Objective To compare the effects of the denudedfreeze-dried-amniotic-membrane and the denuded freeze-dried bovine corneal stroma when they were explanted to repair the corneal defect of rabbits. Methods The amnia from healthy human placentae were prepared with the method reported by LUO Jingcong, which were freeze-dried and sterilized. The bovine cornea was also denuded by typsin, rinsed, freeze-dried, and sterilized. Twenty Japan rabbits weredivided into group A(the amniontic group) and group B(the bovine-corneal-stroma group) at random. The defect was made, which was 7.5 mm in diameter and 1/3 ofthe thickness of the cornea, and the two kinds of materials were explanted to repair the defect. The vascularization and the changes of the operated eye were observed. The samples were taken at 2, 4 and 8 weeks for histologicalexamination. Results The explanted materials were not melted or excluded. There were visible neovessels in both groups, yet there was no significant difference between them. According to the histological observation, there was severe inflammation in both groups 2 weeks after operation, the fibroblasts were proliferated, and the collagen fibers were disorganized; however,the reactions became milder from 4 weeks after operations,andthe neovessles could be seen in groups A and B; at 8 weeks, the collagen fibers were more organized in groups A and B; however,there was still a small area of disorganized fibers left. Conclusion The two materials can lead to rejection to some extent, and so they need to be improved.
Objective To evaluate the relative factors of effect of vitrectomy on corneal endothelial cells. Methods Retrospective analysis of the results of corneal endothelium microscopy performed on 213 eyes of 213 patients undergone vetrectomy operations including single vitrectomy (78 eyes), vitrectomy combined with cataract extraction (135 eyes), silicone oil injection (34 eyes), and C3F8 injection (53 eyes) before and after 1 week, 1 and 3 moths of these surgical procedures. Results There was no significant difference between pre- and postoperative corneal endothelium density in single vitrectomy group and vitrectomy combined with cataract extraction with posterior capsule integrity group (Pgt;0.05). The corneal endothelium density significantly decreased postoperatively in C3F8or silicone oil injection group with broken posterior capsule (Plt;0.05). Conclusion C3F8 and silicone oil may damnify corneal endothelium in patients undergo vitrectom y combined with cataract extraction with broken posterior capsule. (Chin J Ocul Fundus Dis，2004，20：101-103)
The decrease of corneal stiffness is the key factor leading to keratoconus, and the corneal collagen fiber stiffness and fiber dispersion are closely related to the corneal biomechanical properties. In this paper, a finite element model of human cornea based on corneal microstructure, namely collagen fiber, was established before and after laser assisted in situ keratomileusis (LASIK). By simulating the Corvis ST process and comparing with the actual clinical results, the hyperelastic constitutive parameters and corneal collagen fiber stiffness modulus of the corneal material were determined before and after refractive surgery. After LASIK, the corneal collagen fiber stiffness modulus increased significantly, and was highly correlated with central corneal thickness (CCT). The predictive relationship between the corneal collagen fiber stiffness modulus and the corresponding CCT before and after surgery was: k1 before = exp(9.14 ? 0.009CCTbefore), k1 after = exp(8.82 ? 0.008CCTafter). According to the results of this study, the central corneal thickness of the patient can be used to estimate the preoperative and postoperative collagen fiber stiffness modulus, and then a personalized corneal model that is more consistent with the actual situation of the patient can be established, providing a theoretical reference for more accurately predicting the safe surgical cutting amount of the cornea.
Due to lack of the practical technique to measure the biomechanical properties of the ocular cornea in vivo, clinical ophthalmologists have some difficulties in understanding the deformation mechanism of the cornea under the action of physiological intraocular pressures. Using Young's theory analysis of the corneal deformation during applanation tonometry, the relation between the elasticity moduli of the cornea and the applanated corneal area and the measured and true intraocular pressures can be obtained. A new applanation technique has been developed for measuring the biomechanical properties of the ocular cornea tissue in vivo, which can simultaneously acquire the data of the applanation area and displacement of the corneal deformation as well as the exerted applanation force on the cornea. Experimental results on a rabbit's eyeball demonstrated that the present technique could be used to measure the elasticity moduli and creep properties of the ocular cornea nondestructively in vivo.
The aim of this article is to study the effect of tumor necrosis factor alpha (TNF-α) on the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) in keratoconus fibroblasts in vitro. Normal cornea and keratoconus fibroblasts were extracted using enzyme digestion method and were cultured in the medium containing TNF-α (0, 10 and 100 ng/mL). The expression of MMPs proteins in the supernatant of corneal fibroblasts and the expression of TIMPs in the normal cornea and keratoconus fibroblasts were detected by Western blot and real-time quantitative polymerase chain reaction respectively. The active form of MMP1 could be detected in the supernatant of keratoconus fibroblasts and upregulated by TNF-α. TNF-α could increase the protein expression of MMP2, MMP3, MMP9 in the supernatant of keratoconus fibroblasts and decrease the gene expression of TIMP1, TIMP2 in keratoconus fibroblasts. The increased MMPs and the decreased TIMPs can increase the degradation of the extracellular matrix. TNF-α may play an important role in the occurrence and development of keratoconus by regulating the expression of MMPs/TIMPs.
