The surgical correction of refractive error has been a challenge since refractive keratectomy was first offered by Barraquer.1 Several surgical methods have been developed for the correction of the refractive error. LASIK, introduced by Pallikaris et al.,2 is the most widely used method for correction of myopia, hyperopia, astigmatism, and mixed refractive errors. Several studies have evaluated the stability and predictability of the procedure. The inclusion criteria for the refractive error were 15.00 diopters (D)3 for myopia, 6.00 D for astigmatism,4 and 7.00 D for hyperopia.5 Although limits of correction were described as high in the first studies, the outcomes of the latest studies revealed much lower limitations regarding to the evaluation of residual corneal thickness and keratometry readings. Nowadays, surgeons do not prefer such high correction of refractive error with LASIK.2,5–11 Nevertheless, LASIK is still the most commonly used surgical treatment for myopia. However, correction of hyperopia by LASIK is less common due to more limited inclusion criteria than for myopia. Methods such as phakic intraocular lens implantation and refractive lens exchange were preferred due to extended limitations of correction of patients with high hyperopia. Sanders et al.12,13 and Rayner et al.14 showed that Implantable Collamer Lenses (ICLs) are good alternatives for correction of refractive error either below or above the limits of LASIK. The first generation of myopic/myopic toric ICLs revealed good stability, predictability, and refractive outcomes.15–18 However, the demand for ICLs was higher for patients with high diopter hyperopia due to the limitations of LASIK, which was mentioned before. Hyperopic ICL studies also showed good results.14,19–21 However, there were not many studies enrolled for hyperopic toric ICLs. This study aims to present the outcomes of the implantation of hyperopic toric ICLs.22
Patients and Methods
This retrospective study comprised 20 eyes of 11 hyperopic patients (Table 1) with astigmatism between 2014 and 2015 at Dunyagoz Etiler Hospital, Istanbul, Turkey with 1 year of follow-up.
Preoperative ophthalmic examinations consisted of detailed medical history, manifest and cycloplegic refractions, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), anterior segment evaluation with a slit-lamp biomicroscopy, and detailed fundus examination. Furthermore, Orbscan (Bausch & Lomb, Rochester, NY) was used for corneal topographic, horizontal white-to-white (WTW) distance, and anterior chamber depth (ACD) measurements. Endothelial cell count was measured by the SP 3000P specular microscope (Topcon Corporation, Tokyo, Japan). Pentacam (Oculus Optikgeräte, Wetzlar, Germany) was used for measuring corneal thickness.
The inclusion criteria of the study were age older than 21 years, stable refraction for at least 1 year, endothelial cell count of greater than 2,400 endothelial cells/mm2, iridocorneal angle greater than 30°, no anomaly of iris or pupil function, mesopic pupil size smaller than 5 to 6 mm, and ACD greater than 3 mm. Furthermore, patients with unstable hyperopia or astigmatism, active corneal disease, irregular cornea on corneal topography, lens opacities, recurrent or chronic uveitis, glaucoma, ocular hypertension, abnormal retinal condition, previous corneal or intraocular surgery, history of ocular trauma, systemic diseases (eg, autoimmune disorder, connective tissue disease, atopia, or diabetes mellitus), and age younger than 21 years were excluded.
The STAAR Surgical Customer Service Department formula was used to calculate the ICL power. This formula uses horizontal WTW distance (determined by the results of Orbscan), central corneal thickness, mean corneal keratometry reading or central corneal thickness (simulated keratometry), refraction 12 mm from the corneal vertex or with a contact lens, and ACD calculated from the endothelium of the cornea.
Although it was proposed to perform Nd:YAG laser peripheral iridotomies 2 weeks before, all were done 1 day before the ICL (Visian Toric ICL; STAAR Surgical, Monrovia, CA) implantation. By this approach, all remnants of iris particles could be easily washed at the time of surgery. Iridotomies were made in the upper quadrant, 0.5 to 1 mm from the limbus, at the 11- and 1-o'clock positions to avoid the risk of monocular diplopia or ghost images. Pilocarpine 2% solution was instilled every 10 minutes starting 30 minutes before the laser procedure.
