Intacs for the correction of keratoconus: Two-year follow-up

Criteria for patient selection and indication for intracorneal ring segments in keratoconus

BACKGROUND

Keratoconus is an ectatic, progressive corneal disorder characterized by alterations in the morphology of the corneal tissue that leads to limitation of visual function of the patient. Intracorneal ring segments (ICRS) are small synthetic devices that are implanted in the corneal stromal in order to regularize the morphology of the tissue therefore improving the visual function and the quality of life of the patients.

MAIN TEXT

The present narrative review summarizes the main scientific articles developed by the authors in relation to the clinical outcomes and long-term results of ICRS in the treatment of keratoconus. It was found that those patients that benefit the most from this surgical intervention are those that have the most severe form of keratoconus. Additionally, patients with good visual function, those with more than 0.9 in the decimal scale are at risk of losing visual acuity after ICRS implantation. In relation to long-term results, scientific investigations published by the authors demonstrate that ICRS is a stable procedure after long period of time in terms of vision, refraction, and topographic variables in those patients with stable keratoconus. However, in patients with keratoconus and signs of progression, ICRS may not have the capability of halting the progression of the disease. Using artificial intelligence to guide ICRS implantation provide better clinical outcomes and improvement in corneal higher-order aberrations in patients with keratoconus in comparison to those treated using the commercial nomogram of implantation.

CONCLUSIONS

ICRS is a safe surgical procedure in the treatment of keratoconus. Patients that benefit most from the surgery are those with a significant visual impairment. ICRS should not be considered in patients with good visual function because of the risk of losing lines of vision. Long-term follow-up demonstrate stability of the clinical outcomes in patients with stable keratoconus although ICRS may not have the ability of halting the progression of the disease. New technologies based artificial intelligence improved the indications and the clinical outcomes of keratoconus patients treated with ICRS.

Factors predicting the visual outcome of intracorneal ring segment for keratoconus

OBJECTIVES

To identify predictive factors and to construct predictive models using epidemiological and clinical preoperative factors for the visual acuity change after intracorneal ring segment (ICRS) implantation in patients with keratoconus.

METHODS

The medical records of 287 keratoconic eyes of 230 patients implanted with ICRS at Chula Refractive Surgery Center of a tertiary university hospital (Bangkok, Thailand) between January 2012 and March 2022 were retrospectively reviewed for epidemiological and clinical preoperative variables, including those derived from Scheimpflug tomography. After randomly excluding one eye for each bilateral case, the remaining 230 eyes were randomized into two groups: a training group (184 eyes) and a validation group (46 eyes). In the training group, the correlation between the interesting variables and postoperative uncorrected and corrected distance visual acuity change (ΔUDVA and ΔCDVA; logMAR scale) at 6 months was explored, and then the multiple linear regression analysis was used to develop the predictive models. The obtained models were tested using the validation group.

RESULTS

There were 5 and 14 preoperative variables that statistically correlated with ΔUDVA and ΔCDVA respectively. Only the preoperative corrected distance visual acuity (CDVAp) strongly correlated with ΔCDVA (Beta = -0.746). Using multiple regression, the preoperative uncorrected distance visual acuity (UDVAp) and front mean keratometry were selected in the proposed model for ΔUDVA (adjusted R2 = 38.8%), while the CDVAp and index of surface variance (ISV) were selected in the model [Formula: see text] (adjusted R2 = 48.9%). The ΔUDVA and ΔCDVA models were correct in 47.83% and 63.4% of the validation group within 0.20 logMAR, respectively.

CONCLUSIONS

Potential predictive factors and models for ICRS-induced changes in visual acuity are proposed as adjunctive tools for clinicians. Such tools could be used for case selection and during counselling before ICRS implantation to maximize surgical outcomes.

Comparison of two different 360-degree intrastromal corneal rings combined with simultaneous accelerated-corneal cross-linking

PURPOSE

to compare five-year outcomes of two complete intracorneal implants (MyoRing versus annular-shaped intracorneal implant [AICI]) combined with accelerated corneal cross-linking (A-CXL) in progressive KCN.

METHODS

In this historical cohort study, preoperative and postoperative visual, refractive, tomographic, biomechanical, and aberrometric parameters of 27 eyes of 27 patients who underwent implantation of two complete rings (13 AICI and 14 MyoRing) combined with A-CXL were recorded.