ObjectiveTo compare the changes of corneal astigmatism after long-term spherical and toric orthokeratology wearing, and to investigate the effects of different orthokeratology design on corneal astigmatism.MethodsThe medical records of myopic adolescent patients who have been prescribed spherical and toric orthokeratology in the contact lens clinic of West China Hospital, Sichuan University between January 2019 and December 2021 were analyzed retrospectively.The differences of corneal astigmatism changes after wearing spherical and toric orthokeratology for a long time and one month discontinuation were compared. The influencing factors of corneal astigmatism changes were analyzed. ResultsA total of 156 patients were included. There were 76 cases (76 eyes) in spherical orthokeratology group and 80 cases (80 eyes) in toric orthokeratology group. There was no significant difference between the two groups in age, gender, baseline myopia diopter and total lens wearing time (P>0.05). There were statistically significant differences between the spherical orthokeratology group and the toric orthokeratology group in the baseline corneal flat K value [42.1 (41.3, 43.3) vs. 43.1 (42.0, 44.1) D], baseline corneal steep K value [(43.4±1.3) vs. (44.6±1.5) D], baseline corneal astigmatism [(1.1±0.5) vs. (1.6±0.6) D], and baseline total eye astigmatism [?0.6 (?1.2, 0.0) vs. ?1.4 (?1.8, ?1.0) D] before wearing the orthokeratology (P<0.05). Compared with the baseline value, 1 month after the two groups stopped wearing the orthokeratology, the corneal flat K values became flatter [spherical orthokeratology group: 42.09 (41.28, 43.34) vs. 41.73 (40.98, 43.16) D, toric orthokeratology group: 43.09 (41.95, 44.10) vs. 42.61 (41.52, 43.56) D; P<0.05], the changes of corneal steep K values were not statistically significant (P>0.05), but the corneal astigmatism values increased [spherical orthokeratology group: (1.05±0.49) vs. (1.37±0.56) D, toric orthokeratology group: (1.62±0.57) vs. (1.99±0.63) D; P<0.05]. There was no significant difference in the changes of corneal flat K value, corneal steep K value and corneal astigmatism between the two groups (P>0.05). Multivariate analysis showed that age (P=0.011) and the total duration of orthokeratology wearing (P=0.004) were the main factors affecting the changes of corneal astigmatism. ConclusionAfter 1 month of non-wearing, the flat K value of the cornea becomes flat, the steep K value remains unchanged, and the corneal astigmatism increases. There is no difference in the effect of the spherical and toric orthokeratology on corneal astigmatism. The change of corneal astigmatism is related to the patient’s age and the total duration of wearing the orthokeratology. The younger the age, the longer the duration of orthokeratology wearing, the more significant the increase of corneal astigmatism after stopping wearing the orthokeratology.
In the evaluation of tear film stability based on corneal topography, a pretreatment algorithm for tear film video was proposed for eye movement, eyelash reflection and background interference. First, Sobel operator was used to detect the blur image. Next, the target image with highlighted ring pattern was obtained by the morphological open operation performed on the grayscale image. Then the ring pattern frequency of the target image was extracted through the Hough circle detection and fast Fourier transform, and a band-pass filter was applied to the target image according to the ring pattern frequency. Finally, binarization and morphological closed operation were used for the localization of the ring pattern. Ten tear film videos were randomly selected from the database and processed frame by frame through the above algorithm. The experimental results showed that the proposed algorithm was effective in removing the invalid images in the video sequence and positioning the ring pattern, which laid a foundation for the subsequent evaluation of tear film stability.
Objective To review research progress of corneal tissueengineering.Methods The recent articles on corneal tissue engineering focus on source and selection of corneal cells, the effects of growth factors on culture of corneal cells in vitro. The preparation and selection of three-dimensional biomaterial scaffolds and their b and weak points were discussed. Results The corneal tissue engineering cells come from normal human corneal cells. The embryo corneal cell was excellent. Several kinds of growth factors play important roles in culture, growth and proliferation of corneal cell, and incroporated into matrix.Growth factors including basic fibroblast growth factor, keratinocyte growth factor, transforming growth factor β1 and epidermal growth factor was favor to corneal cell. Collagen, chitosan and glycosaninoglycans were chosen as biomaterial scaffolds. Conclusion Human tissue engineering cornea can be reconstructed and transplanted. It has good tissue compatibility and can be used as human corneal equivalents.