All surgeries were performed by the same surgeon (EC). The axis of all patients was marked at a slit lamp in the operating room while the patient was sitting upright to control for potential cyclotorsion when the patient was supine (the zero horizontal axis). The operations were performed under general anesthesia with the same disinfecting, draping, and eye stabilizing techniques of cataract surgery. Two side-port incisions were made and the cohesive ophthalmic viscosurgical device sodium hyaluronate 1.0% was injected. A 2.8-mm main incision was made on the temporal side to avoid additional astigmatism. The ICL was implanted through the tunnel by cartridge and footplates were inserted behind the iris in the correct position. The phakic intraocular lens (IOL) was rotated to the correct axis with a Mendez axis marker (Asico, Westmont, IL) as indicated by markings. The ophthalmic viscosurgical device was irrigated by cannula, acetylcholine chloride was injected into the anterior chamber, and stromal hydration of the incision edges were made. Acetazolamide was given at the second hour of the surgery. Intraocular pressure was measured 2 and 4 hours after the procedure to avoid the risk of glaucoma. Patients received dexamethasone and moxifloxacin four times a day.
Visante OCT (Carl Zeiss, Oberkochen, Germany) was used to measure the iridocorneal angle preoperatively and at 1 and 12 months by the same technician. TIA (trabecular–iris angle), TISA500 (trabecular–iris space area 500 mm from the scleral spur), and AOD500 (angle opening distance 500 mm from the scleral spur) were evaluated. Vault (the distance between anterior pole of the crystalline lens and posterior of ICL) was also measured by Visante OCT at 1 and 12 months postoperatively.
SPSS software (version 22; IBM Corporation, Armonk, NY) was used for the statistical analysis and interpretation of the data. Kolmogorov–Smirnov and Shapiro–Wilk tests for testing the normal distribution and Levene's test for testing the equality of variances were used. Furthermore, the two-tailed paired samples t test (for normally distributed data) and Wilcoxon signed-rank test (not normally distributed data) were applied for analyzing differences for the comparison of the results preoperatively and postoperatively.
Preoperative and 1-week and 1- and 12-month postoperative data are summarized on Table 2.
Preoperative and Postoperative Parameters in Eyes Undergoing ICL Implantation
The mean preoperative UDVA was 0.15 ± 0.11 (decimal) (20/133 Snellen) and the mean 12-month postoperative UDVA was 0.74 ± 0.25 (decimal) (20/27 Snellen). The mean UDVA change was 0.59 (decimal) (20/33.9 Snellen), which was statistically significant (P < .0001). Furthermore, the preoperative mean CDVA was 0.74 ± 0.25 (decimal) (20/27 Snellen) and the mean 12-month postoperative CDVA was 0.78 ± 0.21 (decimal) (20/25.5 Snellen). The change in the mean CDVA was 0.03 (decimal), which was not statistically significant (P < .052). Figure 1 shows the change between 12-month UDVA/CDVA and preoperative UDVA/CDVA.
Visual and refractive outcomes. UDVA = uncorrected distance visual acuity; CDVA = corrected distance visual acuity; D = diopters
The mean preoperative sphere was 6.86 ± 1.77 diopters (D) and the mean preoperative cylinder was −1.44 ± 0.88 D. The mean 12-month postoperative sphere decreased to 0.46 ± 0.89 D and the mean 12-month postoperative cylinder decreased to −0.61 ± 0.46 D. The change in spherical (6.40 D, P < .0001) and cylindrical (0.83 D, P < .001) refraction was statistically significant. The change in spherical equivalent refraction from preoperatively to postoperatively (Figure 1D) is shown in Table 2.
The predictability of the procedure was also analyzed and is shown in Figure 1C. The vertical axis represents the attempted change and the horizontal axis represents the achieved change in the refraction. The diagonal line represents the optimum cases for such desired and achieved corrections. Points below the diagonal line are the overcorrected cases and points above are the undercorrected cases for spherical equivalent. The green diagonal lines define the −0.50 to 0.50 D residual refraction band and the red diagonal lines define the −1.00 to 1.00 D residual refraction band.
The mean postoperative vault was 0.65 ± 0.13 mm at 1 month and 0.613 ± 0.10 mm at 12 months. The difference between the vault at 1 and 12 months postoperatively was statistically significant (0.04 mm, P < .003).
The analysis of preoperative/12-month and 1-month/12-month TIA, TISA500, and AOD500 values is shown nasally, temporally, and inferiorly in Table A (available in the online version of this article). All differences were statistically significant between preoperative/12-month analysis. The only differences between 1-month/12-month analysis were on TISA500 inferior (P < .002) and AOD500 nasal (0.031) values.
Iridocorneal Angle Values
Although several complications were reported intraoperatively and postoperatively in the literature,18,23–25 no complications were observed in our study during the 1-year follow-up period.
There was an increase of 0.75 mm Hg in the postoperative IOP. However, this was not statistically significant (P < .445). Furthermore, there was a change in endothelial cell density that was statistically significant (30 cells, P < .0001), but the difference was not clinically important.