RESULTS

The mean age of patients in "AICI plus A-CXL" and "MyoRing plus A-CXL" groups were 28.1 ± 4.6 and 26.3 ± 3.8 years, respectively. All pre- and postoperative visual and refractive parameters between the two groups were not significantly different (p > 0.05). Comparing pre- and postoperative tomographic measurements showed that anterior corneal surface (ACS) flat-K and corneal thickness at pachymetric apex significantly improved for MyoRing plus A-CXL group after five years (p < 0.05). On the other hand, ACS K-max and mean-K values were significantly improved for AICI plus A-CXL group after five years (p < 0.05). Both groups revealed significant improvements in ACS steep-K and corneal astigmatism (p < 0.05). Five years after surgery, the high order aberration in the AICI group (2.60 ± 0.83) was significantly better than the MyoRing group (1.70 ± 0.43) (p = 0.007).

CONCLUSIONS

Both complete intrastromal rings (MyoRing or AICI) combined with A-CXL significantly Improved visual, refractive, and corneal aberrometric, biomechanical, and tomographic parameters and halt the progression of KCN with comparable long-term outcomes.

Keratoconus Diagnosis and Treatment: Recent Advances and Future Directions

Keratoconus is a disorder characterized by progressive corneal thinning and steepening that may result in significant visual impairment secondary to high astigmatism, corneal scarring, or even corneal perforation. Early detection and screening of keratoconus are essential for effective management and treatment. Several screening methods, such as corneal topography and tomography, corneal biomechanics, and genetic testing, are being developed to detect keratoconus at an early stage. Once detected, prevention of progression is the mainstay of keratoconus management. Corneal collagen cross-linking is a minimally invasive treatment option that can slow or halt the progression of keratoconus. Additionally, recent studies have investigated the potential use of copper sulfate eye drops (IVMED-80) and extracellular vesicles to prevent the progression of keratoconus as non-invasive treatment options. For visual rehabilitation, currently available treatments include scleral lenses, intracorneal ring segments, corneal allogenic intrastromal ring segments, and deep anterior lamellar keratoplasty. The safety and efficacy of these emerging treatment options for keratoconus are currently being investigated.

CLEAR - Medical use of contact lenses

The medical use of contact lenses is a solution for many complex ocular conditions, including high refractive error, irregular astigmatism, primary and secondary corneal ectasia, disfiguring disease, and ocular surface disease. The development of highly oxygen permeable soft and rigid materials has extended the suitability of contact lenses for such applications. There is consistent evidence that bandage soft contact lenses, particularly silicone hydrogel lenses, improve epithelial healing and reduce pain in persistent epithelial defects, after trauma or surgery, and in corneal dystrophies. Drug delivery applications of contact lens hold promise for improving topical therapy. Modern scleral lens practice has achieved great success for both visual rehabilitation and therapeutic applications, including those requiring retention of a tear reservoir or protection from an adverse environment. This report offers a practical and relevant summary of the current evidence for the medical use of contact lenses for all eye care professionals including optometrists, ophthalmologists, opticians, and orthoptists. Topics covered include indications for use in both acute and chronic conditions, lens selection, patient selection, wear and care regimens, and recommended aftercare schedules. Prevention, presentation, and management of complications of medical use are reviewed.

Long-term results of MyoRing implantation in patients with keratoconus

Clinical relevance: This study was conducted to evaluate five-year outcomes of MyoRing implantation in patients with keratoconus. The results showed that MyoRing implantation is a minimally invasive procedure and is safe and effective for improving visual acuity and refraction in most patients with keratoconus.Background: The long-term effects of MyoRing implantation on corneal features were studied.Methods: A total of 48 keratoconic eyes of 43 consecutive patients who had undergone MyoRing implantation using the Pocket Maker microkeratome (Dioptex, gmbh, Linz, Austria) and who had completed five years of follow‑ups were included in this retrospective study. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction and keratometry (K) readings were measured and assessed pre-operation, and five years post-operatively. As well, post-operation satisfaction was assessed using a validated questionnaire.Results: Five years post-operatively, there was a significant improvement in UDVA, CDVA, K readings, spherical equivalent (SE), and manifest sphere and cylinder (p < 0.001). Mean UDVA was 1.20 logMAR before the surgery and 0.42 after the surgery (p < 0.001). Mean CDVA was 0.63 logMAR before the surgery and 0.20 logMAR after the surgery (p < 0.001). SE was improved from -6.53 dioptres (D) before the surgery to -2.23 D after the surgery (p < 0.001). Moreover, the results show that the mean K was reduced by 2.82 D after the surgery (p = 0.001). Overall, 81% of patients were moderately to highly satisfied five years after surgery.Conclusion: MyoRing implantation was found to be a minimally invasive procedure, and is safe and effective for improving visual acuity and refraction in most patients with keratoconus.

