Lensectomy With Intraocular Lens Implantation
Single-piece foldable acrylic IOLs, which can be placed through a 3-mm clear corneal or scleral tunnel incision, have become popular in pediatric cataract surgery, although larger single-piece polymethyl methacrylate (PMMA) lenses are also still used. Silicone lenses have not been well studied in children.
If an IOL is to be placed at the time of cataract extraction, 2 basic techniques can be used for the lensectomy, depending on whether the posterior capsule will be left intact. Many pediatric cataract surgeons leave the posterior capsule intact if the child is approaching the age when an Nd:YAG laser capsulotomy in an awake patient could be performed (usually 5 years of age). Primary capsulectomy is usually preferred for younger children. Studies have shown that in early childhood, the lens capsule opacifies, on average, within 18–24 months of surgery, but this can vary considerably.
Technique with posterior capsule intact
After the cortex is aspirated, the clear corneal or scleral tunnel incision is enlarged to allow placement of the IOL. Placement in the capsular bag is desirable, but ciliary sulcus fixation is acceptable. Viscoelastic material should be removed to prevent a postoperative spike in intraocular pressure. Closure of 3-mm clear corneal incisions with absorbable suture is safe and does not induce astigmatism in children.
Techniques for primary posterior capsulectomy
Posterior capsulectomy/vitrectomy before IOL placement
After lensectomy, the vitrector settings should be set to the low-suction, high-cutting rate appropriate for vitreous surgery. A posterior capsulectomy with anterior vitrectomy is then performed. The anterior capsule is enlarged, if necessary, to an appropriate size for the IOL, and the lens is implanted in the capsular bag or the ciliary sulcus. The surgeon must take care to ensure that the capsulotomy does not extend, the IOL haptics do not go through the posterior opening, and vitreous does not become entangled with the IOL or enter the anterior chamber.
Posterior capsulectomy/vitrectomy after IOL placement
Some surgeons prefer to place the IOL in the capsular bag, close the anterior incision, and approach the posterior capsule through the pars plana. Irrigation can be maintained through the same anterior chamber infusion cannula used during lensectomy. A small conjunctival opening is made over the pars plana, and a sclerotomy is made with a microvitreoretinal blade 2.5–3.0 mm posterior to the limbus. This provides good access to the posterior capsule, and a wide anterior vitrectomy can be performed.
Intraocular lens implantation issues
Because the eye continues to elongate throughout the first decade of life and beyond, selecting an appropriate IOL power is complicated. Power calculations in infants and young children may be unpredictable for several reasons, including widely variable growth of the eye, difficulty obtaining accurate keratometry and axial length measurements, and use of power formulas that were developed for adults rather than children. Studies have shown that in aphakic pediatric eyes, a variable myopic shift in refractive error of approximately 7.00–8.00 D occurs from 1 year to 10 years of age, with a wide standard deviation. This suggests that if a child is made emmetropic with an IOL at 1 year of age, refractive error at 10 years of age can be –8.00 D or greater. Refractive change in children younger than 1 year is even more unpredictable. This assumes that the presence of an IOL does not alter the normal growth curve of the aphakic eye, an assumption that may not be valid based on results of both animal and early human studies.
Lens implantation in children requires consideration of the age of the child, the target refractive error at the time of surgery, and the refractive error of the contralateral eye. Some surgeons implant IOLs with powers that are expected to be required in adulthood, allowing the child to grow into the selected lens power. Thus, the child initially requires hyperopic correction. Other surgeons aim for emmetropia at the time of lens implantation, especially in unilateral cases, believing that this approach improves the treatment of amblyopia and facilitates development of binocular function by decreasing anisometropia in the early childhood years. These children usually become progressively more myopic and may eventually require a second procedure to address the increasing anisometropia.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.