Continuous Intracorneal Ring Implantation in Keratoconus: Efficacy, Predictive Factors, and Complications.

Purpose: To examine the clinical outcomes, predictors of visual improvement and complications of continuous intracorneal ring (ICCR) implantation in patients with keratoconus and confirmed contact-lens intolerance (CLI). Methods: This nonrandomized, multi-centric, retrospective cohort study examined visual, keratometric and clinical outcomes evaluated after a minimum follow-up of 2 months. Among the inclusion criteria for the standard treatment group (STG) were corrected distance visual acuity (CDVA) <20/25 Snellen, no central corneal scars, minimum corneal thickness >350µm, and central mean keratometry reading (meanK) <55 diopters. All other eyes were classified as non-standard treatment group. Results: A total of 118 eyes of 118 patients with aged 32 ± 11 years were included in this study. At a median follow-up of 161 days (interquartile range: 111-372 days) ICCR implantation improved the CDVA from a mean of 0.38 to 0.15 logMAR (p<0.0001). Our correlation analysis showed lower preoperative CDVA to be the single best predictor of CDVA improvement, with eyes of a CDVA of 20/80 or lower improving by 4.3 ± 2.0 lines on average. Eyes with a meanK >55 diopters gained 9.04±4.83 lines in UDVA and 2.86±3.09 lines in CDVA. However, postoperatively these eyes had a CDVA of 0.32±0.21 logMAR which is significantly inferior to the STG outcome (p=0.001372). Fifteen eyes (12.7%) had to undergo a ring exchange procedure because of refractive under- (9 eyes) or overcorrection (6 eyes). Two eyes (1.7%) experienced medical complications. Conclusion: This study confirms the inclusion criteria of ICCR implantation in KC eyes with CDVA <20/25 and CLI. Particularly in eyes with a preoperative CDVA <20/80 and a meanK <55 diopters, ICCR implantation should be considered due to its reversibility and low rates of serious complications. The main challenge remains in the low predictability of the magnitude of this improvement in eyes with CDVA >20/30.

Clinical outcomes after complete ring implantation in corneal ectasia using the femtosecond technology: a pilot study.

PURPOSE: To evaluate the clinical outcomes after implantation of the MyoRing (DIOPTEX GmBH, Linz, Austria) by means of femtosecond laser technology in eyes with corneal ectasia. DESIGN: Retrospective, consecutive, nonrandomized, case series. PARTICIPANTS: A total of 12 eyes of 11 patients with ages ranging from 17 to 50 years were included. All cases were diagnosed with corneal ectasia according to the standard criteria: 1 case of post-LASIK ectasia and 11 cases of keratoconus. All cases presented with reduced best spectacle-corrected visual acuity, contact lens intolerance or discomfort, and central corneal thickness of more than 350 µm. METHODS: MyoRing inserts of 280 µm in thickness and 5 mm in diameter were implanted in all cases into an intrastromal corneal pocket created by means of femtosecond technology. Visual, refractive, corneal topography, and pachymetric changes were evaluated during a 6-month follow-up. In addition, corneal biomechanical changes were evaluated by means of the Ocular Response Analyzer (Reichert, Buffalo, NY). MAIN OUTCOME MEASURES: Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, keratometry, corneal asphericity, corneal higher-order aberrations, pachymetry, corneal hysteresis (CH), and corneal resistance factor (CRF). RESULTS: A significant improvement in UDVA was observed 1 week after surgery (P=0.001), which was consistent with the significant reduction in sphere (P=0.002) and cylinder (P=0.004). No significant changes were detected in these parameters afterward (P ≥ 0.263). Furthermore, a significant corneal flattening of a mean value of 8.03 diopters (D) was found (P=0.005). This keratometric change was correlated with the magnitude of corneal coma-like aberrations (r=0.830, P=0.003) and the CRF (r=-0.782, P=0.008). In regard to aberrometry, a statistically significant increase in primary spherical aberration was found 1 month after surgery (P=0.001). In addition, a significant reduction in higher-order corneal aberrations was found 3 to 6 months after surgery (P=0.027). Significant corneal thickening was also observed postoperatively in the central, nasal, and temporal areas (P ≤ 0.013). No statistically significant changes were detected (P ≥ 0.176) in corneal biomechanics. Explantation was performed in a very advanced keratoconus because of the extremely poor visual outcome. CONCLUSIONS: MyoRing implantation using femtosecond technology in keratoconus allows successful corneal modeling, although the use of large diameters is advisable.

Implantation of a complete corneal ring in an intrastromal pocket for keratoconus.

PURPOSE: to evaluate the refractive and visual results of a new treatment for keratoconus using the corneal intrastromal implantation system (CISIS). METHODS: six eyes of four patients with keratoconus were treated with CISIS. Follow-up was 1, 3, and 6 months. After creating an intracorneal pocket of 9-mm diameter and 300-microm depth, a flexible full-ring implant was inserted via a 4-mm-wide corneal tunnel. RESULTS: no eyes showed loss of lines in uncorrected distance visual acuity (UDVA) or spectacle corrected distance visual acuity (CDVA) at any follow-up examination. Uncorrected and distance corrected visual acuity, keratometry, spherical and cylindrical refractive error as well as spherical equivalent refraction improved significantly (P<.05). Mean UDVA improved from 20/260 to 20/48 and mean CDVA improved from 20/41 to 20/27. A significant centralization and decrease of the corneal apex was found. No intra- or postoperative complications were observed. CONCLUSIONS: the corneal intrastromal implantation system using a complete ring implanted in a stromal pocket can achieve significant improvements in the visual function of patients with keratoconus. Uncorrected distance visual acuity improved by more than seven lines on average and CDVA improved by two lines.

Adjustable intracorneal ring in a lamellar pocket for keratoconus.

PURPOSE: No theory or method currently exists to preoperatively predict the optimal position of an intracorneal implant for the treatment of keratoconus, or a surgical system or technique to adjust and optimize the position of the implant after its implantation. A surgical technique for adjusting the position of the implant inside the cornea is presented, and by adjusting the position of the implant after its insertion into a corneal pocket, the surgical results in keratoconus treatment may be improved. METHODS: After the formation of a closed pocket of 9 mm in diameter and 300 mum in depth within the corneal stroma, a flexible full-ring implant is inserted into the corneal pocket via a narrow incision tunnel. After insertion and evaluation of the clinical data, the implant position can be adjusted inside the pocket to achieve an optimal treatment result. RESULTS: The procedure is quick and easy to perform. An adjustment of the implant position of only 0.5 mm towards the apex of the cone may dramatically improve the surgical result. CONCLUSIONS: The presented technique enables the surgeon to access all three degrees of freedom possible in theory, which are associated with intracorneal implants in a corneal stroma, including implant diameter, implant thickness, and implant position. This is of particular importance for the treatment of irregularly shaped corneas such as in keratoconus.

Corneal intrastromal implantation surgery for the treatment of moderate and high myopia.

I describe a corneal intrastromal implantation technique that uses a new type of microkeratome to create a closed intrastromal pocket as well as a continuous ring-shaped inlay with shape memory for placement in the pocket. The technique is a minimally invasive way to treat patients with moderate and high myopia. It can be considered an alternative to laser in situ keratomileusis and phakic intraocular lens implantation in these cases. The technique can be performed quickly and easily and appears safe and effective.

MyoRing treatment of myopia.

INTRODUCTION: Laser Vision Correction is not always possible for the treatment of myopia. The aim of this paper is to present results after MyoRing implantation in myopic eyes who in their majority were not eligible for LVC. Safety, effectivity and patient selection is discussed. The aim of the treatment was to be spectacle independent in everyday-life. MATERIALS AND METHODS: 19 myopic eyes of 12 patients ranging from -2.25 to -16.5 dioptres (D) in sphere and from 0 to -4D in cylinder were analyzed. RESULTS: After treatment, 84% of the eyes reached uncorrected distance visual acuity (UDVA) of 0.5 or better, 42% reached UDVA of 0.8 or better and 16% reached UDVA of 1.0 or better. Before treatment, no eye reached UDVA of 0.5 or better. Corrected distance visual acuity (CDVA) preoperatively and postoperatively did not differ. The treatment changed the average spherical equivalent from -10.27D to -0.93D. Efficacy index was 0.76 and safety index was 1.02. CONCLUSION: MyoRing implantation for myopia is safe and effective with highly satisfied patents in a particular subgroup of myopic patients. Patient selection is important.

