Repositioning of toric IOL may be needed for best visual results
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The final result of cataract surgery is a combination of our surgical procedure plus the patient’s healing response.
For the spherical refractive outcome, much of it is dependent on the contraction of the capsular bag during the postoperative healing period. If the patient has aggressive or fibrotic contracture of the capsular tissue, then the effective lens position of the IOL optic, and therefore the postop refractive outcome, is less predictable. Similarly, despite a surgeon accurately placing a toric IOL to align with the steep meridian of the cornea, the patient’s tissue response may result is malrotation and incomplete astigmatic correction.
We must accept that a portion of the refractive outcome is out of our hands and due to the patient’s variation in anatomy as well as healing abilities. For a slight movement of the toric IOL axis, the resultant residual astigmatism may be mild and not significant in terms of final visual outcome. This is usually the case if the malrotation is off by a few degrees in either direction. However, keep in mind that if the axis of the IOL shifts by about 1 clock hour (30°), then the astigmatic benefit of the toric IOL will largely be lost. Any further rotation beyond 30° may result in the induction of additional astigmatism at a different axis.
In the case shown here, the patient started off with a trifocal toric IOL aligned at the 180° meridian, and the initial postoperative refraction was close to plano. The patient was noted to have keratometry measurements of 43.00 × 90 and 45.00 × 180, and the toric IOL was designed to address 2 D at the corneal plane. Over the course of the next few months of healing, the IOL shifted about 90° so that it was now aligned at the 90° meridian. Of course, the keratometry measurements did not change, but now the patient had a postop refraction of –2.00 +4.00 × 180, showing the 2 D of corneal astigmatism plus the 2 D of IOL astigmatism leading to 4 D total.
The IOL needs to be rotated back to the 180° meridian in order to return to the postop goal of plano. The patient was previously very myopic with a large capsular bag, and that may have contributed to the malrotation of the toric IOL. In this case, performing corneal refractive surgery such as LASIK is not a great option because the surgeon would be asking the excimer laser to steepen one meridian of the cornea while flattening another.
The key for the toric IOL repositioning is to carefully free the haptics and completely open the capsular bag (Figure 1). We start by making two small paracentesis incisions through which we are able to use a 27-gauge needle with viscoelastic to get under the anterior capsular rim (Figure 2). In order to maintain better anterior chamber stability, we do not open the main phaco incision, which has already healed.
Source: Uday Devgan, MD
Once we are able to viscodissect the optic away from the posterior capsule, time is spent to carefully and fully open the capsular bag so that no adhesions between the anterior and posterior leaflets remain. Now the IOL can be safely rotated into the desired position (Figure 3). The IOL is less likely to become mispositioned again because the capsular bag has already contracted. Removing the viscoelastic from behind the optic so that it can rest directly on the posterior capsule is helpful as well (Figure 4). Using bimanual instrumentation allows for thorough viscoelastic removal through these small paracentesis incisions.
Note that this procedure, although it seems relatively simple, usually takes longer than the original cataract surgery. While it is easier to reposition a toric IOL in the first month after the initial procedure, this can be done many months or even a year later. The more time that has passed since the original cataract surgery will mean more time spent carefully opening the capsular bag and freeing the haptics from adhesions.
Our patient did well and returned to the desired plano refraction the day after this repositioning surgery. Cases like this remind me why it is important to educate patients that their results from cataract surgery will be a combination of our procedure and their healing response, which cannot always be precisely predicted. Fortunately, even if patients end up with a malrotation of the toric IOL, we can go back and successfully reposition the optic to align with the optimal astigmatic meridian for the best visual results.
See full video of this topic at cataractcoach.com.
- For more information:
- Uday Devgan, MD, is in private practice at Devgan Eye Surgery and partner at Specialty Surgical Center in Beverly Hills. He can be reached at 11600 Wilshire Blvd. #200, Los Angeles, CA 90025; email: devgan@gmail.com; website: www.CataractCoach.com.
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