Guoying Mu

Riboflavin/ultravoilet light-mediated crosslinking for fungal keratitis

Collagen crosslinking (CXL) has been used to treat cases with bacterial, Acanthamoeba 1 ,2 and fungal keratitis2 with encouraging results. In this study, we present the clinical outcomes in cases with fungal keratitis that received riboflavin/ultravoilet light A (UVA) light-mediated crosslinking. Patients with microbiologically proven fungal keratitis were included in this study. A written consent was obtained from all the patients. The study protocol was approved by the ethics committee of the Provincial Hospital. Initial treatment was commenced in the form of hourly 5% natamycin eye drops and 0.3% tobramycin eye drops four times a day. A decision was taken to perform CXL after no response to treatment or an exacerbation of infection was observed. Under topical anaesthesia, the epithelium surrounding the infiltrate was removed. Riboflavin (Medio-Cross riboflavin/dextran solution, 0.1%) was administered topically for 30 min at intervals of 2 min. The cornea was illuminated for 30 min using a UV light lamp (UV-X 1000 system, IROC Innocross AG Co, Switzerland; wavelength 365 nm, irradiance 3 mW/cm2, total dose 5.4 J/cm2). Riboflavin administration was …

Corneal ectasia 6.5 months after small-incision lenticule extraction

Our case involves a 19-year-old patient with forme fruste keratoconus. Small-incision lenticule extraction was performed, and 6.5 months after surgery, corneal ectasia was diagnosed. Preoperatively, the minimum central corneal thickness was 546 μm in the right eye and 542 μm in the left eye; the refractive correction was -6.75 -1.00 × 45 and -6.75 -0.75 × 140, respectively; the lenticular thickness was 137 μm and 135 μm, respectively. At 6.5 months, ectasia was diagnosed based on anterior and posterior surface keratometry of 38.4/39.5 diopters (D) and -6.3/-6.8 D, respectively, in the right eye and 38.6/40.8 D and -7.1/-6.6 D, respectively, in the left eye. The keratometry increased gradually and the corneal thickness decreased after surgery, and these trends continued during the 13-month follow-up. This report documents corneal ectasia as a complication of small-incision lenticule extraction and highlights the importance of preoperative evaluation and the need for long-term follow-up.

Role of Corneal Epithelium in Riboflavin/Ultraviolet-A Mediated Corneal Cross-Linking Treatment in Rabbit Eyes

Purpose. To evaluate the role of corneal epithelium in riboflavin/ultraviolet-A (UVA) mediated corneal collagen cross-linking treatment. Methods. Fifty New Zealand rabbits were divided into 5 groups: UVA treatment with or without corneal epithelium, UVA+riboflavin treatment with or without corneal epithelium, and control without any treatment. All rabbits were sacrificed after irradiation and subsequently 4 mm × 10 mm corneal strips were harvested for biomechanical evaluation. Results. UVA irradiation alone did not enhance the maximal stress and Youngs modulus of corneal specimens with (3.15 ± 0.56 mpa, 1.00 ± 0.09 mpa) or without (3.53 ± 0.85 mpa, 0.94 ± 0.21 mpa) the corneal epithelium, compared to specimens in the control group (4.30 ± 0.68 mpa, 1.03 ± 0.24 mpa). However, UVA irradiation combined with riboflavin significantly increased the maximal stress and Youngs modulus of corneal specimens with (5.27 ± 1.09 mpa, 1.23 ± 0.23 mpa, P < 0.05) or without (7.16 ± 1.88 mpa, 1.42 ± 0.16 mpa, P < 0.05) corneal epithelium when compared to the control group. The maximal stress and Youngs modulus of cornea in UVA+riboflavin and “epithelium-off” group were 35.9% and 15.4% higher compared to the UVA+riboflavin and “epithelium-on” group, respectively (P < 0.05). Conclusions. Our study shows that UVA+riboflavin treatment significantly affects the biomechanical properties of the cornea with and without epithelial removal. However, corneas without epithelium seem to benefit more compared to corneas with the epithelium.

A Review of Collagen Cross-Linking in Cornea and Sclera

Riboflavin/UVA cross-linking is a technique introduced in the past decades for the treatment of keratoconus, keratectasia, and infectious keratitis. Its efficacy and safety have been investigated with clinical and laboratory studies since its first clinical application by Wollensak for the treatment of keratoconus. Although its complications are encountered during clinical practice, such as infection inducing risk, minimal invasion merits a further investigation on its future application in clinical practice. Recently, collagen cross-linking in sclera shows a promising prospect. In present study, we summarized the representative studies describing the clinical and laboratory application of collagen cross-linking published in past decades and provided our opinion on the positive and negative results of cross-linking in the treatment of ophthalmic disorders.

