The intrastromal corneal ring segments. Phase II results for the correction of myopia

Clinical outcomes of femtosecond laser-assisted corneal allogenic intrastromal ring segment (CAIRS) in the treatment of keratoconus

BACKGROUND

To evaluate the results of corneal allogenic intrastromal ring segment (CAIRS) implantation in keratoconus.

METHODS

The medical records of patients with keratoconus who underwent CAIRS implantation were reviewed. The CAIRS, prepared by trephination from the donor cornea, was implanted into a tunnel created using the femtosecond laser. The depth of the tunnel was 200 μ; the inner diameter of the tunnel was 4.5 mm; and the outer diameter was 7 mm. Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), keratometry, minimum corneal thickness (CT), endothelial cell density (ECD), and high order aberration values were recorded preoperatively and at the 1st, 3rd, and 6th months postoperatively.

RESULTS

A total of 23 eyes of 23 patients were included in the study. Preoperative UCVA (0.08 ± 0.01) and BCVA (0.25 ± 0. 11) values improved postoperatively and reached 0.40 ± 0.05 and 0.68 ± 0.09, respectively, at the end of the 6-month follow-up period (p1 < 0.001, p2 = 0.016; respectively). A statistically significant flattening of all keratometric values was observed in the postoperative period compared to preoperatively (p < 0.001 for all). There were no statistical differences between CT and ECC values at the preoperative and postoperative visits (p1 = 0.654, p2 = 0.769; respectively). In addition, coma aberration values were lower than the preoperative values at all postoperative visits (p < 0.05 for all).

CONCLUSIONS

These results suggest that CAIRS implantation is a safe treatment option with good visual and keratometric outcomes for suitable patients with keratoconus.

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.

Evaluation of dynamic corneal response parameters and the biomechanical E-staging after Intacs® SK implantation in keratoconus

PURPOSE

This retrospective longitudinal study evaluated the biomechanical E-staging in KC corneas before and after intracorneal ring segment (ICRS) implantation (Intacs® SK, Addition Technology, Illinois, United States).

METHODS

Biomechanical E-staging for ectatic corneal diseases was applied retrospectively on 49 KC corneas of 41 patients who underwent ICRS implantation. The main outcome parameters included the Corvis Biomechanical Factor (CBiF, the linearized Corvis Biomechanical Index and the biomechanical parameters included), the resulting biomechanical E-staging, the stress-strain index, thinnest corneal thickness (TCT), maximal anterior keratometry (Kmax), and the anterior radius of curvature (ARC). They were evaluated at 1.9 ± 1.1 months preoperatively and postoperatively after 2.8 ± 0.7, 5.8 ± 1.0, and 10.6 ± 2.3 months.

RESULTS

The CBiF decreased (4.9 ± 0.5 | 4.7 ± 0.5, P = 0.0013), and the E-staging increased significantly (2.8 ± 0.8 | 3.1 ± 0.9, P = 0.0012, paired t-test) from preoperatively to the first postoperative follow-up. The difference remained significant after 6 months; however, there was no more difference after 11 months. TCT was stable, whereas Kmax and ARC significantly decreased after ICRS implantation (TCT: 464 ± 49, 470 ± 51, 467 ± 38, 461 ± 48; Kmax: 56.3 ± 4.5, 54.7 ± 4.5, 54.2 ± 4.8, 54.1 ± 4.3; ARC: 51.5 ± 3.4, 48.3 ± 3.8, 48.6 ± 3.0, 48.6 ± 3.2 preoperatively and 3, 6, and 11 months postoperatively, respectively). Besides Kmax and ARC, Ambrósio's relational thickness to the horizontal profile (ARTh) was the only parameter that was significantly lower than preoperatively at any follow-up (P ≤ 0.0024, Wilcoxon matched-pairs test).

CONCLUSION

Intacs® SK implantation results in an increasing biomechanical E-staging in the first postoperative months with stabilization near preoperative values after 1 year. Significantly lower ARTh values at any follow-up document the ICRS effect and contribute to a slightly higher postoperative biomechanical E-staging value.

Intracorneal Ring Segment Implantation Results in Corneal Mechanical Strengthening Visualized With Optical Coherence Elastography

PURPOSE

To quantify the mechanical impact of intracorneal ring segment (ICRS) implantation of different dimensions in an ex vivo eye model.

METHODS

A total of 30 enucleated porcine eyes were assigned to ICRS implantation (thickness: 300 µm, angle: 120°, 210°, or 325°), tunnel creation only, or virgin control groups. For mechanical evaluation, each globe was mounted on a customized holder and intraocular pressure (IOP) was increased in steps of 0.5 mm Hg from 15 to 17 mm Hg, simulating physiologic diurnal IOP fluctuations. At each step, an optical coherence tomography volume scan was recorded. Deformations between subsequent scans and the locally induced axial strains were analyzed using a vector-based phase difference method. The effective E-modulus was derived from the overall induced strain as a measure of global mechanical impact.

RESULTS

ICRS implantation increased the effective E-modulus from 146 and 163 kPa in virgin and tunnel-only eyes to 149, 192, and 330 kPa in eyes that received a 5-mm optical zone ICRS with 120°, 210°, and 325° arc length, respectively; and to 209 kPa in a 6-mm optical zone ICRS with 325° arc length. The most consistent effect was a shift toward positive strains in the posterior stroma by 0.1% to 0.46% (factor 1.15 to 2.15) after ICRS surgery.

