Corneal reshaping: an experiment with a type I collagen-based vitrigel for remodeling porcine corneas / Remodelamento corneano: relato de um experimento com um vitrigel a base de colágeno tipo I para remodelamento de córneas porcinas

ABSTRACT Purpose: This study aimed to report an experiment designed to determine anatomical changes in porcine corneas following placement of a novel polymer implant into the cornea. Methods: An ex vivo porcine eye model was used. A novel type I collagen-based vitrigel implant (6 mm in diameter) was shaped with an excimer laser on the posterior surface to create three planoconcave shapes. Implants were inserted into a manually dissected stromal pocket at a depth of approximately 200 μm. Three treatment groups were defined: group A (n=3), maximal ablation depth 70 μm; Group B (n=3), maximal ablation depth 64 μm; and group C (n=3), maximal ablation depth 104 μm, with a central hole. A control group (D, n=3) was included, in which a stromal pocket was created but biomaterial was not inserted. Eyes were evaluated by optical coherence tomography (OCT) and corneal tomography. Results: Corneal tomography showed a trend for a decreased mean keratometry in all four groups. Optical coherence tomography showed corneas with implants placed within the anterior stroma and visible flattening, whereas the corneas in the control group did not qualitatively change shape. Conclusions: The novel planoconcave biomaterial implant described herein could reshape the cornea in an ex vivo model, resulting in the flattening of the cornea. Further studies are needed using in vivo animal models to confirm such findings.

RESUMO Objetivo: Relatar um experimento projetado para determinar alterações anatômicas em córneas porcinas após a colocação de um novo implante de polímero na córnea. Métodos: Foi utilizado olho de porco ex vivo. Um novo agente modelador biocompatível, de colágeno tipo 1, com 6mm de diâmetro foi moldado com excimer laser em sua face posterior, para criar três formatos planocôncavos. Os implantes foram inseridos dentro de um bolsão, dissecado manualmente, a 200 micrômetros (μm). Foram definidos três grupos de tratamento: grupo A (n=3), teve a profundidade máxima de ablação de 70 μm; o grupo B (n=3), profundidade máxima de ablação de 64 μm; e o grupo C (n=3), profundidade máxima de ablação de 104 μm, com buraco central. O grupo controle, D (n=3), foi incluído, com a criação do bolsão estromal, porém sem inserir o material. A avaliação desses olhos foi realizada por tomografia de coerência óptica (OCT) e por tomografia corneana. Resultados: A tomografia corneana mostrou uma tendência para diminuição da ceratometria média em todos os 4 grupos. A tomografia de coerência óptica mostrou córneas com implantes localizados no estroma anterior e aplanamento visível, enquanto as córneas não mudaram qualitativamente o formato no grupo controle. Conclusões: O novo implante de biomaterial planocôncavo descrito aqui foi capaz de remodelar a córnea em modelo de animal ex vivo, resultando no aplanamento corneano. Novos estudos são necessários usando modelos animais in vivo para confirmar tais achados.

Ten-year follow-up of corneal cross-linking and refractive surface ablation in patients with asymmetric corneal topography

Purpose: Compare the safety and efficacy of wavefront?guided photorefractive keratotomy (PRK) 6 months after cross?linking (CXL) to wavefront?guided PRK alone for refractive correction in patients with bilateral asymmetric corneal topography. Methods: Prospective randomized clinical trial with 16 patients (32 eyes). CXL with subsequent PRK after 6 months in one eye, and PRK alone was performed in contralateral eyes. The follow?up was 10 years. We analyzed visual outcomes, Scheimpflug topography, and corneal haze evaluation. Results: Eyes in the PRK group showed better results than in the CXL + PRK group. Mean postoperative CDVA was 0.044 logmar (SD, 0.073) in the PRK group and 0.1 logmar (SD, 0.21) in the CXL + PRK group, the mean sphere was + 0.21 (SD, 0.6) D in the PRK group and 0.87 (SD, 2.3) D in the CXL + PRK group, and mean SE was ?0.35 (SD, 0.65) D in the PRK group and 0.62 (SD, 2.32) D in the CXL + PRK group. In one patient, a steepening of 2.5 D and a thinning of 17 ?m occurred in PRK alone group. Two patients in the CXL + PRK group presented corneal haze. The overall complication rate was 18,75% (haze and ectasia). Conclusion: Non?simultaneous CXL and PRK procedures yielded good refractive results, but worse than those obtained with PRK alone. Although one patient in the PRK group developed corneal ectasia, the CXL + PRK group had a higher loss of vision lines, indicating less safety

Advances in mechanism and regulatory factors of corneal stromal repair / 国际眼科杂志(Guoji Yanke Zazhi)

Corneal stromal is an important structure to maintain corneal transparency. The corneal stroma can be injured by trauma, infection and surgery. Therefore, corneal stromal wound starts repair with phenotype changes in stromal cell, extracellular matrix remodeling and immune cells migration. The corneal scar was the leading cause of blindness worldwide, which can be caused by corneal stromal fibrosis from increased myofibroblasts and deposited extracellular matrix after sever damage. At present, corneal transplantation is the main treatment for corneal scar, which has limited therapeutic effect because of corneal donor shortage, surgical requirements and the risk of postoperative immune rejection. Recently, great progress has been made in the study of control mechanism of corneal stromal wound healing with various molecules, cells and tissues. This paper reviews the repair mechanism of corneal stromal injury and the regulation mechanism of cause of corneal injury, corneal structure and molecule factors towards corneal stromal injury. It aims at providing new ideas for exploring the mechanism of corneal stromal repair and regeneration, which is supposed to help prevent corneal scar clinically.

