From the Department of Ophthalmology, Social Insurance Chukyo Hospital, Aichi (Kojima, Hara, Ichikawa); Nagoya Eye Clinic, Nagoya (Kojima, Horai, Hara, H. Nakamura, T. Nakamura, Ichikawa); and Satoh Yuya Eye Clinic, Sendai (Satoh), Japan.
The authors have no financial interest in the materials presented herein.
Study concept and design (T.K., K.I.); data collection (R.H., Y.S.); analysis and interpretation of data (T.K., S.H., H.N., T.N.); drafting of the manuscript (T.K.); critical revision of the manuscript (R.H., S.H., H.N., T.N., Y.S., K.I.); administrative, technical, or material support (T.K.); supervision (T.N., Y.S., K.I.)
Correspondence: Takashi Kojima, MD, Dept of Ophthalmology, Social Insurance Chukyo Hospital, 1-1-10 Sanjo, Minami-ku, Nagoya-shi, Aichi 457-0866, Japan. Tel: 81 52 691 7151; Fax: 81 52 692 5220; E-mail: firstname.lastname@example.org
Although the surgical techniques and devices for phacoemulsification have advanced and the accuracy of ocular biometry has increased using partial coherence interferometry, residual refractive error remains due to uncertainty about surgical outcomes and errors of biometry.
Several surgical methods including lens-based surgery and laser refractive surgery are available to correct refractive error in pseudophakic eyes. Lens-based surgery, such as refractive lens exchange and piggyback insertion of another lens, has been shown to be safe and effective.1 Similarly, the efficacy of laser refractive surgery, such as photorefractive keratectomy (PRK) and LASIK, has been reported to correct residual refractive error in pseudophakic eyes.2,3
The Implantable Collamer Lens (ICL; STAAR Surgical, Monrovia, California) is a posterior chamber phakic intraocular lens (IOL) with the haptics resting on the ciliary sulcus. In this study, toric ICLs were implanted in pseudophakic eyes to correct residual refractive error.
This is the first report of toric ICL insertion for pseudophakic eyes. This study was designed to evaluate the safety, efficacy, and predictability of ICL piggyback insertion in these eyes.
Patients and Methods
Eight pseudophakic eyes of five patients (one man, four women) were enrolled in the study. All patients presented to our outpatient clinic for refractive error correction. Because all initial cataract surgeries were performed 5 years prior to presentation, IOL types were not identified. All patients were followed for at least 6 months after surgery. Patient demographic data are shown in Table 1. An institutional review board approved the study protocol and all study procedures conformed to the Declaration of Helsinki for research involving human subjects. Informed consent was obtained from all patients after explanation of the nature and possible consequences of taking part in the study.
Table 1: Demographic Data of Five Patients (Eight Eyes) Who Underwent Piggyback Insertion of a Toric Implantable Collamer Lens
ICL Implantation Surgery
Implantation of the ICL was performed using a modification of previously reported methods.4,5 Generally, the nasal haptics of the ICL are inserted on the iris plane initially. However, in these cases, the nasal haptics of the ICL were directly inserted in the ciliary sulcus anterior to the anterior lens capsule, and temporal two additional haptics were inserted behind the iris using a specially designed manipulator. A single peripheral iridectomy was performed for six eyes during surgery and a single laser iridotomy was performed for two eyes using argon and Nd:YAG laser preoperatively.
Evaluation of ICL Vault
The vault was evaluated 6 months postoperatively under slit-lamp microscopy as the distance between the back surface of the ICL and the front surface of the pre-existing IOL. A vault ≥1/2 (50%) the corneal thickness and ≤3/2 (150%) the corneal thickness was defined as moderate. A vault <1/2 corneal thickness was defined as low, and vault >3/2 corneal thickness was defined as high.
At 6 months postoperatively, the ICL was well centered in all eyes, and no inflammation was observed under slit-lamp examination.
Safety and Efficacy
Pre- and postoperative mean Snellen and logMAR CDVA and UDVA are shown in Table 2. Safety index (postoperative CDVA/preoperative CDVA) was 1.14 (0.956/0.842). No eyes lost more than 1 line of Snellen CDVA (Table 2). Efficacy index (postoperative UDVA/preoperative CDVA) was 0.86 (0.723/0.842).
