Hyperguides

Ophthalmology / Cataract

Secondary Piggyback Intraocular Implants

Johnny L. Gayton, MD
Article


Introduction

In 1993, my colleagues and I first described the implantation of two intraocular lenses (IOLs) in the eye, piggybacking, to provide adequate power in a case of microphthalmos.1 Since then, piggybacking IOLs has become an acceptable method for addressing the power requirements of high hyperopes.2-5

Piggybacking IOLs can also be used to correct pseudophakic refractive errors.6 Rather than subject a patient to the trauma of an IOL exchange, which increases the risk of retinal tears, cystoid macular edema, cyclodialysis, and posterior or anterior capsule rupture, a second IOL can be implanted anteriorly to the primary IOL. The power of a secondary piggyback IOL implant is also more predictable than an IOL exchange for three reasons. First, the surgeon can never be certain of the power of the original IOL. Second, the surgeon cannot be confident that an exchanged IOL would be placed in the same plane as the old IOL. Third, the power of the secondary implant is calculated purely by the patient's refraction.

Not only can pseudophakic patients with residual refractive error benefit from piggyback IOL implant strategy, but also, pseudophakic patients who subsequently undergo penetrating keratoplasty (PK) can have the often disabling refractive error created by PK and corrected with a secondary piggybacked implant.7

I have personally piggybacked silicone, PMMA, and acrylic IOLs. Although I have also used silicone, PMMA, and acrylic as the secondary IOL, my preferred IOL is the STAAR AQ5010V 3-piece silicone lens (STAAR Surgical, Monrovia, Calif.), which is available from -4 D to 4 D in 1 D increments. The STAAR Model AQ2010V is used for powers greater than 4 D. I also use the AcrySof MA50BM (Alcon Surgical, Ft. Worth, Texas) in cases requiring greater than 5 D of power. The AcrySof offers the advantage of a thinner, 6.5-mm optic. However, it appears that any lens type can be secondarily piggybacked over any other type of IOL.

Implanting a second IOL anteriorly to an IOL already in place is an easy and relatively atraumatic procedure. In contrast, an IOL exchange involves removing the existing IOL before implanting a new one. The additional manipulation required for the removal process of an IOL, particularly if the IOL is strongly fixated, increases the risk of complications.

The piggyback procedure can theoretically be more predictable than an IOL exchange. The accuracy of the power calculation for an exchange can be affected if the original IOL had been unknowingly mislabeled, or if the new IOL ends up at a different plane than the original. The power calculation for a second implant depends only on the postoperative refraction.

The secondary piggyback procedure is particularly effective in transplant patients for whom there are few viable options to correct significant, visually disabling, spherical refractive errors. Most of the pseudophakic PK patients I see have IOLs that were implanted years ago that would be difficult to remove and exchange. For patients who have myopic error, refractive surgery is an alternative, but is less predictable, especially in transplant patients.

Clinical Experience

We have studied a consecutive series of 39 secondary piggyback IOL implant cases, including nine pseudophakic PK patients. Power calculation for the second IOL was based on the refraction. For moderate to high hyperopia, we added a second plus power IOL. For high myopia, we added a minus power IOL. For underpowered pseudophakic PK patients, we estimated the required power by multiplying the desired change in spherical equivalent by 1.5. For overpowered pseudophakic patients, we used the desired spherical equivalent change. For example, a patient who is pseudophakic by 3 D with a targeted spherical equivalent of -1 D would have been implanted with a 6 D IOL ([3 - (-1)] x 1.5 = 6 D). A patient with -3.5 D of pseudophakia with a target of -0.5 D would have been implanted with a -3 D IOL. All patients were targeted for a range of refraction between -2 D and 0.5 D. Calculations were verified using the Holladay IOL Consultant software.