Effects of small leucine-rich proteoglycans on corneal transparency / 中华实验眼科杂志

Small leucine-rich proteoglycans (SLRPs) are necessary structural ingredients of the cornea, which are vital for the establishment and maintenance of corneal transparency.SLRPs are mainly located in the corneal stroma and can be divided into class Ⅰ, class Ⅱ, and class Ⅲ.The compensatory and cooperative interactions among SLRPs regulate the formation and assembly of stromal collagen fibrils, thereby maintaining the highly ordered arrangement of collagen fibrils, and establishing corneal transparency.Decorin and lumican are the main functional components of class Ⅰ and class Ⅱ SLRPs, respectively, and changes in their expression or abnormities in the structure of their core proteins affect the natural content and arrangement of other stromal extracellular matrix components, ultimately resulting in abnormal fibril formation, assembly, and arrangement, causing corneal opacity.SLRPs can regulate corneal wound healing and stromal matrix remodeling via binding to fibrotic molecules and their receptors, which provides bases for corneal diseases therapy and study of molecular mechanisms of corneal transparency.The bioactivities and the role of SLRPs in corneal transparency were reviewed in this article.

Effects of corneal epithelium and stroma on corneal epithelial basement membrane regeneration / 中华实验眼科杂志

Basement membranes (BMs) are highly specialized extracellular matrices, which widely exist in various tissues of the human body.Since BMs were discovered in the 19th century, the structures and functions of BMs have been gradually recognized.The corneal epithelial basement membrane (EBM) participates in the regulation of corneal scar formation by limiting the activation of fibrotic factors.After an injury, the formation and duration of corneal stromal fibrosis are determined by the degree of EBM injury and the speed of EBM regeneration.Corneal epithelium and stroma participate in the process of EBM regeneration.The rapid regeneration of corneal epithelium is beneficial to the assembly of the nascent EBM.Functional corneal stromal cells provide the rest assembly components for the nascent EBM.The regular surface of corneal stroma is beneficial to the continuous regeneration of EBM, which provides positions for stromal cells.This paper reviewed the understanding of BMs, the composition and function of EBM, the relationship between corneal EBM regeneration and corneal stroma remodeling, the influencing factors of EBM regeneration and related clinical treatment methods to discuss the influence of corneal epithelium and stroma on EBM regeneration.

Comparison of the preservation effect of DX solution and glycerin preservation solution on corneal stromal lens / 中华实验眼科杂志

Objective:To compare the preservation effect of DX preservation solution and glycerin preservation solution on the corneal stromal lens.Methods:Sixty intact corneal stromal lens samples were collected during femtosecond small incision lenticule extraction (SMILE) from 60 myopic eyes of 30 subjects at Qingdao Eye Hospital of Shandong First Medical University from February 2019 to May 2019.The samples were randomized into DX preserved 1-day group, DX preserved 1-week group, glycerin preserved 1-day group, glycerin preserved 1-week group and glycerin preserved 2-week group according to the different preservation methods, with 10 samples in each group.No intervention was done in the samples of the normal control group.Trypan blue staining was used to count the number of dead cells in the corneal stromal lens.The morphological structure of the corneal stromal lens was examined with an optical microscope, and its ultrastructure was observed under the transmission electron microscope.This study adhered to the Declaration of Helsinki.Written informed consent was obtained from each patient prior to any medical intervention.The study protocol was approved by an Ethics Committee of Qingdao Eye Hospital of Shandong First Medical University (No.2019-30).Results:The number of dead cells was (53.1±14.2), (50.8±9.8), (70.4±13.6) and (172.8±31.7) and (182.8±14.2) cells/field in the DX preserved 1-day group, DX preserved 1-week group, glycerin preserved 1-day group, glycerin preserved 1-week group and glycerin preserved 2-week group, respectively, showing a significant difference among the five groups ( F=16.37, P<0.05). There was no significant difference between the DX preserved 1-day group and 1-week group ( P>0.05). The number of dead cells was significantly less in the glycerin preserved 1-day group than that of the glycerin preserved 1-week group and glycerin preserved 2-week group, and the number of dead cells was significantly increased in the glycerin preserved 1-week group compared with the DX preserved 1-week group (all at P<0.05). The arrangement of collagen fibers of the corneal stromal lens was regular and the cells were intact in the normal control group, DX preserved 1-day group and DX preserved 1-week group.The tissue edema, bare cell nuclei and loose collagen fibers were found in the samples in the glycerin preserved 1-day group.The corneal stromal lens was compact and the collagen fibers were dense and the nuclei were intact in the DX preserved 1-day group and DX preserved 1-week group.The distribution of the cells was sparse and the cell structure was abnormal under the transmission electron microscope in various glycerin preserved groups. Conclusions:The structure of corneal stromal lens can be well preserved for one week by DX storage solution.The preservation effect of DX solution is better for fresh human corneal stromal lens than glycerin solution.

Use of viscoelastic substance for preventing Descemet's membrane rupture in deep anterior lamellar keratoplasty / Uso de substância viscoelástica na prevenção da ruptura da membrana de Descemet na ceratoplastia lamelar anterior profunda

ABSTRACT Purpose: This study aimed to investigate the effect of using a viscoelastic substance in Descemet's membrane rupture in "double bubble" deep anterior lamellar keratoplasty. Methods: The medical records and videos of surgeries of 40 patients who underwent surgery between January 2014 and July 2015 were retrospectively evaluated. The patients were divided into two groups: 20 patients whose perforation of the posterior stromal wall was performed without administration of any viscoelastic substance (group 1) and 20 patients whose perforation of the posterior stromal wall was performed with administration of viscoelastic substance onto the posterior stroma (group 2). The Descemet's membrane perforation rate was compared between groups. Results: Perforation of the Descemet's membrane was observed in 12 (60.0%) patients in group 1 and only three (15.0%) patients in group 2. This difference was statistically significant (p=0.003). Only one (5%) patient in group 2 had macroperforation during the procedure, and the surgery was converted to penetrating keratoplasty. Eleven (55.0%) patients in group 1 had macroperforation of Descemet's membrane, and surgeries were converted to penetrating keratoplasty. This difference between the groups was statistically significant (p=0.001). Conclusions: Administering a viscoelastic substance onto the posterior stromal side just before puncture is an effective method to decrease the risk of Descemet's membrane perforation in deep anterior lamellar keratoplasty.(AU)

RESUMO Objetivo: Investigar o efeito do uso de uma substância viscoelástica na ruptura da membrana de Descemet em casos de ceratoplastia lamelar anterior profunda em "bolha dupla". Métodos: Foram avaliados retrospectivamente prontuários e vídeos de cirurgias de 40 pacientes operados entre janeiro de 2014 e julho de 2015. Os pacientes foram divididos em dois grupos: 20 pacientes nos quais a parede posterior do estroma foi puncionada sem a colocação de nenhuma substância viscoelástica (grupo 1) e 20 pacientes nos quais uma substância viscoelástica foi aplicada sobre o estroma posterior ao ser puncionada a parede posterior do estroma (grupo 2). A taxa de perfuração da membrana de Descemet foi comparada entre os grupos. Resultados: Observou-se perfuração da membrana de Descemet em 12 casos (60,0%) no grupo 1 e em apenas 3 casos (15,0%) no grupo 2. Essa diferença foi estatisticamente significativa (p=0,003). Apenas um caso (5%) no grupo 2 teve macroperfuração durante o procedimento, sendo a cirurgia então convertida em uma ceratoplastia penetrante. Onze casos (55,0%) no grupo 1 tiveram macroperfuração da membrana de Descemet e essas cirurgias foram convertidas em ceratoplastias penetrantes. Essa diferença entre os grupos foi estatisticamente significativa (p=0,001). Conclusões: A aplicação de substância viscoelástica sobre o lado posterior do estroma logo antes da punção é um método eficaz para diminuir o risco de perfuração da membrana de Descemet na ceratoplastia lamelar anterior profunda.(AU)

Intraoperative complications and treatment in femtosecond laser small incision lenticule extraction / 中华实验眼科杂志

As a relatively new procedure, femtosecond laser small incision lenticule extraction (SMIIE) is still in its initial stage.Despite the safety, efficacy, predictability and stability it has showed in refractive error correction, there are still reports of intraoperative complications resulting in different clinical outcomes in SMILE.SMILE includes the production of lenticule by femtosecond laser, the separation and extraction of lenticule, and intraoperative complications may occur in every step.The production of the lenticule is completely dependent on the femtosecond laser, so complications related to femtosecond lasers are inevitable, such as suction loss, opaque bubble layer and black spots.Separation and extraction of the lenticule relies on the experience and surgical skills of surgeon, during which, torn corneal cap, difficult lenticule extraction, lenticule remnants, bleeding and lenticule decentration may occur.In this article, the categories, reasons, management and effects of intraoperative complications on outcome in SMILE were summarized to improve the ability of ophthalmologists to handle intraoperative incidents and enhance surgical safety.