CONCLUSIONS

ICRS implantation reduces the overall tissue strain under the load of the IOP and provokes posterior tissue relaxation. This effect is more prominent the longer the arc length and the smaller the optical zone of the ICRS is. ICRS have not only a geometrical, but also a mechanical impact on corneal tissue. This behavior might have clinical implications when ICRS implantation is performed in biomechanically weakened keratoconic corneas. [J Refract Surg. 2022;38(7):459-464.].

Corneal Strain Induced by Intracorneal Ring Segment Implantation Visualized With Optical Coherence Elastography

PURPOSE

To record the axial strain field in the cornea directly after creating a stromal tunnel and implanting an intracorneal ring segment (ICRS).

METHODS

Freshly enucleated porcine eyes were obtained and assigned to either ICRS implantation, tunnel creation only, or virgin control groups. Immediately after manual tunnel creation and ICRS positioning, the entire eye globe was mounted on a customized holder and intraocular pressure (IOP) was adjusted to 15 mm Hg. Then, IOP was inreased to 20 mm Hg, in steps of 1 mm Hg. At each step, an optical coherence tomography volume scan was recorded. Displacements between subsequent scans were retrieved using a vector-based phase difference method. The induced corneal strain direction was determined by taking the axial gradient. In addition, corneal surface was detected and sagittal curvature maps computed.

RESULTS

Corneal tissue presented a localized compressive strain in the direct vicinity of the stromal tunnel, which was independent of IOP change. The central and peripheral (exterior to the ICRS) cornea demonstrated compressive strains on IOP increase, and tensile strains on IOP decrease. ICRS implantation induced an annular-shaped tensile strain at its inner border, particularly during IOP increase. The compressive strains close to the tunnel remained after ICRS implantation. Corneal curvature changes were concentrated on regions where strain was induced.

CONCLUSIONS

ICRS implantation induces localized strains in the regions subjected to refractive changes, suggesting that corneal strain and curvature are directly related. Studying corneal strain in response to surgical intervention may provide new insights on underlying working principles. [J Refract Surg. 2022;38(3):210-216.].

Morphological characterization and clinical effects of stromal alterations after intracorneal ring segment implantation in keratoconus

PURPOSE

To analyze the histological and (ultra)structural stromal tissue changes after femtosecond (Fs) laser-assisted intracorneal ring segment (ICRS) implantation and their refractive and topographic effects in patients with keratoconus.

METHODS

This monocentric retrospective case series included 15 consecutive patients with clinical peri-segmental lamellar channel deposits after treatment with Fs-ICRS implantation for keratoconus. The stromal changes were investigated using in vivo confocal microscopy. Two patients underwent a penetrating keratoplasty after the Fs-ICRS implantation; the explanted corneas were processed for histopathology and transmission electron microscopy (TEM). Refractive and topographic effects were investigated comparing the uncorrected (UDVA) and corrected (CDVA) distance visual acuity, spherical equivalent (SE), flat (K1), steep (K2), and steepest (Kmax) keratometry before and after detection of lamellar channel deposits.

RESULTS

In vivo confocal microscopy revealed diffuse linear and focal granular hyperreflective structures. Histologically, there was mild proliferation of fibroblasts and fibrosis. TEM demonstrated focal accumulations of degenerated keratocytes with cytoplasmic lipid inclusions. There were no significant changes for UDVA (Δ = 0.0 ± 0.2 logMAR; p = 0.67), CDVA (Δ = 0.0 ± 0.1 logMAR; p = 0.32), SE (Δ 0.1 ± 0.9 D; p = 0.22), K1 (Δ = 0.3 ± 1.0 D; p = 0.28), K2 (Δ = 0.1 ± 0.9 D; p = 0.51), and Kmax (Δ = 0.3 ± 1.5 D; p = 0.17).

CONCLUSIONS

Two types of structural stromal changes were identified: (1) diffuse peri-segmental fibrosis and (2) lamellar channel deposits. These structural changes showed no evidence of a relevant refractive or topographic effect.

Delayed Perforation of an Intrastromal Corneal Ring Segment into the Anterior Chamber: A Case Report and Review of the Literature

Intrastromal corneal ring segments (ICRSs) are an effective treatment for stabilizing and normalizing corneal shape in patients with keratoconus and other corneal ectasias. Intraoperative segment perforation through the corneal endothelium into the anterior chamber (AC) is an uncommon but known complication. However, perforation into the AC postoperatively is an exceedingly rare complication with only 3 reported cases in the literature. One case was due to Descemet membrane detachment and another due to ocular trauma. In the third case, the mechanism for perforation was unclear. We present the fourth case of delayed ICRS perforation due to silent migration through the endothelium into the AC. We also present all reported cases in the literature of intraoperative and postoperative perforation into the AC.

Refractive changes of a new asymmetric intracorneal ring segment with variable thickness and base width: A 2D finite-element model

PURPOSE

To evaluate the local geometric effects of a unilateral intrastromal ring segment with a combined variation of ring thickness and base width in a finite element simulation, and to compare it against the isolated effect of thickness or base width variation alone.

METHODS

A two-dimensional finite-element model of a transversely isotropic cornea was created assuming either axisymmetric stress or plane strain condition. The model geometry was composed of a three-layered corneal tissue (epithelium, anterior and posterior stroma) fixed at the limbus. The implantation of a triangular-shape asymmetric ring segment with varying ring thickness (150 to 300 μm) and base width (600 to 800 μm) was simulated. Also, changes induced by thickness or base width alone were studied and compared their combined effect in the asymmetric ring segment. Geometrical deformation of the simulated cornea and sagittal curvature were the main parameters of study.

RESULTS

Increasing ring thickness and base width along the arc of the asymmetric ring segment produced a more pronounced flattening in this part of the ring. The asymmetric design did find a good balance between maximizing corneal flattening at one end and minimizing it at the other end, compared to the isolated effect of ring thickness and width. Ring thickness was the most robust parameter in flattening both, the central and peripheral cornea.

CONCLUSION

The finite-element model permitted a theoretical study of corneal deformation undergoing implantation of realistic and hypothetical ring geometries. Intracorneal asymmetric ring segments with varying thickness and base width can be a good alternative in corneas with asymmetric keratoconus phenotypes.

Comparative Study of Asymmetric Versus Non-asymmetric Intrastromal Corneal Ring Segments for the Management of Keratoconus

PURPOSE

To compare the outcomes obtained with models of asymmetric and non-asymmetric intracorneal ring segments (ICRS) in keratoconic eyes with asymmetric topo-graphic patterns.

METHODS

In this prospective observational study, ICRS were implanted alternately in patients with the same tomographic patterns of keratoconus assigned to four groups. Patients with the "duck" phenotype received one asymmetric or non-asymmetric ICRS and patients with the "snowman" pheno-type received two asymmetric or non-asymmetric ICRS. Visual, refractive, astigmatism, keratometric, and corneal aberrometry changes were evaluated over a 6-month follow-up period.

RESULTS

Sixty-eight eyes were analyzed. No significant difference was observed between the use of one asymmetric and one non-asymmetric ICRS in duck phenotypes. In snowman keratoconus, the inferior-superior index decreased significantly (P = .03) with asymmetric but not with non-asymmetric ICRS implantation. Total corneal higher order aberrations and coma rates were lower, but not significantly so, after the implantation of two asymmetric ICRS in snowman phenotypes (2.85 ± 0.89 to 2.60 ± 0.91 µm, P = .20 and 2.64 ± 0.93 to 2.39 ± 0.98 µm, P = .21), and significantly higher after the implantation of two non-asymmetric ICRS (2.56 ± 1.28 to 3.08 ± 1.62 µm, P = .02 and 2.34 ± 1.27 to 2.84 ± 1.62 µm, P = .02).

CONCLUSIONS

Asymmetric ICRS did not improve the outcomes of ICRS implantation in duck keratoconus. However, the implantation of two asymmetric ICRS was more effective than that of two non-asymmetric ICRS for decreasing vertical asymmetry and preventing increases in corneal aberration in the snowman phenotype of keratoconus. [J Refract Surg. 2021;37(8):552-561.].

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.

Femtosecond Lasers in Cornea & Refractive Surgery

Since the introduction of femtosecond laser (FS) systems for corneal flap creation in laser-assisted in-situ keratomileusis there have been numerous applications for FS laser in corneal surgery. This manuscript details the utility of FS lasers in corneal surgical procedures including refractive laser surgeries, intracorneal ring segment tunnels, presbyopic treatments, and FS-assisted keratoplasty. We also review the role of FS lasers in diagnostic procedures such as two photon excitation fluorescence and second harmonic generation.

MyoRing Implantation with and without Corneal Collagen Crosslinking for the Management of Keratoconus

Purpose

To evaluate the safety and efficacy of femtosecond laser-assisted MyoRing implantation with concurrent corneal collagen crosslinking (CXL) compared to MyoRing alone for the treatment of progressive keratoconus.

Methods

A total of 60 patients were enrolled in this randomized controlled trial. The patients were randomly allocated into two groups. In the first group, MyoRing was implanted, while in the second, it was inserted in the corneal stroma using the same technique, along with simultaneous CXL. Visual, refractive, topographic, and abberometric outcomes were measured preoperatively and at every postoperative visit.

Results

Data of 47 patients were available at the end of the study; 28 in the MyoRing group and 19 in the MyoRing + CXL group. The mean uncorrected distance visual acuity (UDVA) improved from 0.79 ± 0.39 logMAR to 0.52 ± 0.31 logMAR (P < 0.05) in the MyoRing + CXL group and from 0.65 ± 0.38 logMAR to 0.62 ± 0.23 logMAR (P = 0.70) in the MyoRing group. CDVA changed from 0.33 ± 0.19 logMAR to 0.25 ± 0.16 logMAR (P = 0.10) in the MyoRing + CXL group and 0.32 ± 0.22 logMAR to 0.33 ± 0.17 logMAR (P > 0.50) in the MyoRing group. The mean keratometry (Km) decreased from 47.5 ± 2.7 D to 43.8 ± 3.2 D (P < 0.001) in the MyoRing group and 49.3 ± 3.4 D to 45.1 ± 3.0 D (P < 0.001) in the MyoRing + CXL group. Besides, horizontal coma was significantly lower in the MyoRing + CXL group (P = 0.022).

Conclusion

MyoRing insertion combined with CXL is a safe and effective method for the treatment of keratoconus. The visual and topographic outcomes were comparable to that for MyoRing insertion after 10 months; however, horizontal coma was significantly lower in the MyoRing + CXL group.

Optical coherence tomography imaging in keratoconus

Optical coherence tomography (OCT) is being increasingly used as a tool in the diagnosis and management of keratoconus. While elevation-based topography remains essential, there is an expanding role for cross-sectional OCT imaging in the diagnosis of the disease. Images and measurements of corneal thickness, and in particular, epithelial thickness, may be important in diagnosing early cases, and following procedures such as intrastromal corneal ring segments, corneal transplants and corneal collagen cross-linking.