Phakic hyperopic IOL implantation is also an alternative for phakic toric hyperopic IOLs. In Benda et al.'s21 study, 17% gained one line of CDVA, 17% lost one line of CDVA, and CDVA did not change in 66%. The correction of astigmatism may be the source of the difference between their results and ours. Additionally, residual astigmatism can be corrected by laser refractive surgery, astigmatic incision, and one or two opposite clear corneal incisions on the steep axis in hyperopic ICL implantations. Furthermore, the loss of one line that occurred in the amblyopic eyes can be explained by the elimination of the spectacle-induced magnification of the image.26
We used the ICL V4B hyperopic toric lens in this study; the full astigmatic correction was aimed for and no additional astigmatic correction was needed. Benda et al.21 used the ICL V3, which only corrects hyperopic errors. Thus, patients simultaneously underwent limbal relaxing incisions, photorefractive keratectomy, or LASIK after ICL implantation for the correction of the astigmatism.
In our study, Nd:YAG laser peripheral iridotomies were done 1 day before the ICL implantation and no side effects were observed. We believed that all iris particles remnants could be easily washed at the time of surgery, which could be an advantage. On the other hand, Benda et al.21 preferred to do Nd:YAG laser peripheral iridotomies 2 weeks before and Pesando et al.19 did 1 week before the surgery as advised by the manufacturer.
Outcomes of this study showed a reduction of 39% at nasal, 39.4% at temporal, and 37.7% at inferior for mean TIA values; 48.3% at nasal, 47.8% at temporal, and 47.6% at inferior for mean AOD500 values; and 43.9% at nasal, 46.2% at temporal, and 43.3% at inferior for mean TISA500 values when comparing preoperative and 1-year follow-up results.
Fernández-Vigo et al.27 implanted the ICL V4C, which had a central port for aqueous humor outflow for myopic patients and used Fourier-domain OCT. They had a reduction of 42% for mean TIA values, 58.4% for mean AOD500 values, and 59.2% for TISA500 values at 3 months postoperatively. Chung et al.28 implanted the ICL V4 and used ultrasound biomicroscopy. They observed a decrease in 31.7% for TIA and 41.4% for AOD500 values at 1 month postoperatively. Lim et al.29 also used ultrasound biomicroscopy and detected a decrease of 28.4% in TIA and 27.3% in AOD500 values after ICL V4B implantation. These studies did not find any difference between the 1- and 12-month results of angle parameters as we did. In the current study, differences were found in TISA500 inferior and AOD500 nasal values between the 1-month and 12-month results.
Fernández-Vigo et al.27 detected iridotrabecular contact in 16% of eyes, which did not exist before the surgery. In the current study, no iridotrabecular contact was observed.
Vault extent is an important factor for the complications after ICL implantation. Smaller vault is correlated with increased risk of cataract, whereas excessive vault may lead to angle closure, pupil block, and pigment dispersion associated with secondary glaucoma. The ICL has a convex shape in high hyperopic lenses and this convex shape rises when the diopter increases, which may be a risk for angle parameters and vault. However, the difference was not significant for these parameters in highly astigmatic cases when compared with other myopic studies.
Gonvers et al.30 recommended a vault value of greater than 150 μm, but Schmidinger et al.31 advocated 230 μm. In the current study, the minimum vault was 434 μm and the mean vault was 613 μm at 1 year of follow-up, which were within safety zones. Several authors2,9–11,17 also noted that vault decreased with time, which was in concordance with our similar reduction rates.
Endothelial cell loss is one of the complications of ICL implantation. Benda et al.,21 Pesando et al.,19 and Alfonso et al.20 found mean loss endothelial cell densities of 4.91%, 4.7%, and 4.7% respectively. Our endothelial cell density reduction rate was 1%, which may be due to the 1-year follow-up.
No lens rotation was observed during follow-up, similar to Fernández-Vigo et al.'s27 study.
Only one patient complained of halo and glare at every visit but he did not accept the removal of the ICL. He only had difficulties when driving at night.
New ICL designs have a central hole that enables aqueous humor flow to the anterior chamber and is also protective for cataract formation. Although hyperopic ICLs have no central hole and also have a convex shape, no cataract formation or complication related to the pressure was observed in 12 months of follow-up.
The recommended anterior chamber depth is 2.8 mm for ICL implantation. We found that patients with high or moderate hyperopia tend to have an ACD less than 3 mm. Although it was difficult, we enrolled 20 hyperopic eyes with an ACD greater than 3 mm (mean: 3.08 ± 0.14 mm) in this study. We believed that it was safer for angle parameters. Benda et al.21 and Alfonso et al.20 reported ACD values of 2.96 ± 0.27 and 3.16 ± 0.22 mm, respectively.
