Purpose
To compare the outcomes between implantable collamer lenses (ICLs), 1 with and 1 without a central artificial hole.
Design
Comparative study.
Methods
We included 65 eyes of 65 patients with refractive error in our study. The mean manifest refraction spherical equivalent (MRSE) was −9.32 ± 4.02 diopters (range, 6.75 to −16.50 diopters). We divided patients into 2 groups based on the type of ICL used, 1 for those without a central artificial hole (Group I, 21 eyes) and 1 for those with a hole (Group II, 44 eyes). The postoperative changes in visual acuity, endothelial cell density, MRSE, higher order aberrations readings, and objective scatter index between the 2 kinds of ICLs were compared. The follow-up period was 3 months.
Results
There were no statistically significant differences in the postoperative changes in uncorrected distance visual acuity ( P = 0.81), corrected distance visual acuity ( P = 0.24), MRSE ( P = 0.18), and endothelial cell density ( P = 0.76) between the groups. Also, no difference in objective scatter index was found at 3 months ( P = 0.32). None of the higher order aberrations readings showed any significant difference between the groups.
Conclusion
There were no significant differences between the outcomes of these ICLs, either with or without a central artificial hole.
Posterior chamber phakic intraocular lens (pIOL) implantation helps highly myopic patients improve their vision and quality of life by freeing them from their glasses and contact lenses. The Visian implantable collamer lens (ICL; Staar Surgical, Monrovia, CA), a posterior chamber pIOL, has been reported to be effective for the correction of moderate to high ametropia and is designed to be placed in the posterior chamber, behind the iris, with a haptic zone resting on the ciliary sulcus. Postoperative complications have been described. An increase in intraocular pressure (IOP), usually associated with acute pupillary block or with chronic pigment dispersion, is related to inadequate preoperative or intraoperative iridectomies and is also due to the mechanical contact between the pIOL and the iris in eyes with excessive pIOL vault. The Staar pIOL models have undergone successive improvements to minimize these disadvantages. The model V4c pIOL is the latest model and is designed with a 0.36 mm central hole to overcome these disadvantages.
The purpose of our present study was to assess the outcomes of 2 groups of patients who had the ICLs implanted: 1 group who had ICLs without a hole and the other who had ICLs with a central artificial hole.
Patients and Methods
It was a comparative retrospective study. The study conformed to the ethics codes established by the Ethical Board Committee of Japan. The study was carried out with approval from the Institutional Review Board (Matsumoto Clinic, Tokyo, Japan), and all patients signed consent forms. The study comprised 65 eyes of 65 patients with refractive errors who had implantation of a posterior chamber ICL, model V4b (conventional ICL), or V4c (Hole ICL). There were 2 groups, based on the model of lens that was implanted during surgery: group I (conventional ICL implantation, 21 eyes of 21 patients) and group II (Hole ICL implantation, 44 eyes of 44 patients). Inclusion criteria were refractive error in the range that is correctable using V4b (preoperative spherical equivalent between + 10.50 diopters (D) and −18.00 D) and V4c pIOL (preoperative spherical equivalent between −0.50 D and −18.00 D), corrected distance visual acuity (CDVA) of 20/40 or better, stable refraction, no previous ocular pathology, and a clear central cornea. Exclusion criteria included previous corneal refractive surgery, anterior chamber depth from the endothelium of less than 2.8 mm, corneal endothelial cell density (ECD) less than 2,000 cell/mm 2 , and any cataract, history of glaucoma, amblyopia, retinal detachment, diabetic retinopathy, macular degeneration, neuro-ophthalmic disease, or history of ocular inflammation.
All patients had rigorous ophthalmologic examinations, including uncorrected distance visual acuity (UDVA); CDVA; manifest and cycloplegic refractions; slit-lamp evaluation (Carl Zeiss Meditec, Dublin, CA); tonometry (noncontact tonometer, Topcon, Oakland, NJ); keratometry (ARK-530A; Nidek Medical Products, Birmingham, AL); corneal pachymetry (Contact-Pachymeter SP-3000; Tomey, Nagoya, Japan); topography (TMS-4; Tomey); ECD, specular microscope (Noncon Robo FA3609; Konan Medical, Hyogo, Japan); objective scatter index (OSI) (OQAS; Visiometrics, Barcelona, Spain); corneal aberration measurement (Wavefront Analyzer, Topcon); and binocular dilated fundus examinations. Our follow-up period was 3 months.
