Intrastromal Corneal Ring Segment Implantation for the Treatment of Keratoconus

Evaluation of macular function and morphology following accelerated collagen cross-linking in progressive keratoconus

PURPOSE

To assess any changes in macular function and morphology in patients with progressive keratoconus undergoing accelerated corneal cross-linking (CXL).

METHODS

This prospective case series included 9 eyes of 8 patients with progressive keratoconus undergoing CXL using a high intensity accelerated protocol (9 mW/cm² for 14 min) with a total surface dose of 7.5 J/cm². Visual acuity assessment, slit lamp biomicroscopy, dilated fundoscopy, corneal tomography, multifocal electroretinography (mfERG) and spectral domain optical coherence tomography scan were performed at baseline, 2 weeks and 6 weeks postoperatively.

RESULTS

Uncorrected and corrected distance visual acuity did not change significantly at 2 weeks and 6 weeks following accelerated CXL compared to baseline. Retinal response density (RRD) of mfERG significantly decreased at 2 weeks postoperatively compared to baseline (p = 0.008) but did not differ from the baseline value at 6 weeks postoperatively in the fovea (ring 1) (p = 0.95). Similarly, P1 latency significantly decreased at 2 weeks (p = 0.04) but did not change at 6 weeks (p = 1.00) postoperatively compared to baseline in the fovea. No changes in RRD or P1 latency were observed in the retinal rings surrounding the fovea (rings 2 to 5). Central foveal thickness did not change at 2 weeks and 6 weeks postoperatively compared to baseline (p = 0.53 and p = 0.93, respectively).

CONCLUSIONS

A short-term reversible decrease in macular electrical activity without any structural changes seems to occur after accelerated CXL in patients with progressive keratoconus. The return of macular response to the preoperative values shows the safety of the CXL protocol.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

One-Year Outcomes of Intracorneal Ring-Segment Insertion Assisted by Femtosecond Laser Simultaneously Performed with Corneal Collagen Cross-Linking for Treatment of Keratoconus

Purpose

To assess the results of simultaneously performed femtosecond laser–assisted Keraring intrastromal corneal ring–segment insertion and corneal collagen cross-linking for the treatment of keratoconus.

Patients and Methods

In this retrospective, noncomparative, interventional study, 30 eyes of 24 progressive-keratoconus patients of both sexes aged 18–36 years old with poor best-corrected visual acuity (BCVA) and intolerance to contact lenses were included. All patients had been subjected to complete preoperative and postoperative ophthalmological examinations — unaided VA, BCVA, refraction, Pentacam, and contrast sensitivity examinations at 3-month, 6-month, and 1-year follow-ups.

Results

Mean unaided VA had changed significantly from 0.649±0.239 logMAR preoperatively to 0.514±0.222 (P=0.014), 0.419±0.162 (P<0.001), and 0.379±0.142 (P<0.001) logMAR at the three follow-up visits, respectively. Mean BCVA had changed significantly from 0.326±0.144 logMAR preoperatively to 0.231±0.140 (P=0.006) at 1-year follow-up. Mean spherical equivalent refraction had decreased significantly at 6-month (P=0.0298) and 1-year follow-up (P=0.0081). Mean steep keratometry (K2) had also significantly reduced from 51.89±3.81 D to 49.87±4.57 D (P=0.034) at 6 months and 49.40±4.39 D (P=0.011) at 1 year. Mean refractive and keratometric astigmatism had significantly decreased at all follow-up visits.

Conclusion

At 1-year follow-up, keraring intrastromal corneal ring–segment insertion assisted by femtosecond laser performed simultaneously with corneal collagen cross-linking resulted in an improvement in visual, refractive, and topographic outcomes, which may suggest it is an effective treatment of keratoconus.

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.

Comparative analysis of two different types of intracorneal implants in keratoconus: A corneal tomographic study

OBJECTIVE

To evaluate changes in visual acuity and corneal tomographic outcomes at 6 months after femtosecond-laser assisted implantation of two different types of intracorneal implants in keratoconus.

