Comparison of 2 intrastromal corneal ring segment models in the management of keratoconus

Current concepts in the management of cataract with keratoconus

This review analyzed all pertinent articles on keratoconus (KCN) and cataract surgery. It covers preoperative planning, intraoperative considerations, and postoperative management, with the aim of providing a simplified overview of treating such patients. Preoperatively, the use of corneal cross-linking, intrastromal corneal ring segments, and topo-guided corneal treatments can help stabilize the cornea and improve the accuracy of biometric measurements. It is important to consider the advantages and disadvantages of traditional techniques such as penetrating keratoplasty and deep anterior lamellar keratoplasty, as well as newer stromal augmentation techniques, to choose the most appropriate surgical approach. Obtaining reliable measurements can be difficult, especially in the advanced stages of the disease. The choice between toric and monofocal intraocular lenses (IOLs) should be carefully evaluated. Monofocal IOLs are a better choice in patients with advanced disease, and toric lenses can be used in mild and stable KCN. Intraoperatively, the use of a rigid gas permeable (RGP) lens can overcome the challenge of image distortion and loss of visual perspective. Postoperatively, patients may need updated RGP or scleral lenses to correct the corneal irregular astigmatism. A thorough preoperative planning is crucial for good surgical outcomes, and patients need to be informed regarding potential postoperative surprises. In conclusion, managing cataracts in KCN patients presents a range of challenges, and a comprehensive approach is essential to achieve favorable surgical outcomes.

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

PURPOSE

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

SETTING

Ophthalmology Department, Hospital de Braga, Braga, Portugal.

DESIGN

Retrospective cohort study.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Cataract surgery in Keratoconus revisited - An update on preoperative and intraoperative considerations and postoperative outcomes

PURPOSE

This review aims to evaluate and simplify the recent literature on preoperative surgical planning, intraoperative considerations, postoperative surprises, and their management in patients with keratoconus undergoing cataract surgery.

METHODS

A review of the literature was done to analyze all the pertinent articles on Keratoconus and cataract surgery.

RESULTS

The surgical planning of cataracts in eyes with keratoconus needs a multifaceted approach. Preoperatively, techniques such as cross-linking or the use of intra-corneal rings help stabilize the progression. Unreliable biometric measurements are a significant problem in keratoconus patients, especially in an advanced stage of the disease. It is better to consider actual K readings if the K value is less than 55D but for a K value, more than 55D using standard K values will prevent postoperative refractive surprises. For calculation of K values, an elevation-based device like pentacam gives better repeatability in mild to moderate cases whereas for advanced keratoconus none of the keratometers is reliable. Recently, the Kane keratoconus formula performed better in all stages of disease whereas previous studies showed good results with SRK/T formula is a mild and moderate disease. Monofocal intraocular lenses are a better choice in these patients. Toric lenses can be used in mild and stable keratoconus. Intraoperatively, the use of a customized RGP lens can overcome the challenge of image distortion and loss of visual perspective. Despite taking necessary measures, postoperative refractive surprise can occur and can be managed with IOL exchange or Secondary IOLs.

CONCLUSION

There is a spectrum of challenges in managing cataracts in keratoconus which makes thorough preoperative planning important for good surgical outcomes. Despite the measures, there might be post-operative surprises and the patients need to be informed regarding the same.

Femtosecond Laser and Mechanical Dissection for ICRS and MyoRing Implantation: A Meta-Analysis

PURPOSE

The aims of this meta-analysis were to evaluate the results of intracorneal ring segments (ICRSs) and MyoRing in the management of corneal ectasia and to compare the clinical outcomes and complication rates between mechanical and femtosecond (FS) laser-assisted surgery.

METHODS

An online electronic search was performed for pre-post studies published until April 2020. Uncorrected distance visual acuity, corrected distance visual acuity, sphere, cylinder, spherical equivalent, steep, flat, and mean keratometry values were considered as outcomes. Weighted mean difference with 95% confidence interval was used as a pooled estimation of intervention efficacy.

RESULTS

Of 1484 potentially related studies, 115 studies were finally included in the meta-analysis. Findings of this meta-analysis demonstrated considerable improvement in visual, refractive, and keratometric outcomes in all ICRS models and MyoRing. Intrastromal tunnel creation with both methods yielded similar results. Complication rates were without exception higher when mechanical dissection was used.

CONCLUSIONS

ICRS and MyoRing are appropriate treatment options for patients with corneal ectasia. Both techniques for tunnel creation are efficacious in achieving good visual, keratometric, and refractive results. Mechanical intrastromal tunnel creation is associated with much higher complication rates when compared with FS laser-assisted technique.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Postoperative Corneal Epithelial Remodeling After Intracorneal Ring Segment Procedures for Keratoconus: An Optical Coherence Tomography Study

PURPOSE

To assess epithelial corneal remodeling by anterior segment optical coherence tomography (AS-OCT) after intracorneal ring segments (ICRS) implantation in keratoconic eyes.

METHODS

This prospective observational study included patients with keratoconus receiving ICRS of different arc lengths according to their tomographic pattern. AS-OCT and corneal topography (Scheimpflug camera) were performed before and 1, 3, and 6 months after surgery. Corneal pachymetry mapping was performed and total corneal and epithelial thicknesses (3-mm central and 16 points on 6-mm zone) were measured over the pupil center using AS-OCT. Topographic parameters were also assessed.

RESULTS

A total of 68 keratoconic eyes were analyzed (Amsler-Krumeich stages 1 to 4) in four groups of 17 eyes: 210° ICRS, 320° ICRS, double 160° ICRS, and single 160° ICRS. Corneal pachymetry mapping revealed that epithelial thickness increased significantly in the internal zones juxtaposed to the ICRS without smoothing during the postoperative period (P < .05). Mean maximum epithelial thickness increased from 67 ± 6 to 79 ± 7 µm for 210° ICRS, 66 ± 9 to 82 ± 4 µm for 320° ICRS, 63 ± 6 to 78 ± 7 µm for double 160° ICRS, and 62 ± 5 to 77 ± 5 µm for single 160° ICRS (P < .0001). Significant epithelial thickening at the apex of the cone was observed in all groups (P < .05).

CONCLUSIONS

Significant epithelial thickening occurs after ICRS implantation adjacent to the ICRS to compensate for the ridge created with a thickening of epithelium over the cone due to regularization of the stromal surface. [J Refract Surg. 2021;37(6):404-413.].

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.

Corneal Biomechanics After Intrastromal Ring Surgery: Optomechanical In Silico Assessment

Purpose

To provide a biomechanical framework to better understand the postsurgical optomechanical behavior of the cornea after ring implantation.

Methods

Calibrated in silico models were used to determine the corneal shape and stresses after ring implantation. After mechanical simulations, geometric ray-tracing was used to determine the change in spherical equivalent. The effect of the surgical procedure, circadian variation of intraocular pressure, or the biomechanical weakening introduced by keratoconus (KC) were evaluated for each intrastromal ring.

Results

Models predicted the postsurgical optomechanical response of the cornea at a population level. The localized mechanical effect of the additional intrastromal volume introduced by the implants (size and diameter) drives the postsurgical corneal response. However, central corneal stresses did not increase more than 50%, and thus implants did not strengthen the cornea globally. Because of the biomechanical weakening introduced by laser pocketing, continuous implants in a pocket resulted in higher refractive corrections and in the relaxation of the anterior stroma, which could slow down KC progression. Implants can move within the stroma, acting as a dynamic pivot point that modifies corneal kinematics and flattens the corneal center. Changes in stromal mechanical properties did not impact on refraction for normal or pathological corneas.

Conclusions

Implants do not stiffen the cornea but create a local bulkening effect that regularizes the corneal shape by modifying corneal kinematics without canceling corneal motion.

Translational Relevance

In silico models can help to understand corneal biomechanics, to plan patient-specific interventions, or to create biomechanically driven nomograms.

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.].

Femtosecond laser in refractive corneal surgery

The introduction of the femtosecond (fs) laser has revolutionized ophthalmic surgery. With the worldwide application of fs-lasers, clinical outcomes and safety in corneal procedures have improved significantly and they have become an ideal tool for ultra-precise corneal refractive surgery. Flap creation in laser in situ keratomileusis (LASIK) is the most common use of this laser. It can also be used for other corneal refractive procedures including channel creation for the insertion of intrastromal corneal ring segments (ICRS), performing astigmatic keratotomies (AK), femtosecond lenticule extraction including small incision lenticule extraction (SMILE), and the insertion of corneal inlays. This article summarizes recent advanced applications of fs laser technology in corneal refractive surgery.

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.