In order to investigate the effects of mechanical stretching combined with prostaglandin E2 (PGE2) on the gene expression of lysyl oxidases (LOXs) in keratoconus, we treated cultured corneal fibroblasts from healthy human cornea and keratoconus patient cornea with PGE2 and/or cyclic stretch (12% elongation, 0.1 Hz, 12 h). Real-time fluorescent quantitative polymerase chain reaction was used to detect the gene expression of LOXs. The results showed that the gene expression of LOXs in keratoconus group was significantly lower than that in the healthy one. Compared to the static control group, 12% stretching alone up-regulated gene expression of LOXL-2, LOXL-4 in the healthy group, whereas it down-regulated LOXL-3, LOXL-4 in the keratoconus group. Combination of 12% stretching and PEG2 induced LOXL-4 down-regulation in in healthy group, and all LOXs except LOXL-1 in keratoconus group. The results suggested that combination of mechanical stretching and PGE2 down-regulate the gene expression of LOXs in keratoconus. Lower LOXs expression may lead to impaired cross-linking, and thus to a loss of cohesion between collagen fibrils, affecting corneal structural stability by collagen lamellae slippage. This may facilitate the development of keratoconus. Exploring the effects of mechanical stretching and inflammatory factor on the expression LOXs in this paper will help us to understand the possible mechanism of how the keratoconus occurs and develops well, and provide the reference for the prevention and treatment of keratoconus.
Objective
To analyze the risk factors for persistent corneal epithelial defects (PCED) after pars plana vitrectomy (PPV) in patients with proliferative diabetic retinopathy (PDR).
Methods
A total of 201 PDR patients (201 eyes) who received PPV were enrolled in this retrospective study. There were 86 males (86 eyes) and 115 females (115 eyes). The patients aged from 30 to 81 years, with the mean age of (57.94±9.65) years. Among them, 159 patients were ≥50 years of age, and 42 patients were ＜50 years of age. There were 36 patients with HbA1c ＜7.0%, 165 patients with HbA1c ≥7.0%. There were 93 right eyes and 108 left eyes. There were 93 right eyes and 108 left eyes. The diabetic retinopathy stages were as follows: stage Ⅳ in 24 eyes, stage Ⅴ in 78 eyes and stage Ⅵ in 99 eyes. The operation time was ranged from 1 to 4 hours, with an average of 2 hours. Among the 201 eyes, corneal epidermis were scraped on 25 eyes; 70 eyes were combined with cataract surgery; a laser photocoagulation count ＜1000 points was performed in 78 eyes, and ＞1000 points were performed in 123 eyes. Sixty-one eyes involved intravitreal silicone oil tamponade, 18 eyes involved intravitreal tamponade with C3F8, and 122 eyes were not involved with intraocular tamponade. Postoperative persistent intraocular hypertension was defined as an intraocular pressure (IOP) ≥21 mmHg (1 mmHg=0.133 kPa) after PPV with necessary treatment using IOP-lowering medications for ≥2 weeks. The diagnostic criteria for corneal epithelial defects were taken from the Expert Consensus on Clinical Diagnosis and Treatment of Corneal Epithelial Defect in China (2016). The corneal epithelial defect was diagnosed as PCED if it was treated with common methods such as a lacrimal substitute or corneal contact lens, but showed no improvement and no signs of healing for ≥2 weeks. The incidence of PCED after eye surgery was recorded and its related risk factors were analyzed. A multivariate logistic regression was used to analyze the risk factors for PCED, which were expressed as a odds ratio (OR) and a 95% confidence interval (CI).
Results
Of 201 eyes, 16 eyes (7.96%) presented with PCED after surgery and 185 eyes (92.04%) with no PCED. There was no significant difference in the age, sex, and eyes between the patients with or without PCED (χ2=6.548, 0.927, 0.044; P=0.011, 0.336, 0.833). A multivariate logistic regression showed that intraoperative epithelial debridement (OR=13.239, 95%CI 2.999?58.442, P=0.001), intraoperative treatment in combination with cataract surgery (OR=7.448, 95%CI 1.975?28.091, P=0.003), intravitreal tamponade with C3F8 (OR=11.344, 95%CI 2.169?59.324, P=0.004), and postoperative persistent intraocular hypertension (OR=10.462, 95%CI 2.464?44.414, P=0.001) were risk factors for PCED after PPV.
Conclusion
Intraoperative epithelial debridement, intraoperative treatment in combination with cataract surgery, intravitreal tamponade with C3F8, and postoperative persistent intraocular hypertension are risk factors for PCED in patients with PDR after PPV.
