The role of the femtosecond laser in paediatric cataract surgery

Prof. H. Burkhard Dick

Performing cataract surgery on very small children comes with several challenges, partly due to the anatomical peculiarities of an eye that may be just a few weeks old but mainly because the initial operation is usually just the first of numerous interventions that might become necessary over the next couple of years to give the young patient a chance of developing normal, healthy vision. The femtosecond laser, as our considerable experience up to now proves, can play a crucial role in achieving this goal.

And challenges there are indeed. We were one of the first centres to employ the femtosecond laser in paediatric cataract cases, which is, like so many interventions in our youngest patients, an off-label procedure or contraindication for most laser platforms (the Ziemer laser system is the exception because it has a CE mark for laser cataract surgery in paediatric cases).

There are some requirements in paediatric cataract surgery that the surgeon must be aware of before planning the intervention: the surgeon will encounter soft eye tissues, particularly a low scleral rigidity. In addition, the operation and often also pre- and postoperative examinations will have to be performed under general anaesthesia.

There will be a high degree of difficulty in calculating the appropriate IOL power (if IOL implantation is intended). Automated keratometry will be necessary and another consideration is that posterior capsule opacification (PCO) could develop in a relatively short time span after surgery. The occurrence of this complication is almost guaranteed if the posterior capsule is left intact. Finally, the surgeon must be able to perform a vitrectomy.

Risks versus benefits

Intraoperative surgical planning after SD OCT imaging during a paediatric LCS case as a team work collaboration. (Photos courtesy of Dr Burkhard Dick)

Choosing the best possible time to operate on a newborn or a very young child always means weighing the risks and benefits. After early surgery, massive axial elongation and a substantial myopic shift can be expected.

Operating at a very young age increases the likelihood of the major postoperative complication glaucoma. This and other postoperative complications occur at a much higher incidence when surgery takes place at younger than 4 weeks of age.

Waiting too long, on the other hand, can result in deprivation and consequently in amblyopia. A general recommendation might be—with necessary caution—that unilateral congenital cataract should be operated upon 4–6 weeks after birth and bilateral cataract between 6 and 10 weeks.^1,2

We have used the femtosecond laser for paediatric cataract surgery for almost 10 years now and our experience has generally been very positive.³ Unlike in cataract surgery in adults, we do not employ the laser for lens fragmentation (this is done by aspiration) but primarily to achieve a perfect capsulotomy—anterior as well as posterior—which is essential and not only when primary IOL implantation is intended.

With anterior capsulotomy as a crucial step in the operation and for postoperative visual recovery, we were satisfied with even our first paediatric laser cataract surgery cases when we found an optimal circularity of femtosecond-laser-created anterior and posterior capsulotomies.⁴ As expected, the size of the capsulotomy initially did not turn out as planned because of the aforementioned elasticity. There was considerable widening of the capsule opening immediately after laser treatment.

With growing experience, we found out that, particularly in very young children, the capsulotomy diameter tends to turn out larger than planned. In a clinical series involving 22 eyes of 18 patients, we were able to develop what is now known as the Bochum formula, which has proven its value in correcting for this aberration.⁵

A desired capsulotomy diameter can be achieved using the following formula:

Preventing opacification

A true bane of paediatric cataract surgery is the high incidence of PCO. A special surgical technique—more for the experienced surgeon than for the newcomer—has the potential to considerably reduce the chances of this complication developing.

First described by Dr Marie-José Tassignon in 2002, during bag-in-the-lens (BIL) technique the anterior and posterior capsules are placed in this special IOL’s flange after creating both an anterior and a posterior capsulotomy with the femtosecond laser. The laser is particularly crucial for creating a perfectly centred posterior capsulotomy.

The IOL used in this technique is a foldable hydrophilic one-piece IOL that is completely inserted and unfolded in the anterior chamber and whose posterior haptics are placed behind the posterior capsule while the anterior haptics are positioned in front of the anterior capsule. This aims to prevent the proliferation and migration of lens epithelium cells over the long term and thus prevent PCO.

The femtosecond laser has the potential to render this manually challenging technique an option for surgeons who have not previously implanted BIL lenses. The femtosecond laser can safely perform the posterior capsulotomy and keep the anterior hyaloid membrane intact.⁶

Special needs

There are a number of children who have special needs and so it is necessary to make some additional preoperative considerations. A group of young patients with a higher incidence of childhood cataract than the general population are those with Down syndrome.

As Saifee et al.⁷ have stated based on their surgical experience, cataract extraction in paediatric patients with Down syndrome does not appear to have a higher rate of surgical complications than does cataract surgery in the general paediatric population. There is no reason to assume that laser cataract surgery in these patients might be less effective or less safe than in children without this condition.⁷

Patients with Marfan syndrome may need surgery of the lens when they are not suffering from cataract. Their vision is often compromised by a subluxation of the lens that may render the visual axis aphakic, by irregular astigmatism from the lens periphery and also occasionally from lens opacity.

Lens removal with capsule fixation and IOL implantation is a valuable strategy to address these problems. However, as in the younger patients with congenital cataract, challenges with manual capsulorhexis result from the high elasticity of the capsule (which has a tendency toward posterior tears), damage to the zonules from stress during manipulation, and the fact that the desired position for capsulorhexis is off centre, all too often resulting in increased intraoperative complications for these patients who undergo surgery at a relatively young age.

Early experience

In one of the first cases ever treated with a femtosecond laser, we operated on a 10-year-old boy with ectopia lentis in both eyes, employing the femtosecond laser in the right eye under general anaesthesia. After the ocular surfaces were identified with the integrated algorithms, the capsulotomy was automatically placed by the software at the centre of the scanned capsule, which was at the superior, temporal periphery of the pupil.

Docking of a right eye with paediatric cataract under sterile conditions using a small personal interface for LCS. (Photos courtesy of Dr Burkhard Dick)

The selected capsulotomy diameter was 4.1 mm (incision depth: 1,000 μm). No lens fragmentation was performed. The total suction time was 2 minutes and 45 seconds. A microforceps was used to remove the capsular disc and no radial tears were noted. The soft lens was aspirated with standard bimanual irrigation/aspiration devices.

No complications were observed within 10 weeks of follow-up.⁸ Given the fact that paediatric laser cataract surgery for most laser platforms is off-label, which is quite obviously not a major concern for most manufacturers, there are still shortcomings which will—I hope—be overcome in the near future.

At present, there is no software adapted for posterior capsulotomy, which makes it necessary to position the treatment zones manually. Only two laser platforms (J&J Vision’s and Ziemer’s) currently come with an interface for a smaller eye. There is no special formula for choosing the appropriate IOL for our youngest patients: all of them have been created for adults.

Experience has shown the Barrett formula to be more reliable than other formulas. It is worth noting that the ideal target refraction in very young infants seems to be a slight myopia as they primarily focus on near objects like their toys or their mother’s face.⁹

Continuous follow up

The operation is the first step to visual recovery for a child with cataract, to be followed by long-term care provided by the ophthalmologist. The parents (or caretakers) must be educated about the need for continuous follow-up so that complications such as inflammation, glaucoma and PCO can be detected and treated as soon as they arise, refractive errors can be corrected and amblyopia therapy can be pursued.

For this first step, we should use all our expertise and (when indicated) the best technology available. In my view, this is—more often than not—the femtosecond laser.

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H. Burkhard Dick, MD, FEBOS-CR, PhD

E: Burkhard.Dick@kk-bochum.de

Prof. Dick is professor and chair at the University Eye Clinic of Ruhr University, Bochum, Germany. He is consultant on demand for J&J.

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References

1. Chang P, Lin L, Li Z, et al. Accuracy of 8 intraocular lens power calculation formulas in pediatric cataract patients. Graefes Arch Clin Exp Ophthalmol. 2020;258:1123-1131.

2. Self JE, Taylor R, Solebo AL, et al. Cataract management in children: a review of the literature and current practice across five large UK centres. Eye (Lond). 2020;34:2197-2218.

3. Dick HB, Schultz T. Femtosecond laser-assisted cataract surgery in infants. J Cataract Refract Surg. 2013;39:665-668.

4. Gerste RD, Schultz T, Dick HB. Pediatric cataract surgery with the femtosecond laser. In: Dick HB, Gerste RD, Schultz T (eds.) Femtosecond laser surgery in ophthalmology. Thieme: New York. 2018:162-166.

5. Dick HB, Schelenz D, Schultz T. Femtosecond laser-assisted pediatric cataract surgery: Bochum formula. J Cataract Refract Surg. 2015;41:821-826.

6. Dick HB, Canto AP, Culbertson WW, Schultz T. Femtosecond laser–assisted technique for performing bag-in-the-lens intraocular lens implantation. J Cataract Refract Surg. 2013;39:1286-1290.

7. Saifee M, Kong L, Yen KG. Outcomes of cataract surgery in children with Down syndrome. J Ophthalmic Vis Res. 2017;12:243-244.

8. Schultz T, Ezeanosike E, Dick HB. Femtosecond laser-assisted cataract surgery in pediatric Marfan syndrome. J Refract Surg. 2013;29:650-652.

9. Mohammadpour M, Shaabani A, Sahraian A, et al. Updates on managements of pediatric cataract. J Curr Ophthalmol. 2019;31:118-126.