Intrastromal Keratoplasty Research Articles

Advances in the research of femtosecond laser-assisted lenticule intrastromal keratoplasty for the correction of hyperopia

Lenticule intrastromal keratoplasty (LIKE) was introduced clinically in the 1980s as a refractive surgery. With the advancements of femtosecond laser, LIKE has been significantly revitalized. Currently, femtosecond laser-assisted LIKE has been demonstrated to be a safe and effective surgical procedure to correct hyperopia, but the predictability is still a major limitation. In this article, we review the history, procedures, influencing factors of predictability and challenge of LIKE to provide reference for clinical practice of femtosecond laser-assisted LIKE.

Интраоперационная профилактика децентрации роговичного кольца в ходе интрастромальной имплантации при центральном кератоконусе

Original article Intraoperative prevention of corneal ring decentration during intrastromal implantation for central keratoconus A.V. Tereshchenko, E.N. Vishnyakova, I.G. Trifanenkova, S.K. Demyanchenko S. Fyodorov Eye Microsurgery Federal State Institution, Kaluga Branch, Kaluga, Russian Federation Medical Institute of Kaluga Tsiolkovski State University, Kaluga, Russian Federation Purpose. To develop a method for intraoperative prevention of decentration of the corneal ring manufactured by NEP Eye Microsurgery LLC during intrastromal implantation for stage 2 central keratoconus. Material and methods. This work included 5 patients (6 eyes) from 32 to 42 year old diagnosed with stage 2 central keratoconus in combination with high myopia, who required implantation of rings manufactured by NEP Eye Microsurgery LLC from 200–250 microns with an internal diameter of 5 mm. The parameters of the intrastromal ring were calculated using the data from nomograms for MyoRing rings and nomograms for calculating intrastromal segments for the spherical component. A femtosecond laser, Femto LDV Z8 (Ziemer, Switzerland) was used to form an intrastromal channel. Capsulorhexis program for centering on the visual axis was used to perform digital marking of the cornea using the Verion system. Results. In 6 months, in all cases there was an increase in visual acuity, a decrease in the spherical and cylindrical components of refraction, a decrease in keratometry data, and the thickness of the cornea remained stable. All patients had a marked decrease in keratometric parameters. Keratotopography results had a specific appearance, corresponding to the central location of the ring. Not a single case of ring displacement or decentration was identified. Conclusion. Developed technique ensures precision implantation of an intrastromal corneal ring with precise centering along the visual axis, reducing risk of decentration of the ring in the postoperative period. Further studies are needed on larger clinical material and over a longer observation period. Key words: primary corneal ectasia, keratoconus, intrastromal keratoplasty, intrastromal corneal ring

Uneven Corneal Epithelial Redistribution After Femtosecond Laser-Assisted Lenticule Intrastromal Keratoplasty in Correcting Moderate-to-High Hyperopia.

To evaluate the characteristic of corrective epithelial thickness after femtosecond laser-assisted lenticule intrastromal keratoplasty (LIKE) to correct moderate-to-high hyperopia. The prospective case series study of the LIKE procedure was performed to correct moderate-to-high hyperopia. The epithelial thickness map was generated by anterior segment optical coherence tomography (AS-OCT) in the corneal central 9-mm zone. Keratometry and corneal higher order aberrations were analyzed by Pentacam (Oculus Optikgeräte GmbH) preoperatively and postoperatively. In the 26 eyes of 13 participants who underwent the LIKE procedure for moderate-to-high hyperopia, the attempted spherical equivalence (SEQ) was +6.50 ± 1.09 diopters (D). Compared to the preoperative epithelial thickness maps, the postoperative epithelial thickness had become significantly thinner in the central 5-mm zone; the difference was 6 to 7 µm. The paracentral epithelium performed nonuniform remodeling; the thinnest epithelial thickness was located in the inferotemporal section, which has the greatest difference from the superonasal; the difference between these two was approximately 3 µm. Through correlation analysis, it was found that the sections with thinner epithelium were significantly related to corneal curvature and corneal vertical coma. The LIKE procedure can be used to correct moderate-to-high hyperopia. This study further indicated the epithelial remodeling characteristic after the LIKE procedure: the central and paracentral corneal epithelial thickness becomes thinner, and the epithelial thickness distributes non-uniformly, which may be the important factor of the postoperative curvature asymmetric distribution and induction of corneal vertical coma. [J Refract Surg. 2024;40(5):e321-e327.].

Lenticule Intrastromal Keratoplasty for the Correction of Iatrogenic High Hyperopia.

The aim of this study was to evaluate the safety, efficacy, and predictability of lenticule intrastromal keratoplasty (LIKE) for the correction of iatrogenic high hyperopia. Three patients (4 eyes) were referred to our department because of overcorrection of myopia induced by femtosecond laser-assisted in situ keratomileusis. All eyes exhibited hyperopia (between +4.00 and +8.00 D) and thin corneas ranging from 307 to 378 μm. Because of the regression of the use of laser ablation to correct high hyperopia and thin corneas, we initially adopted LIKE to correct iatrogenic high hyperopia in all 4 eyes. The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, corneal topography, and anterior segment optical coherence tomography findings were recorded during each follow-up evaluation. No postoperative complications, such as interface haze and opacification, were observed in the 4 eyes during each follow-up evaluation, with an average follow-up of 9.50 months. All eyes had significantly improved UDVA postoperatively. A total of 3 eyes achieved an UDVA of 20/25 or better while the other 1 eye had an UDVA of 20/40 postoperatively. In addition, 2 of the 4 eyes had a postoperative UDVA equal to or better than preoperative CDVA. No eyes lost any CDVA lines. All 4 eyes were within ±0.50 D of the spherical power (intended target of 0). The central corneal thickness and curvature of the anterior corneal surface in all 4 eyes increased postoperatively. Anterior segment optical coherence tomography revealed that the lenticule was transparent, with no wrinkles or offsets, during each follow-up evaluation. LIKE for the correction of iatrogenic hyperopia has good efficacy and safety. Although an extremely thin cornea after overcorrection may not be suitable for hyperopic laser enhancement, LIKE is a good choice because of its good predictability and ability to restore the normal corneal structure.

Интрастромальная фемтокератопластика с имплантацией роговичных сегментов в коррекции аберраций высшего порядка у пациентов с кератоконусом

Aim. To evaluate the potential of femtosecond laser assisted intrastromal keratoplasty (FLAIK) with implantation of corneal ring segments in the correction of higher order aberrations in patients with stage I–II keratoconus. Material and methods. 15 patients (14 men and 1 woman) were examined and treated surgically, in total of 17 eyes, with stage I and II keratoconus (according to the classification of Izmailova S.B., 2014). All patients underwent FLAIK with implantation of corneal ring segments. Results. The change in the estimated parameters at an average follow-up period of 4.7 months showed that after FLAIK with implantation of corneal ring segments, best corrected visual acuity increased statistically significantly (p < 0.05) in all cases and increased by an average of 0.29 ± 0.09. In addition, there was a statistically significant (p < 0.05) decrease in the total level of higher order aberrations by 1.5 times (by 0.69 ± 0.4 D), a decrease in the level of coma aberration by 1.7 times (by 0.74 ± 0.4 D), a decrease in the level of spherical aberration by 1.6 times (by 0.07 ± 0.12 D). Conclusions. FLAIK with implantation of corneal ring segments is an effective method for correcting higher-order aberrations in patients with keratoconus of stage I–II. FLAIK with keratoconus with implantation of corneal ring segments makes it possible to achieve a significant increase in BCVA in patients with stage I–II keratoconus. Key words: keratoconus, higher order aberrations, corneal segments, refractive surgery

Клинико-функциональные результаты модифицированной фемтолазерной рефракционной аутокератопластики у пациентов с кератоконусом

Purpose. To analyze the clinical and functional results of modified femtolaser refractive autokeratoplasty and evaluate its effectiveness in patients with keratoconus during a follow-up period of 36 months. Material and methods. The study included 24 patients (13 men and 11 women) diagnosed with stage 2 keratoconus according to the Amsler, 1998 classification. The age of the patients ranged from 25 to 37 years (mean 31±6 years). Taking into account the initial parameters of the spherical and cylindrical components, as well as biometric parameters, which indicated the deliberate ineffectiveness of intrastromal keratoplasty (ISKP) in this group, all patients were performed femtolaser refractive autokeratoplasty (FRAK) according to a modified technique using a Femto LDV Z8 femtolaser unit (Ziemer, Switzerland). Results. An analysis of the clinical and functional results of the modified FRAK technique for topographically centrally located keratoconus showed that this technology provides a stable refractive effect in patients with stage 2 keratoconus during a follow-up period of 36 months. Performing personalized FRAK according to indications provides an increase in corrected visual acuity already in the early postoperative period with a tendency to further increase an average up to 0,46±0,08 by 36 months after surgery, as well as stable state of the ecstatic process throughout the entire follow-up. Conclusion. The modified FRAK technology is effective and can be successfully used in the early stages of keratoconus in cases with initial low visual acuity and axial myopia. Key words: keratoconus, femtolaser refractive autokeratoplasty

Visual outcomes and corneal densitometry after allogenic and autologous lenticule intrastromal keratoplasty for the correction of moderate-to-high hyperopia.

This study aimed to evaluate the visual outcomes and corneal densitometry (CD) after allogenic lenticule intrastromal keratoplasty (AL-LIKE) and autologous lenticule intrastromal keratoplasty (AU-LIKE) for the correction of moderate-to-high hyperopia. Ten subjects (14 eyes) underwent AL-LIKE and eight (8 eyes) underwent AU-LIKE. Patients were examined preoperatively and 1 day, 1 month, and 6 months postoperatively. The visual outcomes and CD for both surgical methods were evaluated. No postoperative complications were observed with either method. The efficacy index was 0.85±0.18 and 0.90±0.33 in the AL-LIKE and AU-LIKE groups, respectively. The safety indices were 1.07±0.21 and 1.25±0.37 in the AL-LIKE and AU-LIKE groups, respectively. The CD values of the anterior, central, and posterior layers in the AL-LIKE group increased significantly at 1 day postoperatively (all P < 0.05). The CD values of the anterior and central layers remained significantly higher than the preoperative values at 6 months postoperatively (all P < 0.05). The CD values of the anterior layer in the AU-LIKE group increased significantly 1 day postoperatively (all P < 0.05) and decreased to preoperative values (all P > 0.05) 1 month postoperatively. Both AL-LIKE and AU-LIKE exhibit good efficacy and safety in correcting hyperopia. However, AU-LIKE may have a smaller affected area and faster recovery time than those associated with AU-LIKE related to changes in corneal transparency.

Changes in the posterior corneal surface after femtosecond laser-assisted lenticule intrastromal keratoplasty (LIKE) performed into a pocket (SMI-LIKE) or under a flap (FS-LIKE)

BackgroundTo compare the changes in posterior corneal surface after small-incision lenticule intrastromal keratoplasty (SMI-LIKE) and femtosecond laser-assisted lenticule intrastromal keratoplasty (FS-LIKE) for hyperopia correction.MethodsIn this prospective comparative randomized study, 23 eyes with hyperopia were recruited. Eyes were categorized into two groups—SMI-LIKE group (11 eyes) and FS-LIKE group (12 eyes). Lenticules from myopia small incision lenticule extraction were implanted into a pocket (SMI-LIKE group) or at a depth of 100 µm under a flap (FS-LIKE group). Posterior corneal elevations in the center, mid-periphery, and periphery, as well as mean keratometry of the posterior corneal surface (Kmb) were measured using a Pentacam over a three-month follow-up.ResultsAll surgeries were completed successfully and no complications occurred. At one day postoperatively, there was a slight backward change with SMI-LIKE and a forward change with FS-LIKE in the central region of the posterior corneal elevation. Conversely, the peripheral area showed forward displacement in SMI-LIKE and an apparent backward change in FS-LIKE. The mid-peripheral regions manifested a backward change after the procedure throughout the entire follow-up in both groups. Kmb exhibited flattening at one month postoperatively and subsequently returned to its original level at three months after SMI-LIKE while in FS-LIKE, Kmb steepened after lenticule implantation with a significant change noted at one day postoperatively (P = 0.001).ConclusionsPosterior corneal surface after SMI-LIKE and FS-LIKE exhibited different change patterns in various corneal regions, with the most prominent change occurring at one day postoperatively during the three-month follow-up.Trial registration: Chinese Clinical Trial Registry: ChiCTR-ONC-16008300. Registered on Apr 18th, 2016. http://www.chictr.org.cn/edit.aspx?pid=14090&htm=4

Digital light processing-bioprinted poly-NAGA-GelMA-based hydrogel lenticule for precise refractive errors correction

Refractive disorder is the most prevalent cause of visual impairment worldwide. While treatment of refractive errors can bring improvement to quality of life and socio-economic benefits, there is a need for individualization, precision, convenience, and safety with the chosen method. Herein, we propose using pre-designed refractive lenticules based on poly-NAGA-GelMA (PNG) bio-inks photo-initiated by digital light processing (DLP)-bioprinting for correcting refractive errors. DLP-bioprinting allows PNG lenticules to have individualized physical dimensions with precision achievable to 10 µm (μm). Material characteristics of PNG lenticules in tests included optical and biomechanical stability, biomimetical swelling and hydrophilic capability, nutritional and visual functionality, supporting its suitability as stromal implants. Cytocompatibility distinguished by morphology and function of corneal epithelial, stromal, and endothelial cells on PNG lenticules suggested firm adhesion, over 90% viability, phenotypic maintenance instead of excessive keratocyte-myofibroblast transformation. In-vitro immune response analyzed by illumina RNA sequencing in human peripheral blood mononuclear cells indicated that PNG lenticules activated type-2 immunity, facilitating tissue regeneration and suppressing inflammation. In-vivo performance assessed using intrastromal keratoplasty models in New Zealand white rabbits illustrated that implantation of PNG lenticules maintained stable optical pathway, induced controlled stromal bio-integration and regeneration, avoided complications such as stromal melt, interface scarring, etc, but exerted no adverse effects on the host. Postoperative follow-up examination on intraocular pressure, corneal sensitivity, and tear production remained unaffected by surgery up to 1-month post-implantation of PNG lenticules. DLP-bioprinted PNG lenticule is a bio-safe and functionally effective stromal implants with customizable physical dimensions, providing potential therapeutic strategies in correction of refractive errors.

Intracorneal Implantation of 3D Bioprinted Scaffolds Containing Mesenchymal Stromal Cells Using Femtosecond-Laser-Assisted Intrastromal Keratoplasty.

Injury of the cornea is a complex biological process. Regeneration of the corneal stroma can be facilitated by the presence of mesenchymal stromal cells (MSCs) and application of tissue equivalents. A new tissue-engineering strategy for corneal stroma regeneration is presented using cellularized 3D bioprinted hydrogel constructs implanted into organ cultured porcine corneas using femtosecond laser-assisted intrastromal keratoplasty. The ex vivo cultured, MSC-loaded 3D bioprinted structures remain intact, support cell survival, and contain de novo synthesized extracellular matrix components and migrating cells throughout the observation period. At day 14 postimplantation, the cellularized tissue equivalents contain few or no cells, as demonstrated by optical coherence tomography imaging and immunofluorescent staining. This study successfully combines a laboratory-based method with modern, patient-care practice to produce a cell-laden tissue equivalent for corneal implantation. Optimal bioink composition and cellularization of tissue equivalents are essential in fine-tuning a method to promote the current technique as a future treatment modality.

Comparison of Visual Outcomes and Higher-order Aberrations Between FS-LASIK and SMI-LIKE for Moderate to High Hyperopia: A 2-year Result.

The aim of the study was to evaluate and compare the long-term visual outcomes and higher-order aberrations (HOAs) between femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and small-incision lenticule intrastromal keratoplasty (SMI-LIKE) in the correction of moderate to high hyperopia. In this study, 16 subjects (20 eyes) underwent FS-LASIK and 7 subjects (10 eyes) underwent SMI-LIKE. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, mean keratometry (Km), anterior asphericity (Q), and HOAs preoperatively and 2 years postoperatively were obtained in both procedures. The efficacy indices of the FS-LASIK group and the SMI-LIKE group were 0.85 ± 0.14 and 0.87 ± 0.17, respectively. The safety indices of the FS-LASIK and SMI-LIKE groups were 0.99 ± 0.15 and 1.08 ± 0.24, respectively. No significant difference in safety index or efficacy index was found between the FS-LASIK and SMI-LIKE groups (all P > 0.05). The correlation coefficient of the attempted versus achieved spherical equivalent postoperatively was 0.69 (P < 0.01) and 0.89 (P < 0.01) in the FS-LASIK group and SMI-LIKE groups, respectively. The front Km, negative Q value, negative spherical aberrations (SAs), coma, and total HOAs significantly increased postoperatively in the 2 groups (P < 0.05). The FS-LASIK group had greater changes in Q value and SA postoperatively than the SMI-LIKE group (P < 0.01). SMI-LIKE had similar safety and efficacy to FS-LASIK in the correction of moderate to high hyperopia. However, SMI-LIKE may equip better visual quality postoperatively for its lower Q value and SA changes than FS-LASIK.

Фемтолазерная интрастромальная имплантация роговичных сегментов с использованием цифрового разметочного устройства в хирургическом лечении кератоконуса

Purpose. To develop a technology for topographically oriented positioning of intrastromal segments during femtolaser intrastromal keratoplasty (ISKP) in patients with keratoconus using a digital marking device and to evaluate its clinical efficacy. Material and methods. The study included 102 patients (102 eyes) with stage II keratoconus according to the Amsler – Krumeich classification. According to the type of surgery performed, the patients were divided into groups: the main group (53 patients (53 eyes) – femtolaser ISKP with implantation of polymethyl methacrylate (PMMA) segments was performed using a digital marking device and taking into account the cyclotorsion angle; control group (49 patients (49 eyes)) – femtolaser ISKP with implantation of PMMA segments was performed using the standard method (marking the geometric center of the cornea using the Purkenier – Sanson reflex without taking into account cyclotorsion). Results. The indices of the «success» index, the calculated vector of astigmatism close to the actual postoperative one and a smaller value of the vector of the difference in the axis of astigmatism, confirmed the higher accuracy of ISKP with the use of a digital marker compared to the standard one. The mean values of visual acuity and best corrected visual acuity 12 months after surgery in the main group were 0.58 ± 0.05 and 0.80 ± 0.04, respectively, and in the control group they were at the level of 0.49 ± 0.06 and 0.68 ± 0.05 respectively. After the surgery, there was a statistically significant decrease in the mean values of astigmatism: the main group – after 3 months to -1.8 ± 0.15 diopters (p &lt;0.05), after 6 months – by another 1.7 ± 0.20 diopters (p &lt;0.05); the control group – after 3 months to -2.43 ± 0.17 diopters (p &lt;0.05), after 6 months – by another 2.42 ± 0.17 diopters. Conclusion. The proposed optimized ISKP technique with the use of a digital marking device provides precise positioning of segments during the surgical treatment of keratoconus and allows to obtain higher acuity of vision and best corrected visual acuity, as well as to correct corneal astigmatism more efficiently than using standard technique. Key words: surgical treatment of keratoconus, femtolaser intrastromal implantation of corneal segments, digital marking device.

Possible use of corneal lenticule in surgery of corneal diseases (literature review)

In this review, we analyzed the domestic and foreign literature on the use of corneal lenticula obtained by keratorefractive surgery using the SMILE technology (SMall Incision Lenticula Extraction). Research is being actively carried out on the use of a lenticular tissue for refractive purposes: for the correction of hyperopia (LIKE – Lenticular Intrastromal Keratoplasty), for the correction of presbyopia (PEARL – PrEsbyopic Allogenic Refractive Lenticule). A significant amount of works are devoted to the use of lenticular tissue for the treatment of keratectasias of various origins. For example, a number of authors for the treatment of keratoconus suggest implantation of a lenticule into the recipient’s corneal pocket formed by a femtolaser (SLAK – Stromal lenticule addition keratoplasty). Clinical cases of combined treatment are described: implantation of a lenticule and corneal intrastromal segments for the treatment of corneal pellucid degeneration. A large number of works are devoted to the use of lenticules for tectonic coverage of ulcerative defects, marginal thinning in Mooren’s ulcer. Several clinical cases of the use of a corneal lenticule to cover a deep corneal defect in recurrent pterygium are described. This review also included articles on the storage and decellularization of corneal lenticules. The analyzed articles show a wide area of application of the corneal lenticule; however, more research is required in each of the areas of application, and it is also necessary to solve the problem of procurement and storage of lenticular tissue.

Intra‐corneal implantation of 3D bio‐printed mesenchymal stem cells using femtosecond‐laser‐ assisted intrastromal keratoplasty

AbstractPurpose: Regeneration of the cornea due to trauma or disease is a complex biological process, involving a delicate balance between cell differentiation, migration and a multitude of secreted factors and signalling molecules. We hereby present a tissue‐engineering technique as a possible first step towards getting a bench‐to‐bedside approach to assist corneal regeneration and ultimately, corneal transplantation.Methods: 3D extrusion‐based bioprinting and femtosecond laser‐assisted intrastromal keratoplasty (FLISK) were used in the study. Ex vivo cultured mesenchymal stem cells (MSCs) derived from adipose tissue, bone marrow and corneal stroma were bioprinted in a complex, collagen I‐containing hydrogel. The transparent, cell‐loaded nanocellulose and alginate‐based 3D constructs were then implanted into a pig cornea organ culture model. The 3D printed intrastromal constructs were first cultivated ex vivo, while the de novo extracellular matrix (ECM) synthesis and migration of cells was followed by optical coherence tomography and immunohistochemistry.Results: The ex vivo cultured, MSC‐loaded 3D bioprinted constructs supported cell survival and propagation for all three types of MSCs used. The transparency of the corneal stroma substitute was not compromised by the presence of MSCs in the bioprinted matrix. At day 14, the 3D‐bioprinted scaffolds appeared intact, as analysed by optical coherence tomography, while immunofluorescent staining using ECM and MSCs markers demonstrated the cellular presence in the constructs.Conclusions: Optimization of the bioink composition, cellular content and properties of the bioprinted material to be used in corneal transplantation and regeneration studies are essential in fine‐tuning the technique towards its clinical use.

Achieved Lenticule Diameter and Functional Optical Zone in Hyperopic Eyes After Lenticule Intrastromal Keratoplasty

To investigate achieved lenticule diameter (ALD) and functional optical zone (FOZ) following femtosecond laser-assisted lenticule intrastromal keratoplasty (FS-LIKE) or small incision lenticule intrastromal keratoplasty (SMI-LIKE). Small incision lenticule extraction (SMILE)-derived human lenticules were placed on the surface of a contact glass (CG) and model eye (ME). Ex vivo ALDs were assessed at different hydration times. The ALD and FOZ were obtained using optical coherence tomography and Scheimpflug tomography at 6 months after lenticule implantation. At 1 hour after hydration, lenticules achieved a slightly larger CG-loading ALD (6.63 ± 0.07 mm) and similar ME-loading ALD (6.53 ± 0.07 mm) as compared to a programmed optical zone (POZ) of 6.5 mm (P < .001). At 6 months after surgery, FS-LIKE with a POZ of 6.5 mm obtained an ALD of 6.20 ± 0.21 mm, which was larger than SMI-LIKE with a POZ of 6.64 mm (5.90 ± 0.14 mm, P = .001). The mean FOZ diameters were 5.33 ± 0.28 and 5.11 ± 0.14 mm for the FS-LIKE and SMI-LIKE groups, respectively (P = .022). The absence of significant differences in the ALD and FOZ among the different meridians indicated that the achieved lenticule and optical zone shapes were circular. An accurate lenticular size could be obtained from SMILE, and FS-LIKE could achieve a larger FOZ than SMI-LIKE, attributed to attaining a larger ALD. [J Refract Surg. 2022;38(12):791-796.].

Хирургическое лечение начальных стадий прогрессирующего кератоконуса у детей

Introduction. The review presents the current data on the methods of surgical treatment of the initial stages of keratoconus in children, the possible manifestation of keratoconus as one of the symptoms of undifferentiated connective tissue dysplasia, as well as possible methods of prevention of the disease progression. Purpose. To present current literature data regarding surgical treatment of the initial stages of progressive keratoconus in children. Material and methods. For the review the literature sources were searched through the abstract databases PubMed and Scopus for the period up to and including 2022 using the following key words: ICRS, corneal collagen crosslinking, Keratoconus, connective tissue dysplasia. A total of 51 articles relevant to the review topic were selected. Results. Numerous studies have confirmed the effectiveness of timely surgery for the initial stages of keratoconus in improving the anatomical and functional outcomes of treatment of various diseases. However, even timely and perfectly performed surgery for progressive keratoconus may have different consequences depending on the degree of connective tissue dysplasia. Conclusion. The performed analysis of the literature allows to claim that keratoconus in children should be considered as a pathology related to the disturbance of structures and organization of collagen matrix of the whole body. It is also necessary to note that treatment tactics should be determined individually and be based on the age and values of comprehensive special examination of each particular child. Key words: keratoconus, keratoconus in children, corneal collagen cross-linking, intrastromal keratoplasty, corneal segments, connective tissue, undifferentiated connective tissue dysplasia, cornea, collagen

Comparison of clinical outcome of small-incision lenticule intrastromal keratoplasty and FS-LASIK for correction of moderate and high hyperopia.

To compare the clinical outcome of small-incision lenticule intrastromal keratoplasty (sLIKE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for correction of moderate and high hyperopia. A case-controlled clinical study was performed. Twenty right eyes of 20 moderate and high hyperopia patients underwent sLIKE (sLIKE group) and 22 right eyes of 22 moderate and high hyperopia patients underwent FS-LASIK (FS-LASIK group) were enrolled in this study from October 2015 to October 2017. Visual acuity, refractive error, corneal thickness, and keratometry were compared between the groups before and 1y postoperatively. The postoperative uncorrected near visual acuity (UNVA) and uncorrected distance visual acuity (UDVA) were improved in the two groups. The UNVA reached J1 in 15 eyes (75.0%) in the sLIKE group and 5 eyes (22.7%) in the FS-LASIK group 1y after surgery (χ 2=11.476, P=0.001). The UDVA was equal or better than the preoperative CDVA in 16 eyes (80.0%) in the sLIKE group and 8 eyes (36.4%) in the FS-LASIK group, respectively (χ 2=8.145, P=0.004). No eyes lost any line of best-corrected visual acuity (BCVA) in either group. The amount of postoperative residual hyperopia in the sLIKE group was significantly less than in the FS-LASIK group (Z=-2.841, P=0.004). The postoperative keratometry and corneal thickness were significantly higher in the sLIKE group than in the FS-LASIK group (t=4.411, 10.279, P<0.001). The SRI and SAI of the sLIKE group were significantly higher than that in the FS-LASIK group. There was no statistically significant difference in mean decentration between the two groups. sLIKE has better visual and refractive outcome than FS-LASIK for correction of moderate and high hyperopia.

Comparison of Optical Zone Decentration Following FS-LIKE and SMI-LIKE for Correcting Hyperopia.

To investigate optical zone decentration following femtosecond laser-assisted lenticule intrastromal keratoplasty (FS-LIKE) or small incision lenticule intrastromal keratoplasty (SMI-LIKE) for correcting hyperopia. This study analyzed decentration values obtained from optical coherence tomography (OCT) and tangential topography difference maps of 23 eyes (18 patients) undergoing FS-LIKE (n = 12) or SMI-LIKE (n = 11) via the concentric centration method. Total higher order aberrations (HOAs) and component aberrations were measured preoperatively and 6 months postoperatively. The mean optical zone decentration was 0.27 ± 0.08 and 0.39 ± 0.16 mm for the FS-LIKE and SMI-LIKE groups, respectively (P = .039). A significant difference was noted in lenticule decentration between the two groups (0.18 vs 0.37 mm), whereas no significant difference was observed in stromal bed (pocket) decentration between the two groups (0.10 vs 0.12 mm). Six months after surgery, the spherical equivalent showed a reduction of 6.14 ± 2.44 and 6.10 ± 1.79 diopters (D) for the two groups, respectively (P = .971), whereas the surgically induced astigmatism was 0.68 ± 0.49 and 1.56 ± 0.78 D for the two groups, respectively (P = .004). Furthermore, induction of HOAs in the SMI-LIKE group was significantly larger than that in the FS-LIKE group (P = .013). FS-LIKE can yield improved treatment centration and less induction of total HOAs. [J Refract Surg. 2022;38(3):184-190.].

Toric Lenticule Implantation for Correction of Hyperopia and Astigmatism Following Small Incision Lenticule Intrastromal Keratoplasty With the Triple Marking Method.

To describe the first use of toric lenticule implantation with the triple marking method to correct hyperopia and hyperopic astigmatism following small incision lenticule intrastromal keratoplasty (SMI-LIKE). Five eyes of four patients with hyperopia (+5.25 to +9.50 diopters sphere) were included. Allogenic toric lenticules extracted using myopic small incision lenticule extraction were implanted and rotated into a femtosecond laser-created stromal pocket in hyperopic recipients with triple marking. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, manifest refraction, corneal topography, and Fourier-domain optical coherence tomography images were examined 6 months postoperatively. Six months after surgery, 4 eyes (80%) gained two or more lines of UDVA, and 1 eye (20%) had unchanged UDVA. No eyes lost any lines of CDVA. The spherical equivalent decreased from +6.23 ± 1.34 diopters (D) preoperatively to -0.35 ± 0.27 D postoperatively. The mean refractive astigmatism also decreased significantly from -2.15 ± 1.10 D preoperatively to -0.70 ± 0.21 D postoperatively. Of 5 treated eyes, 2 (40%) had postoperative astigmatism within ±0.50 diopters cylinder and 5 (100%) within ±1.00 diopters cylinder. Corneal topography showed a significant increase in the anterior surface keratometry value, whereas corneal astigmatism decreased from 2.62 ± 1.55 to 1.10 ± 0.44 D. Vector analyses suggested good predictability and efficacy for astigmatism correction. Implantation of toric lenticules following SMI-LIKE with the triple marking method is a feasible alternative for correcting hyperopia and hyperopic astigmatism, and the short-term results seem safe and stable. [J Refract Surg. 2022;38(2):82-88.].

Opto-functional results in keratoconus patients after intrastromal keratoplasty

Analysis of quantitative and qualitative characteristics of vision in patients with stage II and III keratoconus who underwent intrastromal allokeratoplasty. The study included 15 patients (15 eyes) with stage II-III KC (Amsler-Krumeich classification) aged 17 to 38 years old (28.8±6.2). All patients underwent intrastromal keratoplasty with implantation of an allograft in the form of a wide incomplete ring. The following parameters were assessed before and 6 months after surgery: distance VA with and without correction, near VA with and without correction, VA with glare effect, high-order aberrations (HOA), thickness of the tear film lipid layer, spatial contrast sensitivity (SCS) under photopic and mesopic conditions with light filters, reading speed. VA without correction increased from 0.15 to 0.7; with correction from 0.35 to 0.7. The glare effect with varying degrees of illumination did not affect VA either before or after surgery. Statistically significant changes were observed when comparing the aberrations «coma», «spherical», «trefoil» before and after the intervention, they became inverted. The thickness of the tear film lipid layer did not change significantly when comparing pre- and postoperative data. The use of light filters (orange, yellow) did not lead to significant changes in the VA and SCS under photopic and mesopic conditions. The use of a wide intrastromal allograft to correct deformity and stabilize the cornea in keratoconus improves the patients' quality of vision and visual performance.