Noticias 10/13/2021

Foldable phakic iris-claw lenses: results and complications during the surgeon´s learning curve.

Por: Antonio Toro

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Foldable phakic iris-claw lenses
Roberto Fernández-Buenaga MD, PhD aPablo Sanz b, c, Ana Belén Plaza a, Jorge L. Alió MD, PhD, FEBO a,d. a Cornea, Cataract and Refractive Surgery Department, VISSUM Alicante, Spain. / Research & Development Department, VISSUM Alicante, Spain. C/Cabañal 1, 03016, Alicante, Spain. b Carl Zeiss Vision International GmbH, Turnstrasse 27, 73430 Aalen, Germany. c Institute for Ophthalmic Research, Eberhard Karls University Tuebingen, Elfriede-Aulhorn-Straße 7, 72076 Tuebingen, Germany.  Division of Ophthalmology, Universidad Miguel Hernández, Alicante, Spain
Dr Roberto Fernandez Buenaga

Colabora:

Dr. Roberto Fernández – Buenaga

Co-fundador y Director Médico en Fernández Casas Oftalmólogos. 

Abstract

Purpose: To analyse the refractive results, safety and complications of phakic iris-claw IOL implantation surgery during the surgeon´s learning curve.

Methods: This retrospective study included a total of 22 consecutive eyes of 12 patients who were not suitable for corneal laser surgery and underwent phakic iris-claw IOL (Artiflex) implantation. The main analysed parameters were manifest refraction, uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), endothelial cell count (ECC) and complications. Non-parametric tests were used for statistical purposes. 

Results: The median follow-up was 39 months (p25: 24.75; p75: 60). LogMAR UCVA and logMAR BCVA improved significantly after the surgery (p<0.001) and (p=0.005) respectively. In addition, 4 eyes (20.00%) gained at least one line of BCVA while none lost lines of BCVA. Furthermore, 80.00% and 90.00% of eyes were within ±0.5 and ± 1.0 diopters (D) of spherical equivalent (SE) respectively.

Median efficacy and safety index were 1 (p25: 0.96; p75: 1.03) and 1.02 (p25: 1; p75: 1.14). The median preoperative ECC was 2967 (p25: 2341; p75: 3296) cells/mm2 and decreased to 2841 (p25: 2604; p75: 3058) cells/mm2 in the last follow up visit (p=0.532). Regarding complications, 2 eyes (9.09%) required a second surgery to improve the IOL centration and 3 eyes (13.63%) developed inflammatory deposits which were solved with steroid drops. 

Conclusion: Phakic iris-claw IOL implantation showed satisfactory refractive results and safety conditions during the surgeon’s learning curve. Correct IOL centration was the main difficulty found during the learning curve. 

Keywords: phakic intraocular lens; iris-claw intraocular lens; learning curve; ophthalmic surgery.

Declarations:

Funding: No funding.

Conflicts of interest/Competing interests (include appropriate disclosures)

The authors declare that they have no competing interests.

Ethics approval (include appropriate approvals or waivers)

Signed informed consent was obtained from each patient, agreeing to the use of their clinical data and images for scientific purposes. The research approach was in accordance with the tenets of the declaration of Helsinki and approved by the Ethics Commission of Vissum Miranza.

Consent to participate (include appropriate statements)

Signed informed consent was obtained from each patient, agreeing to the use of their clinical data and images for scientific purposes.

Consent for publication (include appropriate statements)

Patients involved in this study signed that they were aware that the information and conclusions obtained in the study could be published in a scientific journal.

Availability of data and material (data transparency)

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Code availability (software application or custom code)

Not applicable.

Authors’ contributions:

RFB and PSD conceptualized the study design. RFB and JLA provided the patients. RFB, PSD and ABPP collected, interpreted and conducted the formal data analysis. RFB, PSD, ABPP and JLA carried out literature research, writing and critical review of the manuscript. All authors read and approved the final manuscript.

Introduction

The standard of care for the correction of refractive defects is laser corneal surgery. The indications and the technology have been refined leading to excellent results with few complications [1]. For those patients who are not adequate for corneal surgery, phakic intraocular lens (IOL) implantation becomes an option to be considered [2,3].

Phakic IOLs offer several advantages such as excellent quality of vision (the corneal shape remains unchanged), tear film stability and the potential reversibility of the procedure [3,4]. Disadvantages are inherent to the intraocular nature of the procedure itself which includes the risk of endophthalmitis, cataract development, endothelial cell loss, pigment dispersion, uveitis, glaucoma and retinal detachment [5-9]. 

Phakic IOLs are classified according to the anatomical site where they are implanted. Posterior chamber IOLs are implanted in the ciliary sulcus, between the iris and the crystalline lens. Anterior chamber IOLs are implanted in front of the iris and they are subdivided into angle supported lenses and iris supported lenses. The surgical technique is completely different for each type of phakic IOL. Therefore, it is essential for the novice surgeon to know the tips and difficulties related to each technique before doing the first implantations.

Iris-claw implantation technique is not similar to any other eye surgery procedure and requires bimanual skills. Because of that, some surgeons might feel stressed before performing their first cases. To the best of our knowledge, this is the first study that reports the outcomes and pitfalls during the surgeon`s learning curve with a phakic iris-claw lens. The goal of this study is to report useful information about the results and difficulties found in the course of the surgeon`s learning curve, in order to help the novice surgeons to anticipate or prevent the most common challenges that they might need to deal with during their first implantations.

Methods

Retrospective study of consecutive cases, starting with the first implantation case of an iris-claw phakic IOL for myopia correction. All the surgeries were performed by the same surgeon (RFB). A senior experienced surgeon (JLA) was available to help if needed. The first surgery was performed in January 2013 and the last one in January 2015. Outcomes were analysed at the 3 months follow-up visit and in the last follow-up visit.

All patients included had stable refraction for at least 1 year and were not candidates for corneal laser surgery. Anterior chamber depth (ACD) from endothelium was ≥ 2.85 mm, ECC was > 2200 cells/mm2, angle opening ≥ 35º, lens rise < 200 microns, astigmatism ≤ 2 diopters and scotopic pupil diameter <6.5 mm.

The basis of the exclusion criteria were patients younger than 21, eye disease, cataract, glaucoma or retinal disease, chronic or recurrent uveitis, previous eye surgery, autoimmune systemic diseases, diabetes, and pregnancy.

Informed consent was obtained from all patients to include clinical information in scientific studies following the tenets of the Declaration of Helsinki. A specific consent to use and publish images was also gathered from the patients. The study was approved by the institutional review board of Vissum Miranza.

Preoperative tests included uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), manifest and cycloplegic refractions, slit lamp examination, Goldmann tonometry, corneal thickness measurement (DHG500, DHG Technology, Inc.), topography (Costruzione Strumenti Oftalmici), ACD measured by optical coherence tomography (Visante, Carl Zeiss Meditec AG), endothelial cell count (ECC) (Noncon Robo, Konan Medical), biometry (IOLMaster, Carl Zeiss Meditec AG), pupillometry in different light conditions (Procyon Pupillometer P2000SA, Procyon Instruments, Ltd.), and funduscopy.

Surgical technique

All surgeries were performed at the same ophthalmic centre (Vissum Alicante, Spain), by a single surgeon (RFB). The IOL power was selected according to the manufacturer’s calculator. The Artiflex IOL (Ophtec) has a flexible silicone optic and 2 rigid polymethyl methacrylate haptics. It provides a dioptric range from -2.00 to -14.50 D of sphere.

During the surgery peribulbar anesthesia (2-4 cc) of 2% lidocaine and 0.5% bupivacaine was used. In addition, Midazolam was used as a sedative agent before the surgery.

Two 1.2 mm vertical paracentesis were placed at 2 and 10 o’clock position, 9 mm away from each other. Acetylcholine was injected into the anterior chamber to protect the crystalline lens. Cohesive viscoelastic (Provisc) was used to enlarge the ACD. The Artiflex IOLs were implanted through a 3.2 mm peripheral corneal incision located at 12 o’clock position. The IOL was fixated using an enclavation needle that pushes the iris into both claws. A peripheral iridectomy was performed with Vannas scissors. Finally, intracameral cefuroxime was injected into the anterior chamber.

In all cases after the surgical procedure, topical ofloxacin drops were used every 6 hours for 1 week, dexamethasone eyedrops (Maxidex) were used 4 times a day for 2 weeks and then it was substituted by fluorometholone (FML) every 8 hours for 3 additional weeks tapering the dose to 1 drop every week. Topical lubricants (preservative free 0.15% sodium hyaluronate [Hyabak]) were prescribed 3-4 times a day for 1 month.

Statistical analysis

The surgical outcomes were analysed using SPSS for windows software (version 17.0, SPSS Inc.). In addition to that, non-parametric tests were used as the sample size was smaller than 30. Due to the same reason, all the variables were reported by means of the median, 25 and 75 percentiles (between parenthesis).

Results

A total of 22 eyes of 12 patients were studied. The median age of the patients was 33 (p25: 30; p75: 39) years old. The median follow-up period was 39 months (p25: 24.75; p75: 60) with a minimal follow-up of at least 12 months in all the cases at the time of the last visit. There was 1 patient (2 eyes) who attended the 3 months postoperative visit but never came back again.

Median uncorrected logMAR visual acuity (UCVA) improved from 2.2 (p25: 2.2; p75: 2.2) to 0.008 (p25: 0.000; p75: 0.031) and 0.008 (p25: 0.000; p75: 0.068) at the 3 months and last follow-up visit respectively; (p<0.001) and (p<0.001). Median preoperative best corrected logMAR visual acuity (BCVA) was 0.00 (p25: 0.00; p75: 0.02) whereas it was 0.00 (p25: 0.00; p75: 0.00) and 0.00 (p25: 0.00; p75; 0.00) 3 months postoperatively and in the last follow up visit respectively (p=0.002) and (p=0.005). In addition, 4 out of 20 eyes (20.00%) gained at least one line of BCVA while no eye lost lines of BCVA at the last follow-up visit. In Table 1, preoperative and postoperative sphere, cylinder and spherical equivalent are summarised.

 

 

Preoperative

3 months postop

Last visit

P

UCVA

2.2 (p25: 2.2; p75: 2.2)

0.008 (p25: 0.0; p75: 0.031)

0.008 (p25: 0.0; p75: 0.068)

<0.001

BCVA

0 (p25: 0; p75: 0.02)

0 (p25: 0; p75: 0)

0 (p25: 0; p75: 0)

0.005

Sphere

-7.75 (p25: -9.31; p75: -6.93)

0 (p25: -0.25; p75: 0)

0 (p25: -0.43; p75: 0)

<0.001

Cylinder

-1.25 (p25: -2; p75: -0.50)

-0.37 (p25: -0.50; p75: 0)

-0.50 (p25: -0.75; p75: 0)

0.001

Spherical Equivalent

-9.12 (p25: -10.03; p75: -7.71)

-0.18 (p25: -0.40; p75: 0)

-0.31 (p25: -0.50, p75: 0)

<0.001

Table 1. Refractive parameters preoperatively, 3 months postoperatively and in the last follow up visit. UCVA and BCVA are reported in LogMAR. All the variables are shown by means of median (percentile 25; percentile 75). P represents the statistical significance by means of the Wilcoxon signed-rank test when preoperative and last visit examination were compared.

The deviation of the achieved SE correction from the intended refractive SE was calculated. After 3 months and 1 year, it was within 0.5 D in 19 out of 22 eyes (86.36%) and 16 out of 20 eyes (80.00%) respectively; and within 1 D of SE in 21 out of 22 (95.45%) and 18 out of 20 eyes (90.00%) respectively (Fig. 1).

Median efficacy (Postoperative UCVA/Preoperative BCVA) and safety index (Postoperative BCVA/Preoperative BCVA) were 1 (p25: 0.96; p75: 1.03) and 1,02 (p25: 1; p75: 1.14) respectively. Both indexes remained unchanged from the 3 months follow-up visit to the last visit.

The median preoperative endothelial cell counting was 2967 (p25: 2341; p75: 3296) cells/mm2 and decreased to 2924 (p25: 2670; p75: 3124) cells/mm2 at the 3 months follow-up visit. Thus, there was a median loss of 43 cells (1.44%) due to the surgical trauma (P= 0.867). The endothelial cell counting during the last follow-up visit was 2841 (p25: 2604; p75: 3058) cells/mm2. The median cell count reduction due to the lens itself, thus from the 3rd month to the last follow-up visit (39th month), was 83 cells/mm2 (2.83%) (p= 0.156). As a result, that meant that the median percentage of cell loss per year was estimated in 0.94%.

Regarding complications, 2 eyes (case 6th and 8th) out of 22 eyes (9.09%) required a second surgery to improve the IOL centration (Fig. 2). Another 3 eyes (13.63%) developed inflammatory deposits after the surgery. These deposits disappeared completely after a steroid course (Fig. 3).

None of the eyes developed any degree of crystalline lens opacity during the follow-up visits.

Finally, 1 eye out of 20 (5.00%) required a laser enhancement surgery in order to achieve the aimed refractive result.

Discussion

In hands of experienced surgeons, the foldable Artiflex phakic iris-claw IOL showed to be predictable, effective and safe for the correction of high myopia in a prospective multicentre study conducted in 299 eyes and with follow-up visits for 2 years [10]. However, to the best of our knowledge, there is no information published regarding the outcomes and complications of this IOL during the surgeon´s learning curve. This study is our contribution to assess the impact of the surgeon learning curve in the results, complications and surgical trauma with this phakic IOL.

The refractive parameters and visual acuity improved significantly after the surgery (Table 1). The predictability analysis showed that after 3 months and 1 year, the SE was within 0.5 D in 86.36% and 80.00% of the cases respectively; and within 1.0 D of SE in 95.45% and 90.00% of the eyes respectively (Fig. 1). This result is similar to those reported by other authors. Dick HB et al.(10), reported in their multicentre prospective study 75.20% of eyes within 0.5D and 94.30% within 1.0 D. Pjano MA et al.[11], 90.00% of eyes within 1.0 D; Qasem Q et al. [12], reported 86.00% of eyes within 1.0 D at 1 year of follow up and Albarrán et al.[13], 89.10% of eyes within 0.5 D of SE. The median efficacy index in our study was 1. Again, this is comparable with the efficacy index reported by other authors [10,12,14]. Considering all these comparisons, we might conclude that the refractive results accuracy does not seem to be affected by the surgeon learning curve.

In terms of safety, the median logMAR BCVA improved significantly from 0 (p25: 0; p75: 0.02) to 0 (p25: 0; p75: 0) in the last visit (p=0.005). Indeed, 20.00% of eyes gained at least 1 line of vision whereas no eye lost lines of vision. In high myopia, it is well known that, the likelihood of gaining lines of vision is greater with phakic IOLs than with laser corneal procedures [13]. This is because of the magnification effect of the intraocular lens. However, other authors reported a higher proportion of eyes gaining lines of vision [10-13], being as high as 50.00% in the series published by Albarrán et al. [13]. One possible explanation for this could be that the vast majority of our patients had an excellent preoperative BCVA with almost no presence of amblyopic eyes in our series. In fact, all the eyes included in our series had a preoperative logMAR BCVA of 0.1 or even better, therefore, the chance of gaining lines of vision could be limited by this factor.

A median safety index of 1.02 (p25: 1; p75: 1.14) was obtained. A safety index over 1 is considered a good result as it indicates that there is some degree of improvement in the BCVA after the surgery. Dick HB et al. [10], reported a safety index of 1.09, 1.11, and 1.09 at 6 months, 1 year, and 2 years after surgery, respectively. Castro de Luna et al.[14], calculated a safety index of 1.1 and 1.02, 1 and 2 years postoperatively. According to those results regarding the surgeon´s learning curve, our safety index does not differ in a relevant way with those published in previous studies which were performed by experienced surgeons.  

Endothelial cell monitoring is one of the most important aspects when a phakic IOL is implanted as phakic IOLs could trigger an endothelial cell loss acceleration in some cases [5,6]. Endothelial cell loss is a common issue for all kinds of phakic IOLs and it might also occur in posterior chamber phakic lenses [15,16]. Indeed, in a long series in which the reasons for phakic IOL explantation were analysed, endothelial cell loss was the second most important reason only after cataract development [17]. Basically, there are two main mechanisms of endothelial cell damage in patients with phakic IOLs. First mechanism is the endothelial cell loss due to the surgical trauma and the second one is the long-term loss that can be higher than the physiological due to the IOL presence itself. Hence, it is advisable to perform an ECC analysis 3 months after the surgery to assess the endothelial damage due specifically to the surgery. In this investigation, this was one of the main outcomes measures as we hypothesised that, during the learning curve, the surgical trauma could be more intense leading to a higher endothelial cell loss in the short term. The median preoperative ECC was 2967 (p25: 2341; p75: 3296) cells/mm2 and decreased to 2924 (p25: 2670; p75: 3124) cells/mm2 at the 3 months follow up visit. Thus, there was a median loss of 43 cells (1.44%) due to the surgical trauma (P= 0.867). Other authors have previously reported endothelial cell loss results with this Artiflex foldable phakic iris-claw lens. We detected that the cell reduction was worse than the published by Dick HB et al. [10], who reported a mean cell loss of 0.05%, 6 months after the surgery. However, other investigators showed greater endothelial reductions; Pjano et al.[11] reported an endothelial cell loss of 6.10% 1 month after the surgery, Castro de Luna et al.[14] had a 8.34% reduction in the cell count 3 months postoperatively, Shajari and colleagues[18], detected a 4.50% cell loss 1 year after the surgery. Karimian et al.[19], reported an endothelial cell loss of 9.00% but after a mean follow up of 30±11 months. They did not provide data from earlier follow-up visits. Hashemi et al.[20], showed an endothelial cell loss of 3.04% 1 year after the IOL implantation. Finally, Jonker et al.[21], reported an endothelial cell loss 6 months after the implantation of artiflex myopia of 2.16%, similar to our findings. Hence, the endothelial cell loss due to the surgical trauma during the learning curve was acceptable and consistent with most of the previous published papers. The ECC reduction from the 3rd month to the last follow up visit (39th month), was 83 cells/mm2 (2.83%). The follow up time of our study was not long enough to assess the impact of this IOL in the endothelium survival in the long-term. However, this long-term loss should not be related to the surgical learning curve, and because of that, it was not a goal of this study.

IOL centration may be challenging in the first iris-claw implantation surgeries. In fact, in two eyes (9.09%) of our series (case 6th and 8th), the IOL was not properly centred (Fig. 2) leading to bad quality of vision and dysphotopsia. Dysphotopsia is related to bad IOL centration or to an insufficient optic diameter for the pupil in low mesopic or scotopic conditions. Those two eyes required a second surgery to improve the IOL centration which was finally achieved. Other authors did not report any incidence of early repositioning surgery to improve IOL centration [10-14]. However, Dick et al.[10], reported glare and halo in 3.40% and 3.00% of cases respectively. It was remarkable that those two eyes with poor IOL centration occurred within the first 8 cases with no more incidences after that. Therefore, achieving good IOL centration is, in our opinion, related to the surgeon´s learning curve. We advocate to check the IOL position at the slit lamp before the patient leaves the operating room. This should help to detect and resolve those cases with insufficient IOL centration before the patient is discharged the day of the surgery.

IOL inflammatory deposits (Fig. 3) were detected in 3 eyes (13.63%). In all the cases these deposits developed early, within 3 months postoperatively. These deposits were located in the IOL optic and a drop of at least 2 lines of vision was detected in all of them. Fortunately, the inflammatory deposits resolved completely after an intensive steroid drop course (Fig. 3). Even though inflammatory reaction has been described after Artisan phakic IOL implantation [22,23], it seems to be more relevant with Artiflex IOL. Dick et al.[10], reported pigment precipitates in 4.80% of the eyes and non-pigment precipitates in 1.40% of eyes. Pigment precipitates did not cause any loss of vision whereas non-pigment ones did. Visual acuity was restored after steroid treatment. Hashemi et al.[20], also detected deposits in 3 eyes in the early postoperative period which resolved with steroid drops. Similarly, Ruckhofer et al.[24], reported giant cell precipitates on the IOL surface in 12.00% of the eyes but these precipitates diminished over time without treatment. In a study performed in children (who are well known to be a population at high risk of postoperative inflammation) one eye out of 11 (9.09%) developed inflammatory deposits which were successfully treated with prednisolone drops[25].  Other investigators reported subclinical inflammation without proper formation of precipitates in 7.50% of cases [11]. In a study by Zuberbühler et al.[26], inflammation was reported in 5.80% of eyes. The reason why those precipitates developed may be due to multifactorial causes. A convex iris or too much iris enclavated, may cause and increased contact between the iris and the IOL breaking the blood-aqueous barrier [27,28]. Other authors suggested that the more demanding surgery of Artiflex compared with Artisan or the silicone material itself may play a role as well [10,11]. After having those cases with inflammatory precipitates, we decided to extend the topical steroid drops for 5 weeks (as described in the methods section) instead of only 3 weeks. Since then, we have not detected inflammatory precipitates again. Thus, an adequate iris configuration selection, avoiding excessive iris tissue enclavation and long enough steroid drops treatment are strategies that may prevent inflammatory precipitates to develop.

We did not find other complications previously described such as hyphema, synechiae, or cataract development in our series.

In summary, foldable phakic iris-claw IOL implantation was an effective, predictable and safe technique during the surgeon´s learning curve. The most common issue related to the learning curve was the correct IOL centration, which was found in 2 eyes, both within the first 8 implantations. As pupil is usually slightly nasally deviated, nasal enclavation is more challenging as there is less room and less iris tissue. We recommend starting by enclavating the nasal haptic as we have found that this helps to improve IOL centration. As above mentioned in the text, we also advocate to check the IOL position at the slit lamp in the operating room. This helps to detect and resolve those cases with insufficient IOL centration the same day of the surgery.

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