Phakic posterior chamber intraocular lens for high myopia

Phakic posterior chamber intraocular lens for high myopia Angel Pineda-Fernández, MD, Jorge Jaramillo, MD, José Vargas, MD, Miguel Jaramillo, MD, José Jaramillo, MD, Alicia Galı́ndez, MD Purpose: To evaluate the efficacy, predictability, stability, and safety of the surgical correction of high myopia using a phakic posterior chamber intraocular lens (PPC IOL). Setting: Centro Oftalmológico de Valencia-CEOVAL, Valencia, Venezuela. Methods: A retrospective study was performed to analyze 18 eyes of 12 patients who had implantation of a modified PPC IOL, the implantable contact lens (ICL), for the treatment of high myopia. The target postoperative spherical equivalent (SE) refraction was emmetropia. Results: The mean follow-up was 26.6 months ⫾ 11.3 (SD) (range 12 to 36 months). The mean preoperative SE was ⫺15.27 ⫾ 3.47 diopters (D) (range ⫺10.0 to ⫺21.25 D) and the mean postoperative SE, ⫺0.62 ⫾ 0.81 D (range ⫺2.75 to ⫹0.75 D). Eleven eyes (61.1%) had an SE within ⫾1.00 D of emmetropia. The best spectacle-corrected visual acuity was maintained or improved in all except 1 eye, which lost more than 2 lines of Snellen visual acuity. Two eyes (11.1%) developed pupillary block the first day after surgery. Four eyes (22.2%) had moderate pigmentary dispersion. Two eyes (11.1%) had lens opacification, 1 with mild peripheral anterior capsule opacification and the other eye with central anterior subcapsular opacification. One eye (5.5%) had a significant decrease in anterior chamber depth after surgery. Conclusions: Implantation of an ICL was effective for the correction of high myopia. Predictability must be improved and the long-term safety of the ICL determined. The main concerns over potential cataract formation, pigmentary dispersion, and angle-closure glaucoma remain. J Cataract Refract Surg 2004; 30:2277–2283  2004 ASCRS and ESCRS T he surgical correction of myopia currently includes intraocular surgery and techniques that produce changes in the corneal shape.1 Keratorefractive surgeries such as photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), and radial keratotomy have Accepted for publication March 9, 2004. From the Centro Oftalmológico de Valencia-CEOVAL (Pineda-Fernández, Jorge Jaramillo, Vargas, M. Jaramillo, José Jaramillo) and Centro Médico Guerra Méndez (Galı́ndez), Valencia, Venezuela. None of the authors has a financial or proprietary interest in any material or method mentioned. Reprint request to Angel Pineda-Fernández, MD, Avenida Bolivar Norte, Edificio Torre Venezuela, Piso 2, Centro Oftalmológico de ValenciaCEOVAL, Valencia, Venezuela. E-mail: [email protected].  2004 ASCRS and ESCRS Published by Elsevier Inc. good results in terms of efficacy, predictability, and quality of vision for low to moderate myopia.2–6 However, these procedures are associated with significant optical aberrations, poor quality of vision, and poor predictability when they are used to correct high myopia.7–12 Intraocular refractive surgery includes clear lens extraction13,14 and phakic intraocular lenses (IOLs) implanted in the anterior or posterior chamber, which provide good refractive results for higher corrections.15–17 However, they are associated with an increased risk for retinal detachment, endothelial cell loss, secondary glaucoma, and cataract formation.18–22 The concept of a phakic IOL for myopia was developed in the late 1950s with the design of a single-piece poly(methyl methacrylate) plate-haptic IOL that was 0886-3350/04/$–see front matter doi:10.1016/j.jcrs.2004.03.035 PPC IOL FOR HIGH MYOPIA fixated in the anterior chamber angle. The long-term data showed a significant incidence of corneal decompensation and uveitis–glaucoma–hyphema syndrome23; thus, these IOLs were soon abandoned. Phakic IOL procedures began a new era with the introduction of the Worst iris-claw lens and Baikoff anterior chamber IOL in the middle 1980s.24,25 In 1986, Fyodorov developed a new model of posterior chamber IOL made of silicone for phakic, highly myopic patients26; however, the lens led to a high incidence of cataract formation.22 In 1993, Staar Surgical AG introduced a modified phakic posterior chamber intraocular lens (PPC IOL), the implantable contact lens (ICL), for the correction of high myopia. Several studies report good refractive outcomes and optical performance with the ICL.17,27–29 Some, however, report cataract formation21 and pigmentary dispersion.30 The purpose of this study was to evaluate the efficacy, predictability, safety, and stability of the correction of high myopia with a PPC IOL. material derived from collagen that is a copolymer comprising porcine collagen and HEMA. It is 6.0 mm wide and comes in 5 diameters (11.0, 11.5, 12.0, 12.5, and 13.0 mm). The lens has a central convex–concave optic zone with a diameter of 4.5 to 5.5 mm, depending on dioptric power. The ICL design has been modified many times. In this study, the first 6 eyes had implantation of the ICM V3 model and the other 12 eyes, of the newer ICM V4 model, which is presumed to offer better vaulting over the crystalline lens than the ICM V3 because the optical zone has greater convex–concave curvature. Lens power calculations were performed with formulas developed by Staar. The variables in the formula are preoperative manifest and cycloplegic refractions (according to protocol, the cycloplegic refraction was used in patients younger than 40 years and the manifest refraction, in patients older than 40 years), vertex distance, average keratometric power, corneal thickness, and central ACD. The length of the implanted ICL was determined based on the patient’s horizontal corneal diameter (white to white) measured with the Nidek Auto Ref/keratometer. The goal was to implant an ICL slightly larger than the ciliary sulcus to produce anterior vaulting and secure fixation. Surgical Technique Patients and Methods A retrospective study was performed using the data from 18 eyes of 12 consecutive patients who had implantation of an ICL since April 1998. The target postoperative spherical equivalent (SE) refraction was emmetropia. Inclusion criteria were older than 18 years, SE of ⫺9.00 diopters (D) or higher, a best spectacle-corrected visual acuity (BSCVA) of 20/80 or worse, no preexisting ocular pathology, no previous surgery, no systemic disease, contact lens intolerance, intraocular pressure (IOP) between 10 mm Hg and 20 mm Hg, anterior chamber depth (ACD) of 3.0 mm or more, and endothelial cell count greater than 2000 cells/mm2. An ophthalmic examination was conducted before surgery and postoperatively at 1 and 7 days and 1, 6, 12, 24, and 36 months. The examinations included distance uncorrected visual acuity (UCVA) and distance BSCVA using a Snellen chart, manifest and cycloplegic refractions, slitlamp and fundus evaluation, Goldmann applanation tonometry, corneal topography (EyeSys), and ultrasound (US) pachymetry. The ACD was measured with a US biometer (Nidek EchoScan US3300). The corneal endothelial cell count (cells per square millimeter) was measured with a noncontact specular microscope (Topcon SP-2000P, Topcon Corp.). Up to 5 measurements in the central cornea were taken at each examination, and the mean was recorded as the corneal endothelial density. The ICL is a plate-haptic single-piece lens designed to be implanted in the posterior chamber with support on the ciliary sulcus. It is made of Collamer, a flexible, hydrophilic 2278 In all cases, 2 peripheral and superior iridotomies were performed 2 weeks before surgery using a neodymium:YAG (Nd:YAG) laser; they were positioned 90 degrees apart to prevent postoperative pupillary block. All surgeries were performed by 1 of 2 surgeons (A.P., J.J.) using peribulbar anesthesia and with good pupil dilation achieved by tropicamide 1% and phenylephrine 5%. Two paracenteses at the 6 and 12 o’clock meridians and a 3.2 mm temporal clear corneal incision