Journal of Refractive Surgery

Review Supplemental Data

Complications and Explantation Reasons in Intracorneal Ring Segments (ICRS) Implantation: A Systematic Review

María-José Bautista-Llamas, OD, PhD; María Carmen Sánchez-González, OD, PhD; Inmaculada López-Izquierdo, OD, PhD; Alfredo López-Muñoz, OD, PhD; Beatriz Gargallo-Martínez, OD, PhD; Concepción De-Hita-Cantalejo, OD, PhD; José-María Sánchez-González, OD, PhD

Abstract

PURPOSE:

To review the intraoperative and postoperative complications after intracorneal ring segment implantation and to report the explantation rate among the available scientific literature.

METHODS:

Three different databases (PubMed, Web of Science, and Scopus) were assessed from January 1995 to June 2019. The keywords used were: ring, rings, ICRS (intracorneal ring segments), segment, segments or Intacs, complication, explantation, explanted, retired, and removal.

RESULTS:

The selection process of this systematic review study is described in a flow diagram. A total of 39 studies published between 1995 and 2019 were included. Sixteen studies were case reports, 21 were case series studies, and 2 were chart analysis works. This study enrolled 1,946 participants, and 2,590 eyes were included. The postoperative complications described in most studies included migration, ring extrusion, corneal thinning, corneal melting, and some type of infective keratitis. These complications together with glare, halos, fluctuating vision, neovascularization, foreign body sensation, or pain represented most of the causes. The percentage rate of explantation ranged from 0.5% up to 83.3%. If we analyze those articles with a high number of implantations (2,124 eyes), an explantation rate between 0% and 1.4% was obtained.

CONCLUSIONS:

The complication rate and explantation ratio in segments of the intracorneal ring segments analyzed in the available scientific literature are minimal. Therefore, patient selection, surgery planning, and postoperative follow-up are critical to the success of surgery.

[J Refract Surg. 2019;35(11):740–747.]

Abstract

PURPOSE:

To review the intraoperative and postoperative complications after intracorneal ring segment implantation and to report the explantation rate among the available scientific literature.

METHODS:

Three different databases (PubMed, Web of Science, and Scopus) were assessed from January 1995 to June 2019. The keywords used were: ring, rings, ICRS (intracorneal ring segments), segment, segments or Intacs, complication, explantation, explanted, retired, and removal.

RESULTS:

The selection process of this systematic review study is described in a flow diagram. A total of 39 studies published between 1995 and 2019 were included. Sixteen studies were case reports, 21 were case series studies, and 2 were chart analysis works. This study enrolled 1,946 participants, and 2,590 eyes were included. The postoperative complications described in most studies included migration, ring extrusion, corneal thinning, corneal melting, and some type of infective keratitis. These complications together with glare, halos, fluctuating vision, neovascularization, foreign body sensation, or pain represented most of the causes. The percentage rate of explantation ranged from 0.5% up to 83.3%. If we analyze those articles with a high number of implantations (2,124 eyes), an explantation rate between 0% and 1.4% was obtained.

CONCLUSIONS:

The complication rate and explantation ratio in segments of the intracorneal ring segments analyzed in the available scientific literature are minimal. Therefore, patient selection, surgery planning, and postoperative follow-up are critical to the success of surgery.

[J Refract Surg. 2019;35(11):740–747.]

Intracorneal ring segments (ICRS) were used in the 1980s1 for low and moderate myopia correction, and anterior cornea curvature flattening occurred by placing ICRS on the stroma. Previous studies reported that it was a safe, effective, and stable method to correct low myopia.2 Currently, the method has been extended to various pathologies, such as keratoconus, pellucid marginal degeneration, and iatrogenic corneal ectasia.3 Three types of ICRS are available: Intacs (Addition Technology, Sunnyvale, CA), Ferrara (Mediphacos, Belo Horizonte, Brazil), and Keraring (Mediphacos). Classic ICRS channel creation by implanting the segments via mechanical dissection is currently being replaced by femtosecond lasers. In addition to being less annoying to the patient, the use of femtosecond lasers is faster and provides greater control of the depth, width, and centering of the tunnel, as well as increased accuracy. In addition, epithelial tissue changes are minimal and recovery after surgery is faster.4,5 Channel creation by both methods yields similar visual and refractive results. Nevertheless, increased intraoperative complications occurred with mechanical ICRS implantation.6,7

