Journal of Refractive Surgery

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Original Article 

Effects of White-To-White Diameter and Anterior Chamber Depth on Implantable Collamer Lens Vault and Visual Outcome

Je Hyun Seo, MD; Mee Kum Kim, MD; Won Ryang Wee, MD; Jin Hak Lee, MD

Abstract

Purpose:

To investigate the effects of anterior chamber depth (ACD) and white-to-white (WTW) diameter on vault in eyes with implantable collamer lenses (ICL V4, STAAR Surgical AG) and to evaluate the effect of vault on visual outcomes and other biometric changes.

Methods:

Twenty-eight eyes of 16 patients who underwent ICL implantation were retrospectively reviewed. Patients were divided into two groups (A1, A2) according to preoperative ACD (≥3.3 mm and <3.3 mm, respectively), two groups (B1, B2) based on WTW diameter (≥11.55 mm and <11.55 mm, respectively), and two groups (C1, C2) according to the difference of ICL diameter and sulcus length (≥0.25 mm and <0.25 mm, respectively). Vault, endothelial cell density, and visual performance were compared between each set of groups. Correlations of vault with WTW diameter, ACD, and diametric difference of the ICL from the sulcus were analyzed.

Results:

The high ACD and WTW groups showed significantly higher vaults (0.59±0.32 mm and 0.57±0.36 mm, respectively) than the low ACD and WTW groups (0.26±0.17 mm and 0.25±0.14 mm, respectively; P=.01 and .01), whereas the differences of diameter between the sulcus and ICL were not related to significant vault differences. The WTW diameter was correlated more closely to the vault than the ACD or sulcus diameter (r=0.70, P<.001), whereas the vault difference did not affect visual quality or endothelial cell density.

Conclusions:

A high WTW diameter or ACD is likely to render a high vault, regardless of any difference in the ICL and sulcus diameters.

Abstract

Purpose:

To investigate the effects of anterior chamber depth (ACD) and white-to-white (WTW) diameter on vault in eyes with implantable collamer lenses (ICL V4, STAAR Surgical AG) and to evaluate the effect of vault on visual outcomes and other biometric changes.

Methods:

Twenty-eight eyes of 16 patients who underwent ICL implantation were retrospectively reviewed. Patients were divided into two groups (A1, A2) according to preoperative ACD (≥3.3 mm and <3.3 mm, respectively), two groups (B1, B2) based on WTW diameter (≥11.55 mm and <11.55 mm, respectively), and two groups (C1, C2) according to the difference of ICL diameter and sulcus length (≥0.25 mm and <0.25 mm, respectively). Vault, endothelial cell density, and visual performance were compared between each set of groups. Correlations of vault with WTW diameter, ACD, and diametric difference of the ICL from the sulcus were analyzed.

Results:

The high ACD and WTW groups showed significantly higher vaults (0.59±0.32 mm and 0.57±0.36 mm, respectively) than the low ACD and WTW groups (0.26±0.17 mm and 0.25±0.14 mm, respectively; P=.01 and .01), whereas the differences of diameter between the sulcus and ICL were not related to significant vault differences. The WTW diameter was correlated more closely to the vault than the ACD or sulcus diameter (r=0.70, P<.001), whereas the vault difference did not affect visual quality or endothelial cell density.

Conclusions:

A high WTW diameter or ACD is likely to render a high vault, regardless of any difference in the ICL and sulcus diameters.

From the Department of Ophthalmology, Seoul National University Hospital (Seo, Kim, Wee); Seoul Artificial Eye Center, Seoul National University Hospital Clinical Research Institute (Seo, Kim, Wee, Lee); and the Department of Ophthalmology, Seoul National University Bundang Hospital (Lee), Seoul, Korea.

The authors have no financial interest in the materials presented herein.

Presented at the European Society of Cataract and Refractive Surgery poster session; September 8–12, 2007; Stockholm, Sweden.

AUTHOR CONTRIBUTIONS

Study concept and design (J.H.S., M.K.K.); data collection (J.H.S., M.K.K., W.R.W., J.H.L.); interpretation and analysis of data (J.H.S.); drafting of the manuscript (J.H.S., M.K.K.); critical revision of the manuscript (J.H.S., M.K.K., W.R.W., J.H.L.); statistical expertise (J.H.S.); administrative, technical, or material support (J.H.S., M.K.K., J.H.L.); supervision (W.R.W.)

