Incidence and Reasons for Intrastromal Corneal Ring Segment Explantation

Intrastromal Corneal Ring Implants Associated Bacterial Infections

PURPOSE

This study examines the incidence of infection and resistance associated with Intracorneal Ring Segment (ICRS) implantation, a common outpatient surgical treatment for correcting refractive errors and corneal ectatic diseases. Although ICRS procedures are typically safe and reversible, there is a low but notable risk of microbial infections, which require prompt and sometimes invasive treatment.

METHODS

Three electronic databases, PubMed, Web of Science (WoS), and Scopus, were utilised to search for literature according to PRISMA guidelines to identify infections related to the implantation of ICRS in the cornea between January 2000 and December 2022.

RESULTS

Gram-positive organisms were involved in 86% of cases: 35.7% S. aureus, 25% coagulase-negative staphylococci species, 17.8% streptococci and 7.1% Nocardia species. Less commonly recorded were Gram-negative bacteria (14%), with Pseudomonas aeruginosa (circa 10%) and Klebsiella pneumonia (4%) being the most common Gram-negative bacteria. In rare cases, fungi have also been reported. ICRS-related bacterial infections can be categorised into early or late onset. Early onset infection typically manifests within the first few weeks after implantation and is often associated with contamination during surgery, unhygienic practices, or inadequate sterilisation techniques. On the other hand, late-onset infection may develop months or even years after the initial procedures and may be associated with persistent bacterial colonisation, secondary infections, or prolonged use of prophylactic antibiotics. S aureus is encountered in both early and late-onset infections, while Nocardia species and K. pneumoniae have generally been reported to occur in late-onset infections. In addition, vision recovery from S. aureus infections tends to be poor compared to other bacterial infections.

CONCLUSION

S. aureus is a predominant pathogen that often requires surgical intervention with poor outcomes. Early infections result from incision gaps and ring segment rubbing, while late infections are linked to prolonged antibiotic use. Further research is needed on novel antimicrobial ICRS to procure the vision.

Phakic intraocular Lens implantation in keratoconus patients

BACKGROUND

Both the anterior chamber and posterior chamber phakic intraocular lenses (pIOLs) implantation are acceptable refractive surgical approaches in keratoconus patients with high anisometropia, contact lens intolerance, or who prefer spectacle and contact lens independent. They are beneficial for correcting anisometropia in stable keratoconus cases or following corneal procedures such as intrastromal corneal ring segments (ICRS), collagen cross-linking (CXL), and keratoplasty. They are suitable for eyes without advanced keratoconus with acceptable best-corrected distance visual acuity (BCDVA) or without highly irregular astigmatism, high comma, and higher-order aberrations (HOAs). Combined procedures for irregular astigmatism reduction and corneal regularization with either ICRS or topography/wavefront-guided transepithelial PRK (with or without CXL) can be associated in advance with pIOLs implantation to improve BCDVA in these cases.

AIM

To study and report the evidence regarding the safety and efficacy of pIOLs for KC patients' visual and refractive rehabilitation, we have analyzed the scientific evidence published within the last 10 years (from 2012 onwards).

RESULTS

No randomized controlled trials but only eleven retrospective case series and two prospective case series were identified. Satisfactory visual rehabilitation was achieved regarding uncorrected and corrected distance visual acuity (CDVA) and predictability of the refractive correction. Both types of pIOL (iris claw and posterior chamber pIOLs) offer very good results in terms of safety and efficacy with indexes close to or even exceeding 1.

CONCLUSION

pIOLs implantation is a valid refractive therapeutic approach for correcting stable keratoconus with moderate-to-high refractive errors, especially anisometropia associated with regular or mildly irregular astigmatism, and good CDVA.