were made with a diamond knife. Sodium hyaluronate 1% (Healon威) was injected into the anterior chamber. The ICL was positioned in the lens insertion cartridge, which was previously filled with Healon. A small piece of a 3.0 mm diameter sponge was placed in the insertion cartridge behind the ICL to protect the eye from the injector arm. The injector tip was then placed in the wound, and the ICL was slowly injected into the anterior chamber anterior to the iris plane, ensuring proper orientation. A Sinskey hook was introduced through 1 paracentesis, and the 2 corners of the temporal haptic were placed beneath the iris with gentle posterior pressure. The 2 corners of the nasal haptic were positioned in a similar fashion. To avoid pigmentary dispersion, the ICL was not rotated. Acetylcholine was injected into the anterior chamber. Remaining viscoelastic material was aspirated using irrigation/aspiration with the Millennium phacoemulsification system (Bausch & Lomb). Topical tobramycin–dexamethasone (TobraDex威) was given at the end of surgery. The eye was patched for 24 hours, and mannitol 20% (250 cc) was given intravenously. TobraDex was prescribed 6 times a day for 2 weeks and then 4 times a day for 2 weeks. J CATARACT REFRACT SURG—VOL 30, NOVEMBER 2004 PPC IOL FOR HIGH MYOPIA Figure 2. (Pineda-Fernández) Stability of the SE refraction in 12 eyes that completed a 24-month follow-up. Figure 1. (Pineda-Fernández) Intended versus achieved correction in 18 eyes at the last examination. The linear regression line shows a tendency toward undercorrection. Statistical Analysis Statistica software (version 4.3) was used to compare the postoperative data by the Student t test. Results were considered statistically significant when P⬍.05. Results The mean age of the patients was 34.5 years ⫾ 5.7 (SD) (range 25 to 41 years) and the mean follow-up, 26.6 ⫾ 11.3 months (range 12 to 36 months). All 18 eyes completed at least 1 year of follow-up, 66.6% (12 eyes) completed 24 months, and 55.5% (10 eyes) completed 36 months. The mean preoperative sphere was ⫺13.94 ⫾ 3.28 D (range ⫺9.75 to ⫺20.00 ). The mean cylinder was ⫺1.80 ⫾ 1.30 D (range ⫺0.50 to ⫺4.00 D) preoperatively and ⫺1.85 ⫾ 0.78 D (range ⫺1.00 to ⫺3.00 D) postoperatively. The mean SE was ⫺15.27 ⫾ 3.47 D (range ⫺10.00 to ⫺21.25 D) preoperatively and ⫺0.62 ⫾ 0.81 D (range ⫺2.75 to ⫹0.75 D) postoperatively. Figure 1 shows the predictability of the procedure. Four eyes (22.2%) had an SE within ⫾0.50 D of emmetropia and 61.1% (11 eyes), within ⫾1.00 D. Figure 2 shows the stability of the SE refraction (P⬎.05 between each postoperative interval). At the last postoperative visit, 8 eyes (44.4%) had a UCVA of 20/40 or better and 1 eye (5.5%) had a Figure 3. (Pineda-Fernández) Cumulative UCVA at the last postoperative visit. Figure 4. (Pineda-Fernández) Change in BSCVA at the last postoperative visit. UCVA of 20/20 or better (Figure 3). Seven eyes (38.8%) gained 1 or more lines of Snellen BSCVA. One eye (5.5%) lost more than 2 lines of BSCVA (Figure 4). Table 1 shows the ACD. There was a statistically significant decrease in ACD from preoperatively to post- J CATARACT REFRACT SURG—VOL 30, NOVEMBER 2004 2279 PPC IOL FOR HIGH MYOPIA Table 1. Anterior chamber depth (mm). Table 2. Endothelial cell density (cells/mm2). Exam Mean ⫾ SD Eyes % Decrease Exam Mean ⫾ SD Eyes % Loss Preoperative 3.50 ⫾ 0.31 18 — Preoperative 2545 ⫾ 298 18 — Postoperative Postoperative 6 months 3.07 ⫾ 0.21 18 12.28 6 months 2420 ⫾ 312 18 4.91 12 months 3.09 ⫾ 0.18 18 11.71 12 months 2418 ⫾ 322 18 4.99 24 months 3.13 ⫾ 0.19 12 10.57 24 months 2309 ⫾ 309 12 5.34 36 months 3.12 ⫾ 0.20 10 10.85 36 months 2390 ⫾ 289 10 6.09 operatively (P⬍.001). There were no statistically significant differences between postoperative visits. Table 2 shows the endothelial cell density. The preoperative endothelial density was statistically significantly greater than all postoperative measurements (P⬍.05). However, there were no statistically