Correspondence: Mee Kum Kim, MD, Dept of Ophthalmology, Seoul National University Hospital, 28 Yongon-Dong, Chongno-Gu, Seoul 110-744, Korea. Tel: 82 2 2072 2665; Fax: 82 2 741 3187; E-mail: kmk9@snu.ac.kr

Received: March 05, 2008
Accepted: August 20, 2008
Posted Online: August 21, 2009

Intraocular refractive surgery for high myopia includes refractive lens exchange (RLE) and implantation of a phakic intraocular lens (IOL) in the anterior or posterior chamber. Phakic IOL surgery offers several advantages, such as a greater amount of correction than can be achieved with corneal refractive surgery, reversibility, and saving the accommodative power of the natural lens compared with RLE.1 However, phakic IOLs have been reported to be associated with complications such as angle-closure glaucoma,2 cataract,3 endothelial cell loss,4 pigment dispersion syndrome,5 damage to the zonules,1 cyclitis,1 and macular edema.1

Recently, the material and design of phakic IOLs have improved, with the complications mentioned above having been reduced significantly. The Implantable Collamer Lens (ICL; STAAR Surgical AG, Nidau, Switzerland) is a good example. Several studies have reported lower rates of short-term complications in ICL-implanted eyes.6,7 However, mismatches between the biometry of an eye and IOL design, such as between IOL diameter and sulcus length, can still cause problems in ICL-implanted eyes.

Preoperatively measured biometric results such as an anterior chamber depth (ACD) <2.8 mm or a white-to-white (WTW) diameter <10.7 mm contraindicate ICL implantation.1 Anterior chamber depth >2.8 mm and a WTW diameter >10.7 mm allows for implantation of an ICL; however, the effects of such ACD and WTW diameter on visual outcomes or changes of biometry have yet to be determined. Currently, STAAR Surgical AG recommends that the ICL diameter be determined by adding 0.5 mm to the WTW diameter when the ACD ranges from 2.8 to 3.0 mm, 0.5 to 0.7 mm when the ACD ranges from 3.1 to 3.5 mm, and 0.8 to 1.0 mm when the ACD ranges from 3.6 to 4.5 mm. The company also proposes that the recommendable ICL vault be 1 to 1.5 mm in corneal thickness on slit-lamp examination. However, we found that this empirical match often failed to achieve the recommended ICL vault. Therefore, we thought it necessary to evaluate the relationship between the ACD, WTW diameter, and sulcus diameter and ICL vault. Also, it seemed important to elucidate whether postoperative ICL vault has any effect on visual performance such as visual acuity, contrast sensitivity, higher order aberrations, and glare or on biometric changes including endothelial cell density and degree or angle pigmentation.

The purpose of the present study was to investigate the effects of biometric differences (differences in ACD and WTW diameter, and differences of diameter between ICL and sulcus) on postoperative vault, as well as the effect of vault on visual performance and biometric changes in ICL-implanted eyes.

Patients and Methods

Patients

The medical records of 16 patients (28 eyes) who underwent ICL implantation by the same surgeon (M.K.K.) at Seoul National University Hospital from 2003 to 2007 were retrospectively reviewed. Patients gave informed consent in accordance with the tenets of the Declaration of Helsinki. Patients were selected based on the following inclusion criteria: age 18 years or older, documented stable refraction for at least 1 year, spherical equivalent refraction >4.00 diopters (D), and corneal astigmatism <3.00 D. The following exclusion criteria were applied: endothelial cell density <2500 cells/mm2, intraocular pressure >21 mmHg, ACD <2.8 mm, and any documentation of intraocular disease.

Surgical Procedure

Two weeks before ICL surgery, patients received two peripheral iridotomies performed at 1:30 and 10:30 with a Neodyminum:yttrium-aluminium-garnet laser to prevent postoperative pupillary blockage. Pupil dilation was achieved with 0.5% tropicamide and 0.5% phenylephrine. The ICL (V4) was loaded in the lens insertion cartridge, which previously had been filled with balanced salt solution and Healon GV (Abbott Medical Optics, Santa Ana, Calif). Two para-centeses were punctured at 6 and 12 o’clock (3 hours away from the main wound), and a 3.2-mm temporal clear corneal incision was made. One-percent sodium hyaluronate (Healon GV) was injected into the anterior chamber. The injector tip was then placed in the inner lip of the wound, and the ICL was slowly injected into the anterior chamber, anterior to the iris plane, ensuring proper orientation. Four haptics were placed beneath the iris using an ICL manipulator (Asico LLC, West-mont, Ill). The remaining viscoelastics were manually irrigated. After the surgical procedure, levofloxacin (Cravit; Santen, Tokyo, Japan), fluorometholone (Flarex; Alcon Laboratories Inc, Ft Worth, Tex) and diclofenac (Decrol; Hanlim, Busan, Korea) were topically administered four times a day for 4 weeks.

Clinical Evaluations

Preoperative WTW diameters had been measured by corneal topography (Orbscan II; Bausch & Lomb, Rochester, NY). Preoperative ACD was measured by corneal topography and ultrasound biomicroscopy ([UBM] Hi Scan; OPTIKON 2000, Rome Italy), an average of two ACD measurements being used in each case. Anterior chamber depth was measured from the corneal endothelium to the anterior surface of the lens.

Visual outcomes and biometric changes were closely monitored during the postoperative period. Uncorrected visual acuity (UCVA) and refractive errors were evaluated, and a contrast sensitivity test, glare test, and aberrometry were performed to determine the visual outcome. Visual acuity was measured with Snellen visual acuity charts, and the values were transferred to a logMAR scale. Contrast sensitivity was measured using the VCTS 6500 testing instrument (Vistech Consultants Inc, Dayton, Ohio), which presents a translucent chart divided into five cycles with spatial frequencies of 1.5, 3, 6, 12, and 18 cycles per degree (cpd). The measurement was performed 2 months postoperatively under mesopic room conditions with 220 lux. All contrast sensitivity data were converted to logarithmic units, and the log contrast sensitivity values were compared. The glare test was performed according to the ALC glare test protocol (v1.3; ALC Clinic, Seoul, Korea).8 Aberrometry (WaveScan; VISX, Irvine, Calif) was performed in a dark room, with patients being illuminated by infrared light without mydriasis. Zernike coefficients including coma ( and ) and spherical aberration () were compared, and the average root-mean-square (RMS) values of the higher order aberrations were evaluated. Aberrometry results show the absolute aberration values and angles of direction. For analysis, we used the absolute values of the coma coefficients ( and ), because no differences were noted in horizontal coma () and vertical coma () coefficients calculated from the cosine and absolute values among the groups.

To determine the biometric changes, endothelial cell counts, gonioscopic results, vaulting, and ACD changes were evaluated. Specular microscopy (Noncon ROBO SP-8000; Konan Medical, Konan, Japan) was used to analyze the characteristics of the corneal endothelial cells as well as the endothelial cell density, covariance, and hexagonality. The differences of endothelial cell density, covariance, and hexagonality were calculated by subtracting the 6-month postoperative values from the preoperative values. The vertical vault between the ICL posterior surface and center of the crystalline lens and the sulcus-to-sulcus diameter were measured by UBM. To determine the sulcus-to-sulcus diameter, the cross-points where the root of the iris encounters the root of the ciliary body were used as reference points and the distance between those two points was measured. Postoperative ACD and angle degree, in undilated eyes, were measured by UBM (Fig 1). A gonioscopic examination and pigmentation dispersion examination were performed by a masked examiner using Shaffer angle width grading.

Ultrasound Biomicroscopy (UBM) Findings to Estimate Vault and Postoperative Angle. A) Postoperative Vault (green Arrow, D2: 0.35 mm) Measured by UBM. B) Postoperative Angle Measured by UBM Was 26.73°.

Figure 1. Ultrasound Biomicroscopy (UBM) Findings to Estimate Vault and Postoperative Angle. A) Postoperative Vault (green Arrow, D2: 0.35 mm) Measured by UBM. B) Postoperative Angle Measured by UBM Was 26.73°.

Statistical Analysis

To compare the effects of ACD, WTW, and sulcus diameter, patients were divided into two groups (A1, A2) according to the preoperative ACD (≥3.3 mm and <3.3 mm, respectively), another two groups (B1, B2) according to the WTW diameter (≥11.55 mm and <11.55 mm, respectively), and two additional groups (C1, C2) according to the difference in ICL and sulcus diameters (≥0.25 mm and <0.25 mm, respectively). The groups were determined with artificial cutoff values, based on the median preoperative ACD (3.30 mm), median WTW diameter (11.55 mm), and median difference in ICL and sulcus diameters (0.25 mm). The visual outcomes and biometric changes were compared between each group pair using the Mann-Whitney U test, chi-square test, and independent T test. The correlations of ICL vault with visual outcomes, biometric changes, preoperative ACD, WTW diameters, and differences in ICL and sulcus diameters were analyzed by means of Spearman’s rank correlation coefficient analysis and multivariate regression analysis. A statistical analysis was performed using SPSS v.12.0 software (SPSS Inc, Chicago, Ill), with two-sided P<.05 being considered statistically significant.