Assessment of ocular higher-order aberrations
Wavefront aberrations were assessed before and 3 months after surgery. Ocular and corneal high-order aberrations for a 4-mm and 6-mm pupil were measured. The root mean square (RMS) of the third-order Zernike coefficients (S3) was used to represent coma-like aberrations, and the RMS of the fourth-order coefficient (S4) to represent spherical-like aberrations. Total high-order aberrations were calculated as the RMS of the third- and fourth-order coefficients for both pupil sizes.
Intraocular lens
The Visian implantable collamer lens posterior chamber pIOLs (both with and without a central artificial hole) are made from collamer, a biocompatible hydrophilic copolymer and hydroxyethyl methacrylate with an ultraviolet light-filtering chromophore. These lenses are designed to correct refractive errors. They have a plate-haptic design with a central convex-concave optical zone and incorporate forward vault to minimize any contact of the pIOL with the central anterior capsule of the crystalline lens. A central hole of 0.36 mm, the KS-AquaPORT (Staar), defines the new design of the V4c pIOL, whereas the conventional V4b does not have the central artificial hole. This hole allows more natural flow of the aqueous humor (CentraFLOW Technology, Staar), eliminating the need to perform preoperative or intraoperative iridectomy.
Surgical Technique
All surgeries were performed at the Shinagawa LASIK Center, Tokyo, Japan. At 60 minutes before surgery, tropicamide and phenylephrine eyedrops were instilled; at 5 minutes before surgery, povidone-iodine 5% (betadine) was applied. The surgical procedure was performed through a single-plane 3.0- to 3.2-mm corneal incision centered at the steepest meridian using topical anesthesia. The anterior chamber was filled with hydroxypropyl methylcellulose (2%, such as OcuCoat Viscoelastic (Bausch + Lomb, Rochester, New York, USA), which was completely removed at the end of the surgery. The pIOL was inserted with the use of an injector cartridge (Staar). By irrigation/aspiration (Infiniti; Alcon, Sinking Spring, PA) the hydroxypropyl methylcellulose was washed out and 1.0% acethylcholine chloride solution (Obisot, Dai-ich Seiyaku, Kyoto, Japan) was injected to the anterior chamber.
Preoperative peripheral Nd:YAG laser iridectomy was performed for all the patients in Group I (conventional ICL) but was not performed for the patients of Group II (ICL with a hole).
Postoperative topical therapy included an antibiotic (moxifloxacin [Vigamox], Alcon), dexamethasone 0.1%, and diclofenac sodium eyedrops every hour the day of surgery, then 5 times a day for 1 week. After 1 week the dexamethasone 0.1% was replaced with fluorometholone 0.1% eyedrops, and all eyedrops were prescribed 4 times daily for 1 month.
Surgical Technique
All surgeries were performed at the Shinagawa LASIK Center, Tokyo, Japan. At 60 minutes before surgery, tropicamide and phenylephrine eyedrops were instilled; at 5 minutes before surgery, povidone-iodine 5% (betadine) was applied. The surgical procedure was performed through a single-plane 3.0- to 3.2-mm corneal incision centered at the steepest meridian using topical anesthesia. The anterior chamber was filled with hydroxypropyl methylcellulose (2%, such as OcuCoat Viscoelastic (Bausch + Lomb, Rochester, New York, USA), which was completely removed at the end of the surgery. The pIOL was inserted with the use of an injector cartridge (Staar). By irrigation/aspiration (Infiniti; Alcon, Sinking Spring, PA) the hydroxypropyl methylcellulose was washed out and 1.0% acethylcholine chloride solution (Obisot, Dai-ich Seiyaku, Kyoto, Japan) was injected to the anterior chamber.
Preoperative peripheral Nd:YAG laser iridectomy was performed for all the patients in Group I (conventional ICL) but was not performed for the patients of Group II (ICL with a hole).
Postoperative topical therapy included an antibiotic (moxifloxacin [Vigamox], Alcon), dexamethasone 0.1%, and diclofenac sodium eyedrops every hour the day of surgery, then 5 times a day for 1 week. After 1 week the dexamethasone 0.1% was replaced with fluorometholone 0.1% eyedrops, and all eyedrops were prescribed 4 times daily for 1 month.
Statistical Analysis
The results are expressed as mean ± standard deviation (SD). The normality of the data was tested by the Shapiro-Wilk test. A paired t test was performed to analyze the postoperative changes, but in those cases where the data was not distributed normally, a Wilcoxon rank sum test was performed using JMP statistical software (v 9, SAS Institute, Cary NC). The difference between the 2 methods’ outcomes was estimated by an unpaired t test and in those cases with data that was not normally distributed, the Mann-Whitney U test was performed. The level for statistical significance was set at P < 0.05.
Results
The patient demographics along with preoperative and postoperative parameters for both groups are presented in Table 1 .
| Demographic | Groups | P value | |
|---|---|---|---|
| Group I (Conventional ICL) | Group II (Hole ICL) | ||
| n | 21 | 44 | |
| Age, years | 35 ± 5.6 (27 to 44) | 35 ± 9.4 (18 to 55) | |
| MRSE, D | |||
| Preop | −9.51 ± 4.65 (6.75 to −17.00) | −10.05 ± 2.72 (−2.75 to−16.38) | |
| 3 M | 1.50 ± 0.20 (0.75 to 1.75) | 0.19 ± 0.40 (1.13 to −0.75) | |
| Δ | 11.01 ± 4.80 ∗ | 10.24 ± 2.76 ∗ | 0.18 |
| OSI | |||
| Preop | 1.24 ± 1.21 (0.30 to 5.30) | 1.03 ± 0.66 (0.30 to 3.60) | |
| 3 M | 0.86 ± 0.52 (0.20 to 2.10) | 1.08 ± 0.80 (0.30 to 3.50) | |
| Δ | −0.38 ± 1.11 | 0.05 ± 0.70 | 0.32 |
| ECD | |||
| Preop | 2812 ± 248 (2114 to 3135) | 2879 ± 343 (1859 to 3472) | |
| 3 M | 2812 ± 303 (2183 to 3344) | 2911 ± 318 (2165 to 3497) | |
| Δ | 12.00 ± 253.92 | 32.35 ± 242.19 | 0.76 |
| UDVA (logMAR) | |||
| Preop | 1.46 ± 0.27 (0.52 to 2.00) | 1.49 ± 0.21 (2.00 to 0.01) | |
| 3 M | −0.13 ± 0.10 (0.15 to −0.18) | −0.13 ± 0.08 (0.10 to −0.30) | |
| Δ | 1.32 ± 0.28 ∗ | 1.35 ± 0.23 ∗ | 0.82 |
| CDVA (logMAR) | |||
| Preop | −0.12 ± 0.09 (0.15 to −0.18) | −0.12 ± 0.08 (0.22 to −0.18) | |
| 3 M | −0.16 ± 0.07 (0.15 to −0.18) | −0.18 ± 0.04 (−0.30 to −0.08) | |
| Δ | 0.10 ± 0.16 ∗ | 0.18 ± 0.22 ∗ | 0.24 |
The mean UDVA by LogMAR for both groups is shown in Figure 1 (Top). There was a statistically significant improvement between the preoperative and 3-month postoperative logarithm of the minimum angle of resolution (logMAR) UDVA for Group I ( P < 0.0001), and Group II ( P < 0.0001). The efficacy index at 3 months was 1.01 (for Group I) and 1.03 (for Group II). There was no significant difference between groups in UDVA and CDVA at the 3-month follow-up ( Table 1 ; Figure 2 ). Figure 3 shows the achieved spherical equivalent for both groups. Both groups separately showed significant differences in manifest refractive spherical equivalent pre- and postoperatively (Group I, P < 0.0001; Group II; P < 0.0001); however, there was no difference in MRSE between the 2 groups ( Table 1 ). The mean CDVA by logMAR for both groups is shown in Figure 1 (Bottom). There was a statistically significant difference between the preoperative and 3-month postoperative logMAR CDVA for Group I ( P = 0.0005) and Group II ( P < 0.0001). No eye lost 1 line or more in either group ( Figure 4 ). The safety index at 3 months was 1.07 (for Group I) and 1.14 (for Group II).
