BLOG: Hypermature cataract calls for urgent femtosecond laser surgery
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Key takeaways:
- Hypermature cataract is one of the few indications for urgent cataract surgery.
- Surgery with a customizable femtosecond laser provides a fast and safe capsulotomy.
A 72-year-old patient presented urgently with vision loss and ocular pain.
Upon examination, her left eye had light perception vision, a dense white cataract, corneal edema and an IOP of 30 mm Hg due to phacomorphic glaucoma secondary to hypermature cataract (Figure 1). The patient stated she had been told she had cataracts years prior but never followed up with annual exams. She was not bothered by the worsening cataract until the pain started because her vision in the fellow eye was still good, with mild nuclear sclerosis.
Preoperative management
Hypermature cataract is one of the few indications for urgent cataract surgery, but first it is imperative to address what is often significant inflammation (in the form of corneal edema and/or uveitis) and elevated IOP. In this case, the patient was started on topical corticosteroid drops every hour while awake, as well as topical glaucoma therapy (brimonidine, timolol and pilocarpine) and oral acetazolamide twice a day.
Lens-induced glaucoma in a white cataract case can be caused by either elevated IOP secondary to iris dilation and narrowing of the chamber with angle-closure glaucoma or spontaneous leakage of lens protein through the capsule. In either case, it has the potential to rapidly damage the optic nerve. A full glaucoma exam will not be possible, of course, until after the cataract surgery. However, a B-scan ultrasound was done and was normal except for the massive lens thickness. Gonioscopy showed a closed angle from the dilated iris.
After 2 days, when the IOP and corneal edema were better controlled, cataract surgery was scheduled. IOL power calculation is difficult in a case like this. Keratometry will be inaccurate because of the corneal edema, and typical biometry is impossible in the presence of a white cataract. Power calculation was therefore based on A-scan ultrasound and keratometry/biometry from the fellow eye to make sure both readings were consistent; a 26.5 D implant was planned for a target of –1 D.
The surgeon should be prepared for at least three different scenarios in terms of IOL placement, depending on what happens during the case. If the capsulotomy is successful and the capsule remains intact, it may be safe to place a single-piece monofocal or monofocal plus lens in the capsular bag. A three-piece lens should be available as a backup lens in case the capsule is compromised during surgery. It should also be discussed with the patient preoperatively that it might not be possible to place an IOL at the time of surgery at all. Typically, the fail-safe lens for a complicated cataract surgery is an anterior chamber IOL. However, placing a lens in front of the iris is not an option in a hypermature case because the iris is essentially ischemic and dilated from the intense pressure of the bulging lens. In these cases, the surgeon may need to leave the eye temporarily aphakic and plan a second surgery later to implant the IOL.
The value of the laser
Manual capsulotomy and phacoemulsification in these eyes are exceedingly difficult. The pressure on the capsule from the hypermature cataract is so intense that it typically splits horizontally as soon as it is punctured with a cystotome, causing the Argentinian flag sign (so called because of the horizontal stripes of trypan blue-stained capsule and white cataract) and explosion of the liquified nuclear material. I remember from fellowship a similar case (pre-femtosecond laser technology), and I was told to give the patient mannitol and perform a blind vitreous tap to try and decompress the anterior chamber. That sounds less than ideal to me now. Fortunately, a customizable femtosecond laser provides an opportunity to perform the case in a more controlled fashion with a fast and safe capsulotomy. The key to success is to make a very rapid capsulotomy with a few setting adjustments.
In this case, I started with femtosecond laser imaging, which showed an anterior chamber depth of 1.8 mm and a very large lens thickness. As the posterior capsule cannot be imaged in such a dense cataract, the fragmentation should be suppressed.
Using my laser’s default settings, the capsulotomy time would be about 1.6 seconds — far better than a complex manual capsulorrhexis starting very small and then enlarging it or, worse, having to do a can-opener save, but still slower than needed in this case. However, the settings on my laser are easily customized. By setting the capsulotomy size for a 4.7 mm capsulotomy (slightly smaller than the typical 5 mm to 6 mm capsulotomy) and increasing the vertical spot spacing to 15 µm, the capsulotomy can be completed in less than 1 second. The power should be maxed to 10 µJ in order to get through the corneal edema. I also increased the laser incision depth to 700 µm. The incision depth setting controls the proportion of pulses above and below the capsule. This ensures that the laser pulses still hit the capsule even when the capsule is rapidly moving up in the chamber, being forced anteriorly from the pressure of the lens.
Even with these advanced settings, you can see that a plume of liquified cataract material escapes the capsule during the capsulotomy (Figure 2), but despite the challenges of the hypermature cataract, the capsule remained intact.
After a slightly anterior main incision to prevent iris prolapse into the wound and staining the capsule with trypan blue (Figure 3), the case proceeded as planned, although extra care during phacoemulsification is important due to the narrow anterior chamber.
The Veritas phaco system (Johnson & Johnson Vision) has a customizable low aspiration setting designed to reduce flow as a safety feature, which is helpful in difficult cases. Then, once the lens is decompressed, the Venturi flow removes the cataract easily with a stable chamber. I implanted a Tecnis Eyhance IOL (Johnson & Johnson Vision). The fact that it is preloaded and unfolds more slowly than a three-piece lens is helpful in a complex eye, in my experience. This monofocal plus lens built on the Tecnis platform exhibits some tolerance for residual refractive error, which I knew was likely given the lack of the usual preoperative biometry.
Postoperative management
Postoperatively, it is important to continue to treat inflammation and to closely monitor IOP, preferably in consultation with a glaucoma specialist, once the eye has healed. Also, a laser iridotomy should be performed in the fellow eye to prevent angle-closure glaucoma. The patient should be informed that cataract surgery on the fellow eye is recommended sooner rather than later to avoid the same above situation.
By 2 weeks postoperatively, this patient’s vision had improved from light perception to 20/100, and the pressure improved to 15 mm Hg. As the corneal edema continues to resolve, her final visual outcome should improve. Fortunately, in this case, the postoperative optic nerve exam appeared to be normal once visible.
I can confidently say that this case would have been more challenging and potentially disastrous if performed manually. After 20 years of cornea and anterior segment surgery, I know if I did not have the femtosecond laser for this case, I would refer to a surgeon who had femtosecond laser access. We all want to avoid potential complications and operative stress. Attempting a case like this, in my opinion, would necessitate a femtosecond laser capable of making a sub-1-second capsulotomy: Safety first.
Reference:
For more information:
Jared Younger, MD, MPH, and Gina Y. Lee, MD, in private practice at Orange Coast Eye Center in Fountain Valley, California, can be reach at youngerjared@gmail.com and ginaleeyoo@gmail.com.
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