significant differences between postoperative visits. Complications Two eyes (11.1%) developed pupillary block with an IOP of 40 to 50 mm Hg on the first day after surgery. In both cases, 1 of the iridotomies was too small. After the iridotomies were enlarged with an Nd:YAG laser, the IOP returned to preoperative values. Four eyes (22.2%), all with a model ICM V4 lens, had moderate, diffuse pigmentary dispersion on the anterior surface of the ICL at 1 month. No case was clinically significant. One eye (5.5%) with a model ICM V3 lens had mild peripheral anterior capsule opacification (ACO) 1 year after surgery. The UCVA and BSCVA in this eye were not altered from the previous postoperative value (6 months), when no lens opacification was present. One eye (5.5%) with a model ICM V3 lens developed central anterior subcapsular opacification 3 years after surgery that significantly decreased the UCVA to 20/400 (Figure 5); this patient received phacoemulsification with posterior chamber IOL implantation, achieving a final UCVA of 20/25. Five eyes (28%) had transient ocular hypertension in the first postoperative month. They were considered corticosteroid responders because their IOP returned to preoperative levels after withdrawal of postoperative topical corticosteroids. One eye (5.5%) had a significant decrease (50% reduction from preoperatively) in ACD and a narrow anterior chamber angle (Figure 6). Because the IOP was 16 mm Hg during the 1-year follow-up and the endothelial cell count showed no significant loss, the ICL was not removed. Discussion Many studies show that phakic IOLs are an effective treatment for the correction of high myopia and have Figure 5. (Pineda-Fernández) Central anterior subcapsular opaci- Figure 6. (Pineda-Fernández) Decrease in ACD after implantation fication 3 years after surgery (model ICM V3). of ICL model ICM V4. 2280 J CATARACT REFRACT SURG—VOL 30, NOVEMBER 2004 PPC IOL FOR HIGH MYOPIA significant advantages such as reversibility, immediate correction, stability, and relative simplicity.15–17,27–29 However, some studies describe complications with these lenses. Worst-Fechner iris-fixated lenses are associated with continuous endothelial cell loss20 caused by persistent inflammation. Pérez-Santonja et al.31,32 report persistent subclinical inflammation (measured with laser flare–cell fluorophotometry) produced by alteration of the blood–aqueous barrier. They also report a decrease in crystalline lens transmittance (measured by fluorophotometry). Although the association between corneal endothelial loss and Baikoff angle-supported lenses apparently has been resolved with the ZB5M model,15,33 other problems such as night halos and pupil ovalization remain. Implantation of the Fyodorov silicone PPC IOL is associated with a risk for pigmentary dispersion and a high incidence of cataract formation (81.9%).22 At present, the designs of all these anterior and posterior chamber phakic IOLs have been modified to avoid these problems; however, long-term studies are necessary to assess the potential risks to the corneal endothelium, anterior uvea, and crystalline lens. In our study, a modified PPC IOL, the ICL, effectively reduced high myopia. We found a different level of efficacy than in other published studies. Limitations in predictability are partly related to the selection of the phakic IOL power based on spectacle refraction. It is well known that refraction may be less reliable in eyes with more extreme levels of myopia. In our study, 22% of eyes had an SE within ⫾0.50 D of emmetropia and 61.1% had an SE within ⫾1.00 D. Zaldivar and coauthors27 report 69% of eyes with an SE within ⫾1.00 D and 44% within ⫾0.50 D, Assetto and coauthors34 report 31% within ⫾1.00 D, and Pesando and coauthors28 report 52.53% within ⫾1.00 D. Although it is necessary to find more accurate phakic IOL power calculation formulas, combining phakic IOL implantation with LASIK or PRK (bioptics) may improve the final