METHODS

A total of 39 keratoconus eyes implanted with two segments KeraRing (n = 22 eyes) or MyoRing (n = 17 eyes) were enrolled. Tomographic data (Pentacam system, Oculus) were analyzed and correlated with enhancement in uncorrected (UDVA) and corrected distance visual acuity (CDVA). The tomographic indices were front maximum keratometry (Kmax), corneal asphericity (Q-value) on both surfaces, average pachymetric progression indices (PPI), maximum Ambrosio relational thickness (ARTmax), Belin-Ambrósio enhanced ectasia total deviation index (BAD-D), index of surface variance (ISV), vertical asymmetry (IVA), height asymmetry (IHA) and height decentration (IHD).

RESULTS

LogMAR UDVA and CDVA improved 2.1 (p = 0.003) and 0.7 (p = 0.074) lines with KeraRing, and 8 and 2.5 lines with MyoRing (p = 0.001). The highest and lowest mean differences in the tomographic indices between both groups were related to ISV and IHD, respectively. Changes in all indices differed significantly between two groups except for changes in front corneal astigmatism, ARTmax, ISV, IVA, IHD and IHA (p > 0.05). Correlation of changes in CDVA with changes in other parameters was statistically significant only for IHD in the KeraRing group, while changes in in UDVA were significantly correlated with changes in spherical equivalent, back Q-value, ISV, IVA, and IHA only in the MyoRing group.

CONCLUSION

Both implants promote corneal shape regularization and an enhancement in UDVA in keratoconus. A considerable flattening effect and reduction in prolateness in the front corneal surface were observed with MyoRing.

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.

Predictors of Successful Outcome following Intrastromal Corneal Ring Segments Implantation

Purpose: To assess the preoperative visual, refractive, corneal topo/tomographic, aberrometric and biomechanical parameters as predictive factors of a successful outcome 6 months following intrastromal corneal ring segments implantation. Methods: Sixty-eight keratoconus eyes implanted with Keraring using femtosecond laser technology were assessed. The preoperative assessed parameters included uncorrected and corrected distance visual acuity (UDVA & CDVA), refraction, placido-disk based topography using TMS-4, Scheimplfug tomography using Pentacam HR, corneal biomechanical assessments using Ocular Response Analyzer (ORA) and the wavefront analysis using i-Trace aberrometer. Other variables were type of astigmatism based on orientation of the steep meridian, keratoconus staging based on the Amsler-Krumeich classification and the difference between the axes of refractive astigmatism, topographic astigmatism and comatic aberration based on a difference less or more than 30°. The success criterion was defined based on CDVA, a post-operative CDVA improvement at least two lines were considered as a success and otherwise were recognized as a failure following Keraring implantation. Results: Only UDVA, coincidence of the most elevated points on the front and back corneal surfaces and the difference between UDVA and CDVA showed significant difference between the eyes with successful outcomes and those with unsuccessful results (P < 0.05). Although corneal curvature and astigmatism were higher and corneal thickness was lower in the unsuccessful group, differences were not statistically significant. Conclusion: It is expected that the greater difference between the preoperative uncorrected and corrected distance visual acuity (Δ UDVA-CDVA) and more coincidence of the most elevated points in the two corneal surfaces on the elevation maps increase the rate of successful outcome following the Keraring implantation. Abbreviations: ICRS: intrastromal corneal ring segments; UDVA: uncorrected distance visual acuity; CDVA: corrected distance visual acuity; logMAR: logarithm of minimum angle of resolution; SE: spherical equivalent; IOP: intra-ocular pressure; Km: mean keratometry; CA: corneal astigmatism; WTR: with-the-rule; ATR: against-the-rule; OBL: oblique; SB: symmetric bow-tie; AB: asymmetric bow-tie; IS: inferior steepening; SRAX: skewed radial axis; Q: asphericity (Q-value); CCT: central corneal thickness; CTP: corneal thinnest point; ORA: ocular response analyzer; CH: corneal hysteresis; CRF: corneal resistance factor; HOAs: higher-orders aberrations; RMS: root mean square; SD: standard deviation; CI: confidence interval.

Comparison of the MyoRing implantation depth by mechanical dissection using PocketMaker microkeratome versus Melles hook via AS-OCT

Background

This paper seeks to evaluate the depth and outcomes of MyoRing implantation using two mechanical dissection procedures including: PocketMaker microkeratome in opposition to the Melles hook method.

Methods

This retrospective study was carried out on 39 eyes of 38 keratoconus patients (28 male and 10 female) with the mean age of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ 28.97\frac{+}{.}10.37 $$\end{document}28.97+.10.37 years and had undergone MyoRing implantation by the two mentioned methods. The MyoRing was inserted into the corneal pocket which was made manually in 18 eyes (Melles hook group) or with PocketMaker microkeratome in 21 eyes (PocketMaker group). The mean follow up time was \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ 9.81\frac{+}{.}3.7 $$\end{document}9.81+.3.7 months with pre-operative and post-operative ophthalmic examination including uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), keratometry readings and central corneal thickness measurement. AS-OCT (Casia, SS-1000, Tomey, Nagoya, Japan) imaging was used to measure MyoRing insertion depth, exactly.

Results

Pre-operative and post-operative UCVA (LogMAR) mean change for the PocketMaker and Melles hook groups were recorded at 0.75 ± 0.32 and 0.78 ± 0.33, respectively. Similarly, BCVA (LogMAR) mean change were 0.27 ± 0.22 and 0.23 ± 0.22. Mean keratometry (Kmean) change were 6.06 ± 4.18 and 6.56 ± 3.55 respectively. UCVA change (P = 0.767), BCVA change (P = 0.77) and Kmean change (P = 0.693) showed that there was no statistically significant difference between both groups for any parameter. Depth measurements achieved from AS-OCT images showed that there was no statistically significant difference in pocket depth between two methods of MyoRing implantation (P = 0.413).

Conclusions

The results of Myoring implantation outcomes using mechanical dissection via PocketMaker microkeratome as against Melles hook are comparable.

Femto-second laser (FSL) techniques and consistency in corneal surgery: experimental study

OBJECTIVE

To investigate the feasibility, effectiveness, and reproducibility of femtosecond laser (FSL) technology in different corneal cuts.

DESIGN

Experimental study at the Brandon Regional Health Centre.

PARTICIPANTS

Twenty two Human Cadaver eyes donated for research and supplied by the eye bank of Manitoba university.

METHODS

In this experimental study, the effectiveness and reproducibility of FSL were investigated in different corneal cuts. The corneas were divided into 5 groups: group I for penetrating keratoplasty; group II for anterior lamellar keratoplasty; group III for corneal pockets for inlays; group IV for intracorneal ring tunnels; and group V for corneal cross-linking pockets. Our primary endpoint was the repeatability of planned versus obtained thickness and diameter of the cuts with FSL. A secondary endpoint was the effectiveness and ease of dissection, rated from 0-4, with 4 being the easiest and 0 the most difficult to dissect.

RESULTS

There was a high correlation between planned and obtained thickness (r = 0.997, p < 0.001) and diameter (r = 0.998, p < 0.001). Both were statistically significant. Linear regression analyses showed that the obtained thickness of corneal cuts in micrometers was significantly predicted by the planned thickness of corneal cuts in micrometers (β = 0.996, t = 56.47, p < 0.001). Likewise, the obtained diameter of corneal cuts in millimeters was significantly predicted by the planned diameter of corneal cuts in millimeters (β = 0.971, t = 70.85, p < 0.001). The surgeons gave 15 out of a total of 22 corneas (68.2%) the maximum score for ease of dissection (Grade 4), where no adhesions were found and the dissection was smooth and steady. Five corneas out of a total of 22 (22.7%) were given a score of 3 of 4 where minor adhesions were found. Two corneas out of a total of 22 (9.1%) were given a score of 2 of 4 where >1 adhesion was found, with some difficulty in separating the cut cornea from the bed. No corneas were given grade 1 or grade 0. No significant differences were obtained for the ease of dissection among the 5 surgery types using Kruskal-Wallis H test (H [4] = 4.971, p > 0.05).

CONCLUSION

The measured corneal-cut geometry correlated well with laser settings in a variety of full- and partial-thickness FSL corneal patterns, including different depths and diameters. This reproducible efficacy and measurement accuracy of the planned versus obtained cuts could have a favourable result on a variety of corneal surgeries. It also yields a favourable ease of dissection of the cut lenticule from the stromal bed.

Three-Year Outcomes of Cross-Linking PLUS (Combined Cross-Linking with Femtosecond Laser Intracorneal Ring Segments Implantation) for Management of Keratoconus

Purpose

To analyze the results of three-year outcomes of combined epithelium-on cross-linking with femtosecond laser ICRS (cross-linking PLUS) for keratoconus management.

Design

A retrospective multicenter clinical study.

Methods

43 eyes of 38 patients were subjected to preoperative and postoperative UCVA, BCVA, refraction, Pentacam pachymetry, and keratometry examinations at 3-, 6-, 12-, 24-, and 36-month follow-up period.