Table 2: Postoperative Visual Acuity and Vault in Eight Eyes that Underwent Piggyback Insertion of an Implantable Collamer Lens
Mean pre- and 6-month postoperative manifest refractive sphere was −3.06±3.75 D and 0.06±0.90 D, respectively. Mean pre- and 6-month postoperative manifest refractive astigmatism was −2.63±0.76 D and −0.72±0.65 D, respectively. All eight (100%) eyes were corrected within ±0.50 D of attempted mean spherical equivalent refraction. Manifest refractive astigmatism was corrected within ±0.50 D in five (62.5%) eyes and ±1.00 D in seven (87.5%) eyes. Manifest refractive cylinder decreased after ICL implantation in all eyes (mean: 1.84±0.46 D [range: 1.25 to 2.50 D]).
Corneal Endothelial Cell Density
Mean preoperative endothelial cell count was 2809.0±439.7 cells/mm2 compared to 2674.6±444.5 cells/mm2 at 6 months postoperatively.
Six (75%) eyes showed high vault whereas the remaining two (25%) eyes showed moderate vault (Table 2). In all eyes with high vault, gonioscopic evaluation showed that the angle was open and no abnormalities such as peripheral iris synechia were apparent.
One eye experienced pupillary block on postoperative day 1. Laser iridectomy using argon and Nd:YAG laser was performed immediately. Intraocular pressure was 45 mmHg at day 1, which decreased to 18 mmHg within 2 hours after laser iridectomy. The visual field at 3 months postoperatively did not show any glaucomatous changes.
Refractive lens exchange surgery has been reported in many clinical settings.1,6,7 However, if the primary surgery is performed more than 1 month earlier, the anterior and posterior lens capsules will be adhered together and inserting a replacement IOL in the bag will be difficult. Piggyback insertion of a conventional in-the-bag IOL offers a means of overcoming such obstacles. However, because two IOL optics are located close to one another, interlenticular opacities and hyperopic shift can occur.
The advantage of LASIK is that it can correct not only spherical and astigmatic error, but also higher order aberrations and irregular astigmatism using wavefront- or topography-guided technology. Another advantage is that LASIK does not affect corneal endothelial cell count. However, a thin and/or abnormal cornea is a contraindication for LASIK, and postoperative dry eye can affect visual function.8
The ICL is used to correct myopia, hyperopia, and astigmatism in the phakic eye. The ICL was designed not to touch the crystalline lens, and therefore the ICL creates a vault. We speculated that the stable anterior vault may contribute to achieving stable refraction. In our study, refractive sphere and astigmatism were stable during the 6 months following surgery.
In a study of the ICL by Sanders et al9, 76.9% of eyes were within ±0.50 D of attempted correction and 97.3% were within ±1.00 D, which showed high predictability of the ICL. This high predictability may also represent an advantage when using the ICL for piggyback insertion.
One of our concerns with ICL piggyback insertion was fixation of the ICL. After removing the crystalline lens, sufficient information is not available regarding fixation of the ICL in the posterior chamber. However, we were able to confirm stable positioning of the ICL during 6-month follow-up.
The determination of ICL size is an issue regarding use of this lens for pseudophakic eyes. Generally, an oversized ICL length results in high vault whereas an undersized ICL length results in low vault. In this study, six (75%) eyes showed high vaulting. Although vaulting was high, gonioscopic observation revealed that the angle was open, and no rise in intraocular pressure was observed. Size of the ICL was chosen based on horizontal white-to-white diameter and anterior chamber depth. Ultrasound biomicroscopy (UBM) has recently been used to directly measure ciliary sulcus diameter. Future application of UBM may overcome the problem regarding determination of ICL size. Generally, the anterior surface of an IOL is located further back in the eye than the anterior surface of the crystalline lens in a phakic situation. This could provide a greater margin of safety for high vault in pseudophakic eyes.
A slight decrease in endothelial cell density was noted during 6-month follow-up, and a minimum clinical effect on corneal endothelial cell was confirmed. Considering the risk of corneal endothelial cell loss in IOL exchange surgery, ICL implantation was considered safe.
One case of pupillary block occurred postoperatively, which we suspected was attributable to insufficient peripheral iridectomy. Although the posterior chamber is wide in the pseudophakic eye, the possibility of pupillary block remains. To avoid this complication, sufficient peripheral iridectomy or laser iridotomy should be performed before or during surgery.