Results

Mean patient age was 26.82±4.97 years (range: 20 to 36 years), and mean follow-up was 19.75±17.14 months (range: 6 to 56 months). Demographic and descriptive data are shown in Table 1. The mean difference in ICL and sulcus diameter was 0.25±0.21 mm, and this difference was within 0.50 mm in most patients (89.2%). Postoperative UCVA showed a marked improvement compared with preoperative UCVA (1.57±0.12 vs −0.002±0.107 logMAR, P<.001). Postoperative refractive errors also showed a significant improvement compared with preoperative errors (−10.91±3.66 vs −0.49±0.66 diopters [D], P<.001). Postoperative contrast sensitivity was within normal range. Mean RMS of higher order aberrations significantly increased after surgery (0.30±0.15 vs 0.40±0.14 μm, P=.02). The absolute values of coma ( and ) (0.14±0.09 vs 0.16±0.08 μm, P=.56) and spherical aberration () (−0.015±0.11 vs −0.07±0.10 μm, P=.09) did not show significant changes. Virtually all patients except one complained of halo and glare, with the quantitative glare test showing that the average glare score after ICL surgery significantly increased (557.0±41.81 mm) compared with normal values (519.4±32.2 mm).9 The change in endothelial cell density was not significant (Fig 2). Average postoperative ACD from the endothelial side to the anterior surface of the ICL was 2.36±0.38 mm, and the UBM-measured vault was 0.44±0.33 mm (Table 2). The angle pigmentation (71.42%) occupied less than 3 clock hours of circumference. The angle widths by Shaffer grading were grade 1, and the mean degree of angle was 23.75±3.82°.

Demographics of Patients Who Underwent ICL Implantation

Table 1: Demographics of Patients Who Underwent ICL Implantation

Differences of Endothelial Cell Changes in Groups A1 (n=14) and A2 (n=14), Groups B1 (n=13) and B2 (n=15), and Groups C1 (n=10) and C2 (n=10). There Were No Significant Differences Between A1 and A2 as Well as B1 and B2 and C1 and C2 (P>.05) in Specular Microscopy. Endothelial Cell Count (ECC): Preoperative ECC – Postoperative 6-Month ECC; Covariance (CV): Preoperative CV – Postoperative 6-Month CV; Hexagonality: Preoperative Hexagonality – Postoperative 6-Month Hexagonality

Figure 2. Differences of Endothelial Cell Changes in Groups A1 (n=14) and A2 (n=14), Groups B1 (n=13) and B2 (n=15), and Groups C1 (n=10) and C2 (n=10). There Were No Significant Differences Between A1 and A2 as Well as B1 and B2 and C1 and C2 (P>.05) in Specular Microscopy. Endothelial Cell Count (ECC): Preoperative ECC – Postoperative 6-Month ECC; Covariance (CV): Preoperative CV – Postoperative 6-Month CV; Hexagonality: Preoperative Hexagonality – Postoperative 6-Month Hexagonality

Mid-Term Results of Visual Outcomes and Biometry Changes of Patients Who Underwent ICL Implantation

Table 2: Mid-Term Results of Visual Outcomes and Biometry Changes of Patients Who Underwent ICL Implantation

Uncorrected visual acuity (0.01±0.13 vs −0.01±0.08 logMAR, P=.62) and refractive errors (−0.55±0.84 vs −0.43±0.43 D, P=.63) showed no differences between groups A1 and A2 (Table 3). Likewise, contrast sensitivity showed no difference at any spatial frequency (Fig 3). Moreover, the average RMS and absolute values of coma ( and ) and spherical aberration () revealed no differences between the two groups (Fig 4). The sulcus and ICL diameters were not significantly different (11.84±0.12 vs 11.68±0.29 mm, P=.25; 0.35±0.15 vs 0.17±0.24 mm, P=.09) between these two groups. The UBM-measured degree of postoperative angle did not reveal any significant differences between groups A1 and A2 (23.43±5.05° vs 24.05±2.39°, P=.71) nor did the changes of endothelial cell density, covariance, or hexagonality (see Fig 2). However, the average UBM-measured vaults in A1 were significantly higher than those in A2 (0.59±0.32 vs 0.26±0.17 mm, P=.01).

Differences of Postoperative Visual Outcomes and Biometry Changes Between Group A1 and A2 (Anterior Chamber Depth), Group B1 and B2 (White-To-White Diameter), and Group C1 and C2 (ICL Diameter to Sulcus Diameter)

Table 3: Differences of Postoperative Visual Outcomes and Biometry Changes Between Group A1 and A2 (Anterior Chamber Depth), Group B1 and B2 (White-To-White Diameter), and Group C1 and C2 (ICL Diameter to Sulcus Diameter)

Comparison of Contrast Sensitivity Values Between Groups. Postoperatively, Mean Contrast Sensitivity Was Normal at All Spatial Frequencies in All Groups. No Significant Differences at Any Spatial Frequency Were Noted Between A1 and A2, B1 and B2, and C1 and C2 (P>.05).

Figure 3. Comparison of Contrast Sensitivity Values Between Groups. Postoperatively, Mean Contrast Sensitivity Was Normal at All Spatial Frequencies in All Groups. No Significant Differences at Any Spatial Frequency Were Noted Between A1 and A2, B1 and B2, and C1 and C2 (P>.05).