Results

The preoperative and postoperative mean UCVA was 1.30 ± 0.48 (logMAR ± SD) and 0.82 ± 0.22 respectively. The preoperative and postoperative mean BCVA was 0.90 ± 0.40 and 0.60 ± 0.30, respectively. The preoperative and postoperative mean K average was 50.63 ± 0.87 (D ± SD) and 45.56 ± 0.98, respectively. The preoperative and postoperative mean pachymetry was 471 ± 92.36 (μm ± SD) and 423 ± 39.58, respectively. The preoperative and postoperative mean astigmatism was 7.55 ± 1.75 and 3.39 ± 1.26, respectively. One eye showed ICRS edge exposure while 6 eyes showed progression of keratoconus.

Conclusion

CXL PLUS was proved to be a successful procedure to halt progression (mainly by CXL) and to correct the refractive status of the keratoconic eye (mainly by ICRS). CXL PLUS performed a synergistic action correcting and maintaining the correction of both myopic and astigmatic components of keratoconus.

Indications and visual outcomes of intrastromal corneal ring segment implantation in a large patient series

OBJECTIVES:

To describe the indications for and visual outcomes of intrastromal corneal ring segment implantation.

METHODS:

A large retrospective case-series chart-review study was conducted using Sorocaba Ophthalmological Hospital medical records. This study included 1222 eyes (1196 patients) that were surgically treated between November 2009 and December 2012. The following preoperative data were collected: age, gender, type of medical care and funding source, surgical technique, best-corrected visual acuity, manifest sphere and cylinder refractive error, maximum and minimum central keratometry, and pachymetry measurements of the cornea at the thinnest point and at the ring channel. The postoperative best-corrected visual acuity and patient satisfaction were also determined. The cases were classified into six groups: four keratoconus groups (severe, advanced, moderate and mild), a pellucid marginal degeneration group and a post-graft irregular astigmatism group. This study was approved by the Brazilian Registry of Clinical Trials (UTN number 1111-1182-6181, TRIAL RBR-6S72RF).

RESULTS:

The age (mean±standard deviation) of the patients was 31.0±10.0 years. The most prevalent pathology was keratoconus (1147 eyes, 93.8%). A correlation was found between ectasia severity and medical assistance (p<0.001), and the most serious cases was treated by the Brazilian public health system. No complications were found in a total of 1155 surgeries, and after surgery, 959 patients were satisfied. Among the 164 dissatisfied patients, the majority failed to show improved best-corrected visual acuity.

CONCLUSION:

Patients in the public health system underwent surgical intervention for keratoconus later than those with private sources of funding. In the vast majority of operated cases, the patients reported improvements in vision.

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.

Effects of Femtosecond Laser-Assisted Cataract Pretreatment on Pupil Diameter: A Comparison Between Three Laser Platforms

PURPOSE

To assess pupil diameter before and after femtosecond laser-assisted cataract surgery (FLACS) pretreatment and compare the outcomes of three laser platforms.

METHODS

This prospective observational case series included consecutive patients scheduled to undergo cataract extraction using FLACS between August 2013 and February 2015. All eyes received FLACS pretreatment using three laser platforms: LenSx (Alcon Laboratories, Inc., Fort Worth, TX), Catalys (Abbott Medical Optics Inc., Santa Ana, CA), and Victus (Bausch & Lomb, Inc., Rochester, NY). The same protocol for preoperative medical mydriasis was used for all patients, and pupil diameter was assessed immediately before and 3 minutes after FLACS using a surgical ruler.

RESULTS

A total of 198 eyes of 161 patients were included in the study. Mean pupillary miosis was 1.42 ± 1.26 mm for the LenSx, 0.66 ± 0.89 mm for the Catalys, and 0.14 ± 0.34 mm for the Victus groups. Furthermore, 8 of the 198 eyes (4.0%) demonstrated a pupil diameter of less than 5 mm after FLACS and 48 eyes (24.24%) demonstrated a pupil diameter of 6 mm or less. There was a statistically significant decrease in pupil diameter for all groups individually (P < .05). There was also a statistically significant difference among the three groups (P < .05), with LenSx inducing the highest degree of miosis, followed by Catalys, and finally Victus. A correlation between the pupil diameter before FLACS and degree of FLACS-induced miosis was demonstrated (P < .05), with larger pupil diameter before FLACS associated with greater miosis.