Long-term outcome of intrastromal corneal ring segments in keratoconus: Five-year follow up

To evaluate the effectiveness of intrastromal corneal ring segment (ICRS) use in keratoconus after five years. ICRS has been widely used to correct astigmatism and improve visual acuity in keratoconus. Although the short-term outcome is well known to be effective, long-term outcome has rarely been reported. A retrospective chart review was done. A total of 30 eyes diagnosed with keratoconus and treated with INTACS (Addition Technology, Sunnyvale, CA, USA) were included. Visual acuity, refraction, indices of corneal irregularity, and higher-order aberration were evaluated at preoperative, two months, one year, three years, and five years postoperatively. Uncorrected distance visual acuity (UDVA) and spherical and spherical equivalent were improved (p < 0.05) for three years. However, they worsened (p < 0.05) at five years to preoperative values. On the other hand, corrected distance visual acuity (CDVA) was improved for five years (p < 0.05). Topographic keratometry was flattened, and corneal irregularity indices were improved at five years (all p < 0.05). Coma RMS was improved (p < 0.05) continuously for five years. ICRS has advantages in improving CDVA with topographic stabilization and decreasing coma in keratoconus for five years.

Femtosecond-assisted intracorneal ring segment complications in keratoconus: from novelty to expertise

Objectives

To document the difference between complication rate in the early curve of practicing intracorneal stromal rings and after gaining experience.

Patients and methods

A retrospective study of 623 eyes of 417 patients with keratoconus who underwent Keraring implantation using femtosecond laser for channel creation.

Results

The main outcome measures were reported intraoperative and postoperative complications. The overall complication rate was 12.7% (79 eyes) over the 4 years with 34 eyes in the first year (5.5%) and six eyes in the fourth year (0.96%). Over the 4 years of our practice, intraoperative complications were 7.1% and postoperative complications were 5.6%. Yet, there was a significant difference in intraoperative complications between the first and the fourth year where it was 3.5% and 0.48%, respectively. This also applies to the postoperative complication rate, which decreased from 1.9% to 0.5% in the fourth year.

Conclusion

Complications with femtosecond-assisted intracorneal stromal ring procedure can be reduced by experience, making this procedure a safe and effective means of treating keratoconus. Yet, there are some complications that cannot be avoided such as sterile keratitis.

Updates on Managements for Keratoconus

Purpose

Keratoconus is a progressive disease of the cornea which can lead to blindness as irregular astigmatism increases. Currently, a variety of methods are available for the treatment of keratoconus, and in certain cases, it may be difficult to choose the most appropriate option. This article reviews available treatment modalities for keratoconus to provide the practitioner with practical and useful information for selecting the most suitable option for each individual patient.

Methods

To review treatment methods for different stages of keratoconus, PubMed (United States National Library of Medicine) and Scopus (Elsevier BV) databases were searched using the keywords “keratoconus”, “contact lens”, “cross-linking”, “Intacs”, “keratoplasty”, “gene therapy”, and “irregular astigmatism”, and related articles were reviewed based on disease assessment parameters and treatment methods.

Results

Various methods are available for the treatment of keratoconus: eyeglasses and contact lenses in the early stages, cross-linking for stabilizing disease progression, intrastromal corneal ring segments (ICRS) for reducing refractive errors or flattening the cornea, and penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK), conductive keratoplasty, gene therapy and more recently, bowman layer transplantation (BL transplantation) in advanced stages of the disease. To achieve optimum results, it is essential to choose the best option for each individual patient.

Conclusions

A commonality of the reviewed papers was the advancement of novel diagnostic and treatment methods in ophthalmology, which can delay the need for corneal grafting. A better understanding of keratoconus treatment options can help enhance visual rehabilitation and prevent blindness in keratoconus patients.

Late extrusion of intrastromal corneal ring segments: A report of two cases

Purpose

To report two cases of patients with late extrusion following uneventful implantation of intrastromal corneal ring segments (ICRS) for myopia.

Observations

Two patients with previously implanted ICRS for low myopia presented with spontaneous onset of extrusion of their ICRS, one at 7 years post-operatively and the other at 17 and 20 years. Both cases underwent explantation and maintained excellent best-corrected visual acuity. These cases represent the longest reported intervals between implantation of the ICRS and subsequent extrusion.

Conclusions and importance

Late extrusion can occur many years following implantation of ICRS, even in eyes without pre-existing thinning or ectasia. The technique for explantation described herein can result in favorable clinical outcomes in such cases. These cases demonstrate the importance of long-term follow up of eyes that have undergone ICRS implantation.

V4B implantable collamer lens versus Intacs corneal rings to manage anisometropic myopic amblyopia in children

OBJECTIVE

To compare the safety and efficacy of phakic intraocular lens (PIOL) versus intrastromal corneal ring segments (Intacs), for correcting high myopic anisometropia in amblyopic children.

DESIGN

Nonrandomized prospective multi-center study.

PARTICIPANTS

Thirty children, aged between 4 and 12 years, with unilateral high myopic anisometropic amblyopia were included in this study.

METHODS

Patients who were prospectively subdivided into group A, with mean preoperative manifest refraction spherical equivalent (MRSE) of -12.96 ± 4.17 D, underwent unilateral phakic posterior chamber intraocular lens implantation. Patients with mean preoperative MRSE of -8.60 ± 1.16 D in group B were treated by Intacs corneal rings. Pre- and postoperative visual acuity, ocular examination, stereoacuity, axial biometry measurements, cycloplegic refraction, and endothelial cell counts were performed in all patients.

RESULTS

Group A revealed prevention of amblyopia with improvement in spectacle-corrected distance visual acuity, where 4-6 lines were achieved in 77% of children, 2-3 lines in 4%, and just 0-1 lines restricted to 19% of children. Improvement in stereoacuity was noted in 93.33% of group A cases, whereas group B showed fewer cases of successfully improved vision, with 4-6 lines in 70% of children, 2-3 lines in 3%, and just 0-1 lines restricted to 27% of children. Improvement in stereoacuity was noted in 86.66% of cases. Two cases of cataract and 1 case of glaucoma with 1 case of uveitis were noted in the implantable contact lens (ICL) group.

CONCLUSIONS

Posterior chamber PIOLs or Intacs may provide a safe alternative in treating anisometropic myopic patients. Intacs implantation is safer with fewer complications than ICL. However, ICL implantation is advantageous over the corneal ring segment procedure owing to the wide range of errors to correct.

Efficacy of Intrastromal Corneal Ring Segments Combined With Flash Collagen Cross-Linking in Keratoconus

PURPOSE

To evaluate outcomes, efficacy, and safety of intrastromal corneal ring segment implantation for treatment of keratoconus combined with collagen cross-linking (CXL) with 1-year follow-up.

METHODS

One hundred nineteen eyes of 82 patients with keratoconus (37 females) underwent femtosecond (Intralase FS; Abbott Medical Optics, Inc) laser-assisted intrastromal corneal ring segment implantation (INTRASEG; Gamma Vision) with flash CXL (18 mW/cm for 5 minutes). The outcome measures were uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (CDVA), subjective refractive error, keratometry values, and corneal thickness.

RESULTS

Mean age of patients at implantation was 31 years (range 12-63, SD 9.5). According to the Amsler-Krumeich scale of keratoconus severity, 62 eyes were type 1 (52%), 43 eyes, type 2 (36%), and 14 eyes, type 3 (11.8%). Statistically significant improvement of UDVA/CDVA and reduction in the mean cylinder and mean keratometry at 1 year were observed. Mean UDVA (logMAR) was 1.11 ± 0.61 (SD) preoperatively and 0.54 ± 0.58 (SD) postoperatively (P < 0.001). Mean CDVA was 0.52 ± 0.18 (SD) preoperatively and was 0.14 ± 0.17 (P < 0.0001) postoperatively. Preoperative Kmax was 48.75 diopters (D) (range 41.0-55.0 D), and postoperative Kmax was 46.18 D (P < 0.0006); preoperative Kmin was 44.69 D (SD) 3.59 and postoperative Kmin was 43.00 D (SD) 2.53. The mean cylinder was -5.19 D preoperatively (range -0.80 to -8.80 D) and -2.6 D (range -1.00 to -7.25) postoperatively. Mean corneal pachymetry was 486.6 μm (range 391-591). No intraoperative complications occurred. No patient lost any lines of UDVA or CDVA.

CONCLUSIONS

Implantation of the INTRASEG with the Intralase combined with flash CXL was apparently safe and effective in treatment of keratoconus. The variety of options in thickness and arc length of the segments enables more precise correction of keratoconus and refractive errors.

Intrastromal Corneal Ring Segments in Children with Keratoconus

Purpose

To evaluate the long-term follow-up of Ferrara intrastromal corneal ring segments (ICRSs) (Ferrara Ophthalmics, Belo Horizonte, Brazil) implantation for the management of keratoconus in children.

Study design

Paulo Ferrara Eye Clinic, Belo Horizonte, Minas Gerais, Brazil.

Materials and methods

A total of 58 eyes of 37 children with keratoconus were included. One or two ring segments were inserted into the cornea, embracing the keratoconus area. Statistical analysis included preoperative and postoperative uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), asphericity, pachymetry, and keratometry.

Results

Ferrara ICRS implantation significantly improved the mean UDVA and CDVA. Corneal tomography (Pentacam®) showed corneal flattening in all eyes implanted with the Ferrara ring. The mean K decreased, and the corneal asphericity and pachymetry increased in all cases.

Conclusion

The Ferrara ICRS improved all parameters after 2 years of implantation in children with keratoconus. There was significant corneal flattening after ring implantation with improvement of the UDVA and the CDVA. All studied parameters remained stable over time.

How to cite this article

Ferrara G, Ferrara P, Torquetti L. Intrastromal Corneal Ring Segments in Children with Keratoconus. Int J Kerat Ect Cor Dis 2017;6(2):45-48.

Depth evaluation of intended vs actual intacs intrastromal ring segments using optical coherence tomography

PurposeEvaluation of actual vs intended intrastromal corneal ring segments (ICRS) implantation depth as measured by anterior segment optical coherence tomography (OCT)MethodsProspective study evaluating 30 Intacs segments implanted manually in 19 eyes of 15 patients suffering from keratoconus. Segment depth evaluation was performed using anterior segment OCT. Measurements were performed above and below the segment at 3 points in relation to the incision site. Statistical analysis was performed using the SAS software for ANOVA, matched t-test, and GLIMMIX procedure.ResultsIntacs segment depth was 153-μm shallower than intended (58% vs 80%). Segment layout demonstrated the proximal and distal portions to be 13-μm shallower and 12-μm deeper (on average), respectively. Intacs segment thickness does not influence implantation depth. Intacs segments implanted in the same eye do not share similar implantation depths. Stromal compression is likely to occur.ConclusionIntacs are implanted at a shallower depth than intended. The 'pocketing' stage prior to implantation most likely has a stronger effect on the segment's final implantation depth than does the incisions' depth.