Intrastromal corneal ring segments for treating keratoconus

BACKGROUND

Keratoconus is a degenerative condition of the cornea that profoundly affects vision and vision-specific quality of life. The axial cornea thins and protrudes, resulting in irregularity and, eventually, scarring of the cornea. There are multiple options available for treating keratoconus. Intrastromal corneal ring segments are small, crescent-shaped plastic rings that are placed in the deep, peripheral corneal stroma in order to flatten the cornea. They are made of polymethylmethacrylate (PMMA). The procedure does not involve corneal tissue nor does it invade the central optical zone. Intrastromal corneal ring segments are approved for use when contact lenses or spectacles are no longer adequate.

OBJECTIVES

To evaluate the effectiveness and safety of intrastromal corneal ring segments as a treatment for keratoconus.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2018, Issue 1); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature Database (LILACS); ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not implement any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 25 January 2018.

SELECTION CRITERIA

Two review authors independently assessed records from the electronic searches to identify randomized controlled trials (RCTs). Disagreements were resolved by discussion.

DATA COLLECTION AND ANALYSIS

We planned for two authors to independently review full-text reports, using standard methodological procedures expected by Cochrane.

MAIN RESULTS

We found no RCTs comparing intrastromal corneal ring segments with spectacles or contact lenses.

AUTHORS' CONCLUSIONS

In the absence of eligible RCTs to review, no conclusions can be drawn.

Three-year follow-up of intrastromal corneal ring segment implantation in central keratoconus with regular astigmatism: ‘Bow-tie’ shape

Purpose:

To assess the outcomes of implanting Ferrara-type intrastromal corneal ring segments in central ‘bow-tie’-shaped keratoconus over 3 years of follow-up.

Methods:

A total of 20 eyes with central ‘bow-tie’-shaped keratoconus were evaluated before and after implanting Ferrara-type intrastromal corneal ring segments (AJL Ophthalmic, Spain). LogMAR uncorrected distance visual acuity and best corrected distance visual acuity and residual refractive errors analysed using vector analysis were recorded preoperatively, at 6 months, 1 year, and 3 years postoperatively.

Results:

The mean uncorrected distance visual acuity (LogMAR scale) rose from a preoperative 0.75 ± 0.28 to a 6-month postoperative 0.38 ± 0.28 (p < 0.0001). The corrected distance visual acuity, in turn, improved from 0.07 ± 0.06 to 0.05 ± 0.06 (p = 0.0008). Both the uncorrected distance visual acuity and corrected distance visual acuity were stable over the postoperative period in both groups (p > 0.05). None of the eyes lost uncorrected distance visual acuity and corrected distance visual acuity lines over the postoperative follow-up period. The spherical equivalent and the refractive cylinder declined steeply after intrastromal corneal ring segments implantation (p < 0.0001). Both the spherical equivalent and refractive cylinder were stable over the postoperative period. None of the eyes had an increase in maximum or minimum keratometry greater than 0.75D over the postoperative period.

Conclusion:

The planning for intrastromal corneal ring segments insertion proposed in this study reduces the spherical equivalent and refractive cylinder in this type of keratoconus, while improving post-surgery uncorrected distance visual acuity and corrected distance visual acuity. These results remain stable over 3 years of follow-up. Therefore, this procedure could be considered as an effective therapeutic alternative in patients affected by this type of keratoconus.

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.

Keratoconus correction using a new model of intrastromal corneal ring segments

PURPOSE

To evaluate the optical value of a new model of intrastromal corneal ring segments (ICRS) (Keratacx Plus) in patients with keratoconus and to quantify subsequent changes in corneal topography and asphericity.

SETTING

Private practice.

DESIGN

Prospective case series.

METHODS

This study comprised patients who had primary keratoconus or keratectasia after laser in situ keratomileusis (LASIK); none wore contact lenses. Rings were implanted through tunnels created manually or with a femtosecond laser. All eyes had clear visual axes and corneal thickness over 450 μm at the incision site. Preoperative and postoperative pachymetry images were acquired. Results were analyzed using a matched-pair t test and the Kolmogorov-Smirnov test.

RESULTS

Twenty-nine eyes (24 patients; mean age 30.1 years ± 10.6 [SD]) were evaluated. The ICRS significantly increased uncorrected and corrected visual acuities from 0.05 to 0.16 and from 0.17 to 0.5, respectively (z = 4.7, P < .001). They reduced the median spherical error from -4.0 to -0.5 diopters (D) (P < .001) and median cylindrical error from -4.4 to -2.5 D (P < .001). All topographic parameters were reduced, including maximum keratometry (K) (49.4 D versus 45.1 D), minimum K (49.4 D versus 45.1 D), mean K (51.4 D versus 48.4 D), astigmatism (-2.0 D versus -0.5 D), and asphericity (eccentricity 0.49 versus 0.23) (all P < .001).