Intracorneal Ring Segments Followed by Simultaneous Topography-Guided Removal of Epithelium and Stroma With Accelerated Collagen Cross-Linking For Keratoconus (I-TRESK/CXL)

PURPOSE

The aim of this study was to assess the visual, topographic, and aberrometric outcomes of a novel tissue sparing technique, topography-guided removal of epithelium, and stroma in keratoconus (TRESK) along with accelerated collagen cross-linking (CXL), 1 month after Intacs insertion.

DESIGN

Prospective interventional study.

METHODS

Fourty-eight eyes (45 patients) with keratoconus underwent femto-assisted Intacs insertion. After 1 month, TRESK and CXL (9 mW/cm2 for 10 minutes) was done. TRESK is a decentered trans-PTK (phototherapeutic keratectomy) with center and area of ablation at the location of the steepest tangential anterior curvature and area of the cone respectively. Total ablation (epithelium plus stroma) was limited to 75 μm. Postoperative measurements were performed 1 month after Intacs, 6 weeks after Intacs followed by TRESK/CXL, and at the final visit 12 months after Intacs followed by TRESK/CXL.

RESULTS

For all eyes studied, uncorrected distance visual acuity and corrected distance visual acuity (CDVA) (logMAR) improved from preoperative means of 1.05 ± 0.05 and 0.31 ± 0.03 logMAR to postoperative means of 0.52 ± 0.05 (P < 0.001) and 0.20 ± 0.02 logMAR (P = 0.009), respectively. The mean preoperative sphere, cylinder and mean refractive spherical equivalent decreased from -4.52 ± 0.98 D, -4.81 ± 0.25 D, -6.93 ± 0.99 D to -0.77 ± 0.53 D (P = 0.029), -3.13 ± 0.24 D (P = 0.002), and -2.34 ± 0.53 D (P = 0.021), respectively with a mean keratometric flattening of 5.06D (P < .0001) at the final visit. In total, 2.08% of the eyes lost 1 Snellen line of CDVA. Sixty eight percent and 27% of the eyes gained 2 Snellen lines or more of uncorrected distance visual acuity and CDVA, respectively.

CONCLUSIONS

Simultaneous TRESK with CXL done 1 month after Intacs insertion (I-TRESK) in keratoconus eyes provided significant visual gain with refractive and topographic improvement. This novel procedure involving customized PTK before CXL is safe, easy to plan and perform, and provides good outcomes.

Intracorneal Ring Segments Implantation Outcomes Using Two Different Manufacturers' Nomograms for Keratoconus Surgery

PURPOSE

To compare the outcomes of intracorneal ring segments (ICRS) implantation in keratoconic eyes with a similar tomographic pattern, using two different manufacturers' nomograms for surgical planning.

METHODS

ICRS were implanted alternately in patients with the same tomographic pattern of keratoconus divided into two groups according to the surgical planning proposed by the ICRS manufacturers (Keraring, Mediphacos, Belo Horizonte, Brazil, and Ferrara Ring, AJL Ophthalmics, Vitoria, Spain). Visual, refractive, keratometric, corneal aberrometry, and optical quality changes were evaluated during a 6-month follow-up. Corneal and manifest refractive astigmatic changes were also analyzed using the double-angle polar plot and the Alpins vectorial method through the following components: target induced astigmatism, surgically induced astigmatism, difference vector, correction index, angle of error, index of success, flattening effect, and torque.