Feasibility of cryopreservation of human corneal stromal lenticules / 中华实验眼科杂志

Objective:To observe the transparency and tissue structure changes of human corneal stromal lenticules after long-term cryopreservation and explore a simple and feasible method for long-term effective preservation of corneal stromal lenticules.Methods:Two hundred samples of intact human corneal stromal lenticules from 200 eyes were obtained during femtosecond laser small-incision lenticule extraction (SMILE) in Hainan Eye Hospital, Zhongshan Ophthalmic Center from 2013 to 2020.The samples were divided into 1-month, 24-month, 60-month and 80-month group and were stored in an ultra-low temperature freezer for 1, 24, 60 and 84 months respectively at -80 ℃ according to grouping, with 50 samples in each group.Transmittance of the corneal lenticules at wavelength of 300-800 nm was measured with an ultra-micro spectrophotometer and every lenticule was measured for 10 times with a 50 nm interval.The histomorphology and collagen fiber structure of the corneal lenticules were examined by hematoxylin-eosin staining and Masson staining, respectively.The arrangement of collagen fibers and ultrastructure changes of keratocytes in the samples were inspected with a transmission electron microscope.The apoptosis rate of keratocytes was determined by TUNEL staining.The study protocol was approved by an Ethics Committee of Hainan Eye Hospital at Zhongshan Ophthalmic Center (No.2013-003). This study complied with the Declaration of Helsinki.Written informed consent was obtained from each subject before surgery.Results:The corneal lenticules were clear and intact in all groups and no significant difference in the transmittance within 450-800 nm wavelength was seen among the 4 groups (all at P>0.05). Masson staining revealed that the collagen fibers in the lenticules were neatly arranged and tightly packed in the 1-month group.In the 24-month group, interfibrous vacuoles were found in some collagen fibers.The arrangement of the collagen fibers was loose and more vacuoles were displayed in the 60-month group, and the loss of some collagen fibers appeared and the lenticules were thinned in the 84-month group.It was found through hematoxylin-eosin staining that the morphological changes of corneal stromal lenticules corresponded to the alterations of collagen fibers.Transmission electron microscopy showed that in the 1-month group, the collagen fibers of the corneal stroma lenticules were neatly arranged and regular, and the corneal stromal cells were elongated and spindle-shaped, and the nuclear membrane was intact and the cytoplasm was abundant.In the 24-month group, the collagen fibers showed slightly loose arrangement, and the corneal stromal cells were deformed with incomplete nuclear membrane.In the 60-month group, the collagen fibers were in loose and irregular arrangement, and the nuclei were atrophied and deformed.The 84-month group showed disorganized arrangement of collagen fibers, wrinkled and atrophied corneal stromal cells, discontinuous nucleus membrane and nucleoplasmic lysis.TUNEL staining showed that the percentage of apoptotic corneal cells in lenticules was (87.80±1.17)%, (89.50±1.05)%, (89.30±1.51)% and (90.20±1.47)% in the 1-month, 24-month, 60-month and 84-month groups, respectively, with no statistically significant difference found in overall comparison ( F=4.525, P=0.053). Conclusions:The disorder of collagen fibers and apoptosis of keratocytes occur in the human corneal stromal lenticules till 84 months after cryopreservation, however, the transparency and integrity remain excellent.The ultra-low temperature preservation technique provides an effective and simple solution for long-term storage of human corneal stromal lenticule.

Clinical research of changes in posterior corneal elevation after small incision lenticule extraction / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM:To assess the changes of posterior corneal elevation after small incision lenticule extraction(SMILE). <p>METHODS:A retrospective study was conducted on 120 patients(240 eyes)who underwent SMILE surgery with myopia. All patients were examined with the Pentacam of preoperation and 1d, 1wk, 1, 3, 6 and 12mo postoperatively, respectively. We analyze the change of the posterior corneal elevation of the apex, and the change of mean posterior corneal elevation in the circle of 2mm, and 6mm diameter.<p>RESULTS:Comparison among the three groups showed that the differences of apex and 2mm circle at a different time and between the groups were statistically significant(apex: <i>F</i>_time=30.09, <i>P</i>_time<0.01; <i>F</i>_group=7.29, <i>P</i>_group<0.01; 2mm circle: <i>F</i>_time=24.72, <i>P</i>_time<0.01; <i>F</i>_group=7.44, <i>P</i>_group=0.01), and there was no statistically significant difference in interaction time and groups(apex: <i>F</i>_time×group=1.65, <i>P</i>_time×group=0.15; 2mm circle: <i>F</i>_time×group=1.81, <i>P</i>_time×group=0.25). The difference of 6mm circle at different time points after the operation was statistically significant(<i>F</i>_time=18.34, <i>P</i>_time<0.01), while the difference in interaction time and groups was not statistically significant(<i>F</i>_group=2.21, <i>P</i>_group=0.12; <i>F</i>_time×group=1.34, <i>P</i>_time×group=0.25). In the low and moderate myopia groups, the changes of the apex, 2mm circle and 6mm circle in the posterior corneal elevation were statistically significant within 1mo after surgery(<i>P</i><0.05); In the high myopia group, there were statistically significant at the apex and 2mm circle within 3mo after surgery(<i>P</i><0.05); There was statistically significant after surgery at 6mm circle within 1mo(<i>P</i><0.05). In all cases, the difference of the posterior corneal elevation between 1wk and 1d was negative at the apex and 2mm circle, after that, the difference became positive and smaller. The reverse was true at the 6mm circle. <p>CONCLUSION:Among three groups after SMILE, the central posterior cornea was slightly backward, and the peripheral cornea was slightly forward, the changes were most obvious after 1wk and then returned gradually. It means the surgery was safe, stable, precise, and predictable.

Precision of corneal ablation thickness in SMILE / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To evaluate the differences between the estimated and measured corneal ablation thickness in myopic eyes with different refractive errors in small incision lenticule extraction(SMILE)and investigate the precision of corneal ablation thickness in SMILE. <p>METHODS: This prospective study included 234 eyes(143 myopic patients), who had undergone SMILE in our hospital from January 2017 to August 2019. The patients were divided into three groups according to a manifest refraction spherical equivalent(MRSE): low myopia(-0.50 to -3.00D, 78 eyes), moderate myopia(>-3.00 to -6.00D, 78 eyes), and high myopia(>-6.00D, 78 eyes). Observe the uncorrected distance visual acuity(UDVA)and MRSE before and after operation. The central corneal thickness(CCT)was measured by Pentacam preoperatively and postoperatively at 1mo. Compare the discrepancy between estimated corneal ablation thickness and measured corneal ablation thickness of three groups to discuss the precision of corneal ablation thickness in different refractive errors in SMILE. <p>RESULTS: The UDVA was 0.8 or better in all eyes and 1.0 or better in 98.3% eyes postoperatively. The average measured corneal ablation thickness was significantly lower than average estimated corneal ablation thickness(84.92±23.15μm <i>vs </i>100.07±26.83μm, <i>P</i><0.01). The average cutting error was 15.15±10.34μm. The measured corneal ablation thickness of low myopia, moderate myopia and high myopia was significantly lower than the estimated corneal ablation thickness, respectively(<i>P</i><0.01). The cutting error of low myopia, moderate myopia and high myopia was 8.81±7.78, 15.59±9.27, 21.05±10.03μm respectively. The average MRSE of all patients was -4.85±2.15D preoperation, there was a linear regression relation between MRSE and cutting error(<i>Y</i>= -2.2495<i>X</i>+3.9287, <i>R</i>2=0.1589). The cutting error increased with MRSE(<i>t</i>=-6.620, <i>P</i><0.001).<p>CONCLUSION: The measured corneal ablation thickness was lower than estimated corneal ablation thickness,the higher the refractive power was, the larger the cutting error would be in SMILE. Although there was significant discrepancy between measured corneal ablation thickness and estimated corneal ablation thickness, the effect of this surgery was ideal, the mismatch did not influence the precision of different refractive errors.

Microscopia confocal no auxílio diagnóstico de Distrofia Corneana de Schnyder / In vivo confocal microscopy as a diagnostic tool in Schnyder Corneal Dystrophy's case

Resumo Neste relato, descrevemos um caso de Distrofia corneana de Schnyder que apresentou o desfecho de seu diagnóstico baseado em achados característicos na microscopia confocal, ferramenta que se aponta em destaque no universo oftalmológico.

Abstract Schnyder's corneal dystrophy (SCD) is a rare corneal condition characterized by cholesterol and phospholipids deposition in the stroma and Bowman's layer. We present a case report of a patient who had a progressive corneal stromal haze in both eyes since he was 15 years old. Etiological diagnosis of SCD was well established by In Vivo Confocal Microscopy (IVCM).

Clinical efficacy of SMILE in patients with different curvatures myopia and analysis of influencing factors / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To analyze the efficacy and influencing factors of femtosecond laser small incision lenticule extraction(SMILE)in the treatment of different curvature myopia.<p>METHODS: Totally 72 patients(144 eyes)with myopia who underwent SMILE were prospectively included. According to the preoperative corneal curvature, they were divided into low curvature group(<41D, <i>n</i>=21 cases, 42 eyes), middle curvature group(41-46D, <i>n</i>=26 cases, 52 eyes)and high curvature group(>46D, <i>n</i>=25 cases, 50 eyes). The refraction state, uncorrected visual acuity(UCVA), best corrected visual acuity(BCVA)and corneal optical quality were compared among the groups before operation and at 1wk after operation and at 3mo after operation, and the influencing factors of SMILE visual acuity recovery in patients with myopia were screened out.<p>RESULTS: There were significant differences in UCVA and BCVA at different time points before and after operation within the three groups(<i>P</i><0.05), and there were no significant differences at different time points among groups(<i>P</i>>0.05). There were no significant differences in the spherical degree, cylindrical degree and spherical equivalent degree among the three groups at different time points(<i>P</i>>0.05). There was a statistically significant difference in the vector change value of subjective optometry refractive power(<i>P</i><0.05), and the value in low curvature group was lower than that in middle curvature group and high curvature group(<i>P</i><0.05). Multivariate Logistic regression analysis showed age, ocular axial length and preoperative spherical equivalent were related factors affecting the efficacy of SMILE surgery(<i>P</i><0.05).<p>CONCLUSION: SMILE can better improve the visual acuity of patients with different curvature myopia, and it is safe and effective, but age, ocular axial length and preoperative spherical equivalent are related factors affecting the visual acuity after SMILE.

Clinical features and corneal optical anisotropies in a rabbit model of limbal stem cell deficiency / Fenótipos clínicos e anisotropias ópticas da córnea em coelhos com deficiência de células tronco limbais

ABSTRACT Purposes: To investigate the intra-laboratory reproducibility of clinical features and to evaluate corneal optical anisotropies in a rabbit model of limbal stem cell deficiency. Methods: Limbal injury was induced in the right eye of 23 adult New Zealand White rabbits using a highly aggressive protocol that combined 360 degrees limbal peritomy, keratolimbectomy, alkaline chemical burn, and mechanical removal of the epithelium. Clinical evaluation of the injured eyes was performed for 28 days and included corneal impression cytology. Corneas with a severe clinical outcome set typical of limbal stem cell deficiency were then collected, subjected to a histopathological examination, and examined for optical anisotropies. Corneas from healthy rabbit eyes were used as controls. Differences in optical path due to stromal collagen birefringence, as well as linear dichroism related to the expression and spatial orientation of glycosaminoglycan chains from proteoglycans, were measured from cross-sections under a quantitative polarized light microscope. Results: One eye showed signs of hypopyon and was excluded. Signs of ocular inflammation were observed in all eyes studied (n=22). Corneal impression cytology did not detect goblet cells. Twelve of the 22 corneas presented a clinical outcome set typical of limbal stem cell deficiency, which is characterized by the presence of epithelial defects, inflammatory cells, moderate-to-severe opacity, and neovascularization. Microscopic studies under polarized light revealed that relative to controls, limbal stem cell deficiency caused a 24.4% increase in corneal optical path differences. Further, corneas with limbal stem cell deficiency were less dichroic than controls. Conclusions: These results suggest that rabbit models of limbal stem cell deficiency must be rigorously screened for use in preclinical studies to ensure experimental homogeneity because protocols used to create limbal stem cell deficiency could be not associated with good intra-laboratory reproducibility of clinical features. Limbal stem cell deficiency, as induced herein, altered the optical anisotropic properties of the corneal stroma. Such alterations are indicative of changes in collagen packing and the spatial orientation of glycosaminoglycan chains from proteoglycans. Knowledge of these changes is important to potentiate strategies aimed at restoring the morphofunctional integrity of the corneal stroma affected by limbal stem cell deficiency.

RESUMO Objetivos: Investigar a reprodutibilidade intra-la­boratorial dos fenótipos clínicos e avaliar anisotropias ópticas em córneas de coelhos com deficiência de células tronco limbais. Métodos: Lesões ao limbo foram feitas no olho direito de 23 coelhos adultos da Nova Zelândia Branco, usando um protocolo altamente agressivo, que envolveu peritomia limbal em 360 graus, ceratolimbectomia, cauterização por álcali, e remoção mecânica de epitélio remanescente. Os olhos foram clinicamente avaliados por 28 dias, inclusive por citologia de impressão corneal. As córneas que manifestaram um conjunto de alterações típicas de deficiência de células tronco limbais foram coletadas e submetidas à estudos em histopatologia e em anisotropias ópticas. Córneas saudáveis foram usadas como controles. Diferenças de caminho óptico de birrefringência relacionada à organização do colágeno estromal, e dicroísmo linear relacionado à expressão e à orientação das cadeias de glicosaminoglicanos dos proteoglicanos estromais, foram quantificados por microscopia de luz polarizada. Resultados: Um olho apresentou hipópio e foi excluído do estudo. Todos os olhos estudados (n=22) apresentaram sinais de inflamação ocular. A citologia de impressão não detectou células caliciformes na superfície corneal. Doze de 22 córneas manifestaram alterações clínicas típicas de deficiência de células tronco limbais, caracterizado por defeitos epiteliais, infiltrados inflamatórios, opacidade de moderada à severa, e neovascularização. Estudos por microscopia de luz polarizada mostraram que a deficiência de células tronco limbais aumentou a diferenças de caminho óptico corneal em 24,4% (versus controles). As cór­neas com deficiência de células tronco limbais foram menos dicroicas do que as córneas controle. Conclusões: Coelhos com deficiência de células tronco limbais, para aplicações em estudos pré-clínicos, devem ser rigorosamente selecionados para assegurar homogeneidade experimental, pois há evidências de que protocolos utilizados para indução de deficiência de células tronco limbais não estão associados com boa reprodutibilidade intra-laboratorial de fenótipos clínicos. A deficiência de células tronco limbais, como induzida aqui, alterou as propriedades ópticas anisotrópicas do estroma corneal. Tais alterações são indicativas de mudanças no empacotamento de colágeno e na orientação das cadeias de glicosaminoglicanos dos proteoglicanos. Conhecimentos nessas alterações são importantes para potencializar estratégias que visam a restabelecer a integridade morfofuncional do estromal corneal acometido pela deficiência de células tronco limbais.

In vivo confocal microstructural analysis of corneas presenting Kayser-Fleischer rings in patients with Wilson's disease / Análise microestrutural confocal in vivo de córneas apresentando anel de Kayser-Fleischer em pacientes com doença de Wilson

ABSTRACT Purpose: To evaluate microstructural differences between corneas with and without Kayser-Fleischer rings in age-matched subjects with Wilson's disease with neurological symptoms, using confocal laser scanning microscopy. Methods: The study included 12 subjects with Wilson's disease with neurological symptoms. Twelve corneas presented clinically with classic Kayser-Fleischer rings, visible on slit lamp examination; the other 12 served as controls. The subjects underwent a comprehensive clinical examination. Microstructural analysis using confocal laser scanning microscopy evaluated increased corneal thickness, decreased number of cells, increased debris or specific deposits, and unusual microstructures. Results: Clinically, the subjects with Kayser-Fleischer rings had similar corneal findings and normal intraocular pressure; two had typical sunflower cataracts and decreased visual acuity. The control eyes all presented normal visual acuity, intraocular pressure, and corneal appearance. The microstructural analysis demonstrated similar findings in all the affected corneas. Compared with the control corneas, there were fewer keratocytes in the anterior stroma (17.380 vs. 22.380/mm3). Round, "hollow" dark areas were observed between the keratocytes; these were universal and similar in appearance in all affected corneas and all cornea layers. In the peripheral posterior stroma, there were dust-like, bright, granular deposits that tended to increase in number and density toward Descemet's membrane, masking the peripheral endothelium. The control corneas presented a normal microstructure apart from dust-like granular deposits in the periphery. Conclusions: In vivo confocal microscopy is a useful tool for evaluating the corneal microstructure when a Kayser-Fleischer ring is clinically present. The ring consists of granular, bright particles that increase in density toward Descemet's membrane, and is associated with a decreased number of keratocytes and peculiar dark, round areas in all stromal layers, probably a sign of corneal damage. When the ring is not visible in subjects with Wilson's disease, changes to the corneal microstructure are insignificant.

