Toric IOL Implantation and Astigmatic Correction
Recently, my colleagues and I investigated the efficacy of the MicroSil Toric IOL (MicroSil Toric 6116 TU; HumanOptics AG, Erlangen, Germany; Figure 1) in the correction of preoperative astigmatism and rotational stability.
The MicroSil IOL has a 6-mm silicon optic and specially designed PMMA haptics that prevent IOL rotation in the posterior capsule. The lens has a spherical anterior surface and a toric posterior surface. The mean diameter of 11.6 mm. Additionally, it is available in lens powers ranging from -28.00 to 31.00 D, with up to 30.00 D of astigmatism.
MATERIALS AND METHODS
Our retrospective evaluation included 22 eyes (17 patients) that underwent surgery for cataract and high refractive error (ametropia and regular astigmatism over 3.00 diopters of cylinder [Dcyl]). All eyes were operated on at Charles University between September 2004 and October 2006. Of the eyes, 11 (11 patients) had astigmatism following penetrating keratoplasty (PK), and 11 eyes (6 patients) had no previous surgery. Additionally, a cataract was found in one patient after a penetrating injury that required PK and iridoplasty.
The mean time between PK and cataract surgery was 4.8 ±3.6 years. Approximately 41% of patients were male and 59% were female, with a mean age of 51.5 ±6.8 years at the time of the operation (range, 39–66 years).
Patients had to be astigmatically stability to participate in the evaluation and confirmed this by using a topographer and an autorefractor. We then determined IOL power by using keratometry (K1, K2) and measuring the anterior chamber depth, axial length of the eye, and subjective and objective refraction, in cooperation with the manufacturer.
INTERVENTION
For the examination, we used the Keratron 179 AR corneal topographer (Optikon 2000; Rome), the autorefractor AR-600 (Nidek Company, Ltd., Gamagori, Japan), the IOLMaster (Carl Zeiss Meditec AG, Jena, Germany), and ultrasonic biometry by Storz CompuScan LT (Bausch & Lomb, Rochester, New York). Visual acuity was determined using the Snellen projector optotypes CP–670 (Nidek Company, Ltd.). Endothelial cell count was measured with the Noncon Robo SP–900 noncontact endothelial microscope (Konan Medical Inc., Torrance, California).
The primary indication for surgical intervention was cataract combined with astigmatism over 3.00 Dcyl, and mean follow-up was 13.2 months (range, 5–28 months).
SURGICAL TECHNIQUE
The angle of IOL implantation was marked at the limbus on the slit lamp prior to surgery, while the patient was sitting. Standard phacoemulsification was then performed under topical anaesthesia. The capsulorrhexis was approximately 5.5 mm. Next, the 3.2-mm incision was enlarged by 0.3 mm, and a folded IOL was introduced into the capsular bag. The IOL was then rotated into position, and the marks on the IOL optic were aligned with previously marked angle of astigmatism on the limbus (Figure 2).
FOLLOW-UP
All patients underwent regular postoperative follow-up at our clinic. During this time, we assessed refraction, UCVA, BCVA, IOL position, the state of the corneal transplant (in the case of PK), and the subjective satisfaction of the patient.
We found a change in spherical refraction in all operated eyes, displayed as a reduction from the mean preoperative value of 3.40 ±5.00 D (range, -11.00–10.00 D) to 0.64 ±0.80 D (range, -1.50–2.00 D) postoperative (Figure 3).
Astigmatism changed from -6.50 ±3.30 Dcyl (range, -3.00 to -12.00 Dcyl) preoperatively, to -1.70 ±0.67 Dcyl (range, -0.25 to -3.00 Dcyl) postoperatively (Figure 4).
We did not perform additional procedures (eg, PRK, LASIK, keratectomy) to correct refractive error in any case. We also noted an improvement in BCVA from 0.35 ±0.25 to 0.58 ±0.26 postoperatively. The mean UCVA value increase was 0.53 ±0.26 compared with a preoperative value of 0.10 ±0.15 (Figure 5).
We found that the preoperative mean endothelial cell count was 1641 ±342 mm² (range, 892–2456 mm²). Mean endotheial cell count reduction was 6.2% after 3 months (22 eyes), 3.1% after 6 months (20 eyes), and 1.8% after 12 months (16 eyes) (Figure 6).
INTRA- AND POSTOPERATIVE COMPLICATIONS
Intraoperative complications included rupture of the posterior capsule in one eye, and one other eye experienced loosening of the zonule of the lens. In both cases, the intraoperative situation allowed for implantation, maintenance of the IOL in the lens bag, and correct positioning.
Postoperatively, we repositioned IOLs in two patients (two eyes) due to a lens decentration of 10° or more. This supplemental procedure was done between postoperative weeks 4 and 6. At follow-up, we also noted the development of secondary cataract in two patients (two eyes), which required Nd:YAG capsulotomy. Laser treatment of the posterior capsule was performed at 9 and 11 months postoperatively. This treatment did not have any effect on the position of the IOL in the posterior capsule, and an improvement of visual acuity was also noted.
Decompensation of the corneal transplant occurred in one patient (one eye) after penetration injury, PK, and iridoplasty. Other postoperative complications such as secondary glaucoma, postoperative inflammation, hyphema, or retinal complications were not recorded in the study group.
DISCUSSION
Various authors have described implantation of toric IOLs in eyes with cataract and a preexisting hypermetropic or myopic astigmatism as well as astigmatism associated with previous keratoplasty.1-5
We used a MicroSil Toric IOL for the treatment of unsatisfactory ametropia and cataract in eyes after PK and in eyes with cataract and a preexisting myopic or hyperopic astigmatism. A good outcome requires using this technique for the correct indications (ie, regular astigmatism of more than 3.00 Dcyl in the central 3-mm zone of the cornea), a delicate phacoemulsification technique, and proper IOL centration. Use of this implant in irregular astigmatism is not indicated. Additionally, price can be a barrier for more frequent use of this technique.
CONCLUSIONS
The results of our study showed that the use of a toric silicone IOL is an effective and safe method of treating even high combined refractive errors and cataract in one session. Careful and accurate implantation of toric IOL is a necessary for a success outcome.
Pavel Rozsíval, MD, is from the Department of Ophthalmology, Charles University, Hradec Králové, Czech Republic. Dr. Rozsíval states that he has no financial interest in the products or companies mentioned. He may be reached at rozsival@lfhk.cuni.cz.
Juraj Urminsky, MD, is from the Department of Ophthalmology, Charles University, Hradec Králové, Czech Republic. Dr. Urminsky states that he has no financial interest in the products or companies mentioned. He may be reached at urminsky@seznam.cz.
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