• Ophthalmic Pearls

    Pediatric Keratoplasty: Strategies to Optimize Outcomes

    By Olivia Dryjski, MD, and Christina Rapp Prescott, MD, PhD
    Edited By: Sharon Fekrat, MD, and Ingrid U. Scott, MD, MPH

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    Pediatric keratoplasty can have a profound impact on a child’s life. Full-thickness corneal trans­plantation in the pediatric population is more challenging and has a higher complication rate than in adults. Car­ing for children with corneal disease requires a multidisciplinary approach including the pediatrician, pediatric ophthalmologist, and cornea specialist, among others. In some complex cases, glaucoma, retina, and oculoplastics spe­cialists may also be involved. The child’s caregivers are particularly important members of this team, and they need to have realistic expectations about the outcomes, challenges, and long-term care that is required.

    Careful preoperative, intraoperative, and postoperative protocols for pedi­atric penetrating keratoplasty (PK) are essential in reducing the risk of surgical complications in children. Here, we de­scribe the modified surgical technique we use in young patients.

    Indications

    Pediatric corneal disease can be divided into congenital and acquired pathol­ogies. In the United States, congenital corneal disease is the most common indication for pediatric PK, but in some countries, infections and scar­ring are more common indications.1 It is important to consider the reason for surgery as well as associated ocular pathology when counseling the family. Isolated acquired corneal scarring or ectasia has the most favorable prognosis, while congenital disease, especially when associat­ed with glaucoma, has the poorest prognosis.2

    Preparation

    When considering surgery, the physician should screen for any social circumstances that would preclude proper postoperative manage­ment. Caregivers need to be prepared for the extensive ophthalmic care required for pediatric transplant recipi­ents, including frequent clin­ic visits, long-term eyedrop use, amblyopia treatment, and multiple trips to the OR for exams, suture removal, and possibly other surgical interventions.

    It is important to discuss realistic expectations about outcomes—in par­ticular, that vision will most likely be closer to 20/200 than 20/20—as well as the lifelong risk of transplant rejection and infection.

    Evaluation. Children with congenital corneal abnormalities should undergo a systemic evaluation, and they often require genetic testing. For children with additional systemic concerns, the ophthalmologist should coordinate with the pediatrician and other special­ists to minimize the number of exams under anesthesia.

    An ocular exam under anesthesia should be considered preoperatively to identify other eye abnormalities that might preclude surgical success or require additional intervention. Ultrasound biomicroscopy or anterior segment optical coherence tomography can help with surgical planning in cases with a limited view of the anterior chamber. Other assessment techniques, including B-scan, visual evoked poten­tials, and corneal topography, may also be helpful.

    Timing. The timing of surgery is controversial. Earlier intervention is better in terms of amblyopia management; however, the risks of general anesthesia are higher for infants, espe­cially those under the age of 3 months. Graft survival is generally better for older children, although this may be related to differences in indication rather than to the timing of surgery.2

    Surgical Technique

    General anesthesia is required. Supple­mental retrobulbar anesthesia may be added to reduce general anesthesia re­quirements and to help with early post­operative pain. Pediatric patients are more likely than adults to experience positive posterior vitreous pressure fol­lowing retrobulbar injection. The use of a Honan balloon prior to surgery, pilocarpine 1% or 2%, and/or reverse Trendelenburg positioning during surgery may be helpful in reducing the risk. Preoperative intravenous mannitol may be considered, depending on the child’s weight and systemic health, and should be given as an infusion over at least 15 minutes rather than as a bolus.

    Following is our preferred surgical approach for PK in children. It is a modification of the “Price graft-over-host” technique.

    1. Pediatric sclera is less rigid than adult sclera, and we recommend the use of a Flieringa ring to stabilize the iris-lens diaphragm. Moreover, because the sclera is thinner in children, the surgeon must be careful not to perfo­rate the globe.
    1. The donor tissue is trephined in the same manner as for an adult PK. Use of tissue from donors over the age of 4 years is recommended, as tissue from younger donors is more difficult to manage during surgery.
    1. We routinely perform at least one peripheral iridotomy because children are more likely than adults to develop postoperative angle closure.
    1. We mark the center of the cornea and use an eight-pronged radial ker­atotomy marker to mark the cardinal meridians. We then use a vacuum or handheld trephine to incise the cornea to approximately 50% to 75% of its depth. We prefer a smaller graft, as it is possible that the child will need multiple surgeries during his or her lifetime. For infants, we typically use a 6-mm host trephine with a graft tre­phine that is 0.5 mm larger. For older children, a 7-mm host trephine with a graft trephine 0.5 mm larger is usually appropriate.
    1. Using a 15-degree blade, the surgeon incises the cornea along the trephina­tion incision and injects viscoelastic into the anterior chamber.
    1. We then proceed with a modified technique for removal of the host cornea to reduce the risk of lens extrusion or expulsive hemorrhage. This technique requires cutting the host tissue with corneal scissors in the same fashion as with an adult trans­plant. However, as each quadrant is cut, a suture is placed in the host cornea approximately 45 degrees from the cardinal positions.
    1. Once the host cornea is completely separated from the host bed and held in place with four 10-0 nylon sutures, it is covered with a cohesive viscoelastic, and the donor tissue is placed on top of the viscoelastic.
    1. Three cardinal sutures are used to secure the donor tissue to the host bed.
    1. The host corneal sutures are then cut and the host cornea is gently removed from under the donor tissue through the area where the last cardinal suture will be placed. During this process, the surgeon should take care to maintain a layer of viscoelastic between the host and donor corneas.
    1. The donor cornea is then sutured using 16 interrupted 10-0 nylon sutures, with all the knots buried. A running suture is contraindicated in pediatric patients, since such sutures loosen more quickly.
    1. Finally, we typically inject dexa­methasone (Decadron) and cefazolin subconjunctivally and then apply pred­nisolone 1% and gentamicin ophthal­mic drops. If the child is monocular, we place a clear shield on the eye; if binoc­ular, we apply erythromycin ointment and a patch and metal shield.

    We recommend oral acetaminophen for postoperative pain control but find that children typically do not complain of pain or appear uncomfortable (al­though they usually dislike the shield).

    Postoperative Management

    Suture removal starting as early as 3 weeks after surgery is indicated in pediatric transplants to reduce the risk of corneal neovascularization. With infants, all sutures should be removed by 3 months postoperatively.

    Children tend to have a strong inflammatory response following PK; thus, a topical steroid should be admin­istered frequently and tapered slowly. In patients with complex surgery, especial­ly in combination with glaucoma, cata­ract, or retinal surgery, a short course of oral steroids may be considered if there are no systemic contraindications.

    Compared with adult patients, children more commonly experience graft rejection, infection, and glaucoma following PK.1 For this reason, caregiv­ers should be taught how to perform a penlight exam, which should be done daily. They should also be educated about signs such as fussiness, photo­phobia, and tearing that might indicate complications.

    Ongoing Follow-up

    Corneal transplantation can lead to profound improvements in a child’s vision and quality of life, but even a clear graft does not ensure clear vision. Amblyopia therapy must be initiated as soon as possible and is usually man­aged in conjunction with the pediatric ophthalmologist. Information about services such as low vision aids for school and home should be provided to families. Finally, it is important to work with the patient’s pediatrician and other specialists to help ensure proper development.

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    1 Trief D et al. Curr Opin Ophthalmol. 2017;28(5):477-484.

    2 Karadag R et al. Am J Ophthalmol. 2016;171:95-100.

    3 Loden JC, Price FW Jr. J Cataract Refract Surg. 1998;24(6):736-738.

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    Dr. Dryjski is a corneal fellow and Dr. Prescott is an assistant professor of ophthalmology; both are at the Wilmer Eye Institute, Johns Hopkins Uni­versity, in Baltimore. Financial disclosure: None.