In our small series of eyes, implantation of a toric ICL appears to be effective and predictable, but potential complications such as pupillary block mandate routine use of iridectomies. Further evaluation of differences in the efficacy and safety between ICL and conventional IOL piggyback insertion with a larger series of patients is warranted.
- Jin GJ, Merkley KH, Crandall AS, Jones YJ. Laser in situ keratomileusis versus lens-based surgery for correcting residual refractive error after cataract surgery. J Cataract Refract Surg. 2008;34(4):562–569. doi:10.1016/j.jcrs.2007.11.040 [CrossRef]
- Ayala MJ, Pérez-Santonja JJ, Artola A, Claramonte P, Alió JL. Laser in situ keratomileusis to correct residual myopia after cataract surgery. J Refract Surg. 2001;17(1):12–16.
- Zaldivar R, Oscherow S, Piezzi V. Bioptics in phakic and pseudophakic intraocular lens with the Nidek EC-5000 excimer laser. J Refract Surg. 2002;18(3 Suppl):S336–S339.
- Assetto V, Benedetti S, Pesando P. Collamer intraocular contact lens to correct high myopia. J Cataract Refract Surg. 1996;22(5):551–556.
- Lackner B, Pieh S, Schmidinger G, Simader C, Franz C, Dejaco-Ruhswurm I, Skorpik C. Long-term results of implantation of phakic posterior chamber intraocular lenses. J Cataract Refract Surg. 2004;30(11):2269–2276. doi:10.1016/j.jcrs.2004.07.018 [CrossRef]
- Akaishi L, Tzelikis PF, Gondim J, Vaz R. Primary piggyback implantation using the Tecnis ZM900 multifocal intraocular lens: case series. J Cataract Refract Surg. 2007;33(12):2067–2071. doi:10.1016/j.jcrs.2007.07.032 [CrossRef]
- Habot-Wilner Z, Sachs D, Cahane M, Alhalel A, Desatnik H, Schwalb E, Barequet IS. Refractive results with secondary piggyback implantation to correct pseudophakic refractive errors. J Cataract Refract Surg. 2005;31(11):2101–2103. doi:10.1016/j.jcrs.2005.05.023 [CrossRef]
- Ambrósio R Jr, Tervo T, Wilson SE. LASIK-associated dry eye and neurotrophic epitheliopathy: pathophysiology and strategies for prevention and treatment. J Refract Surg. 2008;24(4):396–407.
- Sanders DR, Schneider D, Martin R, Brown D, Dulaney D, Vukich J, Slade S, Schallhorn S. Toric Implantable Collamer Lens for moderate to high myopic astigmatism. Ophthalmology. 2007;114(1):54–61. doi:10.1016/j.ophtha.2006.08.049 [CrossRef]
Demographic Data of Five Patients (Eight Eyes) Who Underwent Piggyback Insertion of a Toric Implantable Collamer Lens
|Patient No.||Age (y)||Eye||WTW (mm)||ACD (mm)||ICL Length (mm)||Sphere (D)||Astigmatism (D)||CCT (μm)||Target Refraction (D)|
Postoperative Visual Acuity and Vault in Eight Eyes that Underwent Piggyback Insertion of an Implantable Collamer Lens
|Parameter||Preoperative||6 Months Postoperative|
|UDVA (logMAR)||0.759±0.430 (−1.398 to 0.155)||0.201±0.458 (−0.176 to 1.097)|
|Snellen UDVA||20/125 (20/500 to 20/13.3)||20/30 (20/250 to 20/13.3)|
|CDVA (logMAR)||0.058±0.290 (−0.176 to 0.699)||0.031±0.331 (−0.176 to 0.824)|
|Snellen CDVA||20/25 (20/28.5 to 20/13.3)||20/22 (20/133 to 20/13.3)|
|Manifest refractive sphere (D)||−3.06±3.75 (−9.00 to −0.50)||0.06±0.90 (−1.50 to ±0.50)|
|Manifest refractive astigmatism (D)||−2.63±0.76 (−4.00 to −1.75)||−0.72±0.65 (−1.75 to 0)|
|Change in CDVA (Snellen lines) (%, no. eyes)|
| −2||0 (0/8)|
| −1||12.5 (1/8)|
| No change||50 (4/8)|
| +1||12.5 (1/8)|
| +2||25 (2/8)|
| <1/2 CT (low)||0 (0/8)|
| ≥1/2 CT and ≤3/2 CT (moderate)||25 (2/8)|
| >1.5 CT (high)||75 (6/8)|