Comparison of Higher Order Aberrations Among Groups. No Significant Differences Were Noted at Any Spatial Frequency Between A1 and A2, B1 and B2, and C1 and C2 (P>.05). HOF = Higher Order Fraction (%): Ratio of Higher Order Aberration to All Order Aberrations; RMS = Mean Root-Mean-Square Errors (μm); Coma = Absolute Value of Coma (μm); Spherical = Spherical Aberration (μm)

Figure 4. Comparison of Higher Order Aberrations Among Groups. No Significant Differences Were Noted at Any Spatial Frequency Between A1 and A2, B1 and B2, and C1 and C2 (P>.05). HOF = Higher Order Fraction (%): Ratio of Higher Order Aberration to All Order Aberrations; RMS = Mean Root-Mean-Square Errors (μm); Coma = Absolute Value of Coma (μm); Spherical = Spherical Aberration (μm)

Comparing groups B1 and B2, no differences were found for UCVA (−0.03±0.08 vs 0.03±0.13 logMAR, P=.14) and refractive error (−0.30±0.46 vs −0.71±0.79 D, P=.10) (Table 3). Moreover, the sulcusdiameterandthedifference between the sulcus and ICL diameters did not differ significantly (11.86±0.15 vs 11.63±0.24 mm, P=.07; 0.31±0.20 vs 0.21±0.22 mm, P=.14). Contrast sensitivity values did not differ at any spatial frequency (see Fig 3); RMS, spherical aberration, and coma showed no significant differences, and there was no difference in the endothelial cell changes (see Fig 2) or UBM-measured postoperative angle degree. However, the mean UBM-measured vaults in B1 were significantly higher than those in B2 (0.57±0.36 vs 0.25±0.14 mm, P=.01).

Comparing groups C1 and C2, no differences were found for UCVA (−0.01±0.07 vs −0.01±0.09 logMAR, P=.99) or refractive errors (−0.35±0.29 vs −0.36±0.52 D, P=.95) (Table 3). Contrast sensitivity values did not differ at any spatial frequency (see Fig 3); RMS, spherical aberration, and coma showed no significant difference, and no difference was noted in endothelial cell changes (see Fig 2) or UBM-measured postoperative degree of angle. Unlike the comparisons of the two groups mentioned above, the mean UBM-measured vaults in C1 showed no significant changes compared with those in C2 (P=.16).

The UBM-measured vaults were highly correlated with the WTW diameter (r=0.70, P<.001), preoperative ACD (r=−0.45, P=.04), and sulcus diameter (r=0.55, P=.01), and the WTW diameter showed a stronger correlation with the vault than with the ACD and sulcus diameters (Fig 5). The results of a multiple regression analysis were as follows: (Vaults) = −0.006 × (ACD) −0.54 (WTW diameter) + 1.17 × (differences in ICL and sulcus diameters) + 1.22 × (sulcus diameter), R=0.75. The vaults presented positive correlations with the higher order fractions (r=0.50, P=.06); however, they were only marginally significant. The postoperative UCVA (r=−0.48, P=.052), refractive errors (r=0.48, P=.052), and differences of hexagonality (r=−0.42, P=.056) showed marginally significant correlations with the vaults, whereas the changes of endothelial cell density, covariance, hexagonality, and other parameters did not show any significant correlations with the vaults.

Correlations of Vault on Preoperative Biometry (anterior Chamber Depth [ACD] and White-To-White [WTW] Diameter, Difference of ICL and Sulcus Diameter). White-To-White Diameter (r=0.70, P<.001) Was Highly Correlated to Postoperative Vault Compared with Preoperative ACD (r=0.45, P=.04). The Differences of ICL and Sulcus Diameter (r=0.29, P=.21) Were not Correlated to Postoperative Vault.

Figure 5. Correlations of Vault on Preoperative Biometry (anterior Chamber Depth [ACD] and White-To-White [WTW] Diameter, Difference of ICL and Sulcus Diameter). White-To-White Diameter (r=0.70, P<.001) Was Highly Correlated to Postoperative Vault Compared with Preoperative ACD (r=0.45, P=.04). The Differences of ICL and Sulcus Diameter (r=0.29, P=.21) Were not Correlated to Postoperative Vault.

Discussion

In the present study, the total longitudinal length of the ICL was selected according to the empirical rules, ie, by adding 0.5 to 1.0 mm to the horizontal corneal diameter (WTW diameter),1 despite the method’s lack of scientific verification. STAAR Surgical AG recommends that the ICL diameter be determined by adding to the WTW diameter 0.5 mm when ACD is between 2.8 and 3.0 mm, 0.5 to 0.7 mm when ACD is between 3.1 and 3.5 mm, or 0.8 to 1.0 mm when ACD is between 3.6 and 4.5 mm. However, when we selected the ICL diameter according to that recommendation, the postoperative vault seemed to be larger than expected when the preoperative ACD or WTW diameter was also larger than normal. That is why we focused on the effect of ACD or WTW diameter on the ICL vaults in verifying the accuracy of the current, conventional method.