Long-term results of MyoRing treatment of keratoconus.

PURPOSE: To study long-term results of MyoRing treatment of keratoconus. METHODS: Retrospective study of MyoRing implantation into a corneal pocket for keratoconus. RESULTS: Corneal thickness at the thinnest point remained unchanged, SIM K's, manifest sphere and cylinder were significantly improved at the first follow-up 9 months postoperatively and remained stable until the last follow-up about 5 years after surgery. Uncorrected and corrected distance visual acuity (UDVA, CDVA) were significantly improved at the first follow-up 9 months postoperatively and were further ameliorated until the last follow-up about 5 years after surgery. CONCLUSION: The treatment was safe and effective with continuing improvement of visual acuity during the 5 years after surgery.

Biomechanics of Corneal Ring Implants.

PURPOSE: To evaluate the biomechanics of corneal ring implants by providing a related mathematical theory and biomechanical model for the treatment of myopia and keratoconus. METHODS: The spherical dome model considers the inhomogeneity of the tunica of the eye, dimensions of the cornea, lamellar structure of the corneal stroma, and asphericity of the cornea. It is used in this study for calculating a strengthening factor sf for the characterization of different ring-shaped corneal implant designs. The strengthening factor is a measure of the amount of strengthening of the cornea induced by the implant. RESULTS: For ring segments and incomplete rings, sf = 1.0, which indicates that these implants are not able to strengthen the cornea. The intracorneal continuous complete ring (MyoRing) has a strengthening factor of up to sf = 3.2. The MyoRing is, therefore, able to strengthen the cornea significantly. CONCLUSIONS: The result of the presented biomechanical analysis of different ring-shaped corneal implant designs can explain the different postoperative clinical results of different implant types in myopia and keratoconus.

Corneal crosslinking and visual rehabilitation in keratoconus in one session without epithelial debridement: new technique.

A new surgical technique for the treatment of keratoconus is presented. This technique combines a new corneal crosslinking method with implantation of a flexible full-ring implant into a "closed" corneal pocket via a narrow incision tunnel in 1 surgical session. Riboflavin is not applied in the form of eyedrops onto a corneal surface after epithelial removal but is instilled into the corneal pocket without the need for epithelial debridement. A case of advanced keratoconus treated in this manner is presented. Uncorrected visual acuity increased by 7 lines from 0.05 to 0.25, and the average central K reading decreased by 11 diopters. The haze seen during the early postoperative period diminished in the first month after surgery.

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

PURPOSE: To evaluate intracorneal continuous ring (ICCR) implantation for the treatment of keratoconus. SETTING: Eye specialist centers, Europe and Middle East. METHOD: This study assessed the results of implantation of a MyoRing ICCR in 15 eyes with keratoconus. Outcome measures included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA) (spectacle correction), refraction, complications, and side effects. Postoperative follow-up was up to 1 year. RESULTS: The study evaluated 15 eyes of 11 patients (8 men, 3 women) with a mean age of 35 years +/- 12 (SD) (range 22 to 60 years). Preoperatively, the mean central corneal thickness was 435 +/- 41 mum (range from 350 to 485 mum) and the mean keratometry (K) readings, 48.96 +/- 3.4 diopters (D) (range 43.75 to 56.62 D). Postoperatively, there was a statistically significant improvement in the UDVA, CDVA, K readings, manifest spherical and cylindrical refractive errors, and spherical equivalent (P<.05). The mean UDVA improved by almost 10 lines, from 0.07 (1.24 +/- 0.35 logMAR) to 0.56 (0.27 +/- 0.17 logMAR), and the mean CDVA improved by almost 3 lines, from 0.42 (0.40 +/- 0.17 logMAR) to 0.77 (0.12 +/- 0.10 logMAR). The mean K reading decreased by 5.76 D, from 48.96 D to 43.20 D. No serious intraoperative complications occurred. Side effects included glare and night-vision problems. CONCLUSIONS: Treatment of keratoconus with ICCR implantation significantly improved visual function. The nomogram requires grading the disease using the K readings only. The UDVA and CDVA also improved during the first postoperative year. FINANCIAL DISCLOSURE: Drs. Mahmoud and Venkateswaran have no financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes.