Intrastromal Tunnel Research Articles

One-Step Intraoperative Optical Coherence Tomography Guided Tunnel, Mushroom Femtosecond Laser Big Bubble Deep Anterior Lamellar Keratoplasty.

The aim of our study is to investigate the feasibility and outcomes of using a femtosecond laser (FSL) platform (Ziemer LDV Z8) for deep anterior lamellar keratoplasty (DALK), enabling the creation of mushroom-shaped graft-host junctions, lamellar cuts, and intrastromal tunnels, to facilitate the big bubble, in one step. We included wet lab experiments on nine porcine eyes to assess the laser accuracy and cuts depth using an anterior segment (AS) OCT. This was followed by an interventional prospective case series on 10 eyes with variant corneal pathologies. The Z8 system, with in-built intraoperative optical coherence tomography (iOCT), guided corneal scans and directed the cuts. ASOCT showed visible mushroom configurations, lamellar cuts, and tunnels. Deviations from the target were 1.6%, 2.6%, and 3.5%. Anterior lamellar removal was easy in all clinical cases, including corneal scarring. The intrastromal tunnel was found at the preset location and the mushroom configuration was acquired. A big bubble was achieved in all cases. Type 1, 2, and 3 bubbles were formed in eight, one, and one case, respectively. We describe a new approach to DALK in which the in-built iOCT-guided FSL enables safe, precise, controlled, and reproducible desired cuts in one step. The preliminary clinical outcomes were favorable.

Donut-shaped Corneal Allogeneic Intrastromal Segment as an Alternative to Deep Anterior Lamellar Keratoplasty in Advanced Keratoconus.

The aim of this study was to describe a new technique of selective corneal stromal transplantation for keratoconus treatment, donut-shaped CAIRS (corneal allogeneic intrastromal ring segment). A donut-shaped corneal graft is obtained using a double-bladed trephine. Descemet membrane, endothelium, and epithelium are all removed from the graft. Only stromal tissue is transplanted. A wide 360-degree intrastromal tunnel is created using the femtosecond laser, with a 30-degree angulation. The diameter is from 5.4 mm to 8 mm optical zone. After dehydration, the corneal graft is inserted into the tunnel. We report the clinical and tomographic outcomes after the procedure in 3 patients. The mean follow-up time after donut-shaped CAIRS was 6.01 ± 1.02 months. In case 1, best spectacle-corrected visual acuity improved from 20/150 to 20/40. In case 2, it improved from 20/400 to 20/40, and in case 3 from 20/200 to 20/40. The mean preoperative K was 57.3 ± 4.5 D and reduced to 44.2 ± 2.5 D after donut-shaped CAIRS. The mean spherical equivalent decreased from -9.8 ± 3.2 preoperatively to -3.2 ± 2.2 postoperatively. No intraoperative or postoperative complications were observed. Anterior segment OCT showed a mid-stroma implant, fusiform in shape, equidistant from the epithelium and endothelium. Donut-shaped CAIRS is a variation of the traditional CAIRS technique and showed to be an alternative option for keratoconus treatment, especially in moderate to advanced cases with a central clear cornea without scars. The technique is minimally invasive, and the visual axis remains untouched.

Efficacy and safety of intracorneal allogenic ring segment implantation in keratoconus: 1-year results.

To evaluate the safety and efficacy of corneal allogenic intrastromal ring segments in the management of keratoconus patients. The retrospective, nonrandomized, interventional case series consisted of 65 keratoconic eyes of 49 consecutive patients who had ring segment-shaped corneal allografts (KeraNatural®) implanted in intrastromal tunnels created using a femtosecond laser. The main outcome measures were uncorrected visual acuity (UCVA), corrected distant visual acuity (CDVA), refraction, keratometry, and pachymetry. Computed tomography scans of the corneal surfaces were also performed preoperatively as well as 3, 6 and 12 months postoperatively. Mean age was 29.5 ± 7.3 years (median 29, range: 20-52 years). The mean UCVA improved from 0.91 ± 0.50 logMAR preoperatively to 0.40 ± 0.24 logMAR postoperatively at 6 month follow-up (p < 0.01) and the mean CDVA improved from 0.87 ± 0.20 logMAR preoperatively to 0.27 ± 0.06 logMAR postoperatively (p < 0.01). The mean spherical equivalent improved from -8.82 ± 4.57 to -3.45 ± 4.81D (p < 0.01). Average Keratometry decreased from 49.23 ± 5.22 preoperatively to 45.63 ± 4.89 D postoperatively (p < 0.01). Mean anterior and posterior maximum elevation were also decreased significantly (p < 0.01). In one patient, dislocation of the graft towards the tunnel incision site and dehiscense at the tunnel entrance were observed in the first week of the operation. Yellow-white deposits were observed in the segment tunnels in five cases after 6 months. This study demonstrated that implantation of corneal allograft ring segments is a viable alternative treatment for keratoconus with safety and good visual results.

Clinical comparison of manual and laser-cut corneal tunnel for intrastromal air injection in femtosecond laser-assisted deep anterior lamellar keratoplasty (DALK).

The most crucial step in deep anterior lamellar keratoplasty (DALK) is to achieve a bare Descemet's membrane. We aimed to assess a new femtosecond laser software that allows for a precise intrastromal tunnel creation for big bubble (BB) air injection using a real-time microscope-integrated optical coherence tomography. A retrospective review of 61 eyes of 61 patients with keratoconus. Before introducing the new software update, DALK was performed using a partial-assisted femtosecond laser (partial-thickness circular cut followed by a lamellar cut) with manual intrastromal tunnel creation (partial FS-DALK group). After the software update, the femtosecond laser created the intrastromal tunnel (full FS-DALK group). In the full FS-DALK group, the BB's formation was significantly higher (64.3% vs. 36.4%, p = 0.04), and surgery time was shorter (21.8 ± 5.1 vs. 25.6 ± 6.8min, p = 0.025) than in the partial FS-DALK. Penetrating keratoplasty conversion rate (7.1% vs. 15.1%, p = 0.432) was similar between the groups. Both groups showed statistically significant improvement in uncorrected and corrected distance visual acuity, central corneal thickness, surface asymmetry, and regularity indices. Endothelial cell density loss at 12 and 18months was lower in the full compared with the partial FS-DALK group (12months:10.0% vs. 16; 18months: 10.7 vs. 16.5%, p < 0.001 for both comparisons). Creating the intrastromal guiding tunnel using FS laser for air injection resulted in a higher rate of BB formation, reduced long-term endothelial cell loss, and operating room time.

Correction of postkeratoplastic astigmatism by intrastromal corneal segments implantation using a femtosecond laser

Background. After penetrating keratoplasty, mild to high induced corneal astigmatism was observed in each case. The existing choice of correction of postkeratoplastic astigmatism is aimed at fi nding an individual approach in order to compensate for it and not weaken the biomechanical properties of the corneal graft.The aim: to analyze the clinical, functional, and morphological results of postkeratoplastic astigmatism correction by implantation of intrastromal corneal segments using a femtosecond laser.Methods. 22 patients were examined before and 1 year after surgery. The operation was performed under local anesthesia: stage I – an intrastromal tunnel was formed using a femtosecond laser “Femto Visum” 1 MHz (Optosystems, Russia); stage II – the intrastromal corneal segments were implanted. The results were assessed using standard and special research methods using optical coherence tomography Visante OCT (Zeiss, Germany), keratotopography (Tomey-5, Japan), optical corneal analyzer ORA (Reichert, USA), laser tindalemetry FC-2000 (Kowa, Japan) and confocal microscope Confoscan-4 (Nidek, Japan).Results. Before the operation, uncorrected visual acuity averaged 0.09 ± 0.05, after a year – 0.50 ± 0.16; best corrected visual acuity – 0.30 ± 0.12 and 0.60 ± 0.05 respectively; cylindrical component of refraction – –10.29 ± 3.12 and –2.20 ± 0.64 D respectively; mean keratometry value – 43.59 ± 2.14 and 38.56 ± 1.75 D respectively; corneal hysteresis – 7.92 ± 1.22 and 8.95 ± 1.05 mm Hg respectively; corneal resistance factor – 7.01 ± 1.81 and 8.44 ± 1.44 mm Hg respectively; protein fl ux in the moisture of the anterior chamber – 2.97 ± 0.28 and 3.04 ± 0.24 f/ms respectively; endothelial cell density – 1521 ± 327 and 1475 ± 419 cells/mm2 respectively.Conclusion. Intrastromal corneal segments implantation into a corneal graft using a femtosecond laser has efficiency and safety method in correcting postkeratoplastic astigmatism.

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

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. 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. 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. 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.

Изучение разработанных внутрироговичных гелевых окрашенных имплантатов для кератопигментации на основе различных материалов. Экспериментальное исследование

Purpose. Evaluation of the impact of the developed intracorneal gel stained implants for keratopigmentation based on various materials on the donor human cornea during organotypic cultivation. Material and methods. Three experimental samples of intracorneal gel stained implants were investigated: sample 1 based on sodium hyaluronate with organic pigment, sample 2 based on collagen hydrolyzate with inorganic pigment, and sample 3 based on hydroxypropyl methylcellulose (HPMC) with organic pigment. To determine the toxicity of the studied implants the apoptosis of keratocytes was determined in cryostat sections of the cornea. The method of immunohistochemistry was used to study apoptosis. Scanning electron microscopy was used to visualize the corneal structures in the presence of implants. Results. During the investigation we showed that a gel implant based on a collagen hydrolyzate and a pigment with an inorganic toner (28% in the composition) causes a weak expression of the initiator proteins of apoptosis Caspasa 8 and Cytochrome C, and there is no expression of the BAX and effector proteins Caspasa 3/7. It was revealed that samples No. 1 and No. 3 undergo partial dissolution and washout from the intrastromal tunnel, sample No. 2 based on collagen hydrolyzate has a dense structure and remains in the corneal tunnel throughout the entire cultivation period, for at least 7 days, which is showed using an electron-scanning microscopy. The proposed collagen hydrolyzate gel implant can be considered compact and non-toxic. Conclusion. As a result of organotypic cultivation for 7 days showed the best results intracorneal colored implant № 2 based hydrolyzate of collagen and inorganic toner. Intracorneal colored implant based on collagen hydrolyzate has a more compact and dense structure than the accompanying experimental samples. Key words: keratopigmentation, aniridia, intracorneal colored implant.

Efficacy of progressive thickness intrastromal corneal ring segments in the treatment of duck phenotype keratoconus.

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. 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. 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. 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.

Intracorneal circular ring implant with femtosecond laser: Pocket versus tunnel.

To evaluate and compare visual and refractive outcomes after implantation of the intracorneal continuous ring 360° arc (ICCR) versus the intracorneal ring segment 340° arc (ICRS) using femtosecond laser for central keratoconus. Research Department, Oftalmosalud, Instituto de Ojos, Lima, Peru. Randomized study that included 40 eyes of 32 patients diagnosed with central keratoconus between November 2014 and March 2015. Twenty eyes had an implantation of ICCR (MyoRing, Dioptex GmbH, Austria) through an intrastromal pocket and 20 eyes had an implantation of ICRS (Keraring, Mediphacos, Brazil) through an intrastromal tunnel. Both procedures were performed with a femtosecond laser (LDV Z6 model, Ziemer Ophthalmic Systems AG). Visual acuity (VA), refraction, and Scheimpflug imaging analysis were performed pre- and postoperatively at 1 month and 1 year. Comparisons of means were performed using the Student's t-test. At 1 year, uncorrected VA improved 0.77 LogMAR (p < 0.001) in the ICCR group and 0.79 LogMAR (p = 0.01) in the ICRS group; mean sphere improvement was 5.13 Diopters (D) in the ICCR group and 6.27 D in the ICRS group (p < 0.001 both); mean Steeper Keratometry improvement was 4.24 D in the ICCR group and 5.53 D in the ICRS group (p < 0.001 both). In the ICCR group, mean decrease in the pachymetry at the thinnest point of the cornea was 32.16 µm (p = 0.01), and in the ICRS group, mean increase was 4.2 µm at 1 year (p = 0.61). Intracorneal continuous ring 360° arc (ICCR) and intracorneal ring segment 340° (ICRS) are effective treatments for central keratoconus. No significant differences between rings were found on visual acuity, refraction, and keratometry improvement.

Visual, refractive and topographic outcomes of progressive thickness intrastromal corneal ring segments for keratoconic eyes.

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). 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. 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. 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.

Comparative Analysis of the Clinical Efficacy of Intrastromal Keratoplasty using a Digital Marking Device in Patients with Keratoconus

Purpose— to perform a comparative analysis of the clinical efficacy of intrastromal keratoplasty (ISKP) in patients with keratoconus during surgery with and without Verion digital marking device.Patients and methods. 37 patients (50 eyes) with corneal astigmatism up to -5.0 diopters were included in the study. These patients were operated with the femtolaser method of ISKP with implantation of corneal segments. The average age of the patients was 27.96 ± 3.40 years. The observation period is from 3 to 12 months. All patients were divided into two groups depending on the surgical technique: Verion-assisted, using a digital marking device and taking into account the angle of cyclotorsia, or standard, without taking into account the angle of cyclotorsia. The first main group included 28 eyes (56 %), the second control group included 22 eyes (44 %) accordingly.Results. The functional results after ISKP in both groups were quite good. Stabilization of functional parameters and keratometric data was noted in the postoperative period, by 3 months. Patients of the main group showed a statistically significant (p &lt; 0.05) increase in average uncorrected visual acuity to 0.50 ± 0.16, and visual acuity with maximum correction to 0.70 ± 0.12 (p &lt; 0.05). The average keratometry of the weak meridian decreased to 44.3 ± 1.4 diopters, the average keratometry of the strong meridian decreased to 50.8 ± 3.2 diopters. Patients in the control group showed a statistically significant (p &lt; 0.05) increase in average uncorrected visual acuity to 0.45 ± 0.12, and visual acuity with maximum correction to 0.60 ± 0.17. The average values of keratometry of the weak meridian decreased to 45.3 ± 1.8 diopters, the average values of keratometry of the strong meridian decreased to 51.8 ± 2.2 diopters. The results of the vector analysis reliably indicate a significantly higher accuracy of the Verion-assisted ISKP. Which is confirmed by the achieved indicators of the “success” index, the calculated astigmatism vector close to the actual postoperative astigmatism vector, the smaller the magnitude of the astigmatism axis difference vector compared to the control.Conclusion. The use of the Verion-assisted intrastromal technique for keratoconus reduces the risk of erroneous positioning of the corneal segments in the tunnel during transferring diagnostic data to the operating room. Taking into account the angle of cyclotorsia during cutting into the intrastromal tunnel increases the effective correction of the cylindrical component of refraction, which is confirmed by the main coefficients of the vector analysis by N. Alpins.

Clinical Outcomes of an Asymmetric Model of Intrastromal Corneal Ring Segments for the Correction of Keratoconus

To evaluate the clinical outcomes of a new model of intrastromal corneal ring segments (ICRSs) (Keraring AS) in patients with keratoconus and quantify subsequent changes in refraction and corneal topography. This nonrandomized, single-center, retrospective observational study explores the effect of progressive thickness ICRS implantation in patients with keratoconus with a 3-month follow-up. After creating an intrastromal tunnel using a femtosecond laser, 1 or 2 ICRSs of progressive thicknesses (150/250 μm or 200/300 μm) and 160-degree arc length were implanted. Changes in uncorrected distance visual acuity, best-corrected distance visual acuity, refractive outcomes, corneal astigmatism, and maximum keratometry readings were recorded before and after surgery. The study cohort consisted of 82 patients (104 eyes) with a mean age of 31.2 ± 10 years. At 3 months, ICRS implantation significantly improved uncorrected and corrected visual acuities from 0.82 to 0.46 (logarithm of the minimum angle of resolution [LogMAR]) and from 0.31 to 0.21 (LogMAR), respectively (P < 0.001). The mean spherical error reduced from -1.74 diopters (D) to -0.90 D (P < 0.001), and the mean cylindrical error reduced from -4.22 D to -2.01 D (P < 0.001). The manifest refraction spherical equivalent reduced from -3.85 D to -1.91 D (P < 0.001). All topographic parameters were reduced, including maximum keratometry (53.6 D vs. 50.3 D) and keratometric astigmatism (-4.6 D vs. -2.2 D) (P < 0.001). The Keraring AS provides a new, apparently safe, and effective means of improving visual acuity and reducing the refractive error and mean keratometry in eyes with asymmetric keratoconus.

Possibilities of Intralamellar Keratoplasty in Rehabilitation of Keratoconus Patients

Keratoconus is one of the topical problems in modern ophthalmology. Among the currently used treatment methods is intralamellar keratoplasty that utilizes allomaterials or homotransplants. The surgery technique has obvious advantages over penetrating and deep anterior lamellar keratoplasty. There is no risk of tissue incompatibility, the recovery period is shorter, and prolonged use of corticosteroids is not necessary. In recent years, technological development has made the application of femtosecond laser a standard procedure for various surgical interventions on the cornea, particularly for creation of intrastromal tunnels and corneal bags. This article presents an analysis of the modern literature data about different intralamellar keratoplasty techniques for treatment of keratoconus. The described techniques show its great clinical possibilities, especially the intrastromal keratoplasty variant with implantation of biological tissues. One of such techniques was developed and tried by a group of specialists at Research Institute of Eye Diseases in 2014. It involves recovery of corneal thickness in the ectatic area by intralamellar transplantation of a layered transplant of adequate size, which acts as a bandage. The surgery simultaneously affects the stabilization action, corrects refractive errors and eliminates the structural changes; it was accordingly named bandage therapeutic-optical keratoplasty (BTOK). The indication for its usage is progressing keratoconus in stage II–III patients. Among the described outcomes are cease of the disease progression in long-term follow-up, improvement of corrected and uncorrected visual acuity. The foreign analogue of the technique is Corneal Allogenic Intrastromal Ring Segments (CAIRS) by Jacob S. et al. His study included 20 patients with stages I to IV keratoconus; all patients undergone corneal cross-linking as the first stage, then they had CAIRS implanted into the intrastromal tunnels prepared with femtosecond laser. In both methods, the authors point at the improvement of corrected and uncorrected visual acuity. None of the patients had implant dislocation or keratoconus progression during the follow-up period.

Modification of the Intrastromal Ring Position according to Postimplant Visual and Refractive Failure: Report of Two Cases

Objective The following report presents the adaptation of an existing technique of intrastromal corneal ring (ICRS) implantation enabling repositioning of the ring position postoperatively to manage a refractive failure in two patients with keratoconus. MethodsIn two cases, KeraRing and Ferrara nomograms had suggested different ring positions. To manage with the differences between the two nomograms, a longer corneal tunnel was created followed by the classic intervention to move the ring through the initial intrastromal corneal tunnel according to the topographic values. Once the first ring position has failed, the ring segment was repositioned along the longer corneal tunnel according to the postoperative outcome. Results Significant improvement in both cases was observed in the best corrected visual acuity (BCVA), uncorrected visual acuity (UCVA), and root mean square (RMS) measured with Scheimpflug imaging (Pentacam; Oculus GmBH, Wetzlar, Germany). The participants were followed for one year. Conclusion In patients with keratoconus which exhibit significant differences between KeraRing and Ferrara nomograms, a longer tunnel should be created to enable repositioning of the ring postoperatively if necessary, to avoid extracting the ring or changing it.

THE USE OF DIGITAL MARKING DEVICE WHEN PERFORMING FEMTOSECOND LASER INTRASTROMAL KERATOPLASTY WITH IMPLANTATION OF INTRASTROMAL SEGMENTS

The aim of the study is to assess the practical significance of the use of the digital marking device «VERION™ Image Guided System» in the technology of intrastromal keratoplasty using a femtosecond laser. Material and methods. According to the developed method, 35 eyes of 27 patients with a diagnosis of keratoconus of the 2nd degree were operated. The median age was 26 years. Formation of intrastromal tunnels was performed using «Femto LDV Z8» femtosecond laser («Ziemer», Switzerland), the laser was centered in strict accordance with the markings obtained by the digital marking device «VERION™ Image Guided System» («Alcon», USA). During the implantation of the segment, this device was also used for its precise positioning in the tunnel. Setting the projection of the required axis, the surgeon intraoperatively to visualize the label that corresponds to the exact position of the end of the segment in the intrastromal tunnel, and carried out precise positioning of the intrastromal segments. R esults. When performing operations using the indicated method, it was revealed that the patient’s eye at the aplanation stage of a femtosecond laser has a tendency to rotate and decentralize. Minor decentralizations relative to the pupil center were corrected by the displacement of the intrastromal tunnel pattern in the laser working program along the x-axis by 0.1 ± 0.05 mm, along the y-axis by 0.1 ± 0.04 mm. In patients in the postoperative period there was an increase in uncorrected and corrected visual acuity. By 3 months after the operation, functional parameters and keratometric data stabilized: visual acuity without correction and with maximum correction increased to 0.5 ± 0.16 and 0.7 ± 0.12, respectively, keratometry of flat and steep axis declined to 44.3 ± 1.4 and 50,8 ± 3,2 diopters, respectively. Conclusions. It was found that the applanation of the femtosecond laser aperture on the surface of the conical cornea leads to the rotation of the eye by an average of 9°. The use of femtosecond laser for forming the intrastromal tunnels in the conduct intrastromal keratoplasty requires mandatory marking of the cornea meridian the corresponding to the axis of the cutout for laser centration. Methodology of Verion-assisted femtosecond laser intrastromal keratoplasty allows to position the segments with high precision in accordance with a preoperative calculation that provides high clinical and functional results.

Intraoperative Optical Coherence Tomography-Guided Femtosecond Laser-Assisted Deep Anterior Lamellar Keratoplasty.

To describe the feasibility and outcomes of intraoperative optical coherence tomography (OCT)-guided, femtosecond laser-assisted deep anterior lamellar keratoplasty in which the lamellar and tunnel cuts were completed by laser. The Ziemer Z8 system was used to scan the corneas intraoperatively and guide the stromal lamellar and tunnel cuts created by the laser. Thirty porcine eyes and 3 human cadaver globes were used to evaluate the accuracy of laser-created intrastromal tunnels and the feasibility of achieving big-bubble pneumatic dissection. The tunnel distance above the Descemet membrane (Dt-dm) was set at 100 and 130 μm, and the accuracy of laser cut was assessed by anterior segment OCT and histological sections. Fourteen patients with keratoconus or corneal scars were then included to evaluate the clinical outcomes. The deviation from the targeted Dt-dm was 5.5% to 8.6% and 0.7% to 9.8% for the 100 and 130 μm groups, respectively. The achieved thickness had a significantly and positively strong correlation with the targeted thickness (r = 0.86; P < 0.001). In all cases, the anterior stromal lamella was removed without difficulty, except in the patients with corneal scars in whom some remaining stromal fiber attachments were observed. A type 1 big bubble was successfully achieved in all patients. We present the accuracy and clinical outcomes of femtosecond laser-assisted, intraoperative OCT-guided deep anterior lamellar keratoplasty, in which controlled lamellar and tunnel cuts at desired depths were performed by laser in one step, and a successful big bubble was achieved.

Effects of Preoperative Topometric Indices on Visual Gain After Intracorneal Ring Segment Implantation For Keratoconus.

To assess the corneal topometric parameters that can be predictive for better visual gain after intracorneal ring segment (ICRS) implantation in eyes with keratoconus. A total of 42 eyes of 32 patients who underwent ICRS implantation at Dokuz Eylul University, Deparment of Ophthalmology, Cornea Divison were included. Changes in uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive errors, and corneal topometric indices measured using Scheimpflug topography (Pentacam, Oculus) were evaluated retrospectively. After creation of intrastromal tunnels of 5.01±0.03 mm inner diameter, 5.71±0.03 mm outer diameter and at 384.21±34.12 μm depth, 1 or 2 ICRS of 150 to 350 µm thickness and 90 to 210° arc length were implanted. Preoperative UDVA of 0.09±0.10 and CDVA of 0.29±0.14 Snellen lines improved postoperatively to 0.42±0.26 and 0.62±0.24, respectively (P<0.001 for both). Preoperative spherical equivalent of -6.35±4.58D and refractive astigmatism of -5.89±2.40D decreased to -3.59±3.86 and -2.25±1.66D, retrospectively (P<0.001 for both). Strong negative correlations were detected between preoperative mean simulated keratometry (SimKavg)/index of surface variance (ISV) and changes in UDVA/CDVA (P<0.01, for all). Postoperative change in ISV was positively correlated with thicknesses of implanted rings. Change in topographical keratoconus classification was positively and change in index of vertical asymmetry was negatively correlated with number of implanted rings (P<0.05 for all). Preoperative ISV value seems to be beneficial in predicting visual gain after ICRS implantation, in addition to SimKavg. Future work on new nomograms for ICRS selection that include ISV, besides refractive, topographic, and cone location data, is warranted.

Effect of intracorneal ring segment implantation on corneal asphericity.

To evaluate the visual, refractive and corneal asphericity changes after intrastromal corneal ring segment (ICRS) implantation for visual rehabilitation of keratoconus. A total of 42 eyes of 32 patients were included. After creation of intrastromal tunnels of 5.01±0.03 mm inner diameter, 5.71±0.03 mm outer diameter and at 384.21±34.12 µm depth, 1 or 2 ICRS of 150-300 µm thickness and 90°-210° arc length were implanted. Changes in uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive errors, mean simulated keratometry readings (SimKavg), anterior and posterior corneal asphericity values (Qant and Qpost, respectively) measured with Scheimpflug topography were evaluated retrospectively. There was a significant improvement in UDVA and CDVA, along with a significant decrease in refractive spherical equivalent (SE), cylinder and SimKavg postoperatively (P<0.001 for all). Mean Qant increased from -1.06±0.48 to -0.57±0.58 postoperatively (P<0.001). Change in mean Qpost was insignificant (P=0.92). Postoperative changes in UDVA and CDVA were not correlated with the postoperative changes in SE and cylinder (P>0.05 for all); but were correlated with the preoperative SimKavg and Qant values (P<0.001 for all). ICRS implantation seems to approximate the anterior corneal asphericity of "advanced prolate" shape to "optimal prolate" shape and an "ideal Q value" of -0.46; which may have a role in improved UDVA and CDVA postoperatively, besides decreased refractive cylinder values.

Прочностные характеристики роговицы кролика после интрастромальной имплантации различных имплантов с применением фемтосекундного лазера

Purpose. Comparative experimental study of the effect of the implantation of various intrastromal implants using a femtosecond laser (FSL)on the strength properties of the rabbit cornea. Material and methods . The experimental work was performed on 24 corneas of isolated eyes of 12 rabbits enucleated 1 month after the slaughter. All eyes were divided into 4 groups, depending on the method of operation. Formation of intra-stromal pockets (IP) and tunnels (IT) was performed using the FSL Femto Visum. The eyes of rabbits with intact corneas were included into the first control group. In the group 2, the intrastromal segment 350° was implanted into the IT. In the group 3,the MyoRing was implanted into the IP. In the group 4, the intrastromal closing ring with a «lock» was implanted into the IT. Results. After the implantation of intrastromal implants in comparison with the control group it was noted that the strength of the examined cornea of rabbits was increased to break. The greatest increase in the strength properties of the rabbit cornea was observed after the implantation of the intrastromal closing ring with a «lock» in comparison with the implantation of the intrastromal segment of 350° and the MyoRing. Conclusions. Implantation of intrastromal rings and segments leads to an increase in the strength properties of the cornea. Implantation of an intrastromal closing ring with a «lock» leads to the greatest increase in the strength properties of the cornea compared with the implantation of the intrastromal segment of 350° and the MyoRing.

Strength properties of rabbit cornea after femtosecond laser keratoplasty with and without different intracorneal implants

to conduct a comparative experimental study of the effect of the use of intracorneal implants during femtosecond laser-assisted intrastromal pocket (IP) and intrastromal tunnel (IT) formation on the strength properties of the cornea. The experimental study was performed on 24 corneas of 12 rabbit eyes enucleated 1 month after slaughtering. All eyes were divided into 6 groups according to the method of operation. IP and IT were created with IntraLase FS 60 kHz femtolaser. Group 1 (control group) consisted of rabbit eyes with intact corneas. In group 2 corneas, intrastromal tunnels were formed, in group 3 - intrastromal pockets, and in group 4 - intrastromal tunnels with 2 intracorneal segments (ICS). In groups 5 and 6, intrastromal pockets, each supplemented with an intrastromal ring, were created at the depth of 62-72% and 80% of pachymetry readings from the 5.0-mm optical zone, respectively. Higher voltage had to be applied to stretch the samples from group 2 as compared to those from groups 3 and 6. Distribution of the Young's modulus of the test corneas agreed with voltage distribution in the study groups. IP was associated with greater reduction in corneal biomechanical stability as compared with IT. Ring implantation into an IP yielded a more pronounced increase in the strength properties of the cornea than ICS implantation into an IT. The result was also more favorable at greater depths of intrastromal ring implantation.