CONCLUSIONS

The ICRS provided topographic and visual improvement in keratoconus and post-LASIK keratectasia. Variance in surgical outcomes with manual versus femtosecond tunneling and the effect of different ring sizes are yet to be studied.

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.

Agreement Between Autorefraction and Subjective Refraction in Keraring-Implanted Keratoconic Eyes

OBJECTIVES

To assess the agreement between subjective refraction and autorefraction and to explore the relationship between the magnitude of higher order aberration, and visual acuity and refraction, before and after keraring implantation.

METHODS

This prospective, randomized, interventional study enrolled 27 subjects (mean age 28.1±6.5 years) with keratoconus. Noncycloplegic refraction was performed subjectively by one clinician and with an autorefractor by another clinician, before and 6 months after surgery. The limit of agreement (LoA) between methods was assessed, and the relationships between the corrected distance visual acuity, logMAR on the one hand and refraction measurements and higher-order aberrations on the other, were examined.

RESULTS

The agreement in mean spherical equivalent refraction (MSER) between methods was good postoperatively but poor preoperatively. The autorefractor gave a more myopic refraction than subjective refraction preoperatively (-3.28±3.06 D; LoA -9.27 to +2.71 D, P<0.0001) and postoperatively (-0.63±1.64 D; LoA -3.85 to +2.58 D, P=0.055), and returned higher negative cylinders preoperatively (-1.10±1.17 D; LoA -3.40 to +1.19 D, P<0.0001) and postoperatively (-1.08±1.27 D; LoA -3.60 to +1.41 D, P<0.0001) in keratoconic eyes. The difference in MSER between methods was significantly related to the refractive error at both visits (P<0.05) and to the magnitude of higher-order aberrations in keratoconic eyes preoperatively (P<0.05). The logMAR visual acuity achieved subjectively worsened as the magnitude of higher-order aberrations increased preoperatively (P<0.001).

CONCLUSIONS

The autorefractor returns values that are significantly more myopic in MSER and higher negative cylinders than subjective refraction, preoperatively, but the MSER was similar between devices postoperatively. The autorefactor seems a valid starting point for subjective refraction in keratoconic eyes treated with keraring, but the cylinder should be corrected by about +1 D. The instruments agree more in less myopic than high myopic eyes.

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.

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.

Comparison of visual, refractive and topographic keratometry outcomes of Intacs and Intacs SK in mild to moderate keratoconus eyes

Purpose:

The purpose was to evaluate and compare the visual and refractive outcomes, topographic keratometry (K) and complications of Intacs and Intacs SK for mild to moderate keratoconus.

Methods:

In this retrospective study, all mild to moderate keratoconus eyes that underwent implantation of Intacs (Intacs group) or Intacs SK (Intacs SK group) with minimum follow-up of 12 months were included. Preoperative and postoperative uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, manifest cylinder, spherical equivalent (SE), minimum topographic keratometry, maximum topographic keratometry, and average topographic keratometry were compared in both groups.

Results:

There were 16 eyes in the Intacs group and 18 eyes in the Intacs SK group. Preoperatively, both groups were comparable for most parameters except gender and minimum K and average K. At 6 months postoperatively there were statistically significant improvements in UDVA, CDVA, manifest sphere, SE, minimum K, maximum K, and average K (P < 0.05, all comparisons). Manifest cylinder improved at 6 months, but the improvement was not statistically significant (P > 0.05). The outcomes remained stable with no statistically significant differences between the 6 and 12 months visits. There were no complications in both groups.

Conclusion:

Both models of Intacs significantly improved vision and refractive outcomes, and topographic keratometry in cases of mild to moderate keratoconus. Intacs SK provided better (not statistically significant) results.

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.

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.

Evaluation of intrastromal corneal ring segments for treatment of keratoconus with a mechanical implantation technique

PURPOSE

To evaluate the clinical outcomes of intrastromal corneal ring segment (ICRS) implantation in patients with keratoconus using a mechanical implantation technique.

MATERIALS AND METHODS

Thirty eyes of 17 patients with keratoconus were enrolled. ICRSs (Keraring) were implanted after dissection of the tunnel using Tunc's specially designed dissector under suction. A complete ophthalmic examination was performed, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent, keratometric readings, inferosuperior asymmetry index (ISAI), and ultrasound pachymetry. All 3-, 6-, and 12-month follow-ups were completed, and statistical analysis was performed.