The present study reveals that the high WTW diameter or ACD groups had significantly higher vaults than the low WTW diameter or ACD groups, with significant correlations, whereas the differences in sulcus and ICL diameters did not correlate with significant vault changes, suggesting that the conventional method is not likely to provide accurate vaults, not even if ICL diameters are matched with sulcus diameters in high WTW diameter or ACD patients.

Recently, Choi et al10 reported that the UBM-measuring method achieved significantly more uniform ICL vaults than the conventional WTW method. We somewhat agree with that report, ie, the fact that UBM can directly measure sulcus-to-sulcus diameters and, thereby, ideal vaults in patients who have an average WTW diameter or ACD. However, our results showed that the ICL vault seemed to be in accordance with the WTW diameter regardless of any difference in ICL and sulcus diameters. This means that a patient who has a large WTW diameter or deep preoperative ACD tends to have a high vault, regardless of any difference in the ICL and sulcus diameters. We believe the reason for this is the fact that the currently available formula is not likely to obtain uniform vaults in patients having various ocular dimensions.

Next, we focused on the effect of vaults on visual performances or endothelial and other changes, because the conventional method seemed prone to calculating erroneous vault differences based on biometric differences. Fortunately, we found that the ICL vault is less likely to affect visual performance or endothelial density in the short-term, although the long-term effect needs to be further investigated.

Loss of corneal endothelial cells and cataract formation after ICL implantation remain major concerns. There was no case of cataract development in the short-term follow-up period in our study. Some recent studies have indicated that these complications are related to the ICL vault.11,12 In fact, a relationship between ICL vault and cataract formation (8.5% rate; 3-year follow-up) has been identified.11 Moreover, Gonvers et al13 reported a threshold vault below which all cataracts occur. Thus, the postoperative vault might be one of the factors contributing to cataract development.

In the present study, we observed that, according to the ICL V4 vaults, there were no significant differences in the contrast sensitivity values at any spatial frequency. Previous studies on the effect of ICL implantation on contrast sensitivity presented significant increase at all cpd,13,14 hence it has not been reported whether vault may have an effect on contrast sensitivity.

The correlation of vault with higher order aberrations is another concern. Our study showed a marginally significant relationship between vault and higher order aberrations, although the higher order fraction, by increasing coma and trefoil, increased significantly after ICL implantation compared with the preoperative level. The effect of ICL on higher order aberrations has not yet been reported. A study by Artisan reported no significant change in high order fraction, but was not conclusive as it was only a small case series (4 eyes).15 In our study, it is likely that the distance between the ICL anterior surface and the lens anterior surface was not uniform, resulting in increasing coma. However, a larger case study is needed to verify the direct effect of ICL on higher order aberrations as well as any effect of vault on higher order aberrations.

On the other hand, the average value of the glare test for the ICL-implanted eyes was 557.0±41.81 mm, which seemed to be higher than that in corneal refractive surgery patients.16–18 This can be explained by the fact that the ICL-implanted eyes in the present study were more myopic, which might require a smaller optic zone of ICL than surface-ablated eyes. Nonetheless, vault showed no correlation with glare.

Given the fact that the average lifespan after insertion is more than 40 years, endothelial change is a major issue with regard to phakic IOL implantation. Dejaco-Ruhswurm et al4 reported a progressive loss over 4-year follow-up. In the present study, endothelial cell count was not affected by the ICL vault within the 6-month follow-up period. However, it is important to bear in mind that long-term endothelial loss may still be an issue.19 Therefore, further long-term study on endothelial changes should be conducted.

In concordance with a previous study,20 71% of patients in the present study showed pigmentary changes in less than 3 clock hours of circumference. In most eyes, these pigmentary changes did not progress during follow-up. All postoperative angles were approximately 20°, and the change of angle was not affected by the ICL vault.

Our study has several limitations. Initially, the ICL diameter was chosen according to the WTW diameter, not according to the sulcus-to-sulcus diameter. A limitation of this retrospective review is we cannot accurately verify which measurement is more involved in determining postoperative vault. Another issue is the small study group. To rectify this deficiency, a large case-control study is pending. Nonetheless, we believe the currently available method is flawed in determining the ICL diameter with reference to the sulcus diameter in patients with high WTW diameter or ACD.

In conclusion, a high WTW diameter or ACD is likely to render a high vault, regardless of any difference in the ICL and sulcus diameters. These findings suggest that the currently available, conventional program for determining ICL diameter using the ACD and WTW diameter cannot consistently or reliably provide uniform vaults. Hence, a new ICL calculation program that can achieve uniform vault regardless of original ocular dimensions is required.

