Purpose
To compare the longitudinal vault changes after implantation of a posterior chamber phakic intraocular lens (pIOL) (Visian implantable contact lens) with (ICL V4c) and without (ICL V4) a central artificial hole for moderate to high myopia in Chinese eyes.
Design
Retrospective case series.
Methods
This study comprised 78 eyes implanted with the ICL V4c model and 82 eyes implanted with the ICL V4 model at our department by the same surgeon. The time course of the postoperative pIOL vault changes was quantitatively assessed using ultrasound biomicroscopy over 6 months.
Results
There was a trend toward a decrease in all measures of central vault, peripheral vault, and the endothelium–anterior pIOL distance for both central hole pIOL and conventional pIOL over time, although the variance was not statistically significant (all P > .05). There were no significant between-group differences in the amount of the pIOL central vault, peripheral vault, or the endothelium–anterior pIOL distance at any time point after surgery (all P > .05).
Conclusions
The time course of the central hole pIOL vault changes is essentially equivalent to that of the conventional pIOL vault, suggesting that the presence of the central hole did not significantly affect the pIOL position.
The Visian implantable contact lens (ICL; Staar Surgical, Monrovia, California, USA) is a posterior chamber phakic intraocular lens (pIOL) manufactured by Staar Surgical Company. Various studies including United States Food and Drug Administration trials have reported that ICL implantation is safe and efficacious. However, there are still some potential complications, such as cataract formation, pupillary block, and corneal endothelial decompensation. Of these complications, anterior subcapsular opacities and clinically relevant cataract remain the most significant concerns about ICL implantation. The main theories of the cause of this cataract development are the absent or lower vault and the tendency of the vault to decrease over time, causing constant or intermittent contact between the ICL and crystalline lens. Eyes with insufficient central or peripheral vault (distance between posterior surface of the pIOL and anterior surface of the crystalline lens) were more predisposed to cataract formation. Furthermore, a pIOL is more likely to come in contact with the crystalline lens in the peripheral area as a result of the pIOL’s design, which tends to be thicker at the optic–haptic junction.
Recently the latest model, the V4c, with an artificial hole of 0.36 mm located in the center of the optic, was developed. Considering that the presence of the central artificial hole induces a change in the aqueous humor dynamics, the central hole may affect the amount of pIOL vault. To demonstrate the safety of the new ICL design, it was important to determine if vault values were comparable with the classical ICL model. According to our literature review, there have been no reports of comparison of the vault changes after the pIOLs with and without an artificial hole implantation over time in Han Chinese eyes.
Ultrasound biomicroscopy (UBM) is the most ideal method for visualizing peripheral vault because anterior segment optical coherence tomography and other optical devices are not able to penetrate the iris pigment epithelium; thus, they cannot evaluate the structures behind the iris. In this study, we use UBM to compare the longitudinal position changes after implantation of a posterior chamber phakic intraocular lens with and without a central artificial hole for moderate to high myopia in Chinese eyes.
Methods
This retrospective study included 78 eyes of 39 patients implanted with the Visian ICL V4c model and 82 eyes of 41 patients implanted with the Visian ICL V4 model for the correction of moderate to high myopia at the Department of Ophthalmology, First Affiliated Hospital, College of Medicine, Zhejiang University, China from January 2013 to July 2015. All patients provided written informed consent after the nature and possible consequences of the study were explained fully, in accordance with the Declaration of Helsinki. The study was approved by the ethics committee of the First Affiliated Hospital, Medical College, Zhejiang University, China. The inclusion criteria for pIOL implantation were age between 21 and 45 years, stable refraction, a clear central cornea. Exclusion criteria were keratoconus, previous refractive surgery, glaucoma, cataract, uveitis, history of retinal detachment, anterior chamber depth (ACD) less than 2.8 mm, and endothelial cell density (ECD) less than 2000 cell/mm 2 .
Preoperative Examination
Before surgery, patients had a complete ophthalmologic examination including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest and cycloplegic refractions, keratometry (Canon, Tokyo, Japan), corneal topography (Atlas, Dublin, California, USA), pachymetry (Tomey, Aichi-ken, Japan), the horizontal white-to-white (WTW) distance, and the ACD using scanning-slit corneal topography (Orbscan II, Bausch & Lomb, New York, New York, USA); UBM (Tianjin Suowei Electronic Technology Co Ltd, Tianjin, China) for observing the anterior chamber angle and measuring the sulcus diameter; endothelial cell count (ECC) (Topcon, Tokyo, Japan); A-scan ultrasonography (Aviso, Quantel Medical, France); slit-lamp microscopy (Haag-streit BM 900, Koeniz, Switzerland); tonometry (Tomey, Aichi-ken, Japan); and dilated indirect funduscopy (Volk Optical Inc., Mentor, OH, USA).
Intraocular Lens
The Visian implantable contact lenses (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. A central hole of 0.36 mm, the KSAquaPORT (Staar), defines the new design of the V4c pIOL, whereas the conventional V4 does not have the central artificial hole. The postoperative targeted refraction was emmetropia in all cases. Power calculation for the pIOL was performed using the software provided by the pIOL manufacturer and a modified vertex formula. The pIOL diameter was individually determined based on the horizontal WTW distance and the ACD measured with the scanning-slit corneal topography system following the manufacturer’s recommendations. We calculated the size on the website at https://ocos.staarag.ch/landing . The software is version 4.06 for ICL V4c and version 4.05 for ICL V4.
Surgical Technique
Preoperative peripheral neodymium—yttrium-aluminum-garnet laser iridectomy was performed for all the patients in the ICL V4 group but was not performed for the patients in the ICL V4c group.
All surgeries were performed by the same surgeon (Y.S.). Before surgery, the patients were administered dilating and cycloplegic agents. After peribulbar anesthesia, the pIOL was inserted through a 3.0-mm clear corneal incision with the use of an injector cartridge (STAAR Surgical Co) after the anterior chamber was filled with sodium hyaluronate viscoelastic (Provisc; Alcon Laboratories, Inc). Centration was ensured before pupillar constriction caused by acetylcholine injection into the anterior chamber. Remaining viscoelastic in the anterior chamber and under the ICL was removed with gentle irrigation and aspiraton. After surgery, tobramycin–dexamethasone (Tobradex; Alcon, USA) and levofloxacin (Cravit; Santen, Osaka, Japan) medications were prescribed topically 4 times daily for 7 days, the dose being reduced gradually thereafter.
Outcome Assessment
Postoperative examinations were scheduled at 1 day, 1 week, and 1, 3, and 6 months. The evaluations included UDVA, CDVA, manifest refraction, tonometry, ECC, slit-lamp microscopy, and funduscopy. Ultrasound biomicroscopy was performed by the same examiner (Y.W.) using the SW-3200L full-scale 50 MHz digital system (Tianjin Suowei Electronic Technology Co Ltd), as described in our previous study. Three parameters—endothelium–anterior pIOL distance (distance from corneal endothelium to implantable contact lens), central vault (central distance from implantable contact lens to crystalline lens), and peripheral vault (peripheral distance from implantable contact lens to crystalline lens)—were obtained from each examination with the calipers provided by the manufacturer.
Statistical Analysis
Statistical analysis was performed using SPSS software (version 22.0; SPSS, Inc). Descriptive statistics were obtained. Visual acuity data were converted to logMAR values. Normality of data was checked by the Kolmogorov-Smirnov test. The difference between the 2 groups’ outcomes was estimated by the independent samples t test, and in those cases with data that were not normally distributed, the Mann-Whitney U test was performed. One-way analysis of variance was used to evaluate the position changes over time in each group. Unless otherwise indicated, the results are expressed as mean ± SD, and differences with a P value less than .05 were considered statistically significant.
Results
Table 1 shows the patients’ baseline demographic data and the pIOL characteristics. We found no significant differences in terms of patient age, manifest spherical equivalent, manifest cylinder, or logMAR CDVA. All the patients had uneventful surgery, returned regularly for postoperative examination, and completed a 6-month follow-up. There were no perioperative complications, and no eye required pIOL explantation or repositioning. No pigmentary glaucoma, pupillary block, cataract, or other vision-threatening complications occurred during the follow-up.
| Parameter | ICL V4c | ICL V4 | P Value |
|---|---|---|---|
| Patients | |||
| Number of eyes | 78 | 82 | |
| Age (y) | 29.1 ± 8.3 | 31.9 ± 7.2 | .419 |
| Range | 21, 44 | 21, 44 | |
| Sex | |||
| Male | 21/39 (54%) | 18/41 (44%) | |
| Female | 18/39 (46%) | 23/41 (56%) | |
| Manifest refraction (D) | |||
| Sphere equivalent | −12.55 ± 2.98 | −13.34 ± 3.79 | .086 |
| Range | −17.50, −5.75 | −18.25, −6.50 | |
| Cylinder | 0.80 ± 0.62 | 0.95 ± 0.79 | .488 |
| Range | 0.00, 2.75 | 0.00, 2.75 | |
| CDVA (logMAR) | 0.168 ± 0.121 | 0.137 ± 0.130 | .233 |
| Range | 0.000, 0.301 | 0.000, 0.301 | |
| ECC (cells/mm 2 ) | 2687 ± 319 | 2734 ± 370 | .525 |
| Range | 2003, 3315 | 2054, 3761 | |
| WTW distance (mm) | 11.4 ± 0.4 | 11.4 ± 0.3 | .445 |
| Range | 10.6, 12.5 | 11.0, 12.1 | |
| IOP (mm Hg) | 15.5 ± 1.9 | 15.0 ± 2.5 | .302 |
| Range | 11, 20 | 10, 20 |
Refractive and Visual Outcomes
Table 2 shows the 6-months-postoperative clinical outcomes for both groups. There was a statistically significant improvement between the preoperative and 6-months-postoperative logMAR UDVA for the ICL V4c group ( P < .001) and ICL V4 group ( P < .001). All eyes had a decimal UDVA of 0.5 (20/40) or better at every follow-up visit in both groups. There was a statistically significant improvement between the preoperative and 6-months-postoperative logMAR CDVA for the ICL V4c group ( P < .001) and ICL V4 group ( P < .001). No eye lost 1 line or more in either group. Both groups separately showed significant differences in manifest refractive spherical equivalent preoperatively and 6 months postoperatively (ICL V4c group, P < .001; ICL V4 group, P < .001). There were no significant differences between preoperative and 6-months-postoperative IOP for both groups (ICL V4c group, P = .083; ICL V4 group, P = .512). There was a trend toward a decrease in the endothelial cell density within each group over time; however, comparisons showed no significant differences between preoperatively and 6 months postoperatively (ICL V4c group, P = .676; ICL V4 group, P = .773). There were no significant differences between groups in terms of UCVA, CDVA, manifest refractive spherical equivalent, IOP, or ECD 6 months postoperatively ( P > .05, for all comparisons).
| Parameter | ICL V4c | ICL V4 | P Value |
|---|---|---|---|
| MRSE (D) | –0.07 ± 0.29 | −0.07 ± 0.47 | .770 |
| Range | −0.625, 0.375 | −1.00, 0.75 | |
| UDVA (logMAR) | 0.136 ± 0.104 | 0.100 ± 0.106 | .082 |
| Range | 0.000, 0.301 | 0.000, 0.301 | |
| CDVA (logMAR) | 0.055 ± 0.065 | 0.049 ± 0.095 | .135 |
| Range | −0.792, 0.222 | −0.792, 0.301 | |
| ECC (cells/mm 2 ) | 2633 ± 310 | 2692 ± 341 | .208 |
| Range | 1963, 3248 | 1913, 3586 | |
| IOP (mm Hg) | 14.9 ± 2.0 | 14.7 ± 2.4 | .927 |
| Range | 11, 20 | 10, 20 |
Endothelium–Anterior Phakic Intraocular Lens Distance
Table 3 and Figure 1 show the mean values and ranges of the postoperative endothelium–anterior pIOL distance over time in both groups. There was a trend toward a decrease in the endothelium–anterior pIOL distance whithin each group over time; however, multiple comparisons showed no significant differences between any 2 periods (ICL V4c group, P = .676; ICL V4 group, P = .773). The differences in the endothelium–anterior pIOL distance between the 2 groups were not statistically significant at any time point after surgery (all P > .05).
| ICL V4c | ICL V4 | P Value | |
|---|---|---|---|
| Endothelium–pIOL distance (mm) | |||
| 1 month | 2.307 ± 0.284 | 2.210 ± 0.329 | .124 |
| Range | 1.540, 2.920 | 1.480, 2.780 | |
| 3 months | 2.281 ± 0.281 | 2.186 ± 0.322 | .157 |
| Range | 1.480, 2.900 | 1.470, 2.770 | |
| 6 months | 2.268 ± 0.281 | 2.175 ± 0.295 | .119 |
| Range | 1.450, 2.800 | 1.410, 2.640 | |
| Central vault (μm) | |||
| 1 month | 558.5 ± 267.4 | 551.6 ± 293.5 | .773 |
| Range | 150, 1080 | 110, 1090 | |
| 3 months | 512.3 ± 254.8 | 526.4 ± 287.1 | .856 |
| Range | 120, 1000 | 110, 1060 | |
| 6 months | 499.7 ± 244.3 | 495.0 ± 279.1 | .803 |
| Range | 120, 980 | 100, 990 | |
| Peripheral vault (μm) | |||
| 1 month | 306.0 ± 181.1 | 313.3 ± 237.1 | .598 |
| Range | 45, 980 | 38, 955 | |
| 3 months | 287.1 ± 176.3 | 297.9 ± 232.0 | .667 |
| Range | 53, 950 | 40, 910 | |
| 6 months | 261.4 ± 171.2 | 256.3 ± 210.6 | .690 |
| Range | 43, 905 | 40, 853 |
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