Bryan S. Lee, MD, JD
Although there has been a great deal of innovation in alternative intraocular lens (IOL) fixation techniques, such as the use of Gore-Tex (WL Gore & Associates) suture and intrascleral haptic fixation, the anterior chamber IOL (ACIOL) continues to be a valuable method of IOL placement in the absence of a normal capsule complex.1,2
ACIOLs offer several advantages over other techniques, including a decades-long track record,3 the ability to be used in essentially any eye (Figure 54-1), the lack of reliance on sutures, and on-label use. Furthermore, surgeons can usually place an ACIOL even when dealing with nerves resulting from having had a complication.4,5 Placing an ACIOL is usually faster than alternative fixation methods, which is beneficial if the patient is becoming uncomfortable with the length of surgery or if the corneal clarity is decreasing. The drawbacks to an ACIOL include the large incision it requires and its relative undesirability in eyes with significant iris damage, a shallow chamber, peripheral anterior synechiae, or unhealthy corneal endothelium.6
The first step before placing an ACIOL is to make sure that the anterior chamber is clear of vitreous (Figure 54-2). Using preservative-free triamcinolone acetonide (Triesence) or triamcinolone rinsed through a filter7 allows visualization of remaining vitreous (Figures 54-3 and 54-4). Next, the pupil should be constricted with acetylcholine chloride or carbachol, then a peripheral iridotomy should be made to avoid pupillary block.
Measuring the white-to-white distance with a caliper allows sizing of the ACIOL (Figure 54-5). An undersized ACIOL may be unstable and move, causing endothelial damage. An oversized IOL can cause pupil distortion. Because the vertical white-to-white is smaller than the horizontal, an undersized ACIOL can sometimes be rotated to achieve stable fixation.
If performing a vitrectomy, the vitrector can be used to make the iridotomy (Figure 54-6). Simply turn the vitrectomy port downward so that it is facing the iris, apply vacuum (irrigation-aspiration-cut mode if available), then gently use the vitrector to make a small opening. Other methods include using forceps to pull some of the iris out through a paracentesis, then cutting the retracted iris with scissors, making sure to create a full-thickness incision. Alternatively, a needle can be bent and then used to make an iridotomy with countertraction from another instrument, such as a Sinskey hook.
After constricting the pupil, the surgeon should use an adequate amount of viscoelastic to protect the endothelium and deepen the chamber for the IOL. Because of the size of the incision needed to insert an ACIOL, a cohesive viscoelastic will not remain in the eye as well.
The incision for the ACIOL can be made in the cornea if extending a phaco incision. However, a scleral tunnel will reduce surgically induced astigmatism (Figure 54-7). The surgeon makes a conjunctival peritomy followed by the application of cautery to the sclera. Next comes a partial-thickness scleral groove followed by a tunnel using an angled blade. The incision should be approximately 6.5 mm wide (Figure 54-8). Internal calipers ensure an adequate incision, although standard calipers work well also.
The location of the incision can vary depending on multiple factors. Theoretically, the incision can be placed along the axis of astigmatism to reduce the amount of cylinder as long as care is taken not to overtighten the sutures. In my opinion, having good exposure for the surgery and a comfortable approach are more important, so I usually operate temporally. This should result in less astigmatic effect and is much more comfortable.