Surgical Technique
All patients undergoing a piggyback procedure receive topical anesthesia that includes proparacaine 0.5%, Voltaren (diclofenac sodium, Novartis Ophthalmics), and Marcaine 0.75% (bupivicaine HCl, Abbott). The patients are then prepared for surgery and draped, and the lid speculum inserted. If an acrylic lens is used, a limbal incision is made. If a PMMA lens is required, a corneoscleral tunnel is required. The anterior chamber is entered in a self-sealing fashion, and 1% nonpreserved lidocaine injected into the eye. Viscoelastic is used to deepen the anterior chamber and to deepen the area between the implant and the posterior surface of the iris to avoid iris chafing. The secondary IOL is placed in the sulcus. If the patient's posterior capsule is open, the viscoelastic is removed with the vitrectomy cutter. If the posterior capsule is not open, viscoelastic is removed with the irrigation and aspiration (I&A) unit. A miotic is used to lessen the risk of pupillary capture. The wound is sealed with balanced salt solution, and a drop of Iopidine (apraclonidine, Alcon), a drop of Tobradex (tobramycin and dexamethasone, Alcon), and Pilopine gel (pilocarpine hydrochloride, Alcon) are instilled. No patch is used.

Results
Thirty-nine cases have been performed. Final postoperative data were used in all cases. The median postoperative visit was 12 months, ranging from 3 weeks to 4½ years.

(Slide 1) demonstrates the residual pseudophakic refractive error versus the postoperative refraction. For most patients, the target refraction is between +0.5 to -2 D. Most cases are within this target. Some of the cases with postoperative refraction less than -2 D were targeted for monovision. (Slide 2) shows the target refraction versus the actual postoperative refraction. Eighty-four percent of patients are within 1 D of target.

The number of patients with a visual acuity of 20/40 or better postoperatively is substantially improved (Slide 3). As expected, best-corrected vision is not affected (Slide 4).

Slide 1 Slide 2

Slide 3 Slide 4

Complications

Interlenticular Opacity
Interlenticular opacity (ILO) has recently emerged as a late postoperative complication of piggyback IOL implantation. ILO refers to any visible intercellular growth between the lenses, which can present as a slight opacity, Elschnig pearls, or, in its severe form, a thick membrane. An ILO has been associated primarily with primary piggybacked acrylic lenses, although it has been seen in piggyback cases of PMMA and silicone lenses.

The complication has not been associated with secondary piggybacks, most likely because the secondary piggyback lens is normally implanted in the sulcus, avoiding the lens interface which attracts the growth. However, we have seen one case of ILO in a secondary piggyback.8 In that case, the second lens was successfully implanted in the bag, with the capsulorrhexis on the anterior optic at 360°. At the time, we believed that a bag implantation would be more desirable.

Seven months after the secondary piggyback was implanted, cellular growth between the lenses, or ILO, was noted. There was a hyperopic shift, resulting in a refraction of -0.50 sphere, with best-corrected visual acuity of 20/30.

One year after the ILO was noted, the patient underwent an Nd:YAG laser procedure. The Nd:YAG laser was focused on the interlenticular space in the area of cellular growth, using less than 2 mJ of energy. The area of opacification liquefied and moved inferiorly. One month postoperatively, the refraction was -1.50 + 0.50 x 6, with 20/40 best-corrected vision and 20/80 uncorrected vision. Six months postoperatively, the refraction was -1.25 + 0.25 x 5 with 20/30 best-corrected vision.

When performing an Nd:YAG laser procedure, it is critical that the laser be focused as tightly as possible on the area of interlenticular opacity. It is also important to use as low energy as possible to prevent or decrease lens pitting.

Treating ILO is still in its infancy, and it will be some time before definitive methods of treatments are determined. Of course, it is even more important to prevent this complication in the future. Several methods of prevention have been discussed, including ensuring that the capsulorrhexis margin remains peripheral to the optic margin,9 completely removing all traces of lens epithelial cells,10 and placing the anterior lens in the sulcus.10

Pupillary Capture We have experienced two cases of pupillary capture in secondary piggybacks.11 A pupillary capture in a secondary piggyback is more likely than in a primary piggyback because the zonular lens complex has fibrosed and is not easily moved posteriorly with implantation of a secondary piggyback lens. As a result of the lens residing more anteriorly, when the pupil is dilated, it is easy for the iris to capture the lens optic. This event is more likely to occur with a silicone secondary piggyback because the index of refraction is smaller and the lens is thicker. It would also stand to reason that a myopic lens would be more likely to introduce resulting capture than the traditional lens due to the shape of the myopic lens with its thicker edge.

Optic capture cannot be avoided simply by placing the secondary lens in the capsule. In most cases, a bag implantation of a secondary piggyback lens cannot be easily performed even the day after surgery, and even if it could, would significantly increase the risk of ILO.8 It can be lessened, if not avoided, simply by using a miotic such as Pilopine gel, intraoperative Miochol (acetylcholine chloride, Iolab), and pilocarpine drops in the immediate postoperative period and not dilating these patients until 2 months or more postoperatively.

Optic capture is a newly reported finding. It is managed by using a topical anesthesia at the slit lamp and then using a 30-gauge needle inserted in a self-sealing fashion into the anterior chamber. The optic is pressed back into the ciliary sulcus and pilocarpine is instilled. After the optic is depressed back into the posterior chamber, the patient is placed on pilocarpine for 1 day and told not to have the eye dilated unless absolutely necessary for several months.

Summary

Secondary piggybacks are a powerful way to address residual refractive error in normal and post-PK pseudophakic patients. Secondary piggyback implantation is safe and efficacious, with good predictability. Complications are rare and easily avoided.

References

  1. Gayton JL, Sanders VN. Implanting two posterior chamber intraocular lenses in a case of microophthalmos. J Cataract Refract Surg. 1993;19:776-777.
  2. Holladay JR, Gills JP, Leidlein JL, Cherchio M. Achieving emmetropia in extremely short eyes with two piggyback posterior chamber intraocular lenses. Ophthalmology. 1996;103:1118-1123.
  3. Gills JP. The implantation of multiple intraocular lenses to optimize visual results in hyperopic cataract patients and under-powered pseudophakes. J Cataract Refract Surg, Best Papers of Sessions, 1995 Symposium on Cataract IOL and Refractive Surgery Special Issue; 1996.
  4. Gayton JL, Raanan MG. Reducing refractive error in high hyperopes with double implants. In: Gayton JL, ed. Maximizing Results. 1996: 139-148.
  5. Gills JP, Gayton JL, Raanan MG. Multiple intraocular lens implantation. In: Gills JP, Fenzl R, Martin RG, eds. Cataract Surgery: State of the Art. 1998.
  6. Gayton JL, Sanders V, Van Der Karr M, Raanan MG. Piggybacking intraocular implants to correct pseudophakic refractive error. Ophthalmology. 1999;106:56-59.
  7. Gayton JL. Secondary implantation of a double intraocular lens after penetrating keratoplasty. J Cataract Refract Surg. 1998;24(2):281-282.
  8. Gayton JL, Van Der Karr M, Sanders V. Interlenticular opacification in a secondary piggyback case, with Nd:YAG laser treatment of the interlenticular space. J Cataract Refract Surg, in press.
  9. Shugar JK, Schwartz T. Interpseudophakos Elschnig pearls associated with late hyperopic shift: A complication of piggyback posterior chamber intraocular lens implantation. J Cataract Refract Surg. 1999;25:863-867.
  10. Gayton JL, Apple DJ, et al. Interlenticular opacification: Clinicopathological correlation of a new complication of piggyback posterior chamber intraocular lenses. J Cataract Refract Surg. 2000;26:330-336.
  11. Gayton JL, Sanders V, Van Der Karr M. Pupillary capture of the optic in secondary piggybacks. J Cataract Refract Surg, in press.