CONCLUSIONS

FLACS pretreatment seems to induce significant pupillary miosis with all laser platforms assessed in this study. The decrease in pupil diameter after FLACS reached clinical significance for cataract extraction (< 5 mm) in 4.0% of cases, whereas 20.2% of eyes demonstrated small pupil diameter (≤ 6 mm) after FLACS pretreatment.

Cataract surgery on the previous corneal refractive surgery patient

Cataract surgery in cases with previous corneal refractive surgery may be a major challenge for the ophthalmologist. The refractive outcome of the case deserves special attention in the preoperative planning process, which should be tailored for the type of prior refractive procedure: incisional, ablative under a flap, or on the corneal surface. Avoiding refractive surprise after cataract surgery in these cases is principally dependent on the accuracy of the intraocular lens calculation, together with the selection of the appropriate biometric formula for each case. Modern techniques for cataract surgery help surgeons to move toward the goal of cataract surgery as a refractive procedure free from refractive error. We give practical guidelines for the cataract surgeon in the management of these challenging cases.

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.

Outcome of intrastromal corneal ring segment relative to depth of insertion evaluated with scheimpflug image

PURPOSE

To report the results of intrastromal corneal ring segment (KeraRing; Mediphcose, Belo Horizonte, Brazil) implantation relative to depth of insertion in keratoconic patients.

METHODS

In this retrospective, observational study, we evaluated 29 eyes of 27 patients with keratoconus who underwent implantation of KeraRing SI-5 with mechanical tunnel creation. In the mean follow-up of 8.8 months, all eyes underwent scheimpfluge image of pentacam (Oculus, Germany) to determine insertion depth. Based on the measured implantation depth, cases were categorized into: 40-59% thickness group, 60-79% thickness group, and ≥80% thickness group. Visual, refractive, and shape outcomes were evaluated relative to implantation depth.

RESULTS

The mean insertion depth was 61.7%.We had 41.4% of cases were in the 40-59% thickness group, 51.7% in the 60-79% group, and 6.9% in the >80% group. Results were similar in 40-59% and 60-79% thickness groups: uncorrected visual acuity (UCVA) and best spectacle corrected VA (BSCVA) improved 3 and 2 lines, respectively, maximum keratometry (Kmax) decreased 2.6 D, refractive cylinder improved 2.04 D, and Q value 8 mm anterior changed by 0.35. In the ≥80% thickness group, UCVA and BSCVA improved less than 1 lines, Kmax change was less than 0.5 D, and RC decreased less than 0.25 D.

CONCLUSION

Implantation of KeraRing with mechanical tunnel creation in 40-80% of stromal thickness despite the variable insertion depth is effective.

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.

Intrastromal corneal ring segments for management of keratoconus

Keratoconus is a progressive corneal ectasia, which can be managed both by conservative measures like glasses or contact lenses in non-progressive cases or surgical procedures like collagen crosslinking (CXL) with or without adjuvant measures like intrastromal corneal rings segments (ICRS) or topography guided ablation. Various kinds of ICRS are available to the surgeon, but it is most essential to be able to plan the implantation of the ring to optimize outcomes.

Accelerated corneal collagen cross-linking for progressive keratoconus

PURPOSE

To evaluate the efficacy of accelerated corneal cross-linking (CXL) procedure for progressive keratoconus.

MATERIALS AND METHODS

Twenty-three eyes of 23 patients undergone accelerated CXL procedure were evaluated preoperatively and postoperatively at 1st, 3rd and 6th month for uncorrected distant visual acuity (UDVA), best corrected distant visual acuity (CDVA), spherical error, cylindrical error, spherical equivalent (SE), keratometric values and thinnest corneal thickness (TCT) values with corneal topography by Scheimpflug camera and endothelial cell density (ECD).