visual outcome.35–37 According to our results, PPC IOL implantation appears to be safe; only 1 eye lost lines of BSCVA, and 38.8% gained 1 or more lines. This gain is the result of magnification of the retinal image by eliminating the spectacle-induced minification patients with high myopia experience preoperatively. We found pigmentary dispersion in 4 eyes (22.2%). All had the model ICM V4 lens, which has more vault- ing than the earlier ICM V3 model. The vaulting increases the distance between the ICL and crystalline lens but reduces the distance between the ICL and the pigment layer of the iris. Using ultrasound biomicroscopy (UBM), Trindade and coauthors38 found wide contact between the IOL and iris in all eyes they studied. Because of IOL–iris contact, the expected pigmentary dispersion may lead to pigmentary glaucoma, induction of synechias, iris sphincter erosion, and iris transillumination. However, in our series, pigmentary dispersion had no clinical significance. Pigmentary dispersion has been found after implantation of other phakic IOLs. Pop and coauthors39 studied the Artisan iris-claw phakic IOL in 3 eyes using UBM. They found distortion of the pigment layer located at the iris entrapment that was produced by the 2 arms of the IOL haptics. In our study, 2 eyes, both with the model ICM V3 lens, had lens opacification; 1 eye had mild peripheral ACO, and the other eye developed central anterior subcapsular opacification. The subcapsular opacification was probably because the smaller vaulting of the ICM V3 causes more anterior capsule–crystalline lens contact.30 Trindade and coauthors38 found contact between the ICL and crystalline lens in 8 eyes (89%) using UBM, but this unequivocal touch was impossible to demonstrate because UBM is not able to separate distances smaller than 40 ␮m (instrument resolution). Jiménez-Alfaro et al.40 found peripheral contact between the ICL and crystalline lens in 12 eyes (60%) and central contact in 3 eyes (15%). They also found that crystalline lens transmittance measured by fluorophotometry decreased during the entire 24-month follow-up. The decrease in crystalline lens transmittance after implantation of PPC IOLs can be related to surgical trauma, the effect of Nd:YAG laser treatment of iridotomies,27 subclinical inflammation, and continuous or intermittent contact between the IOL and crystalline lens.40 A decrease in crystalline lens transmittance and subclinical inflammation has also been observed after the implantation of iris-fixated32 and angle-supported41 phakic IOLs. It is important to use a surgical technique that avoids inadvertent crystalline lens trauma. One eye had a significant decrease (50% reduction from preoperatively) in ACD after surgery. According to Staar Surgical AG communications, the optimum vault size is 10% of the ACD. In our study, all eyes except 1 had a decrease in ACD that ranged from 9% J CATARACT REFRACT SURG—VOL 30, NOVEMBER 2004 2281 PPC IOL FOR HIGH MYOPIA to 14% (mean 12.28% at 6 months); the ACD did not increase over time. Vaulting is influenced by the ICL shape and its overall diameter.30 If the ICL is too long, it will vault too much over the crystalline lens and bulge too much in the anterior chamber. In our study, the white-to-white measurements may have been overestimated, leading to an oversized ICL and thus a significant reduction in ACD. In our study, the endothelial cell density loss at 6 months was 4.91% and did not progress over time, suggesting that the initial loss was related to surgical trauma. Jiménez-Alfaro et al.40 found a cell loss of 4.41% at 3 months with no progression during subsequent visits. We achieved good refractive results with the ICL for the correction of high myopia. However, our sample size was too small and it would thus be inappropriate to derive definitive conclusions based on our initial results. The long-term safety of the ICL must be determined. 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