Effect of irradiation time on riboflavin–ultraviolet-A collagen crosslinking in rabbit sclera

Purpose To determine the effect of the duration of irradiation on the biomechanical parameters of combined riboflavin–ultraviolet‐A (UVA) collagen crosslinking (CXL) in rabbit sclera. Setting Department of Ophthalmology, Provincial Hospital affiliated with Shandong University, Shandong, China. Design Experimental study. Methods Thirty‐six New Zealand rabbits were divided into 6 groups based on the duration of irradiation (10, 20, 30, 40, 50, or 60 minutes). After the application of riboflavin 0.1% drops (without dextran) as a photosensitizer, the animals were irradiated with 3 mW/cm2 UVA at 365 nm. Only the left eye of each rabbit was treated. All the animals were humanely killed 24 hours postoperatively. One eye in each treated group was used for light microscopy. The other treated eye and all control eyes were prepared for biomechanical testing. The biomechanical parameters were ultimate stress, Young modulus, and the physiological modulus. Results The eyes irradiated for 10 or 20 minutes did not differ significantly from the control eyes. Stress–strain measurement of scleral strips irradiated for 40 minutes or longer showed a significant increase in the ultimate stress, Young modulus, and the physiological modulus. There was a significant increase in the physiological modulus of scleral strips irradiated for 30 minutes or longer. Eyes that were irradiated for 50 minutes and 60 minutes had retinal damage. Conclusions Riboflavin–UVA CXL can lead to a noticeable increase in the biomechanical stiffness of the sclera. The physiological modulus is the most sensitive tool to measure stiffness. In this study, the optimum duration of irradiation was 40 minutes. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Comparison of riboflavin/ultraviolet-A cross-linking in porcine, rabbit, and human sclera.

Purpose. To compare the biomechanical properties of porcine, rabbit, and human sclera before and after riboflavin/ultraviolet-A (UVA) collagen cross-linking (CXL). Methods. Eight rabbits, 8 porcine eyeballs, and 8 human eyeballs were included. One rabbit eye and half of each bisected human and porcine eyeball were treated with riboflavin/UVA CXL. Untreated fellow rabbit eyes and eyeball halves served as controls. A 10 mm × 20 mm scleral band was harvested from each specimen. From this band, two 3.5 mm × 15.0 mm strips were prepared for biomechanical testing. The biomechanical parameters were ultimate stress, stress and Youngs modulus. Results. Values of stress, and Youngs modulus showed that human sclera was 4 times stiffer than porcine sclera and 3 times stiffer than rabbit sclera. In rabbit sclera, both the stress and Youngs modulus were significantly increased by CXL (P < 0.05). In porcine sclera, only the ultimate stress was significantly increased by CXL (P < 0.05). The biomechanical properties of human sclera were not statistically affected by CXL (P > 0.05). Conclusions. Human sclera has higher biomechanical stiffness than porcine and rabbit sclera. With the same irradiation dose, riboflavin/UVA CXL increases the biomechanical stiffness of rabbit sclera but not porcine or human sclera.

Inhibitory effect of polysulfated heparin endostatin on alkali burn induced corneal neovascularization in rabbits

AIM To investigate anti-angiogenic effects of polysulfated heparin endostatin (PSH-ES) on alkali burn induced corneal neovascularization (NV) in rabbits. METHODS An alkali burn was made on rabbit corneas to induce corneal NV in the right eye of 24 rabbits. One day after burn creation, a 0.2 mL subconjunctival injection of 50 µg/mL PSH-ES, 50 µg/mL recombinant endostatin (ES), or normal saline was administered every other day for a total of 14d (7 injections). Histology and immunohistochemisty were used to examine corneas. Corneal NV growth was evaluated as microvessel quantity and corneal vascular endothelial growth factor (VEGF) expression was measured by immunohistochemical assay. RESULTS Subconjunctival injection of ES and PSH-ES resulted in significant corneal NV suppression, but PSH-ES had a more powerful anti-angiogenic effect than ES. Mean VEGF concentration in PSH-ES treated corneas was significantly lower than in ES treated and saline treated corneas. Histological examination showed that corneas treated with either PSH-ES or ES had significantly fewer microvessels than eyes treated with saline. Additionally corneas treated with PSH-ES had significantly fewer microvessels than corneas treated with ES. CONCLUSION Both PSH-ES and recombinant ES effectively inhibit corneal NV induced by alkali burn. However, PSH-ES is a more powerful anti-angiogenic agent than ES. This research has the potential to provide a new treatment option for preventing and treating corneal NV.

