule to remove the LEC as much as possible. We would ensure anterior capsular overlap onto the optic edge for PCO reduction. IOL of choice would be a single-piece hydrophobic acrylic one.
Suggested Reading:
- William J. Fishkind. In Chapter 15. Management of the soft nucleus. Complications of phacoemulsification. Thieme, 2002.
- Lucio Buratto, David J. Apple. 2nd edition. Phacoemulsification: Principles and Techniques. SLACK Incorporated, 2003.
- Pearls for cataract removal. Cataract & refractive surgery today Europe. May 2009.
- Arup Chakrabarti. Cataract Surgery in the Diseased Eye. Jaypee Brothers Medical Publishers. New Delhi, India;2014.