December 18, 2020
3 min read
December 18, 2020
3 min read
In more than 99% of cataract surgery cases, the IOL that is implanted is left in position for life. However, there are rare cases in which we need to perform an IOL exchange, replacing the old IOL with a different IOL design or power.
Because the capsular bag will contract and shrink-wrap over the IOL that is implanted at the time of cataract surgery, it becomes more challenging to explant it. When planning an IOL exchange, we want to keep as much capsular support as possible, and this can be achieved by carefully dissecting the IOL out of the capsular bag.
At the initial consultation, the patient should be carefully examined to determine the extent of capsular support. The most common scenario is illustrated in this case: a single-piece acrylic IOL in the capsular bag with a capsulorrhexis and an intact posterior capsule. If the patient has a different situation such as status post YAG laser capsulotomy, then there is the issue of potential vitreous prolapse and the inability to place the new IOL in the capsular bag. Similarly, the lack of a complete capsulorrhexis may also necessitate alternate maneuvers.
For a refractive surprise treated with IOL exchange, the source of the miss should be determined if possible. We can also confirm with a simple rule of thumb that 1 D at the spectacle plane equates to about 1.5 D at the IOL optic plane, meaning that if there is a +2 D refractive surprise at the spectacle plane, IOL power needs to be increased by 3 D.
Another common scenario is the inability for the patient to tolerate a multifocal IOL, and that is the case here. This patient has a toric trifocal IOL in the capsular bag and a postop refraction of +1 D, with cataract surgery done about 6 months prior. We first determined if simply treating the refractive error would give the patient satisfaction with the diffractive IOL. A +1 contact lens was placed, and the patient experienced better visual acuity but was still bothered by the nighttime glare and halos from the trifocal IOL. This is why we elected to perform an IOL exchange to explant the trifocal IOL and replace it with a monofocal IOL.
The capsular bag needed to be opened, with care taken to separate the anterior capsule from the posterior capsule. Dispersive viscoelastic was injected between the IOL optic and the anterior capsule to create space and dissect the optic from the posterior capsule (Figure 1). This is a slow and steady process that is gentle to the tissues and is done in all quadrants to completely open the capsular bag. This is critical because the IOL has a bulbous tip at the end of the haptic that needs to be freed.
The haptics were then hooked with the chopper and brought into the anterior chamber through the capsulorrhexis (Figure 2). Once the haptics were free, the IOL optic was brought completely into the anterior chamber as well. The IOL was then removed from the eye with the twist-and-out technique that was previously shown here (Figure 3). This involves holding one side of the optic with straight tying forceps and then rolling the optic within the anterior chamber with the aid of the spatula, which also protects the corneal endothelium. The IOL was explanted through a 2.75-mm incision, which was made on the steep axis to assist with treating the against-the-rule astigmatism.
The new IOL was then placed into the capsular bag (Figure 4). A three-piece design was chosen because it offers more options for placement, such as sulcus fixation or optic capture. In addition, this silicone IOL has a low incidence of visual disturbances, which is helpful because our patient was also bothered by the negative dysphotopsias of the original single-piece acrylic IOL.
Because the trifocal IOL that was explanted had a toric correction, we opted to treat the relatively mild corneal astigmatism of 1 D using paired full-thickness incisions on the steep axis. Because the capsule was already fully contracted, placing a new toric IOL in the bag may not achieve sufficient rotational stability. The patient achieved excellent vision and was pleased with the outcome.
While IOL exchange is a rare procedure, it is important that cataract surgeons are proficient in the technique. By performing delicate dissection, using both viscoelastic and instruments, we can safely remove the IOL from the capsular bag. Preserving the capsular tissue is important because in-the-bag placement of the new IOL tends to be the best option.
Go to https://cataractcoach.com/2020/11/22/how-to-dissect-the-iol-out-of-the-bag to see surgical video of this case at CataractCoach.com.