Evaluation of the in vitro antimicrobial properties of ultraviolet A/riboflavin mediated crosslinking on Candida albicans and Fusarium solani

AIM To evaluate the antimicrobial properties of ultraviolet A (UVA) (365 nm)/riboflavin against Candida albicans and Fusarium solani. METHODS Two fungus isolates were cultured in vitro and prepared with 10-fold serial PBS dilutions of cell concentration. For each dilution of fungus suspension, the concentration (colony-forming units/mL, CFU/mL) and the inactivation ratio of fungal cells were evaluated under 4 conditions: no treatment (control), UVA (365 nm)/riboflavin, riboflavin, and UVA (365 nm). RESULTS The cell concentration decreased in UVA (365 nm)/riboflavin group for Candida albicans at each dilution and Fusarium solani at dilutions of 10(4), 10(3), 10(2) CFU/mL, when compared with that in control, riboflavin, and UVA (365 nm) groups (P<0.01). No difference of cell concentration was detected amongst the culture of control, riboflavin, and UVA (365 nm) groups for the two fungus. There is a negative correlation between suspension concentration (log-transformed) and the inactivation ratio in UVA (365 nm)/riboflavin group for Candida albicans and Fusarium solani (P<0.01). CONCLUSION According to the standard protocol of corneal collagen cross-linking, UVA (365 nm)/riboflavin combination treatment is found to moderately inactivate the viability of Candida albicans and Fusarium solani in vitro. The inactivation ratio was found to increase with the decrease of cell concentration under UVA (365 nm)/riboflavin condition.

A short-term study of corneal collagen cross-linking with hypo-osmolar riboflavin solution in keratoconic corneas

AIM To report the 3mo outcomes of collagen cross-linking (CXL) with a hypo-osmolar riboflavin in thin corneas with the thinnest thickness less than 400 µm without epithelium. METHODS Eight eyes in 6 patients with age 26.2±4.8y were included in the study. All patients underwent CXL using a hypo-osmolar riboflavin solution after its de-epithelization. Best corrected visual acuity, manifest refraction, the thinnest corneal thickness, and endothelial cell density were evaluated before and 3mo after the procedure. RESULTS The mean thinnest thickness of the cornea was 408.5±29.0 µm before treatment and reduced to 369.8±24.8 µm after the removal of epithelium. With the application of the hypo-osmolar riboflavin solution, the thickness increased to 445.0±26.5 µm before CXL and recover to 412.5±22.7 µm at 3mo after treatment, P=0.659). Before surgery, the mean K-value of the apex of the keratoconus corneas was 57.6±4.0 diopters, and slightly decreased (54.7±4.9 diopters) after surgery (P=0.085). Mean best-corrected visual acuity was 0.55±0.23 logarithm of the minimal angle of resolution, and increased to 0.53±0.26 logarithm after surgery (P=0.879). The endothelial cell density was 2706.4±201.6 cells/mm(2) before treatment, and slightly decreased (2641.2±218.2 cells/mm(2)) at last fellow up (P=0.002). CONCLUSION Corneal collagen cross-linking with a hypo-osmolar riboflavin in thin corneas seems to be a promising treatment. Further study should be done to evaluate the safety and efficiency of CXL in thin corneas for the long-term.

Novel Compound Heterozygous CBS Mutations Cause Homocystinuria in a Han Chinese Family.

The cystathionine β-synthase (CBS) gene has been shown to be related to homocystinuria. This study was aimed to detect the mutations in CBS in a Han Chinese family with homocystinuria. A four-generation family from Shandong Province of China was recruited in this study. All available members of the family underwent comprehensive medical examinations. Genomic DNA was collected from peripheral blood of all the participants. The coding sequence of CBS was amplified by polymerase chain reaction (PCR), followed by direct DNA sequencing. Among all the family members, three affected individuals showed typical clinical features of homocystinuria. Two novel compound heterozygous mutations in the CBS gene, c.407T > C (p. L136P) and c.473C > T (p.A158V), were identified by sequencing analysis in this family. Both of the two missense mutations were detected in the three patients. Other available normal individuals, including the patients’ parents, grand parents, her younger sister and brother in this family either carried one of the two mutations, or none. In addition, the two mutations were not found in 600 ethnically matched normal controls. This study provides a mutation spectrum of CBS resulting in homocystinuriain a Chinese population, which may shed light on the molecular pathogenesis and clinical diagnosis of CBS-associated homocystinuria.