One or 2 Intacs segments for the correction of keratoconus

Outcomes of a Single-Segment Intrastromal Corneal Ring in Early Keratoconus and Early Pellucid Marginal Degeneration

PURPOSE

To determine the effect of a single-segment intrastromal corneal ring segment (ICRS; Intacs SK) on early keratoconus (KCN) and pellucid marginal degeneration (PMD).

METHODS

It is a prospective interventional study. One hundred twenty-four eyes (99 patients) with KCN and 36 eyes (26 patients) with PMD at early stage (the maximum keratometric reading less than 55 diopters) were included to ICRS implantation using femtosecond laser at a tertiary university-based hospital and a private outpatient center. The uncorrected distance and spectacle-corrected visual acuity (UDVA and SCDVA), manifest spherical and cylindrical refractions, and keratometry indices were measured preoperatively and postoperatively, 1 week, 2 and 6 months.

RESULTS

One week after surgery, significant improvements were observed in UDVA, SCDVA, cylinder and keratometry readings of both KCN and PMD groups (all P < 0.05) with no significant changes afterward. No significant change occurred in the sphere refraction of PMD group (P = 0.10) in contrast to KCN group (P < 0.001). Corneal irregularity of KCN group in central 3 and 5 mm zones increased at 1 week (both P < 0.001) and then started to decrease up to 6 months. However, the corneal irregularity of PMD group had significant reduction only at 1 week in 5-mm zone (P = 0.02) and 2 months in 3-mm zone (P = 0.01) postoperatively. The final efficacy indexes were 1.44 ± 0.71 and 0.87 ± 0.40 in KCN and PMD groups, respectively.

CONCLUSION

Visual acuity, refractive errors and keratometry values have been improved after one-segment Intacs SK implantation in early KCN and PMD patients.

Ferrara Rings for Visual Rehabilitation in Eyes with Keratoconus and Previous Cross-Linking Using the Ferrara Ring Nomogram

PURPOSE

To report the visual, refractive and tomographic outcomes following the implantation of intrastromal corneal ring segments (ICRS) (Ferrara rings, AJL Ophthalmics, Miñano, Spain) in eyes with a history of keratoconus and corneal cross-linking using the Ferrara ring nomogram.

METHODS

Retrospective, interventional case series performed at the Corneoplastics Unit, Queen Victoria Hospital, East Grinstead, United Kingdom.

RESULTS

21 eyes of 19 patients with a history of keratoconus and prior corneal collagen cross-linking had Ferrara Intrastromal Corneal Ring Segments implanted between December 2015 and October 2017. The number, thickness and length of ring segments was chosen based on the Ferrara ring company nomogram. Mean uncorrected visual acuity (UDVA) improved from 0.88 to 0.52 logMAR (p < 0.001). Mean corrected visual acuity (CDVA) improved from 0.47 to 0.36 logMAR (p = 0.046). The percentage of eyes achieving 20/40 UDVA and CDVA increased from 5% to 38% and from 38% to 67%, respectively. Of the eyes, 52.3% gained at least two lines of CDVA. The spherical equivalent improved from -7.51D to -3.76D (p < 0.001) and the refractive astigmatism magnitude improved from 5.14D to 2.76D (p = 0.004). There were significant improvements in the corneal tomography with mean keratometry (K_M) improving from 50.40D (3.53) to 48.24D (3.00) (p = 0.01) and keratometric astigmatism magnitude improving from 5.14D (2.91) to 2.76D (1.67) (p = 0.004).

CONCLUSION

Insertion of Ferrara rings in keratoconic eyes with a history of prior cross-linking using the company nomogram results in significant improvements in visual, refractive and tomographic outcomes.

Comparison of Keratoconus Cone Location of Different Topo/tomographical Parameters

Purpose: To compare the corneal cone location on different maps and instruments, and their agreements, with elevation maps.Methods: In 90 left eyes with bilateral keratoconus, the apex of cone location was determined based on the maximum simulated keratometry (Kmax) location on the anterior sagittal curvature map by Pentacam HR, the maximum curvature on the mean curvature map by ATLAS 9000, most elevated point of the island of positive elevation relative to the best fit sphere on the front and back corneal elevation maps by Pentacam HR, and thinnest point on the thickness map by Pentacam HR and Orbscan, and the thinnest points on pachymetry and epithelial thickness maps by RTVue OCT.Results: There was a significant difference among the location on different maps along the x- and y-axes (p < .001). The lowest agreement with the cone apex on both front and back elevation maps was for the anterior sagittal curvature map and the highest agreement for the Pentacam thickness map. The majority of keratoconus cone apexes were displaced in the inferotemporal direction on the different maps except for the epithelial thickness maps.Conclusions: Despite the variability between different devices and methods; the thickness map on the Pentacam HR showed the highest correlation with the front and back elevation maps, while the RTVue epithelial thickness map showed the poorest correlation. Based on this study, epithelial thickness maps and anterior curvature maps should be utilized with caution to determine the location of the cone.

The number of intracorneal ring segments in asymmetric and central cones

Background

To compare the results of single versus double intracorneal ring segment (ICRS) (KeraRing) implantation in keratoconus with respect to different cone locations.