RESULTS

The mean preoperative UDVA for all eyes was 1.36 ± 0.64 logMAR. At 12 months, the mean UDVA was 0.51 ± 0.28 logMAR (P = 0.001), and the mean preoperative CDVA was 0.57 ± 0.29 logMAR, which improved to 0.23 ± 0.18 (P = 0.001) at 1 year. There was a significant reduction in spherical equivalent refractive error from -6.42 ± 4.69 diopters (D) preoperatively to -1.26 ± 1.45 D (P = 0.001) at 1 year. In the same period, the mean K-readings improved from 49.38 ± 3.72 D to 44.43 ± 3.13 D (P = 0.001), and the mean ISAI improved from 7.92 ± 3.12 to 4.21 ± 1.96 (P = 0.003). No significant changes in mean central corneal thickness were observed postoperatively. There were no major complications during and or after surgery.

CONCLUSION

ICRS implantation using a unique mechanical dissection technique is a safe and effective treatment for keratoconus. All parameters improved by the 1-year follow-up.

Femtosecond laser technology in corneal refractive surgery: a review

PURPOSE

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

METHODS

Literature review.

RESULTS

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

CONCLUSIONS

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

New clinical pathways for keratoconus

Pre-2000, the clinical management of keratoconus centred on rigid contact lens fitting when spectacle corrected acuity was no longer adequate, and transplantation where contact lens wear failed. Over the last decade, outcome data have accumulated for new interventions including corneal collagen crosslinking, intracorneal ring implantation, topographic phototherapeutic keratectomy, and phakic intraocular lens implantation. We review the current evidence base for these interventions and their place in new management pathways for keratoconus under two key headings: corneal shape stabilisation and visual rehabilitation.

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.

MyoRing Treatment for Keratoconus: DIOPTEX PocketMaker vs Ziemer LDV for Corneal Pocket Creation

Purpose

To compare the results of MyoRing implantation for keratoconus using two different techniques for corneal pocket creation.

Materials and methods

Seven eyes suffering from keratoconus were treated using Ziemer LDV for corneal pocket creation and seven eyes suffering from keratoconus were treated using DIOPTEX PocketMaker for corneal pocket creation.

Results

Both groups did not show any statistically significant difference, neither in the severity of the disease nor in the results.

Conclusion

Ziemer LDV and DIOPTEX PocketMaker give equal results for MyoRing implantation for keratoconus.

How to cite this article

Daxer B, Mahmood H, Daxer A. MyoRing Treatment for Keratoconus: DIOPTEX PocketMaker vs Ziemer LDV for Corneal Pocket Creation. Int J Kerat Ect Cor Dis 2012;1(3):151-152.

Evaluation of intrastromal corneal ring segments for treatment of post-LASIK ectasia patients with a mechanical implantation technique

Aim:

To evaluate the clinical outcomes of Keraring segment implantation in patients with post- laser-assisted in situ keratomileusis (LASIK) ectasia, using a mechanical implantation technique.

Materials and Methods:

Twelve eyes of 10 patients with post-LASIK ectasia were enrolled. Intracorneal ring segments (ICRS) were implanted after dissection of the tunnel using Tunc's specially designed dissector under suction. A complete ophthalmic examination was performed, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent, keratometric (K) readings, inferosuperior asymmetry index (ISAI), and ultrasound pachymetry. All 3, 6, and 12-month follow-ups were completed, and statistical analysis was performed.

Results:

The mean preoperative UDVA for all eyes was 1.28 ± 0.59 logMAR. At 12 months, the mean UDVA was 0.36 ± 0.19 logarithm of the Minimum Angle of Resolution (logMAR) (P=0.002), and the mean preoperative CDVA was 0.58 ± 0.3 logMAR, which improved to 0.15 ± 0.12 (P=0.002) at 1 year. There was a significant reduction in cylindrical refractive and spherical equivalent refractive error from –5.29 ± 2.47 diopters (D) and –5.54 ± 5.04 D preoperatively to –1.47 ± 0.71 D and –0.74 ± 1.07 D (P=0.001, P=0.002), respectively, at 1 year. In the same period, the mean K- readings improved from 47.93 ± 4.84 D to 40.87 ± 2.36 D (P=0.002), and the mean ISAI improved from 5.34 ± 3.05 to 2.37 ± 1.68 (P=0.003). No significant changes in mean central corneal thickness were observed postoperatively. There were no major complications during or after surgery.

Conclusion:

ICRS implantation using a unique mechanical dissection technique is a safe and effective treatment for post-LASIK ectasia. All parameters showed improvement at 1-year follow-up.