References

  1. Lovisolo CF, Reinstein DZ. Phakic intraocular lenses. Surv Ophthalmol. 2005;50:549–587. doi:10.1016/j.survophthal.2005.08.011 [CrossRef]
  2. Bylsma SS, Zalta AH, Foley E, Osher RH. Phakic posterior chamber intraocular lens pupillary block. J Cataract Refract Surg. 2002;28:2222–2228. doi:10.1016/S0886-3350(02)01303-2 [CrossRef]
  3. Brauweiler PH, Wehler T, Busin M. High incidence of cataract formation after implantation of a silicone posterior chamber lens in phakic, highly myopic eyes. Ophthalmology. 1999;106:1651–1655. doi:10.1016/S0161-6420(99)90352-4 [CrossRef]
  4. Dejaco-Ruhswurm I, Scholz U, Pieh S, Hanselmayer G, Lackner B, Italon C, Ploner M, Skorpik C. Long-term endothelial changes in phakic eyes with posterior chamber intraocular lenses. J Cataract Refract Surg. 2002;28:1589–1593. doi:10.1016/S0886-3350(02)01210-5 [CrossRef]
  5. Baikoff G, Bourgeon G, Jodai HJ, Fontaine A, Lellis FV, Trinquet L. Pigment dispersion and Artisan phakic intraocular lenses: crystalline lens rise as a safety criterion. J Cataract Refract Surg. 2005;31:674–680. doi:10.1016/j.jcrs.2004.09.034 [CrossRef]
  6. Mastropasqua L, Toto L, Nubile M, Falconio G, Ciancaglini M. Long-term complication of bilateral posterior chamber phakic intraocular lens implantation. J Cataract Refract Surg. 2004;30:901–904. doi:10.1016/j.jcrs.2003.08.012 [CrossRef]
  7. 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;30:2269–2276. doi:10.1016/j.jcrs.2004.07.018 [CrossRef]
  8. Lee H, Choi C, Kim E, Seong G, Kim S, Kim G, Yoo T, Lee S. Reproducibility of the new computerized program for measuring glare disability. Invest Ophthalmol Vis Sci. 2003;44:E-Abstract 2613.
  9. Jiménez-Alfaro I, Gómez-Telleria G, Bueno JL, Puy P. Contrast sensitivity after posterior chamber phakic intraocular lens implantation for high myopia. J Cataract Refract Surg. 2001;17:641–645.
  10. Choi KH, Chung SE, Chung TY, Chung ES. Ultrasound biomicroscopy for determining visian implantable contact lens length in phakic IOL implantation. J Refract Surg. 2007;23:362–367.
  11. Zaldivar R, Davidorf JM, Oscherow S. Posterior chamber phakic intraocular lens for myopia of −8 to −19 diopters. J Cataract Refract Surg. 1998;14:294–305.
  12. Gonvers M, Bornet C, Othelin-Girard P. Implantable contact lens for moderate to high myopia; relationship of vaulting to cataract formation. J Cataract Refract Surg. 2003;29:918–924. doi:10.1016/S0886-3350(03)00065-8 [CrossRef]
  13. Gonvers M, Othenin-Girard P, Bornet C, Sickenberg M. Implantable contact lens for moderate to high myopia: short-term follow-up of 2 models. J Cataract Refract Surg. 2001;27:380–388. doi:10.1016/S0886-3350(00)00759-8 [CrossRef]
  14. Dick HB, Tehrani M, Aliyeva S. Contrast sensitivity after implantation of toric iris-claw lenses in phakic eyes. J Cataract Refract Surg. 2004;30:2284–2289. doi:10.1016/j.jcrs.2004.03.037 [CrossRef]
  15. Brunette I, Bueno JM, Harissi-Dagher M, Parent M, Podtetenev M, Hamam H. Optical quality of the eye with the Artisan phakic lens for the correction of high myopia. Optom Vis Sci. 2003;80:167–174. doi:10.1097/00006324-200302000-00013 [CrossRef]
  16. Kim TW, Wee WR, Lee JH, Kim MK. Contrast sensitivity after LASIK, LASEK, and wavefront-guided LASEK with the VISX S4 laser. J Refract Surg. 2007;23:355–361.
  17. Chaidaroon W, Juwattanasomran W. Colvard pupillometer measurement of scotopic pupil diameter in emmetropes and myopes. Jpn J Ophthalmol. 2002;46:640–644. doi:10.1016/S0021-5155(02)00556-7 [CrossRef]
  18. Tester R, Pace NL, Samore M, Olson RJ. Dysphotopsia in phakic and pseudophakic patients: incidence and relation to intraocular lens type (2). J Cataract Refract Surg. 2000;26:810–816. doi:10.1016/S0886-3350(00)00427-2 [CrossRef]
  19. Food and Drug Administration Center for Devices and Radiological Health Ophthalmic Devices Panel 107th meeting, February 6, 2004. Available at: http://www.fda.gov/ohrms/dockets/ac/04/transcripts/Pages%20from%204023t2-01.pdf. Accessed June 2004.
  20. Abela-Formanek C, Kruger AJ, Dejaco-Ruhswurm I, Pieh S, Skorpik C. Gonioscopic changes after implantation of a posterior chamber lens in phakic myopic eyes. J Cataract Refract Surg. 2001;27:1919–1925. doi:10.1016/S0886-3350(01)01229-9 [CrossRef]