Methods

Twenty-two eyes of 18 patients with totally asymmetric cones (20–80% or 0–100% distribution along steep axis) were implanted with single ICRS (Group 1), 38 eyes of 32 patients with central or partially asymmetric cones (50–50% or 40–60% distribution along steep axis) were implanted with double ICRS (Group 2), at a depth of 80% of the site of implantation, in channels created with femtosecond laser device. All patients had uncorrected and corrected distance visual acuities (UDVA and CDVA, respectively) of ≤ 0.3 Snellen lines.

Results

In both groups, patients had median UDVA and CDVA gain of 3 Snellen lines (P > 0.05). Postoperative improvement in indices of vertical asymmetry and height decentration in Group 1; simulated keratometry, corneal astigmatism and anterior corneal asphericity values in Group 2 were greater (P < 0.05). A total of 10 eyes (45.5%) in Group 1 were recommended double ring implantation by the manufacturer’s nomogram, but underwent single ICRS implantation and achieved visual, refractive, tomographic outcomes comparable to that in Group 2, although corneal cylindrical correction was less and final topographic astigmatism was greater.

Conclusion

Double ICRS implantation seems to be superior in terms of keratometry, corneal astigmatism and anterior corneal asphericity improvement. Single ICRS implantation in totally asymmetric cones seems to provide satisfactory visual, refractive and tomographic results, similar to double ICRS implantation in central and partially asymmetric cones, by inducing central shift of the cone.

Comparison of Visual, Tomographic, and Biomechanical Outcomes of 360 Degrees Intracorneal Ring Implantation With and Without Corneal Crosslinking for Progressive Keratoconus: A 5-Year Follow-up

PURPOSE

To evaluate the long-term (5 years) results of 360 degrees intracorneal ring (ICR) implantation with and without corneal crosslinking (CXL) in patients with progressive keratoconus (KCN).

METHOD

This historical cohort study was performed on 35 eyes with progressive KCN, which was randomly divided into 2 groups. Fourteen patients were implanted only with ICR, and 21 patients with KCN were treated with ICR plus CXL simultaneously. Uncorrected distance visual acuity (UCDVA), corrected distance visual acuity (CDVA), and refractive components were collected from patients' medical records. The biomechanical properties of patients were measured using the Corvis ST (Oculus, Inc, Weltzar, Germany). Corneal topography and aberrometry parameters were also recorded from the Pentacam HR device (Oculus).

RESULTS

Both UCVA and CDVA increased in both groups after ICR implantation; however, this improvement was more significant in the ICR plus CXL group (P = 0.002 and P = 0.001, respectively). The mean improvement of CDVA in patients with ICR implantation with and without CXL was 0.56 ± 0.67 and 0.33 ± 0.61, respectively. A comparison of the long-term postoperative Tomographic and Biomechanical Index between 2 groups showed a better result in the ICR plus CXL group (P = 0.012). Topographic findings of the anterior corneal surface (flat-K, steep-K, mean-K, and astigmatism) after surgery were significantly better than before surgery in both groups (P < 0.05).

CONCLUSIONS

Although ICR implantation alone might halt the KCN progression with acceptable visual, topographic, and biomechanical outcomes, the combination of ICR and CXL has an adjuvant and synergistic effect, especially in long-term follow-up.

Visual, refractive and topographic outcomes of progressive thickness intrastromal corneal ring segments for keratoconic eyes

PURPOSE

To evaluate one-year visual, refractive, and topographic outcomes of 58 eyes of 53 keratoconus patients who underwent surgery with a progressive thickness intrastromal corneal ring segment (ICRS).

METHODS

This multi-center, retrospective, observational study evaluates the one-year effects of progressive thickness ICRS implanted in keratoconus patients meeting the inclusion criteria. One or two progressive ICRS were implanted in the selected eyes after creating an intrastromal tunnel with a femtosecond laser. Pre- and postoperative uncorrected distance visual acuity, best-corrected distance visual acuity, manifest refraction (both spherical equivalent and cylindrical refractions), corneal astigmatism, maximum keratometry, corneal thickness, and corneal topography measurements and indices were evaluated.

RESULTS

In this retrospective case series, 58 eyes of 53 keratoconus patients were included with a follow-up of 12 months. The mean age was 30.89 ± 11.90 years. There were improvements postoperatively in mean values of visual acuities, both uncorrected from 0.71 (preoperatively) to 0.28 (log MAR), and best-corrected from 0.28 to 0.10 (log MAR), mean cylindrical refraction from - 2.35 ± 1.51 to - 4.15 ± 2.23 D, and mean spherical equivalent from - 2.10 ± 2.25 to - 4.64 ± 3.2 D. There was also a reduction in maximal keratometry from 54.21 D preoperatively to 50.93 D postoperatively.

CONCLUSION

The implantation of the progressive thickness ICRS is an effective and safe method to improve the vision of keratoconic eyes. Corneal stability was maintained at the 12-month mark.