A Comparison of Different Operating Systems for Femtosecond Lasers in Cataract Surgery

The introduction of femtosecond lasers is potentially a major shift in the way we approach cataract surgery. The development of increasingly sophisticated intraocular lenses (IOLs), coupled with heightened patient expectation of high quality postsurgical visual outcomes, has generated the need for a more precise, highly reproducible and standardized method to carry out cataract operations. As femtosecond laser-assisted cataract surgery (FLACS) becomes more commonplace in surgical centers, further evaluation of the potential risks and benefits needs to be established, particularly in the medium/long term effects. Healthcare administrators will also have to weigh and balance out the financial costs of these lasers relative to the advantages they put forth. In this review, we provide an operational overview of three of five femtosecond laser platforms that are currently commercially available: the Catalys (USA), the Victus (USA), and the LDV Z8 (Switzerland).

Technique of simultaneous femtosecond laser assisted Myoring implantation and accelerated intrastromal collagen cross-linking for management of progressive keratoconus: A novel technique

PURPOSE

To describe a novel surgical technique for the management of progressive keratoconus by simultaneous femtosecond laser-assisted Myoring implantation and accelerated corneal intrastromal collagen cross-linking with Dextran Free Riboflavin.

METHODS

After creating a corneal pocket with femtosecond laser, Dextran Free Riboflavin was injected into the intrastromal pocket. Then the Myoring was implanted in the corneal pocket and accelerated corneal intrastromal collagen cross-linking was performed with no epithelial debridement.

RESULTS

The cornea remained clear and the central keratometry was decreased significantly with marked improvement in uncorrected visual acuity up to two years following treatment. Anterior segment OCT revealed good centration and intended implant depth with desirable increase in the corneal stromal reflectivity confirming effective collagen cross-linking.

CONCLUSION

Simultaneous femtosecond laser-assisted Myoring implantation and accelerated corneal intrastromal collagen cross-linking with Dextran Free Riboflavin is a safe and effective technique for management of keratoconus and improving vision.

Cross-linking and intracorneal ring segments--review of the literature

OBJECTIVES

To review and summarize relevant studies on combined use of corneal crosslinking and intracorneal ring segments (ICRS) for the treatment of corneal ectasia.

METHODS

A literature search was performed using the key words "corneal collagen cross-linking" and "intra-corneal ring segments."

RESULTS

Crosslinking is a well-accepted treatment option for corneal ectasia and can be combined with corneal ICRS insertion as needed. The advent of crosslinking has dramatically reduced the number of corneal transplants performed for patients with keratoconus or postrefractive ectasia. Intracorneal ring segments, although flatten the corneal surface, do not prevent the progression of corneal ectasia. This is why the combination of crosslinking and ICRS is potentially synergistic. Previous studies reported that combining these two complementary interventions has been shown to be safe and effective.

CONCLUSIONS

The effects of ICRS are enhanced and stabilized by crosslinking, but the ideal combined technique is not known at present.

Tissue reaction after intrastromal corneal ring implantation in an experimental animal model

PURPOSE

To evaluate corneal wound healing in the hen animal model after additive surgery with an intracorneal ring segment (ICRS).

METHODS

We implanted one ICRS in each eye of 76 hens. In control group 1 (n = 22 hens), the stromal channel was prepared but no ICRS was inserted. In control group 2 (n = 2 hens), no surgery was performed. Animals were randomly separated into groups and euthanized after clinical follow-up of 4 and 12 hours, 1, 2, 3, and 7 days, and 1, 2, 3, 4, and 6 months. Corneas were stained with hematoxylin-eosin. Apoptosis was measured by terminal uridine nick end-labeling assays. Cell proliferation and myofibroblast-like differentiation were assayed by BrdU and α-smooth muscle actin immunofluorescence microscopy. Stromal matrix changes were documented by electron microscopy.

RESULTS

Epithelial and stromal cell apoptosis around the ICRS-implanted and control group 1 eyes peaked at 12 hours, but continued for 72 hours. In ICRS-implanted eyes, epithelial and stromal proliferation was present at 12 and 24 hours, respectively, and peaked at 7 days and 72 hours, respectively. Some proliferation in the ICRS-implanted group continued through the 6-month follow-up, and myofibroblast-like cells differentiated one to three months after ICRS implantation. The segments rotated within the stroma as the limbal inferior angle approached the epithelium.

CONCLUSIONS

Wound healing after ICRS implantation in hen corneas was similar to that of other corneal surgical wounds in stages. However, there were some specific features related to the small size of the epithelial wound and the device permanently implanted inside the cornea.

Intrastromal corneal ring segment implantation (keraring 355°) in patients with central keratoconus: 6-month follow-up

We evaluate the efficacy and safety of Keraring 355° intrastromal corneal ring segment (ICRS) implantation aided by PocketMaker microkeratome for the correction of keratoconus. Patients underwent ICRS insertion using mechanical dissection with PocketMaker microkeratome and completed 6 months of follow-up. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, topographic findings, safety, efficacy index, and adverse events were reported for six months postoperatively. We evaluated 15 eyes of 15 patients (12 men) with a mean age of 28.87 ± 6.94 years (range 21–49 years). At final postoperative examination, there was a statistically significant reduction in the spherical equivalent refractive error compared to preoperative measurements (−5.46 ± 1.52 to −2.01 ± 1.63 D, P < 0.001). Mean preoperative UCVA (logMAR) before implantation was 0.79 ± 0.48, and postoperative UCVA was 0.28 ± 0.15, P = 0.001. Mean preoperative BSCVA (logMAR) before implantation was 0.36 ± 0.21; at final follow-up examination BSCVA was 0.18 ± 0.9, P = 0.009. Mean K decreased from 48.33 to 43.31 D, P < 0.001. All patients were satisfied with ICRS implantation; 86.7% were moderately to very happy with the results. No intraoperative or postoperative complications were demonstrated. This preliminary study shows that ICRS (Keraring 355°) implantation is an efficient, cost-effective, and minimally invasive procedure for improving visual acuity in nipple type keratoconic corneas.

Keratoconus: tissue engineering and biomaterials

Keratoconus (KC) is a bilateral, asymmetric, corneal disorder that is characterized by progressive thinning, steepening, and potential scarring. The prevalence of KC is stated to be 1 in 2000 persons worldwide; however, numbers vary depending on size of the study and regions. KC appears more often in South Asian, Eastern Mediterranean, and North African populations. The cause remains unknown, although a variety of factors have been considered. Genetics, cellular, and mechanical changes have all been reported; however, most of these studies have proven inconclusive. Clearly, the major problem here, like with any other ocular disease, is quality of life and the threat of vision loss. While most KC cases progress until the third or fourth decade, it varies between individuals. Patients may experience periods of several months with significant changes followed by months or years of no change, followed by another period of rapid changes. Despite the major advancements, it is still uncertain how to treat KC at early stages and prevent vision impairment. There are currently limited tissue engineering techniques and/or "smart" biomaterials that can help arrest the progression of KC. This review will focus on current treatments and how biomaterials may hold promise for the future.

Efficacy of intacs intrastromal corneal ring segment relative to depth of insertion evaluated with anterior segment optical coherence tomography

AIM

To evaluate the effect of implantation depth of Intacs microthin prescription inserts (Addition Technology Inc, Fremont, California) on visual and topographic outcomes in patients with post- laser-assisted in situ keratomileusis (LASIK) ectasias.

SETTINGS AND DESIGN

Retrospective, observational case series.

MATERIALS AND METHODS

In this case series, 16 eyes of 12 patients were evaluated. All cases were post-LASIK ectasia that had undergone intrastromal corneal ring segment (ICRS) implantation. The planned insertion depth was 70% of stromal thickness using a manual dissector. At least 12 months postoperatively, all eyes underwent Visante (Carl Zeiss Meditec) AS-OCT to determine insertion depth. Cases were categorized into 3 groups based on the measured implantation depth: 40-59% thickness; 60-79% thickness; and ≥80% thickness. Visual, refractive and topographic outcomes were evaluated relative to implantation depth.

RESULTS

The lowest improvement in the study parameters ocurred when the implantation depth was ≥80%. In this group, uncorrected visual acuity (UCVA) and best spectacle corrected VA (BSCVA) improved less than 0.5 lines. Manifest refractive spherical equivalent (MRSE) and mean keratometry (Km) change was less than 0.5 diopters (D). The greatest improvements were observed with implantation depth of 60-79% where UCVA and BSCVA increased by 4.5 and 2.5 lines respectively, and MRSE and Km changed by approximately 2.00 D. Less improvement was found when ICRS were implanted between 40-59% of stromal thickness.

CONCLUSION

Implantation of ICRS greater than 80% of stromal thickness may have no effect on visual and topographic status.

Femtosecond laser technology in corneal refractive surgery: a review

PURPOSE

To discuss current applications and advantages of femtosecond laser technology over traditional manual techniques and related unique complications in corneal refractive surgical procedures, including LASIK flap creation, intracorneal ring segment implantation, astigmatic keratotomy, presbyopic treatments, and intrastromal lenticule procedures.

METHODS

Literature review.

RESULTS

From its first clinical use in 2001 for LASIK flap creation, femtosecond lasers have steadily made a place as the dominant flap-making technology worldwide. Newer applications are being evaluated and are increasing in their frequency of use.

CONCLUSIONS

Femtosecond laser technology is rapidly becoming a heavily utilized tool in corneal refractive surgical procedures due to its reproducibility, safety, precision, and versatility.

Riboflavin injection into the corneal channel for combined collagen crosslinking and intrastromal corneal ring segment implantation

PURPOSE

To evaluate the effectiveness of intracorneal riboflavin injection for combined collagen crosslinking (CXL) and intrastromal corneal ring segment (ICRS) implantation.

SETTING

Kudret Eye Hospital, Ankara, Turkey.

DESIGN

Noncomparative case series.

METHODS

Keratoconic eyes had combined ICRS (Intacs) implantation and transepithelial CXL with 20% alcohol application and riboflavin injection into the corneal channel. Outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuities, sphere, cylinder, and keratotomy (K) readings.

RESULTS

The study enrolled 131 eyes (105 patients) with a mean follow-up of 7.07 months ± 4.66 (SD). The mean improvement was 0.26 ± 0.16 logMAR in UDVA and 0.24 ± 0.16 logMAR in CDVA (both P<.05). The mean manifest spherical refraction decreased from -3.87 ± 4.55 diopters (D) to -1.25 ± 2.31 D, the mean manifest cylinder improved from -3.89 ± 1.97 D to -2.27 ± 2.18 D, and the mean K reading improved from 50.50 ± 5.26 D to 46.03 ± 4.51 D (all P<.05). There were no intraoperative or postoperative complications.

CONCLUSIONS

Combined ICRS and CXL treatment with intracorneal riboflavin injection was effective in keratoconic eyes. Intracorneal riboflavin injection into the tunnel was safe and may provide more penetration without epithelial removal.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Corneal endothelium after refractive surgery

The endothelium is vital to the health and optical clarity of the human cornea. The safety of procedures to correct refractive errors depends on preservation of an intact corneal endothelium. Disease states and genetic and environmental factors affect the corneal endothelium; an unstable corneal endothelium can impact the success of refractive surgery. Technological advances and recent laboratory findings have improved the ability to assess the endothelium. The status of the corneal endothelium after laser in situ keratomileusis, photorefractive keratectomy, phakic intraocular lenses, and adjuvants to these treatments has been the topic of numerous clinical trials. Safety guidelines for refractive surgery procedures should be followed to minimize deleterious effects on the corneal endothelium.

FINANCIAL DISCLOSURE

Neither author has a financial or proprietary interest in any material or method mentioned.

[New therapeutic approach of keratoconus with intracorneal ring segments aided by femtosecond laser (Tecnolas Perfect Vision): indications, operating technique and results]

OBJECTIVE

To assess the results of intracorneal ring segment implantation assisted by the Tecnolas Perfect Vision(®) femtosecond laser (Heidelberg, Germany).

SETTINGS

Retrospective observational study.

METHODS

The patients were operated on with the Tecnolas Perfect Vision(®) femtosecond laser. The following parameters were evaluated before and after surgery: uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), corneal topography, wavefront analysis, and central corneal thickness. The Wilcoxon test was used for statistical analysis.

RESULTS

Seventeen eyes of 15 patients were included. The mean follow-up was 6.9±0.71 months. Significant improvement of UCVA and BCVA was observed in 82.35% (P=0.027) and 94.12% (P=0.003) of the eyes, respectively. The subjective refraction showed a significant decrease of the sphere from -10.29±5.54 to -6.5±5.03D (P=0.002). The subjective cylinder significantly decreased from 5.43±3.20 to 3.69±2.30D (P=0.026). The SAI also decreased significantly (P=0.011).

CONCLUSION

Femtosecond-assisted intracorneal ring segment implantation is an effective treatment for corneal ectasia. Further studies are needed to improve surgical parameters and outcomes.

Intrastromal corneal ring segments to correct low myopia in eyes with irregular or abnormal topography including forme fruste keratoconus: 4-year follow-up

PURPOSE

To report the 4-year outcomes after Intacs intrastromal corneal ring segment (ICRS) implantation to correct low myopia in patients with abnormal topography.

SETTING

Instituto de Microcirugia Ocular, Barcelona, Spain.

METHODS

This retrospective consecutive interventional case series included eyes with myopia lower than -4.50 diopters (D) and abnormal topography that excluded excimer laser surgery. Evaluation was performed preoperatively and at yearly intervals up to 4 years postoperatively. The 4-year outcomes measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuities, predictability and stability of refractive correction, the efficacy and safety indices, and complications.

RESULTS

After ICRS implantation, 82.05% of 39 eyes (21 patients) were within +/-1.00 diopter (D) of emmetropia and 46.15% were within +/-0.50 D. Refractive correction improved during the first 6 months and remained stable up to 4 years. The UDVA was 20/40 or better in all eyes and 20/20 or better in 38.46% of eyes. Seven eyes (17.95%) lost 1 line of CDVA, and no eye lost 2 or more lines. No intraoperative complications occurred. The ICRS were exchanged for thicker ICRS in 7 eyes (17.9%) because of undercorrection. One patient requested ICRS removal due to unsatisfactory refractive results.

CONCLUSIONS

The 4-year results indicate that ICRS implantation is effective and safe in the correction of low myopia in patients for whom excimer laser surgery is contraindicated because of abnormal topography, including forme fruste keratoconus. The achieved refractive correction remained stable throughout the follow-up.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Bilateral infectious keratitis after implantation of intrastromal corneal ring segments

PURPOSE

To report the development of bilateral infectious keratitis after implantation of intrastromal corneal ring segments (ICRSs).

DESIGN

Retrospective case report.

PARTICIPANTS

A 20-year-old woman presented with photophobia, decreased vision, and pain 11 days after uncomplicated implantation of ICRSs for keratoconus in both eyes. Bilateral corneal stromal infiltrates were noted at the site of ICRSs implantation.

INTERVENTION

The patient was started on frequent topical fortified antibiotics in both eyes. Despite aggressive medical management, stromal infiltrates progressed, necessitating removal of ICRSs from both corneas to control infectious keratitis and melting of cornea.

METHODS

Retrospective case report of a 20-year-old woman who developed bilateral severe infectious keratitis 11 days after uncomplicated implantation of ICRSs for keratoconus.

RESULTS

Cultures obtained at the time of initial presentation yielded Streptococcus viridans. Patient responded well to the treatment and was left with stromal scars in both corneas.

CONCLUSIONS

Although rare, simultaneous implantation of ICRSs may carry a risk of severe bilateral infectious keratitis. Early recognition of infection, aggressive treatment with antibiotics, and, in some cases, removal of ICRSs may be necessary to prevent serious sight-threatening complication of this refractive procedure.

Enhanced effect of double-stacked intrastromal corneal ring segments in keratoconus

We present a patient with poor visual acuity and contact lens intolerance due to advanced keratoconus who had femtosecond-assisted placement of two 0.35 mm intrastromal corneal ring segments (ICRS) in the right eye. Postoperatively, both rings migrated inferiorly and overlapped each other in a double-stacked formation. This resulted in a dramatic central shift of the cone and flattening of the inferior paracentral cornea with significant improvement in vision. To our knowledge, this is the first report of double-stacked ICRS in a human cornea and raises the possibility that significantly thicker segments may provide enhanced anatomic and visual effects in some keratoectatic patients.