Side-port incision in 3-month old child with bilateral nuclear cataract
Our preferred infusion instruments are 23-gauge blunt-tip, angled, beveled irrigating cannula or a 25-gauge anterior chamber maintainer (Lewicky, Bausch & Lomb). For the irrigation supply we highly recommend a Venturi-pump positive-pressure irrigation system. The active pump can be set to the desired fluid delivery rather than adjusting a gravity-fed bottle-height. Anterior chamber stability for soft infant eyes is much better with the Venturi-pump system. The irrigation should be turned on and set to the irrigation continuous mode before entering the eye. We prefer an initial setting of 50 for the fluid flow on the Constellation machine. This is adjusted up or down depending on how much fluid leaks out around the instruments and how much lens cortex and nucleus is aspirated from the eye.
A 23 or 25-gauge vitrectomy handpiece (Constellation, Alcon) is often used for aspiration and cutting. We now prefer the 25-gauge size because it has demonstrated efficiency and effectiveness even when we have used it to remove dense fibrotic membranes and gummy cortex. The aspiration handpiece that matches the bimanual irrigation cannula is also placed on the surgical table for use during cortex aspiration, if needed. However, using the vitrector handpiece for both the cutting steps and the aspiration steps reduces the need to enter and exit the eye multiple times. Another consideration is that the instruments be equal or nearly equal in size. At present, bimanual I/A handpieces are not available smaller than 23-gauge. Therefore, we use a 23-gauge irrigation cannula and a 25-gauge vitrector (Fig 7.2). As mentioned previously, switching hands and instruments is a useful strategy for aspirating subincisional lens material. An alternative to switching hands is to use the irrigation cannula to hydrodissect the stubborn cortex and push it to the pupillary space, so that it can be more easily aspirated. For surgeons who prefer to use an AC maintainer, the 25-gauge Lewicky (Bausch and Lomb) instrument is now available along with the larger 23-gauge of the same name. This is a matter of surgeon preference.
Irrigation cannula and vitrector performing vitrectorrhexis
The anterior chamber is entered first with the irrigating cannula in the surgeon’s non-dominant hand. The beveled tip is inserted into the incision along the plane of the incision, using slight twirling motions if necessary. The vitrector is inserted similarly. Twirling motions facilitate entry once again. Resist the temptation to enlarge the incision.
The anterior capsulorhexis is made first. We recommend using a vitrectorhexis technique unless a primary IOL is being inserted. A manual tear capsulorhexis is more suited for IOL insertion but the vitrectorhexis works well for the lensectomy and vitrectomy technique we are describing here. A Venturi-pump driven vitrector cuts anterior capsule more easily than a vitrector handpiece attached to a peristaltic-pump machine. We now use the 25-gauge vitrector set at 7500 cuts per minute. The cutting port is placed in the eye facing directly posterior. The aspiration foot petal is depressed until there is enough aspiration to bring the capsule into the cutter. The vitrector cutter is used to create a round 4.5 mm central vitrectorhexis.
The vitrector is then taken off of the cutting mode so that it functions as an aspiration-only instrument. This is done using the foot petal and without removing the instruments from the eye. Bimanual aspiration of lens cortex and nucleus is accomplished (Fig 7.3a, b). The vitrectomy cutter can then be turned back on, using the foot petal, and a matching posterior vitrectorhexis is created (Fig 7.4). We recommend a generous central anterior vitrectomy, aiming to remove 1/3rd of the vitreous volume.
(a, b) Bimanual aspiration of the lens cortex and nucleus. Note posterior capsule plaque
Posterior capsulectomy and vitrectomy
The paracentesis incisions are most often closed with a single interrupted 10-0 Vicryl suture each (Fig 7.5). A drop of 5 % povidone-iodine along with atropine and steroid/antibiotic drops is placed on the eye at the end of surgery. An appropriate Silsoft aphakic contact lens placed on the eye as well (Fig 7.6). The child is then awakened and recovered.
10-0 Vicryl suture to close both the incisions
Silsoft contact lens (26 D, 7.5 mm base curve) inserted immediately at the end of the surgery
7.4 Pars Plana Approach
When an IOL is being implanted, many surgeons prefer a pars plana/plicata approach for the central posterior capsulectomy. However, when an IOL is not being implanted at the time of cataract surgery, this approach is not commonly used unless vitreoretinal pathology is also being addressed during the surgery. Pediatric retina surgeons favor this approach, but pediatric anterior segment surgeons are more likely to favor a limbal/corneal approach. The pars plana approach is advantageous because it minimizes the risk of trauma to the iris and cornea, due to its inherent lack of maneuvering within the anterior chamber. The disadvantage is that there is an increased likelihood of removing too much capsule, so that a sulcus-fixated or capsular-fixated secondary IOL cannot be supported.
The pars plana/pars plicata lensectomy technique utilizes the same vitrectomy cutting handpiece described above. To begin, two incisions are made in the conjunctiva to expose the sclera at the level of the pars plana/plicata: one at the 10 o’clock position and one at the 2 o’clock position. Next, two scleral perforations are made using a microvitreoretinal (MVR) knife or a Stiletto knife (DORC, the Netherlands) to match the gauge of the instruments used for the rest of the procedure (20, 23, 25, 27 gauge). The perforations are also made at the level of the pars plana/plicata, one for the infusion cannula and one for the vitrectomy probe. A guideline for stab incision placements is 2 mm posterior to the limbus for infants. When completing a lensectomy and anterior vitrectomy via this approach, leave a peripheral rim of capsular bag, with anterior, equatorial, and posterior capsule. The capsular remnants are important for secondary IOL implantation later on, as they create a shelf for a posterior chamber implant to rest on. The pars plana/plicata scleral incisions are usually closed using 8-0, 9-0, or 10-0 synthetic absorbable suture. Sutureless pars plana sclerotomies in children have been reported, however, suturing these wounds in children is recommended . The conjunctiva overlying the incisions may be closed as well.