ICRS implantation involves intraoperative complications, such as incomplete tunnel creation, corneal surface perforation, or anterior chamber perforation. In the first case, the complication can be resolved by mechanical dissection. The perforation rates are low, which is one of the most serious complications.8,9 Another intraoperative complication is vacuum loss, which occurs during femtosecond laser suction; however, it is possible to recreate the same corneal plane and the intrastromal channel. Among postoperative complications, segment migration can occur, which may be due to an excessive ICRS width in a thin cornea. Coskunseven et al.8 and Mounir et al.10 reported a high ring migration rate. ICRS implantation near the incision implies a great risk of corneal melting, and ICRS should be explanted immediately in these cases.11 Another reason for explantation reported in the current literature is poor visual acuity or fluctuations in visual quality. The first to describe an explantation for this reason was Asbell et al.12 He noted glare, halos, and fluctuating vision. Other authors13–19 have also reported poor visual acuity as a reason for explantation.

One of the main goals of ICRS surgery is to treat keratoconus or ectasia after laser in situ keratomileusis (LASIK). The use of a permanent suture at the incision site and avoiding eye rubbing have been proposed.20 Infection risk is noted with ICRS implantation. Multiple microorganisms can cause this complication, and both bacteria and fungi can cause infectious keratitis. For example, Staphylococcus aureus21 appears in up to 25% of cases, followed by Pseudomonas species and Streptococcus pneumoniae, among others.22,23

Several factors have been detected in relation to the onset of this complication, such as previous traumas, use of contact lenses, or systemic diseases such as diabetes mellitus.24 The most efficient method to treat infectious keratitis after ICRS implantation is topical antibiotic therapy. Bourcier et al.25 reported that topical antibiotic therapy alone was sufficient to treat the infection. On the other hand, in some publications, ICRS explantation was considered as the first therapeutic option to treat this complication. Deep corneal neovascularization is another complication that can be caused by the implant and is not associated with the surgical wound. Treatment with topical corticoid agents and surgical removal of the ring may induce vessel regression.26

This systematic review reports intraoperative and postoperative ICRS complications and explantation rates among the available scientific literature.

Methods

This review is registered at the PROSPERO International prospective registry. The study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement recommendations. PubMed, Web of Science, and Scopus databases were searched from January 1995 to June 2019. The keywords used were ring, rings, ICRS (intracorneal ring segments), segment, segments or Intacs, complication, explantation, explanted, retired, or removal. Experts identified and evaluated the articles selected according to inclusion and exclusion criteria. Two independent reviewers extracted and selected studies. Duplicate articles were assessed by the authors. Among the inclusion criteria were: (1) case reports, case series, chart analysis, and randomized controlled trials reporting intraoperative and postoperative complications in ICRS implantation; (2) ICRS explantation studies and the reasons; (3) there were no restrictions on publication type (conference abstract versus full article); and (4) abstracts were included only if they fulfilled our eligibility criteria and if no subsequent study had been published. Among the exclusion criteria were: (5) narrative reviews, systematic reviews, letters to the editor, and correspondence; (6) animal studies; and (7) non-English and non-indexed publications. The authors designed the tables to extract the study data.

Systematic review data were extracted according to study characteristics and main outcome measures. Among the first part, extracted data items included: (1) authors and publication year; (2) study design (case report or retrospective case series); (3) conflict of interest declaration (yes or no; which, if yes); (4) participant inclusion and exclusion criteria; (5) period of total patient follow-up from the first complication to its total resolution expressed in weeks; (6) percentage of male participants involved in the study; (7) number of participants and eyes involved in the study; (8) ICRS type, manual or femtosecond laser implantation, and ICRS brand and/or design; (9) number of segments per eye (ie, one, two, or both numbers were provided if one and two ICRS implantations were reported among different participants); and (10) mean participant age expressed in years. Among the outcome measures, the following data items were reported: (11) previous eye history, such as previous treatments, ocular pathologies, or eye surgeries; (12) intraoperative complications, and (13) postoperative complications with the percentage of total eyes in this study in brackets; (14) explantation rate; and (15) explantation reasons. Finally, (16) treatment used to resolve the complications was recorded. In this case, the treatment reported was the one that was ultimately effective. In-between unsuccessful treatments were avoided.

To determine the risk of bias in individual studies, two reviewers (M-JB-L and J-MS-G) with adequate reliability worked independently and blindly to create a summary chart (Table A, available in the online version of this article) based on the Quality Assessment Tool for Case Series Studies from the National Heart, Lung, and Blood Institute.27 For disputes between the two reviewers, a third unblinded reviewer (AL-M) resolved the issue. Questions included in the tool were: (1) Was the study question or objective clearly stated?; (2) Was the study population clearly and fully described, including a case definition?; (3) Were the cases consecutive?; (4) Were the participants comparable?; (5) Was the intervention clearly described?; (6) Were the outcome measures clearly defined, valid, reliable, and implemented consistently across all study participants?; (7) Was the length of follow-up adequate?; (8) Were the statistical methods well described?; and (9) Were the results well described? This analysis did not result in the elimination of any article. Articles with a high risk of bias had a lower weight for data synthesis. The primary summary measures used in this systematic review were incidence and percentage of complications and explantations among all included studies. Furthermore, the average changes in terms of visual acuity and mean keratometry were also reported. Finally, we also included ICRS design and implantation technique with more complications and common treatments used in complication resolution as summary measures.

Quality Assessment Tool for Case Series Studies

Table A:

Quality Assessment Tool for Case Series Studies

Results

This systematic review study selection process is described by a flow diagram (Figure A, available in the online version of this article). A total of 39 studies published between 1995 and 2019 were included in this systematic review. Sixteen studies were case reports, 21 were case series studies, and only 2 were chart analysis works. Only 3 studies reported conflicts of interest.17,28,29 The inclusion criteria included participants with grade I, II, and III keratoconus; residual myopia after LASIK; ICRS explantation; keratitis infection; ectasia after LASIK; contact lens intolerance; ICRS migration; atopic keratoconus; or ICRS surgery simultaneously with cross-linking. Regarding exclusion criteria, most studies omitted ICRS implantation cases without complications. Other authors excluded studies for different reasons: corneal scarring,30 leucoma,31 keratitis,8,32 non-Intacs ICRS,15 manual ICRS implantation,17 or corneal hydrops10,28 in grade IV keratoconus. The postoperative follow-up ranged from 2 to 240 weeks. The mean follow-up for the reported studies was 56.9 weeks. This systematic review enrolled 1,946 participants. In total, 62.34% of these participants were male, and 2,590 total eyes were included. The mean age of participants was 33.45 years. Many of the studies reported that surgery was performed manually or with a femtosecond laser and the type of segment, but did not report the percentage of each type of surgery. Therefore, a quantitative analysis could not be performed using the studies. Detailed study characteristics are reported in Table B (available in the online version of this article).

Study selection process according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.

Figure A.

Study selection process according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.

Study CharacteristicsStudy Characteristics

Table B:

Study Characteristics

Table 1 describes the complications caused by the ICRS and the explantation provided in the revised studies. In relation to the previous ocular history of the patients, we found 8 articles with ectasia after LASIK,14,15,19,22,29,30,33,34 6 articles with low and moderate myopia,12,14,18,23,24,35 2 articles with pellucid marginal degeneration,14,33 and only 1 article with keratoplasty.14 In addition, atopic asthma and blepharoconjunctivitis,36 lagophthalmos and dry eye,37 herpetic keratitis,38 and blepharitis39 were described in the ocular history.

Data Extraction for Complications and ExplantationsData Extraction for Complications and Explantations

Table 1:

Data Extraction for Complications and Explantations

Intraoperative complications were described in five publications: some epithelial damage at the incision site35; perforation of the anterior chamber (only 5% of the 20 eyes)20; difficult insertion in one case and intra-operative suction loss28; incomplete tunnel creation, misdirection of the ring segment, perforation into the anterior chamber, decentration of the ring segments, inverted implanted rings, broken ring segments, broken orifice of the ring10; and galvanometer lag error and endothelial perforation.8

Postoperative complications were described in most studies: migration, ring extrusion, corneal thinning, corneal melting, and type of infective keratitis (bacterial, Staphylococcus aureus, Streptococcus mitis, Staphylococcus epidermidis, annular herpetic, and Aspergillus fumigatus). These complications together with glare, halos, fluctuating vision, neovascularization, foreign body sensation, or pain account for 100% of the rings explanted in 50% of the articles. The percentage rate of explantation ranged from 0.5% up to 83.3%. If we analyze those articles with a high number of implantations8,10,28,33,40 (2,124 eyes), an explantation rate between 0% and 1.4% was obtained.

According to ICRS type reviewed, Ferrara and Keraring ICRS reported a 1% explantation rate, and Intacs reported a 19% explantation rate. Only 4 studies reported no explantation in the case.28,38,41,42 The most commonly used treatment was antibiotics in those articles in which it was described. Some articles did not report it, and two of the articles recommended suturing of the incision.17,42

Risk of bias assessment within the studies was grouped into three outcome levels: low (yes = 0 and 3),11,12,18,19,23,36–38,42–47 medium (yes = 4 to 6),14–16,22,24,29,33,35,39,40,41,48,49 and high (yes = 7 to 9).8,10,13,17,20,28,30–32,34,50,51

Discussion

Mechanical technique complications comprise anterior or posterior perforation by manual spreader, epithelial defects, decentration, and incision enlargement to the limbus or central cornea due to surgeon manipulation. Most cases of extrusion and final removal of ICRS were experimental in manual ICRS implantation. During ICRS implantation surgery, keratocyte activation52 and apoptosis were noted. Twa et al.53 demonstrated lipid formation and increased keratocyte density following ICRS implantation. Kugler et al.40 postulated that additional trauma to the incision and tunnel results in increased keratocyte apoptosis, major tissue degradation, and a subsequently increased number of complications, such as corneal melting. Femtosecond laser ICRS channel creation is less aggressive. Femtosecond laser treatment is associated with reduced complications for corneal melting. Corneal confocal microscopy has been used for assessment after manual54 and femtosecond laser55 ICRS implantation; however, to our knowledge, no studies have reported keratocyte activation scores in femtosecond laser versus manual techniques.

Nevertheless, the femtosecond laser introduced new complications to ICRS implantation. All of these complications were intraoperative, including incomplete channel creation, galvanometer lag error, and vacuum loss. Incomplete tunnel creation was solved by completing the channel using a mechanical separator; thus, complications of manual segment implantation were also noted. Coskunseven et al.8 proposed increasing the energy level of the femtosecond laser or reducing the space between spots. The false channel causes difficulty in implantation. As described by Jacob et al.,56 the situation can be overcome by removing the segment and turning it around so it is inserted in the opposite direction through the entry incision. It is then advanced using the second segment as an intra-channel instrument. When galvanometer error occurs, the surgical procedure must be suspended. During the second surgery, the same cone should be used. The tunnel channel depth must be 30 µm above the original tunnel.8 If an error occurs during incision formation, the cut should be continued with the knife edge. On the other hand, if vacuum loss occurs during incision, it is possible to create the vacuum again at the same conjunctival and corneal plane.8

One of the main reasons for the extrusion of the ICRS is segment migration. In this sense, the depth at which the segment is placed is key. Femtosecond laser tunnel creation is faster, easier, and more reproducible and offers accurate tunnel dimensions (width, diameter, and depth).57 This implies more control of intraoperative and postoperative complications.58 With mechanical dissectors, segment depth may be near the corneal surface, which increases late spontaneous ICRS extrusion risk.58 The femtosecond laser procedure generates more precise stromal separation compared with manual tunnel creation, which is based on the surgeon's skills. For both manual and femtosecond laser ICRS implantation, a suture can be placed in cases of segment migration that prevents the segment from migrating again.42

Of the 39 articles analyzed in this review, two did not report the type of implanted ring. Specifically, 16 Intacs (448 eyes), 13 Keraring or Ferrara Ring (1,804 eyes), and 8 cases with both (Intacs and Keraring) were reported without specifying how many of each type there were. The number of eyes with reported explantation is greater with Intacs (19%) compared with Keraring (1%) despite the fact than Intacs was implanted in a considerably smaller number of eyes. Most Intacs13,15–17,19,29 were explanted for low quality vision reasons.