Refractive surgical correction and treatment of keratoconus

Keratoconus is an ectatic corneal disorder that causes severe vision loss. Surgical options allow us to correct, partially or totally, the induced refractive error. Intracorneal ring segments (ICRS) implantation represents a minimally invasive surgical option that improves visual acuity, with a high success rate and a low overall complication rate. Corneal allogenic ICRS consists of ring segments derived from allogenic eye bank-processed donor corneas. Selective topography-guided transepithelial photorefractive or phototherapeutic keratectomy combined with CXL is another way in selected cases to improve spectacles corrected distance visual acuity. The microphotoablative remodeling of the central corneal profile is generally planned by optimizing the optical zones and minimizing tissue consumption. Phakic intraocular lens (PIOL) implant is considered in patients with stable disease and acceptable anatomical requirements. The two types of pIOLs, depending on their implantation inside the eye, are anterior chamber-pIOLs, which fixate to the anterior surface of the iris by using a polymethomethacrolate claw at the two haptics, and posterior chamber-pIOLs. In patients with both cataracts and keratoconus, the correct IOL power is difficult to obtain due to the irregular corneal shape and K values. Toric IOL is recommended, but carefully judging the topography and the possible need of subsequent keratoplasties.

Efficacy and safety of intracorneal allogenic ring segment implantation in keratoconus: 1-year results

BACKGROUND

To evaluate the safety and efficacy of corneal allogenic intrastromal ring segments in the management of keratoconus patients.

METHODS

The retrospective, nonrandomized, interventional case series consisted of 65 keratoconic eyes of 49 consecutive patients who had ring segment-shaped corneal allografts (KeraNatural®) implanted in intrastromal tunnels created using a femtosecond laser. The main outcome measures were uncorrected visual acuity (UCVA), corrected distant visual acuity (CDVA), refraction, keratometry, and pachymetry. Computed tomography scans of the corneal surfaces were also performed preoperatively as well as 3, 6 and 12 months postoperatively.

RESULTS

Mean age was 29.5 ± 7.3 years (median 29, range: 20-52 years). The mean UCVA improved from 0.91 ± 0.50 logMAR preoperatively to 0.40 ± 0.24 logMAR postoperatively at 6 month follow-up (p < 0.01) and the mean CDVA improved from 0.87 ± 0.20 logMAR preoperatively to 0.27 ± 0.06 logMAR postoperatively (p < 0.01). The mean spherical equivalent improved from -8.82 ± 4.57 to -3.45 ± 4.81D (p < 0.01). Average Keratometry decreased from 49.23 ± 5.22 preoperatively to 45.63 ± 4.89 D postoperatively (p < 0.01). Mean anterior and posterior maximum elevation were also decreased significantly (p < 0.01). In one patient, dislocation of the graft towards the tunnel incision site and dehiscense at the tunnel entrance were observed in the first week of the operation. Yellow-white deposits were observed in the segment tunnels in five cases after 6 months.

CONCLUSION

This study demonstrated that implantation of corneal allograft ring segments is a viable alternative treatment for keratoconus with safety and good visual results.

Late-onset distal-apical intracorneal ring-segments keratopathy: an analysis of a large sample in a multicenter study

PURPOSE

To review the prevalence and describe the characteristics, of cases with late-onset intracorneal ring segments (ICRS) keratopathy in a multicenter study.

METHODS

A retrospective multicentric case-series study was performed in a specialized keratoconus service, from Buenos Aires, Argentina. An electronic clinical chart from patients with ICRS keratopathy between January 1999 and January 2019 was reviewed. We included cases with late-onset distal-apical ICRS keratopathy, which was defined as a persistent corneal lesion developed 12 months or later after implantation, located over, around, or closer to the ICRS. All the surgeries were performed by a manual corneal tunnel creation technique. Samples were taken to rule out infectious etiology.

RESULTS

From 5217 eyes that underwent ICRS implantation, 13 cases (0.24%) were detected. The keratopathy onset was 72 ± 42.98 months (29-133) after ICRS implantation. Cultures were negative in all cases. An ICRS exchange was made for five cases in stage I and four in stage II. Four cases presented with partial ICRS extrusion in stage III. ICRS exchange was possible in two of them and a penetration keratoplasty was necessary for the rest. All cases remained stable 1 year after surgical procedures.

CONCLUSIONS

A late-onset distal-apical ICRS keratopathy was detected with low prevalence (0.24%) in a large sample. It was classified into three stages according to its severity. Different treatments were selected for each stage, obtaining stable results 1 year after treatment.

Intrastromal corneal ring segments: effect of depth of implantation in visual, refractive, and topographic outcomes in patients with keratoconus

PURPOSE

To evaluate visual, refractive, and topographic outcomes of intracorneal ring segment implantation in relation to the achieved segment depth, using the manual technique.

SETTING

Ophthalmology Department, Hospital de Braga, Braga, Portugal.

DESIGN

Retrospective cohort study.

METHODS

We obtained 104 eyes of 93 patients with keratoconus submitted to Ferrara intracorneal ring segment (ICRS) implantation, using a manual technique. Subjects were divided into 3 groups according to the achieved depth of implantation: 40% to 70% (Group 1), 70% to 80% (Group 2), and 80% to 100% (Group 3). Visual, refractive, and topographic variables were evaluated at baseline and 6 months. Topographic measurement was performed using Pentacam. Thibos-Horner and Alpins methods were used to analyze the vectorial change of refractive and topographic astigmatism, respectively.

RESULTS

We found a significant improvement of uncorrected distance visual acuity and corrected distance visual acuity in all groups at 6 months ( P < .005); no differences were observed regarding safety and efficacy indexes in the 3 groups ( P > .05). Manifest cylinder and spherical equivalent significantly reduced in all groups ( P < .05). Topographic evaluation showed a significant improvement of all parameters in the 3 groups ( P < .05). A shallower (Group 1) or deeper (Group 3) implantation was associated with topographic cylinder overcorrection, a higher magnitude of error, and a higher mean centroid postoperative corneal astigmatism.

CONCLUSIONS

ICRS implantation with the manual technique showed to be equally effective in visual and refractive outcomes despite the depth of implantation; however, shallower or deeper implants were associated with topographic overcorrection and a higher mean centroid postoperative astigmatism, which explain the lower topographic predictability associated with manual surgery for ICRS implantation.

Effectiveness of toric IOL and capsular tension ring suturing technique for rotational stability in eyes with long axial length

OBJECTIVE

To evaluate the efficacy of the toric intraocular lens (IOL) and capsular tension ring (CTR) suturing technique in eyes with long axial length (AL) with a high risk of toric IOL rotation.

METHODS

This is a retrospective observational case series. The data files of patients who underwent a one-piece acrylic toric IOL (Tecnis Toric IOL and Acrysof IQ Toric IOL) implantation with the toric IOL and CTR suturing technique for cataract and astigmatism or toric IOL repositioning were analyzed. Inclusion criteria were a regular total corneal astigmatism of ≥ 1.5 D and an AL of ≥ 26.0 mm. Preoperative and postoperative astigmatism, uncorrected distance visual acuity (UDVA), IOL rotation, intraoperative, and postoperative complications were evaluated.

RESULTS

A total of 30 eyes of 29 patients were included in this study. The mean AL was 27.82 ± 1.53 mm (range, 26.08-31.07). UDVA revealed a statistically significant improvement from 0.84 ± 0.20 logMAR preoperatively to 0.04 ± 0.06 logMAR postoperatively (p < 0.001). The mean preoperative corneal astigmatism was 3.08 ± 1.01 D reduced to the postoperative residual astigmatism of 0.59 ± 0.32 D which was found also statistically significant (p < 0.001). Only 2 eyes (6.2%) had postoperative toric IOL rotation of 5° and 10°, respectively. The mean degree of postoperative rotation was 0.50 ± 2.01.

CONCLUSION

This technique provided excellent rotational stability even in eyes with longer AL and did not require additional intervention.

ByLimb: Development of a New Technique to Implant Intracorneal Ring-Segments from the Perilimbal Region

A new technique that allows implanting intracorneal ring-segments (ICRS) from the limbal zone is described. Using a femtosecond laser (FSL), a 360° corneal tunnel is created with an internal diameter of 5.4 mm and an external diameter of 7.0 mm, with a wider area (0.2 mm inner and 0.2 mm outer) in the upper 60° of the tunnel (called landing zone). Next, a 4.36 mm-long corneal-limbal incision was created with the FSL, which connects to the bubbles created in the landing zone. The entire procedure was performed using intraoperative optical coherence tomography (OCT). Once the two incisions were connected using blunt-edged Mac Pherson forceps, the bubbles were released from the surgical plane. The programmed ICRS(s), 6 mm in diameter, are then placed in the corneal tunnel from the limbal incision with the aid of Sinskey forceps. Finally, when the ICRS is in place, the surgery is complete.

Repeated Femtosecond Laser-Assisted Astigmatic Keratotomies in Post-Keratoplasty Eyes

Visual rehabilitation after a keratoplasty is often compromised due to high amounts of residual astigmatism. Femtosecond laser-assisted astigmatic keratotomy (FLAK) is gaining popularity in decreasing this astigmatism. Though one set of two incisions suffices in most cases, sometimes the treatment proves insufficient and additional treatment is required. This case series evaluates the outcomes in patients who underwent two consecutive FLAK sets to correct post-keratoplasty residual astigmatism. All repeated FLAK cases performed on post-keratoplasty eyes were reviewed in a high-volume clinic as a non-comparative retrospective case series. The data extracted include the procedure parameters, time between procedures, refraction including sphere, astigmatism, spherical equivalent (SE), and uncorrected and best-spectacle-corrected distance visual acuity (UDVA, BSDVA, respectively). Eleven eyes of eleven patients aged 25.5 ± 10 treated with more than one FLAK procedure were identified. The average follow-up time was 6 months after the first FLAK and 24 ± 10 months after the second. The second FLAK was performed six months after the first. The preoperative mean astigmatism was −9.59 ± 2.36 D. At the final follow-up, the mean astigmatism decreased to −5.38 ± 1.79 D (p = 0.001). Repeated FLAK procedures achieved a significant and stable reduction of astigmatism in post-keratoplasty eyes. This procedure shows safety and effectivity in these complex eyes and may prevent the need for a further keratoplasty.

Management of Anterior Stromal Necrosis After Polymethylmethacrylate ICRS: Explantation Versus Exchange With Corneal Allogenic Intrastromal Ring Segments

PURPOSE

To evaluate management of keratoconic eyes with anterior stromal necrosis overlying the intracorneal ring segment (ICRS), by either ICRS explantation alone or exchange with corneal allogenic intrastromal ring segments (CAIRS).

METHODS

Among 643 Intacs SK (Additional Technology, Inc) inserted at one institutional center, 16 eyes (15 patients) with overlying spontaneous anterior stromal necrosis were identified. Data included size of stromal defect and refractive and topographical findings before ICRS insertion, before anterior stromal necrosis, and 6 months after intervention.

RESULTS

The 10-year incidence of anterior stromal necrosis after femtosecond laser-assisted ICRS insertion was 5.5%. Eight eyes underwent ICRS removal only and 8 eyes had ICRS exchanged with CAIRS. In the first group, CDVA worsened from 0.14 before melt to 0.28 logMAR after removal (P = .10), simulated keratometry (SimK) and maximum axial keratometry (Kmax) increased from 44.73 to 46.34 diopters (D) (P = .14) and from 49.23 to 52.26 D (P = .14), respectively, and coma worsened from 0.87 to 1.52 D (P = .02). In the CAIRS group, CDVA of 0.16 before melt improved to 0.11 logMAR postoperatively (P > .99), and topographic indices stabilized with SimK, Kmax, and coma mildly altering from 45.31 to 45.44 D (P > .99), from 49.25 to 49.64 D (P > .99) and from 0.87 to 0.81 D (P > .99), respectively. Whether the ICRS were explanted or exchanged, the visual and topographic mean values were better than those reported before ICRS implantation, whereas higher order aberrations in eyes without CAIRS regressed to levels before ICRS insertion. At the site of melt, thinnest residual stromal thickness averaged 327 µm with ICRS removal and 490 µm with CAIRS. Eyes with larger melt areas resulted in less optimal results with CAIRS implantation.

CONCLUSIONS

Early experience in the management of anterior stromal necrosis by exchange of polymethylmethacrylate ICRS with CAIRS seems to avoid stromal thinning and confer better visual and topographic results, which were more pronounced with thicker segments. The benefit of CAIRS in large stromal melts needs to be investigated. [J Refract Surg. 2022;38(4):256-263.].

A Combined Procedure of Intrastromal Corneal Rings Explantation and Penetrating Keratoplasty in a Patient With Keratoconus: A Case Report

Keratoconus is a non-inflammatory and degenerative corneal ectasia that determinate progressive steepening of paracentral cornea with development of irregular astigmatism and visual function deterioration. According to the stage of the pathology, different methods of correction can be used: rigid contact lenses may be used to alter corneal shape and partially correct astigmatism, corneal collagen cross-linking (CXL) and intrastromal corneal ring segment (ICRS) implantation can reinforce corneal stroma to slow disease progression. Late-stage treatment comprehend anterior lamellar keratoplasty or penetrating keratoplasty. We evaluated a 31-year-old patient who was subjected to bilateral ICRS implantation combined with CXL due to keratoconus. This led, after 9 months, to ring extrusion in his left eye, corneal thinning and microperforation into the aqueous chamber with residual irregular astigmatism of 4.50 D. cyl. 10°. The patient underwent ICRS explantation and PKP during the same surgical session. After 15 months of follow-up, the BCVA was 0.2 LogMAR with a residual astigmatism of 6.3 dpt.

Corneal collagen cross-linking epithelium-on vs. epithelium-off: a systematic review and meta-analysis

BACKGROUND

The purpose of the study was to determine the advantages and disadvantages of epi-on corneal cross-linking (CXL) techniques compared with standard epi-off CXL.

METHODS

We searched MEDLINE and EMBASE for randomized controlled trials (RCTs) and non-randomized studies of interventions (NRSIs) and we evaluated the selected papers according to the Cochrane risk of bias tool. We considered, as primary outcomes, average Kmax flattening, changes in uncorrected and corrected distance visual acuity (UDVA and CDVA); as secondary outcomes, we considered changes in pachymetry values and endothelial cell density (ECD). We also investigated adverse events related to the treatments and treatment failure. Meta-analysis was conducted with a fixed or random-effects model using weighted mean difference (MD) with 95% confidence interval (CI) as the effect size.

RESULTS

A total of 15 studies were included and among these 15 trials, 9 were RCTs and 6 were NRSIs, but only 4 studies showed no high risk of bias and were included in this meta-analysis. Our analysis revealed significant postoperative differences in CDVA (MD = 0.07; 95% CI 0.04 to 0.10; P < 0.001), and no significative differences in UDVA, Kmax, central corneal thickness (CCT) and ECD (P > 0.05). Epi-on CXL protocol was found to be significantly less prompt to have risks of delay in epithelial healing (P = 0.035) and persistent stromal haze (P = 0.026).

CONCLUSION

Epi-on CXL is as effective as epi-off CXL. Except for a higher significant improvement in CDVA with current epi-on protocols, our meta-analysis demonstrates that epi-on and epi-off CXL have comparable effects on visual, topographic, pachymetric, and endothelial parameters. Epi-on CXL has clinical advantages in terms of comfort and avoidance of complications as it reduces the risk of developing delay in epithelial healing and persistent stromal haze.

Astigmatic Change as a Predictor of Intrastromal Corneal Ring Segment Late Extrusion

PURPOSE

To evaluate changes in keratoconic corneas implanted with intracorneal ring segments (ICRS) that have been explanted due to late extrusion of the segment after >2 years.

SETTING

Vissum Miranza, Alicante, Spain; OftalmoSalud, Lima, Peru; Minya University Hospital, Egypt.

METHODS

Retrospective, multicenter, series of cases of 23 keratoconic corneas that have been implanted for > 2 years and have been explanted due to natural extrusion of the segment. Clinical measures of visual, refractive, topographic, pachymetric and aberrometric data were analyzed. To perform exploratory factor analysis, the Kaiser-Meyer-Olkin (KMO) test was used to evaluate sampling adequacy. Factor analysis with VARIMAX rotation was used to determine the main factors of the inventory.

RESULTS

Mean time interval 5 years. Topographic findings were reversed nearly to the baseline level after segment explantation (p>0.05). Significant worsened in refractive cylinder was found pre-ICRS extrusion (p<0.05). KMO revealed a suitability of 0.528 in the preimplantation matrix (p<.001), 0.534 in the postimplantation matrix (p<.001), 0.549 in the preexplantation matrix (p=.009). Main factor obtained in the preimplantation moment included keratoconus grade, keratometric readings and visual acuities. After ICRS implantation, the most strength components were the refractive cylinder, CDVA and UDVA. Corneal aberrations were the main factors in the preexplantation analysis.

CONCLUSIONS

ICRS can be safely extracted, with a reversal of the corneal topographic data to the preoperative level. We showed a significant astigmatic change in patients implanted with ICRS before late extrusion of the segment, suggesting the role of this parameter as a prognostic factor of extrusion.

Evaluation of Demarcation Line after Epithelium-Off Iontophoresis Corneal Collagen Cross-Linking for Progressive Keratoconus

The aim of the study was to visualize and evaluate the characteristics and depth of the demarcation line with anterior segment optical coherence tomography (AS-OCT) after epithelium-off iontophoresis corneal collagen cross-linking (epi-off I-CXL). In this prospective, consecutive, single center study 18 eyes of 18 patients with keratoconus were involved. One month after epi-off I-CXL, all the patients underwent an AS-OCT scan to search for a demarcation line and its characteristics. The corneal stromal demarcation line was identified in all the eyes. Mean depth of the corneal stromal demarcation line was 261.8 ± 46.7 μm (range: 184 to 362 μm), at 56.7 ± 12% corneal depth. In conclusion, epi-off I-CXL determines a demarcation line that can be visualized with AS-OCT, which seems clearly distinguishable and similar to that created in standard CXL.

Clinical Outcomes of a New Type of Continuous Intrastromal Corneal Ring for Treatment of Keratoconus

PURPOSE

The purpose of this study was to evaluate the efficacy and safety of implantation of a new continuous corneal ring in keratoconic corneas of an Iranian population.

METHODS

This study was conducted on 95 contact lens-intolerant keratoconic eyes with clear central corneas. A continuous corneal ring, annular intrastromal corneal inlay (AICI), was inserted using femtosecond laser in all cases. Patients were followed up for 1, 3, and 12 months postsurgery. Visual and subjective refractive outcomes were evaluated in each examination. Besides, keratometry and aberrometric values were recorded before and 12 months after surgery. Finally, vector analysis of refractive astigmatism was performed using the Alpins method.

RESULTS

The uncorrected and corrected distance visual acuities improved significantly 12 months after surgery from 0.91 ± 0.39 to 0.38 ± 0.22 (P < 0 0.001) and 0.33 ± 0.21 to 0.13 ± 0.11 logMAR (P < 0.001), respectively. Moreover, spherical and cylindrical refractive components reduced from -2.52 ± 2.62 to -0.76 ± 1.78 D (P < 0.001) and -4.14 ± 1.64 to -1.91 ± 1.18 D (P < 0.001), respectively. The mean anterior keratometry had a significant reduction 12 months after AICI insertion (P< 0.001). Primary coma and spherical aberration values showed a significant increase (both, P < 0.05). Our results showed 100% safety (safety index: 1.8) and 45% efficacy (efficacy index: 1).

CONCLUSIONS

AICI implantation seemed to be a safe and effective procedure for improving visual acuity and refractive outcomes in subjects with keratoconus.