RESUMO Objetivo: Avaliar, ao nível microestrutural, através de microscopia confocal in vivo a lazer, 12 córneas com anel de Kayser-Fleischer visível ao exame da lâmpada de fenda e compará-las com 12 córneas clinicamente normais de indivíduos com idades correspondentes aos pacientes com doença de Wilson e sintomas neurológicos. Métodos: O estudo incluiu 12 indivíduos com doença de Wilson e sintomas neurológicos (24 córneas). Doze córneas apresentavam clinicamente o anel clássico de Kayser-Fleischer e as outras 12 serviram como controle. Todos os pacientes foram submetidos a um exame clínico abrangente e a uma análise microestrutural subsequente utilizando microscopia confocal in vivo de varredura a laser. Os principais resultados observados foram: aumento da espessura da córnea, diminuição do número de células, aumento de resíduos/depósitos específicos e microestrutura atípica. Resultados: Clinicamente, todos os indivíduos com anel de Kayser-Fleischer (12 olhos) apresentaram achados similares da córnea e pressão intraocular normal. Dois indivíduos também apresentaram uma catarata de girassol típica e diminuição da acuidade visual. Todos os olhos do grupo controle apresentaram acuidade visual, pressão intraocular e aparência corneana normais. A microscopia confocal in vivo com varredura a laser revelou achados semelhantes em todas as córneas afetadas. O número de ceratócitos no estroma anterior era menor, 17.380/mm3 (22.380/mm3 no grupo controle), e entre eles foram identificadas áreas escuras arredondadas "vazias". Essas zonas escuras eram generalizadas e similares em todas as córneas examinadas e em todas as camadas da córnea. No estroma posterior periférico, havia presença de depósitos granulares brilhantes e com aparência de pó que tendiam a aumentar em número e densidade no sentido da membrana de Descemet, mascarando o endotélio periférico. As córneas controle apresentaram estrutura normal, com exceção de depósitos granulares com aparência de pó na periferia. Conclusões: A microscopia confocal in vivo é uma ferramenta útil para a avaliação da microestrutura da córnea quando o anel de Kayser-Fleischer está clinicamente presente. O anel é constituído de partículas granulares brilhantes com densidade aumentada no sentido da membrana de Descemet. Sua presença está associada com uma diminuição do número de ceratócitos e com áreas circulares escuras "peculiares" em todas as camadas estromais, que representam, provavelmente, um sinal de dano da córnea. Quando o anel não está clinicamente visível, a estrutura da córnea in vivo encontra-se insignificantemente alterada.

Advances in corneal wound healing and stroma remodeling / 中华实验眼科杂志

Stroma is the major part of cornea.The factors maintain corneal stroma transparency include the ultrastructural anatomy and physiology of the cornea and its cellular and extracellular components.During corneal development,neural crest cells and keratoblasts differentiate into keratocytes,which synthesize high levels of collagen and proteoglycans.The production and assembly of collagen fibers need a series of intracellular and extracellular components.The assembled collagen fibers deposite in ECM,assemble into high-order structures to synthesize small fiber bundles,and then form a larger structure in a particular tissue.Corneal wound healing is completed in highly coordinate by various cells and cytokines in time and space.The keratocytes phenotype changes and the remodeling of corneal stroma ECM are two important factors in this process.Corneal refractive surgery are carried out in the worldwide,although most corneal refractive surgery are successful,But the stromal opacity formed during the remodeling of corneal stroma is the most important cause of visual impairment and visual quality decline after refractive surgery.Well understanding the course of stroma remodeling after corneal injury,is meaningful for the exploration of decreasing corneal opacity formation.In this paper,the corneal stroma structure and its synthesis and assembly,the pathophysiological process of stroma remodeling in corneal wound healing and after corneal refractive surgery were reviewed.

Effect of compound betamethasone on immunological rejection after xenogeneic corneal lamellar transplantation / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To observe the sustained-release effect of compound betamethasone by subconjunctival injection on immunological rejection after ostrich-rabbit lamellar keratoplasty.METHODS:Sixteen healthy New Zealand white rabbits with 6wk old received corneal lamellar keratoplasty,and the corneal graft was ostrich acellular corneal stroma.After surgery all subjects were divided into two groups,Group A (experimental group) were administrated with subconjunctival injection of compound betamethasone injection (once every 7d),and Group B (control group) were administrated with subconjunctival injection of dexamethasone sodium phosphate (once every 7d).At 1,2wk,1,2mo after the surgery,rabbit corneas were taken for paraffin sections,and were observed with H-E staining,in the meantime changes of CD4+ and CD8+ T lymphocytes were observed by immunofluorescence.RESULTS:Two months after surgery,in Group A corneal grafts remained transparenct,and showed little neovascularization;HE staining and indirect immunofluorescence showed that only a few neutrophil infiltration,no CD4+ and CD8+T lymphocytes.In Group B,the inflammatory reaction was observable at different time points,the corneal graft was turbid;and the tissue sections and indirect immunofluorescence staining showed that neutrophil infiltration was predominant,and CD4+,CD8+T lymphocytes were also seen.CONCLUSION:Compound betamethasone is able to inhibit the ostrich-rabbit corneal transplantation immune rejection,prolong the survival time of the grafts.The present study lay the foundation for further research and clinical application.

Complete depigmentation of a small aperture corneal inlay implanted for compensation of presbyopia / Despigmentação completa de um implante corneano de pequena abertura para correção da presbiopia

ABSTRACT We describe a case of late-onset remarkable depigmentation of a small aperture corneal inlay implanted for presbyopia compensation. The patient was a participant in a clinical trial designed to evaluate the safety and efficacy of the AcuFocusTM ACU-10R160, which is a 10 µm-thick polyimide film tinted with an organic dye. Inlay implantation occurred under mechanical microkeratome Lasik flaps set for a depth of 120 µm. The patient returned to the clinic 11 years after surgery and reported loss of near-vision acuity. Clinical examination showed the complete absence of pigments in the device and the total loss of the initial effect on near vision, despite normal distance vision. Manifest refraction remained stable during the follow-up period. Scheimpflug images characterized the loss of the small aperture effect on incoming light. Confocal analysis revealed small hyper-reflective round images on the endothelium and no signs of inflammation.

RESUMO Descrevemos um caso de importante despigmentação de início tardio de implante corneano de pequena abertura implantada para compensação de presbiopia. O paciente foi um dos participantes de ensaio clínico destinado a avaliar a segurança e eficácia do AcuFocusTM ACU-10R160, uma película de poliimida de 10 microns de espessura, tingida com um corante orgânico. A implantação ocorreu sob um flap de Lasik criado por microcerátomo mecânico ajustado para profundidade de 120 µm. O caso aqui descrito foi avaliado 11 anos após a cirurgia, relatando diminuição de acuidade de visão para perto. O exame clínico mostrou ausência total de pigmentos no dispositivo e perda total do efeito inicial na visão de perto, apesar da visão normal para distância. A refração manifesta permaneceu estável durante o período de seguimento. As imagens de Scheimpflug caracterizaram a perda do efeito da abertura pequena na luz entrante. A análise de microscopia confocal revelou pequenas imagens hiper-reflexivas redondas sobre o endotélio, sem sinais de inflamação.

Clinical study on human lamellar keratoplasty for fungal corneal ulcers with porcine acellular corneal stroma / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To observe the transplantation of acellular porcine corneal stroma on the treatment of superficial keratitis by drug-resistant fungal.METHODS:We performed a retrospective analysis of 16 cases of fungal keratitis received the transplantation of acellular porcine corneal matrix from June 2015 to March 2016 with a follow-up of 6mo.We analyzed on items as postoperative visual acuity, corneal graft status, postoperative recurrence and postoperative complications.RESULTS:We observed a healing time of corneal epithelium in 7 to 10d postoperatively generally and the absence of corneal edema in 1mo, while the cornea gradually returned transparent in the 16 cases.Two cases required medication for an epithelial recovery and 3 cases received intervention for decreasing intraocular pressure to a certain level.During the follow-up we observed no cases of cornea degeneration, recurrence of infection or rejection.The vision acuity showed 1.27±0.22, 1.11±0.13, 0.79±0.22 in 1, 3 and 6mo after operation respectively.There was no statistical difference between vision in 1mo and the vision before surgery (P=0.06);while we found a statistical difference when comparing the vision of 3 and 6mo with vision before surgery (P=0.01,0.001).The vision in 6mo increased with a statistic difference to the vision at 1 and 3mo (P<0.001) while no statistic difference was observed between 1 and 3mo(P=0.11).CONCLUSION:Transplantation of acellular porcine corneal matrix is a safe and efficient treatment for fungal keratitis.

Comparison of corneal ablation depth predictability between small incision lenticule extraction and femtosecond laser-assisted in situ keratomileusis for myopia / 中华实验眼科杂志

Background Recently,small incision lenticule extraction (SMILE) procedure is used to correct myopia.The clinical safety and efficiency of SMILE have been approved,but its predictability to corneal ablation depth is brought into focus.Objective This study was to compare the predictability of ablation depth in central cornea between SMILE and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for myopia.Methods A nonrandomized controlled clinical study was performed.Two hundred and seventy eyes of 135 myopic patients who were going to receive corneal refractive surgery were included in Beijing Tongren Hospital from October 2015 to May 2016.SMILE and FS-LASIK were performed on 138 eyes of 69 patients and 132 eyes of 66 patients matched in demography respectively under the informed consent.Central corneal thickness was measured by RTVue FD-OCT before and 1 week after surgery.The refractive power,actual ablation depth (difference of central corneal thickness before and after surgery) and central corneal cutting error (difference between theoretically expected ablation depth and real ablation depth) were intergrouply compared,and the correlation of real ablation depth with theoretically expected ablation depth was assessed.Results No significant difference was found in spherical power,astigmatic power and spherical equivalent after surgery between SMILE group and FS-LASIK group (t =-1.826,-1.405,-1.420,all at P＞0.05).The actual ablation depth was (76.96± 15.27)μm in the SMILE group,which was significant lower than (96.76± 16.52) μm of theoretically expected ablation depth (t =-23.016,P ＜ 0.01);however,there was no significant difference in the FS-LASIK group between actual and expected ablation depth ([77.92 ± 18.69] μm versus [77.42± 15.60] μm) (t =-0.604,P =0.547).The central corneal cutting error was (20.55 ± 8.51) μm in the SMILE group and (7.17±5.97) μm in the FS-LASIK group,showing a significant difference between them (t=14.950,P＜0.01).The positive linear correlations were seen between actual and expected ablation depth in both SMILE group and FS-LASIK group (r=0.799,0.867,both at P＜0.01).The actual ablation depth was increased over expected ablation depth,with the regression equations of Y=3.892+0.749X in the SMILE group and Y=3.443 + 0.957X in the FS-LASIK group.Conclusions The actual corneal ablation depth is less than expected corneal ablation depth in SMILE procedure,while in FS-LASIK procedure,the actual corneal ablation depth appears to be consistent with the expected one,inferring a good predictability in corneal ablation depth in FS-LASIK surgery.