Keraring and Ferrara Ring are more effective in the treatment of keratoconus compared with Intacs.59 Piñero et al.60 reported that astigmatism correction in ectatic cornea was more limited with Intacs, demonstrating that it increases the spherical corneal aberration. This finding implies a worsening of the visual quality, increasing the halos and glare. This notion is justified by the larger diameter of the Intacs, which induces minimal corneal central flattening.61

Among the limitations of this systematic review, the authors of the majority of cases only indicated the number of segments with complications and did not report the total number of segments implanted successfully. Thus, given that this information is not present in the published literature, it is not possible to establish the real prevalence of intraoperative and postoperative complications.

The femtosecond laser has reduced postoperative complications related to migration and corneal melting but has introduced new intraoperative complications, such as incomplete channel or vacuum loss. If patient selection is adequate and exhaustive, surgery planning can be implemented and intraoperative and postoperative complications will be minimized, representing the results of unpredictable surgery in most cases.

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Data Extraction for Complications and Explantations

Author (Year)Previous Eye HistoryIntraoperative ComplicationsPostoperative ComplicationsExplantation Yes/No (%)Explantation ReasonTreatment Used
Quantock et al.43 (1995)Nonfunctional eye or glaucomaNoneCrescentic iron lineYes (100%)Study protocolNR
Asbell et al.12 (1999)MyopiaNoneFaint haze in stromal channelYes (100%)Glare, halos, & fluctuating visionTobramycin/dexamethasone
Bourges et al.23 (2003)MyopiaNoneLamellar channel depositsYes (100%)Stromal thinning & extrusionBacitracin/polyvinyl alcohol
Shehadeh-Masha'our et al.22 (2004)PLENoneBacterial keratitisYes (100%)StaphylococcusCefamezin/gentamicin
Güell et al.35 (2004)Residual myopia PLEpithelial damageProgressive stromal lysisYes (7.7%)Progressive stromal lysisNR
Alió et al.48 (2004)KCNoneMigration (100%), partial extrusion (80%), moderate melting (80%), & corneal thinning (20%)Yes (100%)Segment migration & partial extrusionNR
Hofling-Lima et al.24 (2004)KC and low myopiaNoneInfectious keratitisYes (62.5%)Infectious keratitisNR
Kwitko & Severo50 (2004)KCNoneRing decentration (3.9%), extrusion (19.6%), disciform keratitis (1.9%), & bacterial keratitis (1.9%)Yes (3.9%)Extrusion after traumaNR
Kanellopoulos et al.20 (2006)KCAC perforation (5%)Movement, exposure and corneal thinning (30%), CM, & infiltrate (5%)Yes (35%)Repeated exposure and/or corneal thinningNR
McAlister et al.36 (2006)KC, atopic asthma, & BCNoneWhite infiltrate & deposit formationYes (100%)Infection keratitisDexamethasone chloramphenicol
Galvis et al.37 (2007)KC, lagophthalmos, & dry eyeNoneStaphylococcus aureusYes (100%)Infection keratitisVancomycin, imipenem, amphotericin B, & moxifloxacin
Carrasquillo et al.30 (2007)KC & PLENoneNeovascularization & fungal infectionYes (3%)Herpes simplex keratitisNR
Zare et al.31 (2007)KCNoneICRS exposureYes (13%)Extrusion (13%) & bacterial keratitis (3%)NR
Cosar et al.11 (2009)KCNoneNeovascularizationYes (100%)NeovascularizationFML/ciprofloxacin
Ibáñez-Alperte et al.44 (2010)NRNoneCorneal ulcer & hypopyonYes (100%)Extrusion/bacterial keratitisVancomycin/ceftazidime