RESULTS

After ICRS implantation, both groups showed significant improvement (P < .05) in visual and keratometric data. Corneal aberrometric changes and optical quality improvement were also statistically significant in both groups, except for trefoil (P > .05 in all intervals). The Alpins method analysis showed a better performance in the Keraring group, but with no statistically significant difference between groups (P > .05). Comparison between groups showed a statistically significant difference only in tomographic astigmatism in double-angle polar plot analysis (P = .03), with more significant improvement in the Keraring group.

CONCLUSIONS

Both manufacturers' nomograms resulted in statistically significant improvement in most of the parameters analyzed, with greater correction of corneal tomographic astigmatism in the group operated on according to the spherical equivalent/tomographic astigmatism nomogram. [J Refract Surg. 2019;35(10):673-683.].

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.

Comparison of Complication Rates between Manual and Femtosecond Laser-Assisted Techniques for Intrastromal Corneal Ring Segments Implantation in Keratoconus

Purpose: To compare the incidence of complications between manual and femtosecond-laser assisted surgery for intrastromal corneal ring segments (ICRS) implantation.Material and methods: This study included keratoconus patients who had ICRS implantation using manual dissection and using the femtosecond laser with a minimum follow-up of 12 months. Uncorrected (UDVA) corrected (CDVA) distance visual acuity (CDVA), refraction, corneal topography and aberrometry, pachymetry map and slit-lamp microscopy were assessed before and after surgery.Results: The study included 265 eyes in the manual group and 111 in the femtosecond laser group. In the manual group, there were complications in 48 eyes (18.11%); while in the femtosecond laser 4 eyes had a complication (3.6%). In the manual group, the most frequent complications were ICRS exchange/adjustment for visual and refractive enhancement (25 eyes; 9.43%) and late ICRS spontaneous extrusion (15 eyes; 5.66%). In the manual group, 81.25% of complications were observed during the first 3 years of surgeon's experience. Eyes who suffered a complication had preoperatively higher mean refractive (p = .002) and topographic cylinder (p = .003) and lower UDVA (p = .005) and CDVA (p = .002). After a second surgical procedure for complication management visual, refractive and topographic outcomes significantly improved.Conclusion: Manual mechanical ICRS surgery shows a higher rate of intra- and postoperative mechanical and refractive complications when compared to femtosecond laser assisted technique. The incidence is specially higher during the surgeon's first years of implementation of the technique.

Efficacy of Different Procedures of Intra-Corneal Ring Segment Implantation in Keratoconus: a Systematic Review and Meta-Analysis

Purpose

To evaluate the efficacy of the functional, keratometric, and refractive postoperative parameters of intracorneal ring segment (ICRS) implantation in keratoconus and its association with collagen cross-linking (CXL), photorefractive keratectomy (PRK), and intraocular lenses (IOLs).

Methods

We conducted a systematic review and meta-analysis on case series published between 2007 and 2017.

Results

We included 95 case series with a total of 4560 patients. We included 64 studies of the ICRS procedure, 20 studies of ICRS+CXL, 9 studies of ICRS+CXL+PRK, and 5 studies of ICRS+IOL. We demonstrated an overall improvement of all parameters in all procedures. Cylinder was decreased with an overall effect size (ES) of −1.15 (−1.36 to −0.95; I² = 93.7%). Corrected distance visual acuity was improved with an overall ES of 0.89 (0.78 to 1.00; I² = 81.9%). Maximal keratometry was decreased with an overall ES of 0.98 (0.85 to 1.11; I² = 78.9%). ICRS+IOL is the best procedure to improve spherical equivalent and uncorrected distance visual acuity (P < 0.05) compared with other procedures. ICRSs versus ICRS+CXL are similar in all parameters except for corrected distance visual acuity. ICRS+CXL+PRK is better than ICRS alone in all parameters except for the correction of spherical equivalent.

Conclusions

Although the quality and strength of the data are questionable, ICRS implantation is an effective strategy to preserve visual function in keratoconic patients. Particularly, ICRS+CXL+PRK could be a low invasive procedure to propose to young keratoconic patients.

Translational Relevance

To propose an overview of postoperative parameters on each ICRS procedure on keratoconus.

Late Onset of Deep Corneal Vascularization: A Rare Complication of Intrastromal Corneal Ring Segments for Keratoconus

Purpose

To report deep corneal vascularization noted 3 years after intrastromal corneal ring segments (Intacs) implantation for the treatment of keratoconus.

Methods

A 33-year-old male keratoconus patient intolerant to rigid gas permeable contact lens in the right eye underwent Intacs implantation. At 2 years postoperatively, slit-lamp examination of the right eye revealed superficial corneal vascularization inferotemporally, extending 1.5 mm from the limbus. At 3 years postoperatively, the slit-lamp examination of the right eye revealed deep stromal vascularization extending to and arborizing along the temporal segment. Also, superficial vascularization was noted along the nasal segment inferiorly. The Intacs segments were then explanted.

Results

On post-explantation day 10, the deep vessels regressed to ghost vessels with topical corticosteroid therapy.

Conclusions

The authors present a rare case where deep corneal vascularization was noticed 3 years following Intacs implantation for keratoconus. All patients having superficial vascularization away from the incision site need to be followed for this rare complication.

Visual and Refractive Outcomes and Tomographic Changes after Femtosecond Laser-assisted Intrastromal Corneal Ring Segment Implantation in Patients with Keratoconus

Purpose:

To evaluate the visual, refractive, and tomography changes after femtosecond laser-assisted intrastromal corneal ring segment (ICRS; Intacs^® SK) implantation in patients with keratoconus.

Methods:

In this prospective interventional case series, Intacs SK ICRSs were inserted using a femtosecond laser into eyes with stage I–IV keratoconus. Visual, refractive, and corneal tomography changes, along with surgical complications, were analyzed 1 week, 2 months, and 6 months postoperatively.

Results:

The study evaluated 71 eyes of 52 patients (mean age: 27.5 years). Six months postoperatively, the spherical equivalent, mean sphere, and mean cylinder were decreased by 2.07, 1.47, and 1.13 diopters (D), respectively. The mean preoperative uncorrected distance visual acuity (UDVA) increased from 0.87 ± 0.26 to 0.46 ± 0.19 LogMAR and the mean preoperative corrected distance visual acuity (CDVA) increased from 0.55 ± 0.21 to 0.28 ± 0.17 LogMAR (P < 0.001). Flat and steep keratometry decreased by a mean corneal power in the 3-mm zone, and mean anterior elevation decreased by 0.91 D, 2.52 D, and 1.03 microns (P < 0.001), respectively. Among all eyes, 93.0% gained one or more lines of CDVA. Mean internal anterior chamber depth decreased from 3.25 ± 0.33 to 3.14 ± 0.45 mm (P = 0.001), and mean irregularity in the 3-mm zone decreased from 5.63 ± 1.71 to 5.24 ± 1.82 (P = 0.006). However, mean posterior elevation and irregularity in the 5-mm zone did not change significantly.

Conclusion:

Implantation of one or two Intacs SK segments is safe and effective to treat keratoconus, leading to significant improvement in UDVA, CDVA, and refractive error.

Safety and Efficacy of Sequential Intracorneal Ring Segment Implantation and Cross-linking in Pediatric Keratoconus

PURPOSE

To evaluate the safety and visual outcome of intracorneal ring segment (ICRS) implantation followed by cross-linking in pediatric keratoconus patients.

DESIGN

Retrospective interventional case series.

METHODS

This retrospective study included pediatric patients (aged ≤14 years) with keratoconus and poor corrected distance visual acuity (CDVA) that underwent ICRS implantation and cross-linking (CXL). ICRS were inserted under topical anesthesia after creating a corneal tunnel with a femtosecond laser. Cross-linking was performed 1 month subsequently. Records were reviewed and data collected preoperatively and at 6 months, 1 year, 2 years, and 4 years postoperatively.

RESULTS

Twelve patients (17 eyes; 10 male, 2 female) aged 9-14 years (mean age 12.3 years) received ICRS implantation followed by CXL. Follow-up times ranged from 6 months to 4 years after surgery. At the 6-month follow-up all eyes were evaluated; at the 1-year, 2-year, and 4-year follow-up 11, 10, and 7 eyes were evaluated, respectively. At the 6-month follow-up, mean CDVA in comparison to preoperative levels improved significantly (P = .001) from 0.30 ± 0.19 logMAR to 0.12 ± 0.1 logMAR; mean uncorrected distance visual acuity (UDVA) also improved significantly from 0.90 ± 0.50 logMAR to 0.43 ± 0.31 logMAR. A significant decrease in both keratometry readings and spherical equivalent (from -4.0 to -1.56 diopters) was also noted after ICRS insertion. At the 1-year, 2-year, and 4-year follow-up refractive values remained relatively stable in comparison to the 6-month follow-up, except for a minor but significant improvement in cylinder and, at 4 years, in UDVA. All patients tolerated the surgery well and no intraoperative or postoperative complications were reported, except for 1 ring segment that had to be removed after 2 years owing to vascularization and corneal thinning.

CONCLUSION

ICRS implantation is a safe and effective procedure for visual rehabilitation in children with keratoconus and poor CDVA.

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.

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.

MyoRing Implantation in Keratoconic Patients: 3 years Follow-up Data

Purpose:

To evaluate long-term follow-up data on implantation of a full-ring intra-corneal implant (MyoRing) for management of keratoconus.

Methods:

A total of 40 keratoconic eyes of 37 consecutive patients who had undergone MyoRing implantation using the Pocket Maker microkeratome (Dioptex, GmbH, Linz, Austria) and completed 3 years of follow-up appointments were included in this retrospective study. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction and keratometry (K) readings were measured and evaluated preoperatively, and 3 years, postoperatively.

Results:

No intraoperative complications were observed in this case series. Three years postoperatively, there was a significant improvement in UDVA, CDVA, K readings, spherical equivalent (SE), and manifest sphere and cylinder (P < 0.05 for all comparisons). UDVA was significantly improved from 1.14 ± 0.27 to 0.30 ± 0.21 LogMAR (P = 0.001), CDVA was also improved from 0.52 ± 0.23 to 0.18 ± 0.12 LogMAR (P = 0.001), SE was decreased by 4.35 diopters (D) and average keratometric values were reduced by 2.34 D (P = 0.001). Overall, 81% of subjects were moderately to highly satisfied 3 years after surgery and 64.90% agreed to have the fellow eye implanted with MyoRing.

Conclusion:

MyoRing implantation using the Pocket Maker microkeratome was found to be a minimally invasive procedure for improving visual acuity and refraction in the majority of the patients with keratoconus.

Contemporary Treatment Paradigms in Keratoconus

The past 20 years have witnessed an explosion in our knowledge of keratoconus, accompanied by a radical transformation of management options. A 2-hit hypothesis proposes an underlying genetic predisposition coupled with external environmental factors, including eye rubbing and atopy. The variable prevalence and natural history have been better defined including significant cone progression in middle age. Therefore, current management must include early diagnosis, regular monitoring, and treatment of environmental cofactors. Spectacles and contact lenses remain fundamental to the optical management of keratoconus. Intrastromal corneal ring segments have been increasingly used, providing improvement in the corneal shape, corrected visual acuity, and contact lens wear. However, like contact lenses, intrastromal corneal ring segments do not treat the underlying disease process. Therefore, current approaches must also consider treatments to minimize keratoconus progression. Fortunately, there is increasing evidence that corneal collagen crosslinking will halt or slow progression in most cases. Until relatively recently, penetrating keratoplasty was the preferred intervention for advanced keratoconus, with long-term success in the region of 90%; however, the greatest risk of failure remains endothelial allograft rejection. Deep anterior lamellar keratoplasty has emerged in the new millennium as a preferred approach to conserve the host endothelium and avoid rejection. Nonetheless, the overall superiority of deep anterior lamellar keratoplasty compared with penetrating keratoplasty, in terms of optical and survival benefits, is still debated. This perspective provides an overview of our current knowledge of keratoconus and current management options. A step-ladder approach to managing keratoconus is outlined to provide the practitioner with a contemporary management paradigm.

[Corneal collagen cross-linking for keratoconus]

Over the last decade, corneal collagen cross-linking (CXL) has become a conventional treatment method for progressive keratoconus. Laboratory studies have shown that CXL increases the diameter of collagen fibers and also the number of intra- and interfibrillar cross-links, thus, increasing biomechanical strength of the irradiated cornea. As confirmed by a series of clinical and randomized controlled trials, CXL is able to slow down and, perhaps, to stop the progression of keratoconus. In most post-CXL patients visual acuity improves, while keratometric readings, spherical equivalent, and higher order aberrations reduce. Although published results prove CXL effective in the treatment of progressive keratoconus, its late consequences are yet unknown. This article reviews the stages of CXL development and results of published experimental and clinical studies. Prospects for CXL modifications that do not require epithelial debridement are discussed.

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.

Treatment options for advanced keratoconus: A review

Traditionally, the mainstay of treatment for advanced keratoconus (KC) has been either penetrating or deep anterior lamellar keratoplasty (PK or DALK, respectively). The success of both operations, however, has been somewhat tempered by potential difficulties and complications, both intraoperatively and postoperatively. These include suture and wound-healing problems, progression of disease in the recipient rim, allograft reaction, and persistent irregular astigmatism. Taken together, these have been the inspiration for an ongoing search for less troublesome therapeutic alternatives. These include ultraviolet crosslinking and intracorneal ring segments, both of which were originally constrained in their indication exclusively to eyes with mild to moderate disease. More recently, Bowman layer transplantation has been introduced for reversing corneal ectasia in eyes with advanced KC, re-enabling comfortable contact lens wear and permitting PK and DALK to be postponed or avoided entirely. We offer a summary of the current and emerging treatment options for advanced KC, aiming to provide the corneal specialist useful information in selecting the optimal therapy for individual patients.

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.

Efficacy and safety of Intacs SK in moderate to severe keratoconus

Purpose:

To examine the safety and efficacy of Intacs SK for moderate to severe keratoconus (KC) using femtosecond technology.

Materials and Methods:

This prospective, non-comparative study included 37 contact lens intolerant keratoconic eyes (stage II-III) of 24 patients who underwent femtosecond-assisted Intacs SK implantation. Inclusion criteria were mean K readings <56.00 D, corneal thickness >400 μm at the incision site, mesopic pupil <6.50 mm. Evaluation included manifest refraction, slitlamp examination, corneal topography, uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA). P < 0.05 was statistically significant.

Results:

Thirty-one (83.8%) eyes were classified as Amsler-Krumeich′s stage II and 6 (16.2%) were stage III. Mean central pachymetry was 490.3 ± 37.4 μm. UDVA at 6 months post-operatively was significantly better than pre-operatively (0.90 log MAR ± 0.52 standard deviation [SD] versus 0.32 ± 0.27 logMAR; respectively, P < 0.0001), as was the spherical equivalent (SEq) (−3.64 ± 2.52 D vs. −1.84 ± 2.2 D; P < 0.0001). The mean CDVA and manifest cylinder improved compared with pre-operatively (P = 0.319 and P = 0.078, respectively). Average keratometry decreased significantly from 48.50 ± 3.08 D to 44.40 ± 3.03 D (P < 0.0001).

Conclusion:

Implantation of Intacs SK using femtosecond laser in moderate to severe KC is safe and effective.

Outcomes of intrastromal corneal ring segments for treatment of keratoconus: five-year follow-up analysis

PURPOSE

To report the long-term refractive and optical quality outcomes of patients with intrastromal corneal ring segments (ICRS) to treat keratoconus and to analyze the results according to the patients' age.

SETTING

Vissum Instituto Oftalmologico de Alicante, Alicante, Spain.

DESIGN

Case series.

METHODS

The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, corneal topography, and aberrometry were evaluated before and after ICRS implantation in eyes with keratoconus. The follow-up was 5 years in all cases.

RESULTS

The study comprised 51 eyes (35 patients; age range 15 to 56 years). After 6 months, the improvement in the UDVA, CDVA, spherical equivalent, and mean keratometry (K) value was statistically significant (P<.05). Five years postoperatively, these parameters remained unchanged (P=.31). Slight regression (0.97 diopter [D]) was observed in the mean K between 6 months and 5 years; the regression was not statistically significant (P=.39). Anterior corneal aberrometric values decreased; however, the changes were not statistically significant (P ≥.10). Linear regression analysis showed no correlation between the age of the patients and the changes observed in the mean K throughout the follow-up (P>.05, r(2) = 0.001).

CONCLUSIONS

Intrastromal corneal ring segment implantation in keratoconus patients provided long-term improvement of the refractive and topographic status. There was no correlation between the amount of individual changes in the mean K reading and patient age.

Partial visual rehabilitation using a toric implantable collamer lens in a patient with keratoconus: a case report with 20 months of follow-up

We report the case of a 37-year-old man with a high myopic keratoconus eye that was treated with a posterior chamber toric implantable collamer lens (ICL) in Korea. The patient had a history of contact lens intolerance and did not want to have a corneal transplantation. His uncorrected visual acuity (UCVA) and best spectacle corrected visual acuity were 0.02 and 0.4 in the left eye, respectively. Preoperatively, the manifest refraction was -12.0 -3.5 × 30A. Postoperatively, the manifest refraction was -1.75 × 180A. UCVA improved markedly after implantation. No intraoperative or postoperative complications were observed during 20 months of follow-up. Toric ICL implantation may be a possible alternative surgical option for the visual rehabilitation of high myopic astigmatism in keratoconus patients with rigid gas permeable contact lens intolerance and in patients who do not want to get a corneal transplant.

The thinnest, steepest, and maximum elevation corneal locations in noncontact and contact lens wearers in keratoconus

PURPOSE

To assess the relationship between the thinnest corneal location and the steepest and maximum elevation corneal locations in subjects with keratoconus and the effect of gas permeable contact lens wear on the location of these points.

METHODS

Sixty-one consecutive subjects (98 eyes) with keratoconus. Thirty-one (49 eyes) and 30 (49 eyes) subjects were gas permeable contact lens (CL-W) and non-contact lens wearers (N-CL), respectively. Thinnest, steepest, and maximum elevation corneal locations were evaluated from topographies collected with Pentacam Eye Scanner.

RESULTS

In the entire sample and in N-CL and CL-W, the thinnest location does not overlap with the steepest or maximum elevation corneal locations (all P > 0.05). The thinnest and maximum tangential curvature locations were found to be located further away from the geometric center of the cornea in CL-W versus N-CL (P < 0.05).

CONCLUSION

The thinnest corneal location does not overlap with maximum axial and tangential curvatures or with the front and back elevation locations in keratoconus subjects. Contact lens wear does not affect this lack of overlapping.

Two-year corneal cross-linking results in patients younger than 18 years with documented progressive keratoconus

PURPOSE

To report refractive, topographic, aberrometric, and tomographic outcomes 24 months after corneal cross-linking (CXL) in patients up to 18 years of age with progressive keratoconus.

DESIGN

Prospective, interventional case series.

METHODS

Forty eyes underwent riboflavin-ultraviolet A-induced CXL. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), sphere and cylinder, topography, aberrometry, tomography, and endothelial cell counts were evaluated at baseline and at 1, 3, 6, 12, and 24 months.

RESULTS

Mean logarithm of the minimum angle of resolution baseline UCVA and BSCVA were 0.79 ± 0.21 and 0.39 ± 0.10, respectively. Mean UCVA and BSCVA at 2 years were 0.58 ± 0.18 and 0.20 ± 0.09, respectively. The improvement in UCVA and BSCVA was significant throughout the postoperative follow-up (P < .05). Mean spherical equivalent refraction showed a significant decrease of 1.57 diopters (D) at 24 months (P = .02). Mean baseline simulated keratometry was 46.32 D in the flattest meridian and 51.48 D in the steepest meridian; at 2 years, the values were 45.30 D (P = .04) and 50.21 D (P = .07), respectively. For a 3-mm pupil, there was a significant reduction (P < .05) in whole eye (total), corneal, higher-order, and astigmatic wavefront aberrations at 24 months. A significant difference (P < .05) in total coma and total spherical aberration 2 years after CXL also was observed. Mean baseline pupil center pachymetry decreased significantly (P = .04) at 6 months, but recovered by 12 months and remained stable thereafter through the 2-year follow-up. Endothelial cell counts did not change significantly (P = .32).

CONCLUSIONS

CXL improved UCVA and BSCVA in the study patients, most likely by significantly reducing corneal asymmetry and corneal as well as total wavefront aberrations.

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.