Better Iridotomies Prior to ICL Implantation

The UltraQ laser offers significant advantages.

BY ANDREW RABINOWITZ, M.D.

The use of implantable contact lenses (ICLs) is rapidly growing in popularity as a safe and effective option in the treatment of higher levels of hyperopia and myopia. As those who use the STAAR Visian ICL, (STAAR Surgical, Monrovia, Calif.) are well aware, there remains a risk of pupillary block. This is why surgeons are required to create peripheral iridotomies prior to ICL implantation to avoid this complication, which can lead to angle-closure glaucoma. In this article, I'll briefly review the benefits of laser peripheral iridotomies, look at potential complications and then explain our approach to creating these iridotomies prior to ICL implantation.

The Necessity of Iridotomies

Years of experience and previously published studies have proven the efficacy of creating peripheral iridotomies in order to avoid pupillary block in eyes implanted with an anterior phakic IOL or an ICL. A study published just last year in the journal Eye found that when a laser peripheral iridotomy (LPI) was performed in patients with primary angle closure, the anterior chamber volume increased significantly after an LPI. In addition, the iris flattened and the peripheral anterior chamber increased.¹ These findings confirm that the use of LPIs prior to implantation of ICLs or phakic anterior chamber IOLs helps to lessen the risk of pupillary block and angle closure.

Another study looked specifically at LPIs in eyes implanted with the ICL to determine what changes occurred in IOP, angle structures and pupil diameter.² In the study, the authors performed a gonioscopic examination at 1 day after LPI and then at 6 and 12 months following ICL implantation in 81 eyes. The gonioscopic exams found some angle narrowing in 16 eyes. They also found an increase in iris pigment but that this returned to preoperative levels at 12 months postoperative. An increase in IOP was seen at 1 week and 1 month, but this was attributed to topical steroids. The authors conclude that the combination of LPIs and ICL implantation is safe and effective.

The UltraQ Nd:YAG Laser offers advantages in iridotomies.

Although it is clear that there is great benefit to creation of an LPI with these refractive IOLs, successful creation of a peripheral iridotomy is not always easy to achieve, particularly in patients with dark irides.³ There can also be complications associated with some forms of LPI. A number of reports have recently reported corneal complications, including bullous keratopathy associated with the use of argon lasers in creations of LPIs.^4,5 In the latter study, the authors note that this is a growing problem, particularly in Asian countries.

A Better Way for LPIs

Because there is a potential for complications with some forms of lasers, as well as the complexity of performing this procedure in eyes with dark irides, we now use a Q-switched Nd:YAG laser that we have found helps to really simplify the LPI procedure prior to ICL implantation. The UltraQ Laser (Ellex, Adelaide, Australia) is a 1064 nm laser with energy levels of between 0.3 and 10 mJ, pulse duration of 4 nanoseconds and a spot size of 8 μm. This means that the laser delivers a quick, narrow burst of energy that only affects the targeted point of tissue. With some lasers, the energy can bleed into the surrounding tissue, causing thermal damage.

This laser is very precise and effective at tissue disruption. This apparently has to do with what's known as "optical breakdown" at low energy levels. This means that the energy the laser creates results in a more confined shockwave, making it more effective at delivering energy to the desired spot. The aiming of the laser is also extremely precise (±8 μm). All of these aspects combine to give us a laser that can create a precisely sized iridotomy, normally in just a single shot.

A significant benefit is that in eyes with dark irides, which here in Arizona represents a vast majority of our patients, the UltraQ gives us a much more effective way to create an LPI. Dark irides are about four times thicker than light irides. Before the UltraQ, we normally needed two different lasers to make the iridotomy — an argon laser to create a crater in the iris and then a YAG laser to break through the tissue to create the opening. Now we can perform the entire procedure with the UltraQ.

Typical Approach

I perform the LPI between 4 days and 1 week prior to ICL implantation. This allows the IOP to normalize, ensure that the LPIs are patent and to make certain any pigment that's dispersed in the process has time to settle down. However, with the UltraQ, we see much less pigment dispersion than with other lasers, which means we now have fewer problems with pressure spikes after creation of the LPIs. This is likely due to the precise focus of the laser. My standard setting for an LPI with the UltraQ is 5 to 8 mJ of energy. Normally, we need between 1 and 4 laser shots to break through the iris, depending on the thickness of the iris. After the treatment, topical prednisolone acetate 1% drops are instilled hourly on the day of treatment, then four times daily for 4 additional days.

An added benefit with this laser is that patients are much more comfortable during the procedure. In our experience, up to 30% of patients undergoing laser peripheral iridotomies will faint during the procedure because the pain is so intense. With the UltraQ, we've found that patients tolerate the procedure much better.

Although there have been some reports in the literature of pupillary block with ICLs even in eyes with LPIs, these cases have generally been linked to improperly sized lenses.⁶

Our practice has now implanted almost 400 ICLs with very good visual results, particularly in patients with higher levels of refractive error. In our experience, success with the Visian ICL is most definitely improved by using the UltraQ Laser to create the laser peripheral iridotomies. The laser provides a safe and effective method for iris tissue disruption without some of the drawbacks seen with other lasers. OM

References

1. Lei K, Wang N, Wang L, Wang B. Morphological changes of the anterior segment after laser peripheral Iridotomy in primary angle closure. Eye December 2007 (Epub).
2. Chun YS, Park IK, Lee HI, Lee JH, Kim JC. Iris and trabecular meshwork pigment changes after posterior chamber phakic intraocular lens implantation. J Cataract Refract Surg. 2006;32:1452-458.
3. deSilva DJ, Gazzard G, Foster P. Laser Iridotomy in dark irides. Br J Ophthalmol. 2007;91:222-225.
4. Kataoka T, Zako M, Takeyama M, Ohno-Jinno A, et al. Cooling prevents induction of corneal damage by argon laser peripheral Iridotomy. Jpn J Ophthalmol. 2007;51:317-324.
5. Ang LP, Higashihara H, Sotozono C, Shanmuganathan VA, et al. Argon laser Iridotomy-induced bullous keratopathy a growing problem in Japan. Br. J Ophthalmol. 2007;91:1613-1615.
6. Vetter JM, Tehrani M, Dick HB. Surgical management of acute angle-closure glaucoma after toric implantable contact lens implantation. J Cataract Refract Surg. 2006;32:1065-1067.