Demographics of Patients Who Underwent ICL Implantation

ParametersMean±SD
Age (y)26.82±4.97
Follow-up (mo)19.75±17.14
UCVA (logMAR)1.57±0.12
BSCVA (logMAR)−0.007±0.10
ICL diameter (mm)12.00±0.30
Sulcus diameter (mm)11.75±0.22
Gender, Male (%)14.28
Laterality, right eye (%)46.4

Mid-Term Results of Visual Outcomes and Biometry Changes of Patients Who Underwent ICL Implantation

ParametersPreoperativePostoperativePValue*
Visual outcomes
  UCVA (logMAR)1.57±0.12−0.002±0.107.001
  Refractive errors (D)−10.91±3.66−0.49±0.66.001
  Higher order aberration
    Higher order fraction (%)2.85±1.5331.35±13.82.001
    RMS errors (μm)0.30±0.150.40±0.14.02
    Coma (Z31 and Z31) (μm)0.14±0.090.16±0.08.56
    Spherical aberration (Z40) (μm)−0.015±0.11−0.07±0.10.09
Biometry
  Endothelial cell changes
    Endothelial cell count (cell/mm2)3001.7±280.83029.0±265.6.71
    Coefficient of variation (%)33.3±6.333.6±5.9.87
    Hexagonality (%)59.3±13.056.2±11.1.35
  UBM-measured ACD (mm)3.24±0.182.36±0.38.001
  UBM-measured vault (mm)0.44±0.33
  Angle pigmentation (n, %)0 (0.0)20 (71.42).001

Differences of Postoperative Visual Outcomes and Biometry Changes Between Group A1 and A2 (Anterior Chamber Depth), Group B1 and B2 (White-To-White Diameter), and Group C1 and C2 (ICL Diameter to Sulcus Diameter)

Group A1 (n=14)Group A2 (n=14)PValue*Group B1 (n=13)Group B2 (n=15)PValue*Group C1 (n=10)Group C2 (n=10)PValue*
Visual outcomes
  UCVA (logMAR)0.01±0.13−0.01±0.08.62−0.03±0.080.03±0.13.14−0.01±0.07−0.01±0.09.99
  Refractive errors (D)−0.55±0.84−0.43±0.43.63−0.30±0.460.71±0.79.10−0.35± 0.29−0.36±0.52.95
Glare test (mm)550.4±21.8561.9±52.6.55549.8±20.2563.5±55.0.47560.4±42.5568.3±31.6.69
Biometric changes
UBM-measured postoperative ACD (mm)2.32±0.452.47±0.29.552.28±0.432.55±0.23.112.23±0.422.60±0.22.03
Sulcus diameter (mm)11.84±0.1211.68±0.29.2511.86±0.1511.63±0.24.07
Difference of sulcus and ICL diameter (mm)0.35±0.150.17±0.24.090.31±0.200.21±0.22.14
UBM-measured vault (mm)0.59±0.360.26±0.17.010.57±0.360.25±0.14.010.50±0.380.31±0.16.16
UBM-measured angle examination (°)23.43±5.0524.05±2.39.7123.39±4.9024.15±2.31.6423.17±5.3923.43±1.60.88
Angle pigmentation (n, %)10 (71.42)10 (71.42)1.0011 (73.3)9 (69.2).828 (80)8 (80)1.00
Authors

From the Department of Ophthalmology, Seoul National University Hospital (Seo, Kim, Wee); Seoul Artificial Eye Center, Seoul National University Hospital Clinical Research Institute (Seo, Kim, Wee, Lee); and the Department of Ophthalmology, Seoul National University Bundang Hospital (Lee), Seoul, Korea.

The authors have no financial interest in the materials presented herein.

Presented at the European Society of Cataract and Refractive Surgery poster session; September 8–12, 2007; Stockholm, Sweden.

Correspondence: Mee Kum Kim, MD, Dept of Ophthalmology, Seoul National University Hospital, 28 Yongon-Dong, Chongno-Gu, Seoul 110-744, Korea. Tel: 82 2 2072 2665; Fax: 82 2 741 3187; E-mail: kmk9@snu.ac.kr

10.3928/1081597X-20090707-08

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