Intracorneal Ring Segment Implantation in the Management of Keratoconus: An Evidence-Based Approach

Intracorneal ring segment (ICRS) implantation represents a modern, minimally invasive, surgical option for visual improvement in patients with keratoconus. ICRS modify the corneal geometry in a manner that enhances its refractive properties and thereby, they improve visual acuity. It is well-documented that implantation of ICRS decreases the keratometric readings, spherical equivalent and cylinder, reduces high-order aberrations and improves uncorrected distance visual acuity (UDVA) and best-corrected distance visual acuity (BCDVA) in patients with keratoconus. Success rate after ICRS implantation is high, depending on appropriate patient selection and adherence to suitable implantation nomograms, and most important, the overall complication rate is very low. This review is summarizing current indications/contra-indications for ICRS implantation, implantation techniques, clinical outcomes and potential complications, shedding light on myths and realities related to this innovative surgical option.

Pediatric keratoconus: a review of the literature

PURPOSE

To describe the epidemiology and prevalence, rates of progression, difference between adult and pediatric populations, and therapeutic approaches to pediatric keratoconus from documented literature.

METHODS

A literature search was done on PubMed using key words including pediatric keratoconus, children with keratoconus, adult keratoconus, penetrating keratoplasty, corneal cross-linking and intracorneal ring segments. The literature was reviewed and reported to explore the key epidemiological differences between the pediatric and adult population with regards to presentation and treatment options.

RESULTS

Pediatric keratoconus is more aggressive than adult keratoconus, which has been explained by structural differences in the cornea between both populations. High rates of progression were documented in pediatric populations. While corneal collagen cross-linking, intracorneal ring segments and penetrating keratoplasties have been used as therapies in the pediatric population, the literature overwhelmingly shows higher rates of failure and progression despite these measures as compared to adults.

CONCLUSION

Pediatric keratoconus is more aggressive than adult keratoconus, and current therapies used in adults may not be sufficient for the pediatric population.

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.

Template-based methodology for the simulation of intracorneal segment ring implantation in human corneas

Keratoconus is an idiopathic, non-inflammatory and degenerative corneal disease characterised by a loss of the organisation in the corneal collagen fibrils. As a result, keratoconic corneas present a localised thinning and conical protrusion with irregular astigmatism and high myopia that worsen visual acuity. Intracorneal ring segments (ICRSs) are used in clinic to regularise the corneal surface and to prevent the disease from progressing. Unfortunately, the post-surgical effect of the ICRS is not explicitly accounted beforehand. Traditional treatments rely on population-based nomograms and the experience of the surgeon. In this vein, in silico models could be a clinical aid tool for clinicians to plan the intervention, or to test the post-surgical impact of different clinical scenarios. A semi-automatic computational methodology is presented in order to simulate the ICRS surgical operation and to predict the post-surgical optical outcomes. For the sake of simplicity, circular cross section rings, average corneas and an isotropic hyperelastic material are used. To determine whether the model behaves physiologically and to carry out a sensitivity analysis, a [Formula: see text] full-factorial analysis is carried out. In particular, how the stromal depth insertion, horizontal distance of ring insertion (hDRI) and diameter of the ring's cross section ([Formula: see text]) are impacting in the spherical and cylindrical power of the cornea is analysed. Afterwards, the kinematics, mechanics and optics of keratoconic corneas after the ICRS insertion are analysed. Based on the parametric study, we can conclude that our model follows clinical trends previously reported. In particular and although there is an improvement in defocus, all corneas presented a change in their optical aberrations. The stromal depth insertion is the parameter that affects the corneal optics the most, whereas hDRI and [Formula: see text] are less important. Not only that, but it is almost impossible to achieve an optimal trade-off between spherical and cylindrical correction. Regarding the mechanical behaviour, inserting the rings at 65% depth or above will cause the cornea to slightly bend. This abnormal stress distribution greatly distorts the corneal optics and, more importantly, could be the cause of clinical problems such as corneal extrusion. Not only that, but our model also supports that rings are acting as restraint elements which relax the stresses of the corneal stroma in the cone of the disease. However, depending on the exact spatial location of the keratoconus, the insertion of rings could promote its evolution instead of preventing it. ICRS inserted deeper will prevent keratoconus in the posterior stroma from growing (relaxation of posterior surface), but will promote its growing if they are located in the anterior surface (increment of stress). In conclusion, the methodology proposed is suitable for simulating long-term mechanical and optical effects of ICRS insertion.

Implantation of intracorneal ring segments in pediatric patients: long-term follow-up

Purpose

To analyze the long-term outcomes of intracorneal ring segments (ICRS) implantation for keratoconus management in pediatric patients.

Methods

Retrospective case series review of the long-term (>5 years) outcomes of Intacs^® ICRS implantation for keratoconus in pediatric patients (age <18 years old at the time of surgery) between January 2008 and December 2011 at Ophthalmology Department of Hospital de Santo António. Demographic data, follow-up time, preoperative and postoperative uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) in decimal scale, and corneal topography were evaluated. Statistical analysis was done using SPSS for windows (version 24). Significance was set at p<0.0125.

Results

Fourteen eyes of 14 patients, with a mean age of 15.36 years (range 10-18 years), were included in this study. All patients had been diagnosed with keratoconus with reported progression in the 6 months prior to surgery. Follow-up time was 6.36±0.97 years. UCVA and BCVA improved after ICRS implantation (p<0.0125). Keratometry (K) minimum (Kmin) and K maximum (Kmax) decreased after surgery (p<0.0125). During follow-up, UCVA, BCVA, Kmin, and Kmax values ranged, showing a tendency to worsen at the end of follow-up. However, statistically significant differences were not observed.

