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Confirming the progression of keratoconus is of paramount relevance to providing the appropriate treatment. Real change should be considered consistent over time. It must be greater than the variability of the measurement of the device used to monitor the cornea. The present study aimed to assess the intraobserver repeatability and intersession reproducibility of a Scheimpflug camera in measuring corneal parameters in virgin keratoconus and intrastromal corneal ring segments (ICRS) implantation eyes to discriminate real change from measurement noise. Sixty keratoconus and 30 ICRS eyes were included. Corneal parameters were determined in three consecutive measurements and were repeated 2 weeks later. The precision within the same session for all parameters was better in the keratoconic eyes, with mean repeatability limits 33% narrower (range 13% to 55%) compared with ICRS eyes. Mean reproducibility limits were 16% narrower (range +48% to -45%) compared with ICRS eyes. The cutoff values to consider a real corneal shape change were lower for virgin keratoconic than for ICRS, except for the thinnest corneal thickness and Stage C (ABCD system), which were the opposite. Corneal tomography measurements in ICRS eyes showed worse accuracy than in virgin keratoconus, which should be taken into account by practitioners in patients' follow up.

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Intrastromal corneal ring segments (ICRS) of in various shapes are used to correct structural changes in the cornea and improve visual acuity in keratoconus (KC). The most serious complications of the technology infection, vascular ingrowth, and extrusion. In this study a 44-year-old patient underwent deep anterior lamellar keratoplasty (DALK) 5 years after implantation of ICRS in the shape of an incomplete ring to treat its extrusion of up to 30%, vascular ingrowth into the cornea and corneal syndrome. The following DALK technique was used: excision of the free part of the corneal segment, removal of the remaining part of the corneal segment, excision of 80% of thickness of the corneal block with a 8.5-mm trepan, pneumatic dissection of the stroma down to the Descemet membrane (DM), removal of the remaining stroma on the viscoelastic pillow, laying and suture fixation of the donor graft. There were no complications during the postoperative period, the graft remained transparent for up to 10 months. Uncorrected visual acuity (UCVA) increased from 0.01 to 0.4, best corrected visual acuity (BCVA) increased from 0.3 to 0.7. The number of endothelial cells decreased from 2980 to 2670 cells/mm2 (10.4%). This clinical case demonstrates that DALK surgery can be a reliable method of patient rehabilitation in cases of extrusion of ICRS in the shape of an incomplete ring and vascular ingrowth.

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ABSTRACT Objective To analyze the short, medium and long-term efficacy and stability in 46 eyes with keratoconus, operated with Ferrara intrastromal corneal ring segments. Methods The primary endpoint was the mean keratometry of total corneal refractive power. We also studied the effects of age, degree of keratoconus and clinical phenotype on the results, as well as the following keratometry variations and aberrometry variations: flattest, most curved, mean, maximum, astigmatism, root mean square of primary coma aberration and root mean square of secondary coma aberration. Results The immediate postoperative reduction in mean keratometry of total corneal refractive power was 3.08±1.51 diopters (D) (p<0.001). At 4 years, the mean keratometry of total corneal refractive power increased to 0.57±0.96D (p=0.005). Between 4 and 7 years, there was no change in mean keratometry of total corneal refractive power (p=0.727). The degree of keratoconus was a factor affecting the efficacy of the intrastromal corneal ring segments, achieving a greater effect in those with a greater degree of keratoconus (p=0.012 between groups). The immediate postoperative reduction was 1.77±1.88D for the flattest, 3.91±2.30D for the most curved, 2.76±1.63D for the mean, 4.42±3.26D for the maximum, 2.15±2.68D for astigmatism, 1.03±0.83µm for root mean square of primary coma aberration and root mean square of secondary coma aberration (p<.001 in all cases). At 4 years, most curved increased by 0.42±0.78D (p=0.001), mean increased by 0.54±0.64 (p<0.001) and root mean square of primary coma aberration decreased 0.14±0.27µm (p=0.020). Conclusion Ferrara intrastromal corneal ring segment implantation is an effective and stable long-term treatment for patients with keratoconus. There is, however, partial regression in the medium term.

RESUMO Objetivo Analisar a eficácia e a estabilidade a curto, médio e longo prazo em 46 olhos com ceratocone, operados com segmentos de anel intrastromal corneano de Ferrara. Métodos A meta primária foi a ceratometria média de poder refrativo total da córnea. Também estudamos os efeitos da idade, grau de ceratocone e fenótipo clínico nos resultados, bem como as seguintes variações de ceratometria e variações de aberrometria: mais plana, mais curva, média, máxima, astigmatismo, raiz quadrada média da aberração comática primária e raiz quadrada média da aberração comática secundária. Resultados A redução pós-operatória imediata da ceratometria média do poder refrativo total da córnea foi de 3,08±1,51 dioptrias (D) (p<0,001). Aos 4 anos, a ceratometria média do poder refrativo total da córnea aumentou para 0,57±0,96D (p=0,005). Entre 4 e 7 anos, não houve mudança na ceratometria média da potência refrativa total da córnea (p=0,727). O grau de ceratocone foi um fator que afetou a eficácia dos segmentos do anel intrastromal da córnea, alcançando um efeito maior naqueles com maior grau de ceratocone (p=0,012 entre grupos). A redução pós-operatória imediata foi de 1,77±1,88D para a mais plana, 3,91±2,30D para a mais curva, 2,76±1,63D para a média, 4,42±3,26D para a máxima, 2,15±2,68D para o astigmatismo, 1,03±0,83µm para a raiz quadrada média da aberração comática primária e raiz quadrada média da aberração comática secundária (p<0,001 em todos os casos). Aos 4 anos, a maioria das curvas aumentou 0,42±0,78D (p=0,001), a média aumentou 0,54±0,64 (p<0,001) e a raiz quadrada média da aberração comática primária diminuiu 0,14±0,27µm (p=0,020). Conclusão O implante de anel intrastromal corneano Ferrara é um tratamento eficaz e estável a longo prazo para pacientes com ceratocone. Há, no entanto, uma regressão parcial a médio prazo.

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Intrastromal corneal ring segments (ICRS) improve corneal topographic symmetry and reduce corneal aberrations through regularization of the corneal surface, thereby functioning as a viable surgical intervention for patients with keratoconus. This study aims to evaluate changes in lower- (LOAs) and higher-order aberrations (HOAs) amongst varying pupil sizes pre- and post- ICRS implantation in keratoconus patients. We specifically investigate the impact of pupil size on total corneal HOAs up to the 6th order. Twenty-one eyes that underwent ICRS implantation were included in this prospective interventional study. LOAs and HOAs measurements at the 6 mm, 4 mm, and 2 mm pupil diameters were collected preoperatively and at 6 months postoperatively using the Zernicke analysis function on a Scheimpflug device. ICRS implantation demonstrated a statistically significant effect in vertical coma with a −0.23 reduction (p = 0.015) for a 4 mm pupil size and a −1.384 reduction (p < 0.001) for 6 mm, with no significant effect at 2 mm. Horizontal coma, astigmatism 0°, astigmatism 45°, trefoil 5th order 30°, and RMS HOA demonstrated significant reductions at 4 mm or 6 mm pupil sizes but not at 2 mm. Our analysis demonstrates a favorable effect of ICRS implantation on larger pupil sizes, suggesting the importance of pupil size as it correlates with HOAs reduction.

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PURPOSE: To compare different intraocular pressure (IOP) readings in corneas with intrastromal corneal ring segments (ICRS) taken by three different tonometers; Goldmann applanation tonometry (GAT), air puff tonometer, and ocular response analyzer (ORA) corneal-compensated IOP (ORA-IOPcc) and determine the relation of these measurements to different corneal parameters taken by Pentacam. METHODS: An observational cross-sectional analytic study included patients who underwent ICRS keraring implantation at 3 months. In each eye, the two rings were placed using the femtosecond laser assisted technique 5.5 or 6 mm from the center. IOP was measured using three different tonometers; GAT, air puff tonometer, and ocular response analyzer (ORA) corneal-compensated IOP (ORA-IOPcc). RESULTS: Fifty eyes of 30 patients (20 males and 10 females) aged 27.56 ± 6.38 years were included. IOP measurements by GAT, air puff tonometer, and ORA-IOPcc were 13.28 ± 2.13 mmHg, 10.47 ± 2.55 mmHg, and 13.19 ± 2.78 mmHg, respectively. Comparisons between air puff and each of GAT and ORA-IOPcc were statistically highly significant (p-value <0.001). CONCLUSION: IOP measurements taken by air puff tonometer were significantly lower than those taken by GAT and ORA-IOPcc. These differences were not constant across the pressure range but increased as the pressure values determined using GAT and ORA increased. ORA-IOPcc and GAT showed similar readings. No correlation was found between any of the IOP readings taken by the three tonometers and the central corneal thickness.

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Intrastromal corneal ring segments (ICRSs) are an effective treatment for stabilizing and normalizing corneal shape in patients with keratoconus and other corneal ectasias. Intraoperative segment perforation through the corneal endothelium into the anterior chamber (AC) is an uncommon but known complication. However, perforation into the AC postoperatively is an exceedingly rare complication with only 3 reported cases in the literature. One case was due to Descemet membrane detachment and another due to ocular trauma. In the third case, the mechanism for perforation was unclear. We present the fourth case of delayed ICRS perforation due to silent migration through the endothelium into the AC. We also present all reported cases in the literature of intraoperative and postoperative perforation into the AC.

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PURPOSE: To report the visual, refractive and tomographic outcomes following the implantation of intrastromal corneal ring segments (ICRS) (Ferrara rings, AJL Ophthalmics, Miñano, Spain) in eyes with a history of keratoconus and corneal cross-linking using the Ferrara ring nomogram. METHODS: Retrospective, interventional case series performed at the Corneoplastics Unit, Queen Victoria Hospital, East Grinstead, United Kingdom. RESULTS: 21 eyes of 19 patients with a history of keratoconus and prior corneal collagen cross-linking had Ferrara Intrastromal Corneal Ring Segments implanted between December 2015 and October 2017. The number, thickness and length of ring segments was chosen based on the Ferrara ring company nomogram. Mean uncorrected visual acuity (UDVA) improved from 0.88 to 0.52 logMAR (p < 0.001). Mean corrected visual acuity (CDVA) improved from 0.47 to 0.36 logMAR (p = 0.046). The percentage of eyes achieving 20/40 UDVA and CDVA increased from 5% to 38% and from 38% to 67%, respectively. Of the eyes, 52.3% gained at least two lines of CDVA. The spherical equivalent improved from -7.51D to -3.76D (p < 0.001) and the refractive astigmatism magnitude improved from 5.14D to 2.76D (p = 0.004). There were significant improvements in the corneal tomography with mean keratometry (KM) improving from 50.40D (3.53) to 48.24D (3.00) (p = 0.01) and keratometric astigmatism magnitude improving from 5.14D (2.91) to 2.76D (1.67) (p = 0.004). CONCLUSION: Insertion of Ferrara rings in keratoconic eyes with a history of prior cross-linking using the company nomogram results in significant improvements in visual, refractive and tomographic outcomes.

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PURPOSE: To evaluate clinical outcomes in patients with asymmetric duck phenotype keratoconus implanted with asymmetric progressive thickness intrastromal corneal ring segments (PT-ICRS, Keraring AS, Mediphacos, Belo Horizonte, Brazil), and to demonstrate improved visual acuity and symmetry in corneal flattening. METHODS: This single-center, retrospective, observational study evaluated the clinical outcomes at 1, 3, and 6 months after implantation of PT-ICRS in patients with duck phenotype keratoconus. After creating the intrastromal tunnel with a femtosecond laser, one 160-degree arc length PT-ICRS, either 150/250 µm or 200/300 µm, was implanted. Changes in uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction (MR), manifest refraction spherical equivalent (MRSE), mean keratometry (Kmean), maximum keratometry (Kmax), Coma@5mm, and manifest and topographical astigmatism were documented. RESULTS: The study cohort included 23 eyes of 17 patients with a mean age of 24.6 years. From baseline to 6 months following implantation, mean UDVA improved from 0.70 logarithm of the minimum angle of resolution (logMAR) (20/100 Snellen) to 0.22 logMAR (20/33 Snellen), CDVA improved from 0.33 logMAR (20/42 Snellen) to 0.14 logMAR (20/27 Snellen), the mean sphere and MRSE decreased from -1.05 diopters (D) and -2.70 D to -0.25 D and -0.80 D, respectively, and the Kmean and Kmax improved from 46.5 D and 53.7 D to 44.6 D and 48.7 D, respectively. CONCLUSIONS: The Keraring AS ICRS offers a safe, effective means of improving visual acuity while reducing refractive error, mean and max keratometry, and aberrations in patients with duck phenotype keratoconus.

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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.

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AIM: To evaluate the clinical results after implantation of a new intrastromal corneal ring segment (ICRS) associated with photorefractive keratectomy (PRK) to correct high myopia (HM) patients with thin corneas. METHODS: We evaluated 42 eyes of 23 HM patients that had ICRS implantation followed by PRK. The mean age of patients was 29.1±7.12y (range 18 to 40 years old). Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), keratometry, spherical equivalent, pachymetry, and aberrometry were compared using ANOVA with repeated measurements evaluated preoperatively and at last follow-up visit after the procedures. The refractive predictability and simulated/real corneal ablation were also assessed. RESULTS: The mean follow-up time after PRK was 6.8±1.6mo. The mean preoperative UCVA improved from 20/800 preoperative to 20/100 after ICRS and 20/35 after PRK. The mean preoperative BCVA was 20/25 (range from 20/30 to 20/20) and remained unchanged after ICRS implantation. Following the PRK the mean BCVA was 20/25 (range from 20/30 to 20/20). The mean spherical equivalent decreased from -7.25±1.12 (range -5.00 to -9.00) preoperatively to -3.32±1.0 (range -2.00 to -5.00) postoperatively (P<0.001) after ICRS implantation and decreased from -2.44±1.51 preoperatively to 0.32±0.45 (range -0.625 to 0.875) postoperatively (P<0.001) after PRK. The change in BCVA and topographic astigmatism was statistically significant (P<0.0001). CONCLUSION: ICRS in HM associated with PRK can be a tissue saving procedure and an alternative surgical option for correction of moderate to high myopia.

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PURPOSE: To evaluate one-year visual, refractive, and topographic outcomes of 58 eyes of 53 keratoconus patients who underwent surgery with a progressive thickness intrastromal corneal ring segment (ICRS). METHODS: This multi-center, retrospective, observational study evaluates the one-year effects of progressive thickness ICRS implanted in keratoconus patients meeting the inclusion criteria. One or two progressive ICRS were implanted in the selected eyes after creating an intrastromal tunnel with a femtosecond laser. Pre- and postoperative uncorrected distance visual acuity, best-corrected distance visual acuity, manifest refraction (both spherical equivalent and cylindrical refractions), corneal astigmatism, maximum keratometry, corneal thickness, and corneal topography measurements and indices were evaluated. RESULTS: In this retrospective case series, 58 eyes of 53 keratoconus patients were included with a follow-up of 12 months. The mean age was 30.89 ± 11.90 years. There were improvements postoperatively in mean values of visual acuities, both uncorrected from 0.71 (preoperatively) to 0.28 (log MAR), and best-corrected from 0.28 to 0.10 (log MAR), mean cylindrical refraction from - 2.35 ± 1.51 to - 4.15 ± 2.23 D, and mean spherical equivalent from - 2.10 ± 2.25 to - 4.64 ± 3.2 D. There was also a reduction in maximal keratometry from 54.21 D preoperatively to 50.93 D postoperatively. CONCLUSION: The implantation of the progressive thickness ICRS is an effective and safe method to improve the vision of keratoconic eyes. Corneal stability was maintained at the 12-month mark.

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PURPOSE: Surgical management of keratoconus aims to improve corneal curvature, prevent progression of corneal ectasia, and manage refractive error. In older individuals with concurrent cataracts, management can be challenging due to topographic irregularity and difficult-to-interpret IOL calculations. We describe a sequential combination of two surgical techniques-intrastromal corneal ring segments (e.g. intacs) insertion and toric pseudoaccomodating lens implantation-to successfully manage concurrent keratoconus and cataracts. OBSERVATIONS: In this case series, we present three eyes with corneal ectasia in two cataractous patients successfully managed by (1) Intacs placement to normalize corneal contour/asymmetry and enable more regular keratometry measurements, followed by (2) correction of astigmatism and presbyopia by placement of toric pseudoaccommodating IOL (Trulign) after cataract extraction. CONCLUSIONS AND IMPORTANCE: This is the first description, to the authors' knowledge, of the use of intraocorneal ring segments + toric pseudoaccommodating intraocular lenses for the management of concurrent keratoconus, cataract, and presbyopia.

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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.

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PURPOSE: To compare the clinical and histological outcomes after intrastromal corneal ring segment (ICRS) implantation with and without plasma rich in growth factors (PRGF) in an experimental animal model. MATERIALS AND METHODS: First, the toxicity of PRGF was tested in hen's keratocyte cultures. Then, an animal model with 18 hens was randomly divided into 2 groups. In the first group, one ICRS was implanted in each eye (ICRS group). In the second group, the ICRS was firstly immersed 30 min in PRGF-Endoret solution, then implanted and, finally, PRGF-Endoret was inoculated into the channel (PRGF-ICRS group). Animals of each group were also separated into 3 groups regarding the time they were sacrificed, and corneal tissue was fixed for histological analysis at 2, 7 and 30 days. Cell death was detected by terminal uridine nick end labelling (TUNEL) assay. Proliferation was labelled by 5-bromo-2-deoxyuridine (BrdU) incorporation and myofibroblast differentiation by alpha-smooth muscle actin (αSMA) immunodetection. Clinical examination, analyzing epithelial wound closure, deposits and stromal haze, was carried out at the different study times. RESULTS: No toxic effect was observed by PRGF in hen stromal cell cultures. Clinically, in PRGF-ICRS corneas at 7 days, there were more deposits with higher intensity than in ICRS group. Histologically, at day 2 there was less epithelial damage over the segment in the PRGF-ICRS group, corneal oedema around the segment disappeared earlier and, at day 7, there was also double the number of cells around the segment than in the ICRS group displaying different morphologies. The number of TUNEL-positive cells was statistically higher in the PRGF-ICRS group at 7 and 30 days, and the number of BrdU-positive cells was statistically higher at all analyzed times. However, there were no differences in the number of αSMA-positive cells at 30 days between both groups. CONCLUSIONS: The ICRS immersion in PRGF-Endoret prior and after to its corneal implantation, in an experimental animal model, enhances clinical deposits and histological cell turnover without increasing myofibroblast differentiation reducing stromal wound-healing time after surgery.

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@#A variety of therapeutic methods can be used to treat keratoconus. This article provides practical information for clinicians to make the most appropriate choices by reviewing the treatment of keratoconus. Search for keywords such as “keratoconus” “contact lenses” “corneal collagen cross-linking” “Intacs(corneal ring)” “keratoplasty” “gene therapy” “irregular astigmatism” through a database. According to the related literature, the treatment methods of keratoconus are reviewed. Glasses and contact lenses can be used for early keratoconus, while bowman layer transplantation, penetrating keratoplasty(PK), deep anterior lamellar keratoplasty(DALK), conductive keratoplasty and gene therapy can be used in advanced disease. In addition, cross-linking can prevent keratoconus progression, and intrastromal corneal ring segments(ICRS)reduce refractive error for therapeutic purposes by flattening the deformed cornea. In general, the development of ophthalmic diagnostic techniques and treatments can slow the progression of keratoconus, thereby reducing the need for corneal transplantation in patients with advanced keratoconus. Choosing the right keratoconus treatment can help patients with vision recover and prevent blindness.

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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.

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PURPOSE: The ex-vivo feasibility of creating corneal ring segments (ICRS) from biological tissue (xenograft porcine cornea) and combining intra-corneal implantation with Corneal CrossLinking (CXL). METHODS: The ring segments from gamma-irradiated porcine donor cornea were shaped and implanted in human cadaver host cornea using a femtosecond laser for their dissection and host cornea channel preparation. Intra-channel 0.25% riboflavin solution combined with higher fluence CXL of 15 joules total energy followed their implantation. Anterior segment Optical Coherence Tomography (OCT), Scheimpflug tomography and Placido-disc topography were used to monitor the positioning and refractive effect. RESULTS: The novel xenograft ring segments were positioned as planned at 85% corneal depth and mid-peripheral, with documented, up to 7 diopters central cornea flattening. CONCLUSION: Xenograft intracorneal ring segments combined with CXL may offer an alternative to the synthetic materials used clinically so far, aiming in reducing complications of intracorneal opaque deposit accumulation, segment migration, corneal erosion and potential extrusion. Combining CXL may enhance their refractive effect and stabilize potential or documented host ectasia.

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PURPOSE: To evaluate the topographic, refractive, and pachymetric changes after ethanol-assisted transepithelial corneal cross-linking (CXL) to stabilize progression of keratoconus (KC). PATIENTS AND METHODS: This study retrospectively evaluated the long-term topographic, refractive, and pachymetric changes in patients diagnosed with KC who underwent corneal cross-linking and/or intrastromal corneal ring segment (ICRS) implantation. The subjects were divided into three groups, corresponding to eyes treated with CXL alone (group 1), CXL and ICRS at the same time (group 2), and CXL after ICRS implantation (group 3). Corrected visual acuity and refraction, steep keratometry (SteepK) values, steepest keratometry reading on sagittal curvature map, and corneal thickness were recorded preoperatively and at each visit. Changes between measurements were assessed during follow-up. RESULTS: Corrected distant visual acuity (CDVA) values improved in all groups compared with baseline, but the differences were not statistically significant except for the first year (p > 0.05). In groups 1 and 3, SteepK values did not change statistically significantly during the entire follow-up (p > 0.05). In group 2, SteepK values statistically significantly decreased at all follow-up examinations compared with baseline, determined as the first month after ICRS implantation (p < 0.05). Complication rates were acceptable without any need for surgical intervention. CONCLUSIONS: Single-session ethanol-assisted transepithelial CXL with or without ICRS implantation was a safe and effective procedure to halt progression of KC.

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  Introduction: The intrastromal corneal ring segments implantation is widely used as an effective method for keratoconus correction. Femtosecond laser technology represents very precise and modern approach in corneal tunnel creation. Nevertheless complication like an extrusion of the implanted ring segment rarely appears. There are few different types of intrastromal corneal segments available. Keraring (Mediphacos Ltd.) is primary designed for keratoconus treatment. MATERIALS AND METHODS: We evaluated results of the Keraring implantations in 32 patients (48 eyes) with keratoconus or with marginal pellucid degeneration. We implanted 78 segments totally in the period from January 2015 to February 2017, with the assistance of femtosecond laser. We present our data collected after the 6 months follow up. Uncorrected visual acuity - UCVA and best corrected visual acuity - BCVA were evaluated. We scored the changes in the subjective and objective refraction. The complications were observed. RESULTS: Preoperative UCVA was in 44 (91,60%) eyes under or equal 0,3. Postoperative UCVA after 6 months was in 29 (60,41%) eyes over or equal 0,3. Visual acuity improved in 38 (79,16%) eyes totally with the gain of 1 to 9 lines, BCVA improved in 27 (56,25%) eyes and in 15 (31,25%) eyes stayed postoperatively unchanged. There was reduction of the spherical equivalent (SE), in the subjective and objective refraction. In our group there we detected 9 (18,75%) extrusions of the implanted ring segment, which occurred on average 7,3 months (range 2/ 16 months) after the surgery. CONCLUSION: Intrastromal corneal ring segments implantation with the femtosecond laser assistance is an effective approach in the keratoconus treatment. Complications are not often observed. With careful selection of the suitable patient it is possible to avoid them. Key words: keratoconus, intrastromal corneal ring segments, femtosecond laser.

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@#AIM: To evaluate the clinical effectiveness of intrastromal corneal ring segments among the patients suffering from keratoconus. <p>METHODS: A retrospective and comparative interventional design had been utilized on the basis of postoperative follow up among 56 keratoconus patients. Visual acuity was significantly assessed during complete ophthalmic examination of the patients. The femtosecond laser had been used to create the corneal tunnels in 15 eyes; whereas, the corneal tunnels were created in 72 eyes mechanically. <p>RESULTS: The ranges and standard deviations had been used to obtain results. It had been revealed through ophthalmic assessment that the mean preoperative uncorrected visual acuity observed was 1.38±0.37 Logarithm of Minimal Angle of Resolution. Moreover, a significant improvement was observed postoperatively in visual acuity by 0.58±0.32 during the fourth month. The improvement was also witnessed in the 16^th month by 0.48±0.30. <p>CONCLUSION: The implantation of intrastromal corneal ring segments is an efficient and effective surgical intervention for the treatment of keratoconus. Thus, identified intervention seems to be associated with appropriate visual outcomes and safety after the development of femtosecond as well as mechanical tunnels.