Alió et al.13 (2010)KeratoconusNoneICRS extrusion & vascularizationYes (100%)Extrusion (33%), VA (57%), & neovascularization (10%)NR
Ferrer et al.14 (2010)KC (79%), PLE (12%), PMD (5%), KP (2%), & myopia (2%)NoneICRS migration, keratitis, CM, & corneal perforationYes (100%)Extrusion (48%), VA (38%), keratitis (7%), CM (5%), & perforation (2%)NR
Mulet et al.33 (2010)KC (81%), irregular astigmatism (10%), PLE (5%), & PMD (4%)NoneStreptococcus mitis and aureusYes (1%)Infection keratitisCeftazidime/amikacin, ofloxacin/vancomycin
Chalasani et al.45 (2010)KeratoconusNoneStaphylococcus epidermidisYes (50%)Infection keratitisVancomycin/tobramycin
Kugler et al.40 (2011)NRNoneCorneal melt (1.4%)Yes (1.4%)Incision overlappingBCL/steroids
Rayward et al.38 (2011)RGP, CL, & herpetic keratitisNoneAnnular herpetic keratitisNo (100%)NAAcyclovir/antibiotics
Coskunseven et al.8 (2011)NoneIncomplete channel (2.6%), galvanometer lag (0.6%), enodthelial perforation (0.6%), channel entrance (0.2%), & vacuum (0.2%)ICRS migration (0.8%), corneal melting (0.2%), & corneal abscess (0.1%)Yes (0.5%)Corenal meltingAntibiotics
Shihadeh49 (2012)CL intoleranceNoneAspergillus fumigatusYes (100%)Microbiological infectionGatifloxacin/itraconazole
Bali et al.15 (2012)KC & PLENoneEpithelial ingrowthYes (100%)Poor VA/epithelial ingrowthNR
Yeung et al.16 (2013)NRNoneICRS migration (33.3%)Yes (83%)Poor VA/ICRS migrationCXL
Jarade et al.42 (2013)NRNoneICRS migrationNo (100%)NAIncision suturing
Neira et al.39 (2014)Atopic dermatitis, AKC, blepharitis, & GPCNoneCorneal melting (100%)Yes (100%)Corneal meltingTopical steroids
Chhadva et al.17 (2015)NRNoneVA (80%), overlapping, & VA (20%)Yes (100%)Overlapping & visual qualityIncision suturing/PKP
López-Ferrando & Medrano- Ruiloba41 (2016)Eye rubbingNoneLate breaks (6%), ICRS migration (4%), & overlapping (2%)No (100%)NANR
Ibrahim et al.28 (2016)KCVacuum lossICRS broke/inverted ICRSNo (100%)NAMoxifloxacin/prednisolone
Abdelmassih et al.32 (2017)KCNoneVascularization & corneal thinningYes (5,9%)ICRS migrationTobramycin/gatifloxacin
García de Oteyza et al.46 (2017)KCNoneWhitish infiltrate, hypopyon, & CMYes (100%)Staphylococcus aureus keratitisVancomycin, ceftazidime, moxifloxacin, tobramycin, dexamethasone, & loteprednol
Oatts et al.18 (2017)MyopiaNoneEpithelial defect, thinned cornea, & extrusionYes (100%)FBS, photophobia, & VANR
Chan & Hersh19 (2017)KC & PLENRVA, diplopia, & halosYes (83,3%)Low vision qualityAntibiotic and corticosteroid
Mounir et al.10 (2018)KCVacuum loss, incomplete tunnel creation, ICRS migration, AC perforation, inverted ICRS, & broken ICRSICRS migration, extrusion, Incision opacification, steroid-induced glaucoma, infectious keratitis, crystalline sterile keratitis, & CMYes (0,8%)ICRS migration, infectious keratitis, & perforation into the anterior chamberMoxifloxacin/prednisolone
Elbaz et al.47 (2018)KCNoneSpontaneous in situ breakageYes (100%)Pain, redness, & FBSAntibiotics & corticosteroid
Nguyen et al.29 (2019)KC & PLENRMicrobial keratitis, photophobia, FBS, & VAYes (6%)Refractive/topographic considerationsGatifloxacin & vancomycin
Iqbal et al.51 (2019)KCNRMigration (1,6%), extrusion (4,7%), & KC progression (6,4%)Yes (6,3%)ICRS migration & extrusionGatifloxacin/prednisolone
Tabatabaei et al.34 (2019)PLENRKeratitisYes (100%)KeratitisCefazolin/amikacin/vancomycin

Quality Assessment Tool for Case Series Studies

Author (Year)Q1Q2Q3Q4Q5Q6Q7Q8Q9
Quantock et al.43 (1995)YesYesNoNoYesNoNoNoNo
Asbell et al.12 (1999)YesYesNoNoYesNoNoNoNo
Bourges et al.23 (2003)YesYesNoNoYesNoNoNoNo
Shehadeh-Masha'our et al.22 (2004)YesYesNANAYesNoNoNAYes
Güell et al.35 (2004)YesNoNoYesYesNoYesYesYes
Alió et al.48 (2004)YesYesNoYesYesYesNoNoYes
Hofling-Lima et al.24 (2004)YesYesNoYesNoNoYesNoNo
Kwitko & Severo50 (2004)YesYesNoYesYesYesYesYesYes
Kanellopoulos et al.20 (2006)YesYesNoYesYesYesYesYesYes
McAlister et al.36 (2006)NACDNANAYesYesYesNANA
Galvis et al.37 (2007)NACDNANAYesYesYesNANA
Carrasquillo et al.30 (2007)YesYesNRYesYesYesYesYesYes
Zare et al.31 (2007)YesYesNRYesYesYesYesYesYes
Cosar et al.11 (2009)NACDNANAYesYesYesNANA
Ibáñez-Alperte et al.44 (2010)YesYesNANANoNoNRNANo
Alió et al.13 (2010)YesYesYesYesYesYesYesYesYes
Ferrer et al.14 (2010)YesNoNoNRYesYesYesNAYes
Mulet et al.33 (2010)YesYesNoNAYesYesNoNAYes
Chalasani et al.45 (2010)NACDNANAYesYesYesNANA
Kugler et al.40 (2011)YesNoNoNoYesNoYesNAYes
Rayward et al.38 (2011)NRNoNANANoNoNRNANo
Coskunseven et al.8 (2011)YesYesNoYesYesYesYesNoYes
Shihadeh49 (2012)YesYesNANANoNoYesNAYes
Bali et al.15 (2012)YesYesNoNoYesYesYesNoYes
Yeung et al.16 (2013)YesYesNoNoYesYesYesNAYes
Jarade et al.42 (2013)YesNoNoYesYesNRCDNANR
Neira et al.39 (2014)NRYesNoYesYesYesNRNAYes
Chhadva et al.17 (2015)YesYesNoYesYesYesYesNAYes
López-Ferrando & Medrano-Ruiloba41 (2016)NRNoNoNoYesYesYesNAYes
Ibrahim et al.28 (2016)YesYesYesYesYesYesYesYesYes
Abdelmassih et al.32 (2017)YesYesYesYesYesYesYesYesYes
García de Oteyza et al.46 (2017)NACDNANAYesNANANAYes
Oatts et al.18 (2017)NACDNANAYesNANANAYes
Chan & Hersh19 (2017)NACDNANAYesNANANAYes
Mounir et al.10 (2018)YesYesYesYesYesYesYesYesYes
Elbaz et al.47 (2018)NACDNANAYesNANANAYes
Nguyen et al.29 (2019)YesNoYesNAYesNoNANAYes
Iqbal et al.51 (2019)YesYesYesYesYesYesYesYesYes
Tabatabaei et al.34 (2019)YesYesYesYesNoYesYesYesYes

Study Characteristics

Author (Year)DesignConflictInclusion CriteriaExclusion CriteriaFollow-up (wks)Patients (% Male)N (Eyes)ICRS TypeICRS Per EyeAge (y)
Quantock et al.43 (1995)CRNoNANA321(100%)1Manual Keraring146
Asbell et al.12 (1999)CRNoNANA401 (NR)1Manual Keraring228
Bourges et al.23 (2003)CRNoNANA2401 (0%)1Manual Intacs241
Shehadeh-Masha'our et al.22 (2004)CRNoEctasiaNo complications121 (100%)1Manual Intacs253
Güell et al.35 (2004)CSNoMyopia PLNA12 to 408 (NR)13Manual Intacs2NR
Alió et al.48 (2004)CANoICRS explantedNA484 (NR)5Manual Intacs1/232, 51 (50% NR)
Hofling-Lima et al.24 (2004)CSNoKeratitisNA888 (37.5%)8Ferrara (87.5%), Intacs (12.5%)NR32
Kwitko & Severo50 (2004)CSNoKCNA5247 (NR)51Manual Ferrara2NR
Kanellopoulos et al.20 (2006)CSNoKCNA4815 (40%)20Manual Intacs230.2
McAlister et al.36 (2006)CRNoNANA31 (100%)1Manual Ferrara234
Galvis et al.37 (2007)CRNoNANA161 (0%)1Manual Ferrara242
Carrasquillo et al.30 (2007)CSNoKC & PLECorneal scarring6 to 4929 (55%)3350% Manual; 50% FS Intacs1/239
Zare et al31 (2007)CSNoKC & CLILeucoma2422 (77%)30FS Intacs1/226
Cosar et al.11 (2009)CRNoNANA1441 (100%)1Manual Intacs233
Ibáñez-Alperte et al.44 (2010)CRNoKCNAapprox 71 (NR)1Manual Intacs236
Alió et al.13 (2010)CSNoKC, ICRS explantedNR2421 (NR)21Manual / FS Intacs & Keraring1/236
Ferrer et al.14 (2010)CSNoICRS explantedNR33647 (51%)57Manual / FS Intacs & Keraring1/237
Mulet et al.33 (2010)CSNoKeratitisNR4149 (59%)212Manual / FS Intacs & Keraring1/235
Chalasani et al.45 (2010)CRNoNANA121 (0%)2Ferrara140
Kugler et al.40 (2011)CSNoEctasiaNo complicationsapprox 28279 (NR)279FS Intacs1/244.25
Rayward et al.38 (2011)CRNoKC G IINA21 (100%)1NR126
Coskunseven et al.8 (2011)CANRKC G II to III, CT > 350 µmHerpes or keratitisNR531 (NR)850FS KeraringNR28.32
Shihadeh49 (2012)CRNoKC moderate myopiaNAapprox 201 (100%)2NR134
Bali et al.15 (2012)CSNoKC (4), ectasia (6)No Intacs surgeries489 (66.6%)10FS Intacs1/244.5
Yeung et al.16 (2013)CSNoKCNA123 (66.6%)6Intacs221.6
Jarade et al.42 (2013)CSNoICRS migrationNo surgery complications242 (NR)2Intacs / Keraring1NR
Neira et al.39 (2014)CSNRAtopic dermatitis AKCNo surgery complicationsNR5 (40%)5Manual Intacs1/232.6
Chhadva et al.17 (2015)CSYesKCManual implantation48.58 (50%)10FS INTACTS238
López-Ferrando & Medrano-Ruiloba41 (2016)CSNRKCNA36 to 16835 (NR)50Manual Ferrara1/2NR
Ibrahim et al.28 (2016)CSYesKC, CLI, CT > 450 µmHaze, hydrops infection24100 (43%)160FS Keraring1/221.77
Abdelmassih et al.32 (2017)CSNoICRS & CXLKeratitis or IOL24 to 20812 (83.35%)17FS Keraring & Intacs1/212.3
García de Oteyza et al.46 (2017)CRNoNANANR1 (100%)1FS Ferrara213
Oatts et al.18 (2017)CRNoNANA84 to 2402 (50%)3Manual Intacs233
Chan & Hersh19 (2017)CRNoNANA8 to 1043 (33%)3FS Intacs1/249.67
Mounir et al.10 (2018)CSNoKC G II to III, CT > 350 µmPLE, hydrops, KC G IV52417 (49.4%)623FS Keraring1/222.27
Elbaz et al.47 (2018)CRNoNANA161 (100%)1Manual Ferrara237
Nguyen et al.29 (2019)CSYesKC PLENANR31 (71.4%)35FS Intacs1/241
Iqbal et al.51 (2019)CSNoKC G I, II, or IIINA7237 (NR)63FS Keraring1/29 to 17
Tabatabaei et al.34 (2019)CRNRNANA2611 (72,7%)11Keraring, Intacs, MyoRing, & AICINR29
Authors

From the Department of Physics of Condensed Matter, Optics Area, University of Seville, Seville, Spain.

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

AUTHOR CONTRIBUTIONS

Study concept and design (M-JB-L, J-MS-G); data collection (M-JB-L, MCS-G, IL-I, AL-M, BG-M, CD-H-C, J-MS-G); analysis and interpretation of data (M-JB-L, MCS-G, IL-I, AL-M, BG-M, CD-H-C, J-MS-G); writing the manuscript (M-JB-L, MCS-G, IL-I, AL-M, BG-M, CD-H-C, J-MS-G); critical revision of the manuscript (M-JB-L, J-MS-G); supervision (M-JB-L, MCS-G, IL-I, AL-M, BG-M, CD-H-C, J-MS-G)

Correspondence: José-María Sánchez-González, OD, PhD, Department of Physics of Condensed Matter, University of Seville, Reina Mercedes St., Seville, Spain. E-mail: jsanchez80@us.es

Received: July 18, 2019
Accepted: October 10, 2019

10.3928/1081597X-20191010-02

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