Conclusion

ICRS implantation showed good visual and topographic results in pediatric patients. Long-term follow-up suggests that, despite ICRS implantation, there is still progression of keratoconus. To the best of our knowledge, there are no reports regarding the long-term efficacy of ICRS implantation in pediatric patients.

Keratoconus Treatment Algorithm

Keratoconus management has significantly changed over the last two decades. The advent of new interventions such as cornea cross-linking, intrastromal corneal ring segments, and combined treatments provide corneal clinicians a variety of treatment options for the visual rehabilitation of keratoconus patients. This review summarizes current evidence for these treatments and highlights their place in keratoconus management while new promising emerging therapies are being investigated.

New Technique of Femtosecond Laser-Assisted Intracorneal Ring Segment Implantation

PURPOSE

To describe a new technique of femtosecond laser-assisted intracorneal ring segment implantation.

METHODS

The study included 6 eyes of 5 patients. Software of the LDV Z6 femtosecond laser was modified to create a 110-degree reverse side cut between the corneal surface and incision instead of the conventional 90 degree angle (which changed the angle between the incision and tunnel from conventional 90-70 degrees) and 2 disjointed tunnels separated by 10 degrees arc length at the proximal and distal ends.

RESULTS

One-year postoperatively, there were no cases of segment extrusion or touch/overlap. Anterior segment optical coherence tomography showed appropriate position of the rings in all eyes postoperatively. Improvement was also found in visual, refractive, keratometric, and asphericity parameters.

CONCLUSIONS

The results of this pilot study are promising. A comparative prospective study with more eyes and longer follow-up may confirm whether this technique is better than the conventional femtosecond laser-assisted one.

Mathematical analysis of corneal remodelling after intracorneal ring surgery in keratoconus

AIM

To represent mathematically the intersection between the ectatic corneal geometry and the plane of intracorneal ring implants (ICRS) in order to determine the corneal response to ICRS surgery in keratoconus (KC). Thereafter, to present the concept and early results of a newly derived topography-guided nomogram for ICRS surgery for the treatment of keratectasia.

METHODS

The corneal rings plane intersection was modelled to a conic section. Ring effect was the result of: the ring size, position (steep vs flat), location (distance from the geometric centre of the cornea), and the discrepancy between the ring's curvature and the tunnel's curvature. Femtosecond laser was used to create the tunnels and the incision sites were chosen according to the nomogram in order to place the thickest ring in the steepest portion of the cornea regardless of the astigmatism axis of refraction.

RESULTS

The conic section had a more prolate shape in the steep area of the cornea than in the flat area, depending on the corneal sagittal curvature. Equal ring size had more flattening effect in the steep area than in the flat area. Thick segment should be implanted under the steep portion of the cornea regardless of the cylinder axis of refraction. Single segment in the steep area was sufficient in early and moderate cases of KC. The new nomogram provided more topographic regularity with significant reduction of astigmatism and better improvement in uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) than the conventional nomogram.

CONCLUSION

The newly derived nomogram can produce better results than the conventional nomogram. Moreover, based on this concept, a new nomogram can be integrated into the femtosecond laser software to create topography-guided, customized, elliptical tunnels with modified focal asphericity that allows for customized focal flattening of the irregularly steepened ectatic cornea.

Mini-scleral Contact Lens for Management of Poor Visual Outcomes after Intrastromal Corneal Ring Segments Implantation in Keratoconus

Purpose:

To evaluate the feasibility and efficacy of mini-scleral design (MSD) contact lenses to treat keratoconus patients who were unsatisfied with the results of corneal inlay.

Methods:

In this prospective interventional case series, 9 eyes of 6 keratoconus patients who were unsatisfied with the results of corneal inlay were fitted with MSD contact lenses. Demographic data, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and higher order aberrations (HOAs) were evaluated before contact lens fitting. Corrected visual acuity by placing the MSD contact lens with or without over-refraction, and HOAs were measured one hour after contact lens fitting. One month after contact lens wearing, corrected visual acuity by placing the MSD contact lens with over-refraction and possible contact lens related problems were assessed. Ocular comfort and contact lens handling problems were asked in follow-up visits. The data was analyzed using descriptive statistical tests.

Results:

Nine eyes of 6 patients were successfully fitted with the mini-scleral lens. Fitting was ideal in 7 eyes and acceptable in 2 eyes. Mean corrected visual acuity by placing the MSD lens without over-refraction was 0.09 (range, 0.00-0.15) LogMAR which was significantly better than the mean BSCVA of 0.38 (range, 0.2-0.6) LogMAR (P = 0.007). The mean root mean square (RMS) of third-order coma and trefoil significantly decreased after MSD contact lens fitting (P = 0.012 and P = 0.015, respectively); however, changes in the fourth-order spherical aberration were not statistically significant (P = 0.336).

Conclusion:

Mini-scleral contact lenses may be helpful in the management of visually unsatisfied patients after corneal inlay.