RESULTS

The mean UDVA was improved from 0.97 ± 0.41 logarithm of minimal angle of resolution (logMAR) to 0.76 ± 0.45 logMAR at the 6th month after CXL (p = 0.332). The mean CDVA was improved from 0.49 ± 0.30 logMAR to 0.34 ± 0.22 logMAR at the 6th month after CXL (p = 0.026). The mean sphere was decreased from -4.47 ± 4.1 diopter (D) to -3.79 ± 3.86 D and the mean cylinder was decreased from -5.60 ± 2.2 D to -4.55 ± 1.98 D and the mean SE was decreased from -7.22 ± 4.48 D to -6.36 ± 4.34 D at the 6th month after CXL (p = 0.128, p = 0.002 and p = 0.045, respectively). Flat keratometry, steep keratometry, mean keratometry and maximum keratometry were significantly reduced at the 6th month after CXL (p = 0.025, p < 0.001, p = 0.004 and p = 0.03, respectively). TCT and ECD were not changed significantly the 6th month after CXL (p = 0.135 and p = 0.082, respectively).

CONCLUSION

Accelerated CXL procedure was effective to stabilize progression of keratoconus with significant reduction in topographic keratometric values and significant increase in CDVA in 6 months.

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.

Intracorneal Ring Segment Reimplantation in Keratectasia

PURPOSE

The objective of this study was to evaluate the safety and potential for visual improvement of replacing INTACS with Kerarings in patients with keratectasia.

DESIGN

Retrospective case series.

METHODS

A review of patients undergoing intracorneal segment exchange was conducted. Ten eyes of 9 patients that underwent INTACS explantation and Keraring re-implantation were included. Visual acuity, manifest refraction, keratometry, and corneal asphericity readings were collected. Data were analyzed preoperatively, immediately before Keraring insertion, and at 3, 6, and 12 months after Keraring implantation.

RESULTS

The mean age of subjects was 44.5 ± 11.23 years. The mean time to exchange was 13.9 ± 9.8 months. The initial indications for surgery were post- Laser-Assisted in Situ Keratomileusis ectasia (n = 6) and keratoconus (n = 4). The removal and re-implantation procedure were successfully completed in all eyes without significant complications. No statistical difference was observed with respect to keratometry readings, manifest sphere, and manifest cylinder during follow-up. There was a significant improvement in mean decimal corrected distance visual acuity at 3, 6, and 12 months after Keraring insertion (P>0.05). The Q values were -0.37 ± 0.94 after INTACS implantation and -0.18 ± 0.62, 0.06 ± 0.31, and 0.00 ± 0.38 at 3, 6, and 12 months after insertion of Kerarings.

CONCLUSIONS

Replacement of INTACS with Kerarings appears to be a safe procedure and may lead to an increase in corrected distance visual acuity in some eyes. This may be related to the change in corneal asphericity as experienced by our cohort.

Sequential topical riboflavin with or without ultraviolet a radiation with delayed intracorneal ring segment insertion for keratoconus

PURPOSE

To report refractive, topographic, pachymetric, tonometric, and corneal biomechanical outcomes 24 months after corneal cross-linking (CXL), followed by insertion of intrastromal corneal ring segments (ICRS) in keratoconic eyes.

DESIGN

Prospective randomized clinical trial.

METHODS

SETTINGS

Institutional.

STUDY POPULATION

Thirty-nine eyes of 31 patients, allocated into 2 groups.

INTERVENTION

Patients in the CXL group underwent corneal CXL with riboflavin and ultraviolet A (UVA) light. Patients in the riboflavin eyedrops group received riboflavin 0.1% (w/v) eyedrops - 20% dextran solution for 1 month. After 3 months, all patients underwent insertion of ICRS.

MAIN OUTCOME MEASURES

Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and topography were evaluated at baseline, at 1 month and 3 months after CXL or riboflavin eyedrops, and again at 1-, 3-, 6-, 12-, and 24-month intervals after ICRS insertion.

RESULTS

Mean (standard deviation [SD]) baseline UCVA and BSCVA in the CXL group and the riboflavin eyedrops group were 1.12 (0.59) and 0.84 (0.49), and 0.68 (0.43) and 0.45 (0.23), respectively; 24-month mean (SD) UCVA and BSCVA in the CXL group and the riboflavin eyedrops group were 0.79 (0.50) and 0.62 (0.28), and 0.52 (0.45) and 0.32 (0.21), respectively, with no statistically significant difference between groups (P = .70 and P = .78).There were no statistical differences between groups postoperatively at 24 months for all 3 topographic parameters, flattest-K1 (P = .81), steepest-K2 (P = .68), and average keratometry (mean power; P = .52).

CONCLUSIONS

ICRS insertion, with or without prior CXL, showed no difference between groups in terms of refractive, topographic, pachymetric, tonometric, and corneal biomechanical results at 24 months.