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Certain challenging cataract cases can benefit from femtosecond laser
These difficult cases may involve intumescent white cataracts, weak zonules or brunescent cataracts.
The femtosecond laser can be a useful tool for cataract surgery. In routine cataract cases, the benefit is typically mild and in expert hands may not provide a meaningful improvement over manually performed steps of surgery. For this reason, in most of my cataract cases, I do not find myself using the femtosecond laser during cataract surgery. But in certain challenging cataract cases, the femtosecond laser can be helpful in producing a better outcome and avoiding certain complications.
Capsulorrhexis creation in white cataracts
In the vast majority of cataract surgeries, an experienced surgeon can perform continuous, curvilinear, centered capsulorrhexis with consistency. However, in cases in which there is poor visualization of the capsule, an intumescent cataractous lens or significantly weak zonular structures, the femtosecond laser can assist the surgeon by making the anterior capsular opening before making the first incision into the eye.
For intumescent white cataracts, the challenge is that the lens capsular bag is filled with the opaque and liquefied cortex material. This creates an intralenticular pressure that is higher than the anterior chamber pressure in manual surgery. This forward push can cause the capsulorrhexis to run out and result in the so-called Argentinian flag sign, which is when the blue-stained capsule splits down the middle so that the resultant appearance of blue-white-blue resembles the Argentinian flag. This is a precarious situation because if the capsular tear extends to the posterior, it can result in displacement of the lens nucleus and prolapse of vitreous.
Source: Uday Devgan, MD
In manual surgery, this can be mitigated by keeping the anterior chamber pressure higher than the intralenticular pressure by inflating it with viscoelastic and using only incisions of 1 mm or smaller. The femtosecond laser also can maintain the pressure within the anterior chamber by applying suction to the patient interface ring and avoiding incisions into the anterior chamber during the firing of the laser. Once the laser-based steps are completed, a paracentesis can be made into the anterior chamber, which is infused with trypan blue dye and then filled with viscoelastic (Figure 1). The anterior capsule can then be lifted with forceps in a gathering motion to ensure that no tags of capsular attachment remain (Figure 2).
The femtosecond laser encounters difficulty with placing energy within a lens nucleus that is very opaque, thereby limiting the effectiveness of the laser-based nucleus fragmentation or softening patterns. In the case of our patient with the dense, white cataract, the lens nucleus was disassembled using the vertical quick-chop technique (Figure 3). Once the first quadrant is removed, the remaining lens nucleus can be further fragmented and then phaco-aspirated from the eye (Figure 4).
Capsulorrhexis creation in the setting of weak zonules
When performing a manual capsulorrhexis, the anterior lens capsule is carefully torn in a controlled manner. This works best when the anterior lens capsule is taut and firmly held by zonular structures without significant laxity. If the zonular support is weak or even partially absent, tearing the capsulorrhexis is difficult because there is not enough countertraction to allow control. This is a case in which the femtosecond laser can be of benefit because it can create the anterior capsulotomy even in the setting of poor zonular support because no shearing forces are applied.
If the cataract is partially subluxed and not well-centered in the pupil and visual axis, we must take that into account when centering our femtosecond laser treatment. We want to center the anterior capsular opening on the crystalline lens, and that will mean shifting the laser centration to achieve that. The capsular bag will then be realigned within the pupil by means of a capsular tension ring and suture fixation. Care should be taken to use sufficient laser energy to ensure a complete anterior capsular opening without tags or an aberrant run-out because these could make placement of a capsular tension ring difficult.
Softening brunescent cataracts
The femtosecond laser can help to divide a cataract into quadrants or sextants, but it can also be used to soften the nucleus by means of laser energy. This can help decrease phaco time because the softened nucleus will require less ultrasound energy for phaco-aspiration. In most cataract cases, this decrease in phaco time is very modest and often minimal, producing very little if any benefit in real terms of endothelial cell loss or faster visual recovery. In cases in which the nucleus is dense, this can amount to a more significant decrease in phaco energy. Cases of brunescent cataracts in which the lens nucleus is dense but still translucent enough to allow delivery of laser energy can benefit from the use of the femtosecond laser.
The femtosecond laser can also assist surgeons who are not proficient in certain techniques such as phaco chop. The femtosecond laser can divide the lens nucleus for the surgeon before entering the eye with the phaco probe. The surgeon then simply separates the pre-divided segments and performs phaco-aspiration. The same applies for surgeons who are having difficulty consistently creating a capsulorrhexis because the femtosecond laser can perform this step reproducibly over and over again. This should not be used as a crutch for novice surgeons to avoid learning these key steps of surgery because there are cases, such as those with poorly dilating pupils, in which the femtosecond laser cannot be used.
The femtosecond laser is an important tool for cataract surgeons, and it can prove beneficial particularly in certain challenging situations.
- For more information:
- Uday Devgan, MD, is in private practice at Devgan Eye Surgery, Chief of Ophthalmology at Olive View UCLA Medical Center and Clinical Professor of Ophthalmology at the Jules Stein Eye Institute, UCLA School of Medicine. He can be reached at 11600 Wilshire Blvd. #200, Los Angeles, CA 90025; email: devgan@gmail.com; website: www.DevganEye.com.
Disclosure: Devgan reports no relevant financial disclosures.