Combined femtosecond laser-assisted intracorneal ring segment implantation and corneal collagen cross-linking for correction of keratoconus

Purpose

To assess the safety, predictability, and effectiveness of Keraring intrastromal corneal ring segments (ICRS) insertion assisted by femtosecond laser and corneal collagen cross-linking (CXL) for keratoconus correction.

Patients and methods

In this prospective, noncomparative, and interventional case series, 160 eyes of 100 adult keratoconus patients with poor best-corrected visual acuity (BCVA) (less than 0.7) and intolerance to contact lens wear were included. Patients underwent femtosecond laser-assisted placement of ICRS and CXL. All patients were examined for a complete ophthalmological test: uncorrected visual acuity (UCVA), BCVA, spherical equivalent, keratometry (K1-flat and K2-steep), pachymetry, and Scheimpflug imaging with the Pentacam at 1 week and at 1, 3, and 6 months postoperatively.

Results

At 6 months, a significant difference was observed (P<0.001) in mean UCVA and BCVA from 0.92±0.677 and 0.42±0.600 logMAR preoperatively to 0.20±0.568 and 0.119±0.619 logMAR, respectively. Mean spherical equivalent refractions were significantly lower (P<0.001) at 6 months. Mean keratometry (K) also significantly reduced (P<0.001) from 50.93±5.53 D (K1-flat) and 55.37±5.76 D (K2-steep) to 47.32±4.61 and 51.08±5.38 D, respectively. In terms of pachymetry, no significant difference was observed preoperatively versus postoperatively (P=1.000).

Conclusion

Keraring ICRS insertion assisted by femtosecond laser and corneal CXL provided significant improvement in visual acuity, spherical equivalent, and keratometry, which suggests that it may be effective, safe, and predictable for keratoconus correction.

The use of intracorneal ring segments in keratoconus

Keratoconus is a corneal degeneration that usually appears during puberty and may seriously deteriorate the quality of life of the patients. This corneal disease is today the first indication of corneal transplantation in young patients. Until the last decade of the XX century, keratoplasty procedures were the only alternative to treat this pathological condition. In the beginning of the XXI century, intracorneal ring segments implantation was proposed as a therapeutic choice for treating keratoconus patients. Since then, several published articles have reported the benefits of this surgical procedure in treating this type of corneal ectatic disorder.

The purpose of the present investigative work is to summarize the characteristic of the intracorneal ring segments and also to review the different features published in the literature in relation to this surgical technique for the treatment of keratoconus patients.

Femtosecond-assisted intrastromal corneal single-segment ring implantation in patients with keratoconus: a 12-month follow-up

OBJECTIVE

To determine visual rehabilitation in patients with keratoconus who received femtosecond-assisted intrastromal corneal single-segment ring implantation.

METHODS

This prospective study was conducted on 62 eyes of 45 patients with keratoconus who received single-segment Intacs. The FS200 femtosecond laser was used for tunnel creation. Patients were examined for astigmatism, uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and manifest refraction spherical equivalent (MRSE) before the operation and 1, 6, and 12 months after operation. Scheimpflug imaging including minimum keratometry reading (min-K), maximum keratometry reading (max-K), average of minimum and maximum keratometry readings (mean-K), central corneal thickness (CCT), asphericity (Q-value), index of surface variance (ISV), index of vertical asymmetry (IVA), keratoconus index (KI), center keratoconus index (CKI), index of height asymmetry (IHA), index of height decentration (IHD), and minimum sagittal curvature (Rmin) was performed before and 12 months after the operation.

RESULTS

The mean preoperative UCVA was 20/130, which increased to 20/62 1 year after the operation (P < 0.001). The mean BCVA in the last follow-up was 20/32, which improved when compared with preoperative BCVA (20/40) (P = 0.008). One year after the operation, MRSE and cylinder decreased to 1.33 ± 1.90 diopter (D) and 0.46 ± 1.50 D, respectively (P < 0.001 for both). Min-K, max-k, and mean-k reduced to 1.67 ± 0.1.40 D, 2.08 ± 1.84 D, and 1.85 ± 1.30 D (P < 0.001 for all). Q-value decreased to 0.81 ± 1.14 (P < 0.001). In contrast, CKI had a significant increase of 0.02 (P = 0.002). Other evaluated indexes did not show any significant differences.

CONCLUSION

Implantation of the single-segment ring in patients with keratoconus improved vision because of regularizing the cornea and centralization of the corneal cone.

Analysis and quantification of collagen organization with the structure tensor in second harmonic microscopy images of ocular tissues

The important biological role of collagen-based tissues and the changes produced in the fiber distribution under particular situations (surgery, pathology, external damage, etc.) require tools for the analysis of the collagen organization that might potentially help in early diagnoses. Since collagen structures provide efficient second harmonic generation (SHG) signals, SHG microscopy has emerged as a powerful technique to visualize collagen fibers and qualitatively discriminate normal from abnormal tissues. Here we propose a quantitative method based on the structure tensor to quantify the different organization of collagen patterns in SHG images of ocular tissues. Results show that well-organized collagen distributions present a high degree of isotropy (DoI), a dominant orientation (PO), and a low structural dispersion (SD). On the other hand, the PO vanishes when the collagen tissue is not organized as a consequence of an increase in the SD and a decrease in the DoI. The proposed method is also able to discriminate partially organized samples. The combination of SHG microscopy and the structure tensor is a useful method to objectively classify collagen distributions. Clinical applications of this technique could help in the diagnosis and tracking of pathologies related to collagen disorders in connective tissue.

Reshaping procedures for the surgical management of corneal ectasia

Corneal ectasia is a progressive, degenerative, and noninflammatory thinning disorder of the cornea. Recently developed corneal reshaping techniques have expanded the treatment armamentarium available to the corneal specialist by offering effective nontransplant options. This review summarizes the current evidence base for corneal collagen crosslinking, topography-guided photorefractive keratectomy, and intrastromal corneal ring segment implantation for the treatment of corneal ectasia by analyzing the data published between the years 2000 and 2014.

FINANCIAL DISCLOSURE

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

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.

Outcomes of Single Segment Implantation of Conventional Intacs versus Intacs SK for Keratoconus

Purpose:

To compare the visual, refractive, and keratometric outcomes of single-segment conventional and severe keratoconus (SK) types of Intacs for correction of inferior keratoconus (KCN).

Methods:

A total number of 41 consecutive eyes of 23 patients with a diagnosis of inferior KCN underwent Intacs implantation. Eight eyes were excluded due to postoperative complications (4 eyes) and loss to follow-up (4 eyes) and finally 33 eyes underwent statistical analysis. Two groups were created according to Intacs type insertion; conventional group (17 eyes) and SK groups (16 eyes). Intracorneal ring segments (ICRS) implantation was indicated in keratoconic patients with contact-lens intolerance or reduced best spectacle-corrected visual acuity (BSCVA).

Results:

In the conventional group, mean uncorrected distance visual acuity (UCDVA) improved from 0.45 ± 0.41 preoperatively to 0.69 ± 0.39 six months after surgery representing a gain of 2 Snellen lines, and in the SK group mean UCDVA changed from 0.40 ± 0.35 preoperatively to 0.58 ± 0.48 equivalent to two Snellen lines improvement 6 months after operation (P = 0.48). Mean preoperative BSCVA in the conventional group improved from 0.72 ± 0.41 to 0.86 ± 0.39 (2 lines improvement) postoperatively and in the SK group improved from 0.71 ± 0.69 to 0.75 ± 0.45 (0.50 line improvement) (P = 0.29). Mean preoperative spherical equivalent (SE) decreased from −4.86 ± 2.26 D to −3.57 ± 2.21 D (conventional group) and from −4.20 ± 1.82 D to −3.60 ± 1.89 D (P = 0.34), mean astigmatism (AST) decreased from −5.20 ± 2.07 D and −4.50 ± 2.26 D to −4.02 ± 2.57 D and − 3.18 ± 2.14 D in the conventional and SK groups, respectively (P = 0.68). Finally, mean K min decreased from 47.11 ± 2.51 D to 45.40 ± 3.30 D in the conventional group and from 45.05 ± 2.59 D to 44 ± 3.88 D in the SK group (P = 0.63) and mean K max was decreased from 52.82 ± 3.23 D to 50.52 ± 3.57 D and from 49.72 ± 3.17 D to 48.55 ± 4.50 D, respectively (P = 0.48).

Conclusion:

Single-segment implantation of conventional and SK Intacs improved UCDVA and BSCVA, decreased corneal AST and keratometry in both groups with comparable outcomes.

Decision making nomogram for intrastromal corneal ring segments in keratoconus

Purpose:

To create a nomogram for the insertion of intrastromal corneal ring segments (ICRS) (Intacs^® ) in eyes with keratoconus.

Setting:

Tertiary eye care center in South India.

Materials and Methods:

This prospective, non-randomized, interventional case series used a self-designed decision-making nomogram for the selection of ICRS in keratoconus patients based on the centration of the cone, mean refractive spherical equivalent (MRSE), and mean keratometry (Km) values. The 3, 6, and 12 months clinical outcomes were compared to historical controls. Primary endpoints were improvement in uncorrected and best-corrected vision and change in the keratometric values.

Results:

Group A comprised of 52 eyes of 50 patients that followed the nomogram, while Group B comprised of 25 eyes of 23 non-nomogram historical controls matched for baseline parameters. In Group A, the uncorrected distance visual acuity (UDVA) improved from 0.16 ± 0.15 to 0.25 ± 0.16 (P < 0.001), corrected distance visual acuity (CDVA) from 0.58 ± 0.2 to 0.69 ± 0.21 (P = 0.022), MRSE from -5.41 ± 4.94 to -1.71 ± 2.88 (P < 0.001), Km from 51.77 ± 5.45 to 48.63 ± 4.37 (P < 0.001), and astigmatism reduced from 5.86 ± 2.61 to 4.91 ± 2.72 diopters (P < 0.001).In Group B, improvement in the average MRSE was from -6.44 ± 5.32 to -3.26 ± 2.82 (P < 0.013) and in the average Km from 53.64 ± 5.32 to 50.31 ± 5.02 (P < 0.001). Other parameters did not improve significantly. A statistically significant difference was present in the percentage of patients achieving a good clinical outcome between the two groups (P < 0.001; Chi-square).

Conclusion:

The nomogram provides a means to choose the appropriate ICRS, hence improving the outcome in patients with keratoconus.

Intrastromal corneal ring segments: how successful is the surgical treatment of keratoconus?

This review evaluates the outcomes of intrastromal corneal ring segment (ICRS) implantation for the treatment of keratoconus considering a new grading system based on the preoperative visual impairment of the patient. Additionally, a five-year follow-up analysis of patients with stable and progressive keratoconus is performed in order to assess the long term stability of the surgical procedure. Corrected distance visual acuity decreased statistically significantly in patients with mild keratoconus (P < 0.01) but statistically significantly increased in all other grades (P < 0.05). The improvement in visual acuity and the decrease of keratometric and aberrometric values were stable throughout a long period of time in patients with stable keratoconus. In patients with progressive form keratoconus, a significant improvement was found immediately after the procedure, however clinically relevant regression greater than 3 D was observed at the end of the follow up period.

Single-Segment Intacs Severe Keratoconus 80% Stromal Depth Insertion With a Femtosecond Laser for Asymmetric Keratoconus: A Case Series

PURPOSE

To study the efficacy of inferior, single-segment, 80% stromal depth Intacs severe keratoconus (SK) intracorneal ring segment implantation.

DESIGN

A prospective case series.

METHODS

Eighteen eyes from 15 patients with asymmetric keratoconus underwent 80% stromal depth Intacs SK single inferior segment implantation, using an IntraLase femtosecond laser for tunnel creation. Parameters studied included preoperative and postoperative uncorrected and best-corrected visual acuity (VA), manifest refraction and elevation-based computerized corneal topography.

RESULTS

Patients' VA was tested with Early Treatment Diabetic Retinopathy Study (ETDRS) chart. All the eyes demonstrated a significant ETDRS line improvement of 5.4 ± 2.0 after a follow-up period of 8.9 ± 3.9 months. Thirteen eyes (72%) showed a line improvement of 4 or more. Best-corrected VA remained unchanged in 8 eyes (44%) while 7 eyes (39%) showed a line improvement of 1 to 8. Sixteen eyes (89%) had a significant change in manifest cylinder [3.0 ± 2.2 diopters (D)]. Of the 18 eyes, astigmatism reduction was 3.44 ± 1.98 D, from 5.6 ± 2.2 D preoperatively to 2.5 ± 1.5 D postoperatively (P < 0.05). Implant placement reduced both preexisting hyperopic and myopic spheres in 14 cases (78%). Although one case showed a significant postoperative regression of the obtained correction, Intacs SK implantation was safe and effective in all the other cases.

CONCLUSIONS

Femtosecond laser-assisted single-segment Intacs SK (80% depth intrastromal placement) is a safe and effective technique for improving uncorrected and best-corrected VA and correcting both spherical and cylindrical refractive errors in eyes with severe asymmetric keratoconus.

Transepithelial phototherapeutic keratectomy combined with implantation of a single inferior intrastromal corneal ring segment and collagen crosslinking in keratoconus

PURPOSE

To evaluate the efficacy of phototherapeutic keratectomy (PTK) combined with implantation of a single inferior intrastromal corneal ring segment (ICRS) and riboflavin with ultraviolet-A collagen crosslinking (CXL) performed sequentially on the same day in the management of keratoconus.

SETTING

Cornea Unit, Toronto Western Hospital, Toronto, Ontario, Canada.

DESIGN

Case series.

METHODS

This retrospective review comprised consecutive patients with progressive keratoconus having transepithelial PTK followed by femtosecond laser-enabled placement of a single inferior ICRS and CXL on the same day by the same surgeon between December 2010 and August 2011. The main outcome measures included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), mean refraction spherical equivalent, keratometry (K), and total higher-order aberrations.

RESULTS

Sixteen eyes of 13 patients were included in the study. Six months after same-day PTK combined with implantation of a single inferior ICRS and CXL, there was a significant improvement in UDVA, CDVA, and the mean and steep K values. No patient lost CDVA lines.

CONCLUSION

Phototherapeutic keratectomy combined with implantation of a single inferior ICRS and CXL on the same day was a safe, effective treatment for improving visual acuity in select patients with progressive keratoconus.

Outcome analysis of intracorneal ring segments for the treatment of keratoconus based on visual, refractive, and aberrometric impairment

PURPOSE

To analyze the outcomes of intracorneal ring segment (ICRS) implantation for the treatment of keratoconus based on preoperative visual impairment.

DESIGN

Multicenter, retrospective, nonrandomized study.

METHODS

A total of 611 eyes of 361 keratoconic patients were evaluated. Subjects were classified according to their preoperative corrected distance visual acuity (CDVA) into 5 different groups: grade I, CDVA of 0.90 or better; grade II, CDVA equal to or better than 0.60 and worse than 0.90; grade III, CDVA equal to or better than 0.40 and worse than 0.60; grade IV, CDVA equal to or better than 0.20 and worse than 0.40; and grade plus, CDVA worse than 0.20. Success and failure indices were defined based on visual, refractive, corneal topographic, and aberrometric data and evaluated in each group 6 months after ICRS implantation.

RESULTS

Significant improvement after the procedure was observed regarding uncorrected distance visual acuity in all grades (P < .05). CDVA significantly decreased in grade I (P < .01) but significantly increased in all other grades (P < .05). A total of 37.9% of patients with preoperative CDVA 0.6 or better gained 1 or more lines of CDVA, whereas 82.8% of patients with preoperative CDVA 0.4 or worse gained 1 or more lines of CDVA (P < .01). Spherical equivalent and keratometry readings showed a significant reduction in all grades (P ≤ .02). Corneal higher-order aberrations did not change after the procedure (P ≥ .05).

CONCLUSIONS

Based on preoperative visual impairment, ICRS implantation provides significantly better results in patients with a severe form of the disease. A notable loss of CDVA lines can be expected in patients with a milder form of keratoconus.

Treatment of moderate to severe keratoconus with 6-mm Intacs SK

AIM

To evaluate the effect of Intacs SK corneal ring segment implant for treatment of patients with moderate to severe keratoconus, who have clear central cornea and cannot tolerate contact lens.

METHODS

In this prospective, non-comparative, interventional case series study performed in Dena Hospital, Shiraz, Iran, thirty-seven eyes of thirty-six patients with moderate to severe keratoconus, clear central cornea, and contact lens intolerance were enrolled and underwent Intacs SK corneal ring segment implantation. Preoperatively, uncorrected distance visual acuity (UCDVA), best-corrected distance visual acuity (BCDVA), central corneal thickness(CCT) and average keratometry (Av-K) were measured and compared with post-operative results at one week, one month, three months, and six months.

RESULTS

Mean preoperative UCDVA and BCDVA were (1.32±0.31)logMAR and (1.07±0.27)logMAR, respectively. Av-K was (52.13±0.39)D, and the CCT was (432±39.5)µm. Post-operative examinations showed a clinically significant improvement in both UCDVA and BCDVA (P<0.001). There was also a significant effect based on the time of assessment on both UCDVA and BCDVA and both parameters had a continuous improvement during the follow-up period. Three months after operation there was a statistical significant reduction of Av-K (P=0.0001), but there were no significant changes in CCT (P=0.149).

CONCLUSION

Intacs SK corneal ring segment implants seem to be a safe and effective treatment option for patients who have keratoconus, clear central cornea, and contact lens intolerance.

Keratoconus: overview and update on treatment

Keratoconus is a non-inflammatory, progressive thinning process of the cornea. It is a relatively common disorder of unknown etiology that can involve each layer of the cornea and often leads to high myopia and astigmatism. Computer- assisted corneal topography devices are valuable diagnostic tools for the diagnosis of subclinical keratoconus and for tracking the progression of the disease. The traditional conservative management of keratoconus begins with spectacle correction and contact lenses. Several newer, more invasive, treatments are currently available, especially for contact lens-intolerant patients. Intrastromal corneal ring segments can be used to reshape the abnormal cornea to improve the topographic abnormalities and visual acuity. Phakic intraocular lenses such as iris-fixated, angle-supported, posterior chamber implantable collamer and toric lenses are additional valuable options for the correction of refractive error. Corneal cross-linking is a relatively new method of stiffening the cornea to halt the progression of the disease. The future management of keratoconus will most likely incorporate multiple treatment modalities, both simultaneous and sequential, for the prevention and treatment of this disease.

Intracorneal continuous ring implantation for keratoconus: One-year follow-up

PURPOSE

To evaluate intracorneal continuous ring (ICCR) implantation for the treatment of keratoconus.

SETTING

Eye specialist centers, Europe and Middle East.

METHOD

This study assessed the results of implantation of a MyoRing ICCR in 15 eyes with keratoconus. Outcome measures included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA) (spectacle correction), refraction, complications, and side effects. Postoperative follow-up was up to 1 year.

RESULTS

The study evaluated 15 eyes of 11 patients (8 men, 3 women) with a mean age of 35 years +/- 12 (SD) (range 22 to 60 years). Preoperatively, the mean central corneal thickness was 435 +/- 41 mum (range from 350 to 485 mum) and the mean keratometry (K) readings, 48.96 +/- 3.4 diopters (D) (range 43.75 to 56.62 D). Postoperatively, there was a statistically significant improvement in the UDVA, CDVA, K readings, manifest spherical and cylindrical refractive errors, and spherical equivalent (P<.05). The mean UDVA improved by almost 10 lines, from 0.07 (1.24 +/- 0.35 logMAR) to 0.56 (0.27 +/- 0.17 logMAR), and the mean CDVA improved by almost 3 lines, from 0.42 (0.40 +/- 0.17 logMAR) to 0.77 (0.12 +/- 0.10 logMAR). The mean K reading decreased by 5.76 D, from 48.96 D to 43.20 D. No serious intraoperative complications occurred. Side effects included glare and night-vision problems.

CONCLUSIONS

Treatment of keratoconus with ICCR implantation significantly improved visual function. The nomogram requires grading the disease using the K readings only. The UDVA and CDVA also improved during the first postoperative year.

FINANCIAL DISCLOSURE

Drs. Mahmoud and Venkateswaran have no financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes.