Principles of Incision Construction, Location, and Closure in Pediatric Cataract Surgery
Rupal H. Trivedi
M. Edward Wilson
Principles of incision construction in pediatric cataract surgery generally follow the techniques and innovations developed for adult cataract surgery.1 As in adults, pediatric cataract incisions are getting smaller. Intraocular lens (IOL) insertion devices are being constantly redesigned to allow the IOL to be inserted through eversmaller openings. Bimanual surgical tools are now available in very small gauge sizes giving the surgeon more options than ever before. Unlike in adults, the wound is more likely to be traumatized by the child during the postoperative period. Children are more likely to rub the eyes and fight the installation of the postoperative drops.
The most immediate goal when planning the incision strategy is to aid intraoperative maneuvering. Consideration must be given to the intraocular maneuvers that are anticipated for the surgery being planned. Where do the incisions need to be made and how many incisions will be needed in order to easily accomplish the goals of surgery? Will membranes need to be cut? Will synechia need to be severed? Will a small pupil need to be enlarged? Will the lens equator need to be directly assessed from a specific angle? Are zonular fibers missing or loose in one quadrant or another? What IOL will be used and what size incision will be required to implant it? Will the incisions be sutured? Will the sutures need to be removed or will they be absorbable? Each of these considerations is important to the incision planning. Each of the 360 degrees of the eye’s circumference is available for incision planning. Proper consideration and selection among all of the options helps make even the most difficult intraocular gymnastics more safe and effective.
Tunnel incisions have replaced limbal incisions made with corneoscleral scissors in children, just as in adults.2 As incision construction has gotten better and surgical entry wounds have gotten smaller, worries about induced astigmatism have diminished. However, surgical incisions can still create unwanted astigmatism and can also be used (in a limited way) to reduce preexisting astigmatism as astigmatism may complicate the management of amblyopia.3 These considerations are covered in more detail later in the chapter.
Before moving forward, it is important to remember the applied anatomy of the child’s eye and how it is different from the adult eye in relation to the construction of the incision. The cornea in premature and full-term babies is thick and reaches adult levels within the first 2 to 4 years of life.4 The sclera has a low rigidity and is not as thick. The anterior chamber is shallower in infant eyes compared to adult eyes. It is now generally agreed that there is a higher prevalence of against-the-rule astigmatism during infancy, which decreases with increasing age, while the prevalence of with-the-rule astigmatism increases.3,5,6
TUNNEL INCISION ARCHITECTURE
Location
Superior/Temporal/Meridian of Steepest Curvature
Most adult cataract surgeons have moved toward the temporal side as the “preferred location” for a cataract surgical incision. The temporal wound presents similar advantages in children as it does in adults. However, the superior approach allows the wound to be protected by the brow and Bell phenomenon in the trauma-prone childhood years. Both scleral and corneal tunnels can be easily made from a superior approach since children rarely have deep-set orbits or overhanging brows.
There is very little emphasis given in reducing, minimizing, or altering surgically induced astigmatism. An incision at the steepest meridian would help decrease surgically induced astigmatism.7,8 However, in eyes with pediatric cataracts, it may be difficult to accurately document the steep corneal axis. Refraction by retinoscopy is difficult when a cataract is present. The reliability of handheld autokeratometers, while reasonably good for corneal curvature measurement, may be dubious for the purpose of axis measurement.9 Corneal topography requires cooperation and fixation. Also, pediatric eyes undergo changes in astigmatism with growth. Since it is likely that children will wear glasses after cataract surgery to correct for residual refractive error or at least for reading, less emphasis has been given in children to surgical maneuvers designed to treat preexisting astigmatism.
Scleral/Corneal
Pros and cons of a corneal tunnel are listed in Table 14.1. Eyes operated on for cataracts during infancy are at increased risk for glaucoma. A scleral incision involving the conjunctiva increases the number of conjunctival fibroblasts and inflammatory cells. This may account for the increased risk of trabeculectomy failure.10 Today, angle surgery or seton implantation would likely be chosen over a trabeculectomy in an aphakic or pseudophakic child, making the state of the conjunctiva less important. Our survey of preferences back in 2001 indicated that only 38% of American Society of Cataract and Refractive Surgery (ASCRS) respondees and 27% of American Association of Pediatric Ophthalmology and Strabismus (AAPOS) respondees preferred a corneal tunnel.16 It is likely that the use of corneal tunnels in children is now much higher. Over the last decade, the adult literature has contained many reports indicating that unsutured clear corneal incisions are a statistically significant risk factor for acute post-cataract surgery endophthalmitis when compared to scleral tunnel incisions.13 Most of the adult corneal tunnels were left unsutured, but pediatric corneal tunnels are nearly always sutured. The additional risk of endophthalmitis may diminish or disappear when suture closure is added to the corneal incision location.
Table 14.1 CORNEAL TUNNEL INCISION | |||||||||||||
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