The positive outcomes are closely related to the indication criteria and patient selection. We believe that if ACD depth is safe enough (greater than 3 mm), ICL hyperopic toric implantation is a safe method and provides stable refractive outcomes in patients with high hyperopia (up to 10.00 D) and astigmatism (up to 6.00 D). Furthermore, preoperative and postoperative anterior chamber parameters and vault evaluation by OCT is helpful to prevent the potential complications.
This study only reported outcomes and complications up to 12 months postoperatively. The long-term results will be reported in future studies.
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|No. of patients|
|No. of eyes|
| Mean ± SD||32 ± 6.55|
| Range||21 to 40|
Preoperative and Postoperative Parameters in Eyes Undergoing ICL Implantation
|Parameter||Preop||1 Week Postop||1 Month Postop||12 Months Postop||P|
|Mean ± SD||Range||Mean ± SD||Range||Mean ± SD||Range||Mean ± SD||Range|
|UDVA (decimal)||0.15 ± 0.11||0.05 to 0.40||0.71 ± 0.22||0.30 to 1.00||0.74 ± 0.23||0.30 to 1.00||0.74 ± 0.23||0.30 to 1.00||< .0001|
|CDVA (decimal)||0.74 ± 0.25||0.20 to 1.00||0.76 ± 0.21||0.30 to 1.00||0.78 ± 0.21||0.30 to 1.00||0.78 ± 0.21||0.30 to 1.00||< .052|
|Sphere (D)||6.86 ± 1.77||4.00 to 10.75||0.86 ± 0.79||−0.75 to 2.50||0.60 ± 0.69||−0.75 to 1.75||0.46 ± 0.89||−1.25 to 2.50||< .0001|
|Cylinder (D)||−1.44 ± 0.88||−3.25 to 0.00||−0.64 ± 0.46||−1.75 to −0.25||−0.66 ± 0.50||−2.00 to −0.25||−0.61 ± 0.46||−1.75 to −0.25||< .001|
|IOP (mm Hg)||14.65 ± 3.00||10 to 19||15.45 ± 2.58||12 to 20||15.20 ± 2.28||12 to 19||15.4 ± 2.95||11 to 22||< .445|
|ECD (cells/mm2)||2,881 ± 191||2,450 to 3,231||2,811 ± 186|| 2,390 to 3,140||2,837 ± 202||2,410 to 3,219||2,853 ± 203||2,420 to 3,220||< .0001|
|Vault (mm)||N/A||N/A||0.65 ± 0.13||0.43 to 0.96||0.61 ± 0.10||0.40 to 0.78||< .001|
Iridocorneal Angle Values
|Mean ± SD||Mean ± SD||Mean ± SD||Mean ± SD||Reduction||Pa||Mean ± SD||Reduction||P||Mean ± SD||Reduction||Pa|
|Preop vs 12 months postop|
| TIA||45.57 ± 2.57||46.09 ± 2.06||45.77 ± 2.15||27.77 ± 1.55||39.06%||.001||27.85 ± 1.47||39.59%||.001||28.46 ± 1.14||37.82%||.001|
| TISA500||0.302 ± 0.333||0.325 ± 0.039||0.306 ± 0.025||0.168 ± 0.013||44.25%||.001||0.173 ± 0.014||46.86%||.001||0.173 ± 0.016||43.38%||.001|
| AOD500||0.803 ± 0.053||0.805 ± 0.056||0.815 ± 0.068||0.414 ± 0.027||48.43%||.001||0.420 ± 0.041||47.85%||.001||0.426 ± 0.040||47.67%||.001|
|1 month vs 12 months postop|
| TIA||27.85 ± 1.97||28.69 ± 2.54||28.25 ± 1.90||27.77 ± 1.55||0.27%||.783||27.85 ± 1.47||2.93%||.085||28.46 ± 1.14||−0.74%||.260|
| TISA500||0.164 ± 0.016||0.173 ± 0.017||0.164 ± 0.011||0.168 ± 0.013||−2.75%||.121||0.173 ± 0.014||0.37%||.466||0.173 ± 0.016||−5.29%||.002|
| AOD500||0.398 ± 0.028||0.413 ± 0.048||0.428 ± 0.038||0.414 ± 0.027||−3.95%||.031||0.420 ± 0.041||−1.68%||.126||0.426 ± 0.040||0.35%||.896|