Femtosecond laser boosts chances of pediatric patients developing normal vision

Docking of a right eye with pediatric cataract under sterile conditions using a small personal interface for LCS. (Images courtesy of H. Burkhard Dick, MD, PhD, FEBOS-CR)

Performing cataract surgery on very young 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 may be necessary over the next few years to give the patient a chance of developing normal, healthy vision. The femtosecond laser can play a crucial role in achieving this goal.

We were one of the first centers to employ the femtosecond laser in pediatric cataract cases, which is, as with 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 pediatric cases).

There are some things in pediatric cataract surgery that the surgeon must be aware of before planning the intervention. There will be soft eye tissues with a low scleral rigidity, and the operation—and often the pre- and postoperative examinations—will have to be performed under general anesthesia.

There likely 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) may develop in a relatively short time after surgery. This complication is almost guaranteed to occur if the posterior capsule is left intact. Finally, the surgeon must be able to perform a vitrectomy.

Risks versus benefits

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 of glaucoma. This and other postoperative complications occur at a much higher incidence when surgery takes place when a patient is younger than 4 weeks.

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A general recommendation might be—with necessary caution—that unilateral congenital cataract should be operated upon 4 to 6 weeks after birth and bilateral cataract done at 6 to 10 weeks after birth.1,2

We have used the femtosecond laser for pediatric cataract surgery for almost 10 years 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 pediatric 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 elasticity. There was considerable widening of the capsule opening immediately after laser treatment.

With experience, we found 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 the Bochum formula, which corrects for this aberration.5

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

Preventing opacification

A true bane of pediatric 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 chance of this complication developing.

First described by Marie-José Tassignon, MD, in 2002, during bag-in-the-lens (BIL) technique the anterior and posterior capsules are placed in a 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 centered posterior capsulotomy.

The IOL used is a foldable hydrophilic 1-piece IOL that is completely inserted and unfolded in the anterior chamber. Its posterior haptics are placed behind the posterior capsule and the anterior haptics are positioned in front of the anterior capsule. This prevents the proliferation and migration of lens epithelium cells over the long term and thus prevents PCO.

The femtosecond laser may make 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

Intraoperative surgical planning after SD OCT imaging during a pediatric LCS case as a team work collaboration.

Special needs

For patients with special needs, there are additional preoperative considerations. For instance, patients with Down syndrome have a higher incidence of childhood cataract than the general population.

But as Saifee et al7 stated based on their experience, cataract extraction in pediatric patients with Down syndrome does not appear to have a higher rate of surgical complications than does cataract surgery in the general pediatric 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 even when they do not have a 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.

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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 center, 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 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 anesthesia. After the ocular surfaces were identified with the integrated algorithms, the capsulotomy was automatically placed by the software at the center of the scanned capsule, which was at the superior, temporal periphery of the pupil.

The selected capsulotomy diameter was 4.1 mm (incision depth: 1000 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 pediatric laser cataract surgery for most laser platforms is off label, there are still shortcomings that hopefully will be overcome in the near future.

There is no software adapted for posterior capsulotomy, which makes it necessary to position the treatment zones manually. Only 2 laser platforms (Johnson + Johnson Vision and Ziemer) 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 such as 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 caregivers) 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 the best technology available. In my view, this is—more often than not—the femtosecond laser.

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

E: Burkhard.Dick@kk-bochum.de

Dick is professor and chairman at the University Eye Clinic of Ruhr University, Bochum, Germany. He is a consultant on demand for Johnson + Johnson.

References

• 1 Chang P, Lin L, Li Z, Wang L, Huang J, Zhao YE. Accuracy of 8 intraocular lens power calculation formulas in pediatric cataract patients. Graefes Arch Clin Exp Ophthalmol. 2020;258(5):1123-1131. doi: 10.1007/s00417-020-04617-8
• 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(12):2197-2218. doi:10.1038/s41433-020-1115-6
• 3 Dick HB, Schultz T. Femtosecond laser-assisted cataract surgery in infants. J Cataract Refract Surg. 2013;39(5):665-668. doi:10.1016/j.jcrs.2013.02.032
• 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; 2018:162-166.
• 5 Dick HB, Schelenz D, Schultz T. Femtosecond laser-assisted pediatric cataract surgery: Bochum formula. J Cataract Refract Surg. 2015;41(4):821-826. doi:10.1016/j.jcrs.2014.08.032
• 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(9):1286-1290. doi:10.1016/j.jcrs.2013.07.014
• 7 Saifee M, Kong L, Yen KG. Outcomes of cataract surgery in children with Down syndrome. J Ophthalmic Vis Res. 2017;12(2):243-244. doi:10.4103/jovr.jovr_212_16
• 8 Schultz T, Ezeanosike E, Dick HB. Femtosecond laser-assisted cataract surgery in pediatric Marfan syndrome. J Refract Surg. 2013;29(9):650-652. doi:10.3928/1081597X-20130819-06
• 9 Mohammadpour M, Shaabani A, Sahraian A, et al. Updates on managements of pediatric cataract. J Curr Ophthalmol. 2019;31(2):118-126. doi:10.1016/j.joco.2018.11.005