Treatment Results of Corneal Collagen Cross-Linking Combined with Riboflavin and 440 Nm Blue Light for Bacterial Corneal Ulcer in Rabbits

Comparison of modified corneal cross-linking with intrastromal voriconazole for the treatment of fungal corneal ulcer

The present study aimed to evaluate the efficacy of modified corneal cross-linking (CXL) for the treatment of fungal corneal ulcers compared with that following intrastromal voriconazole injection. In total, 31 patients with fungal corneal ulcers treated at The General Hospital of Northern Theater Command between October 2017 and October 2019 were enrolled. Among them, 10 eyes were treated with ultraviolet A (UV-A)/riboflavin CXL (CXL group), whilst 21 eyes were treated with debridement combined with intrastromal voriconazole (stromal injection group). Preoperative microbiological examination was performed in both groups, and evaluated using Fisher's exact test. Postoperatively, infection control and total efficacy rates, localized lesion, ulcer healing rate 1 week after surgery, visual acuity and complications were evaluated using Fisher's exact test, however visual acuity was analyzed by mixed-model ANOVA. The results showed that the pre-operative species distribution between the CXL and stromal injection groups did not significantly differ. The infection control rate in the CXL group was notably higher compared with that in the stromal injection group (P=0.04). Furthermore, the total efficacy rate in the CXL group was also markedly higher compared with that in the stromal injection group, though no statistically significant differences were observed. Localized lesions were observed in nine eyes (90.0%) in the CXL group and nine eyes (42.9%) in the stromal injection group (P=0.02). However, the rate of ulcer healing at 1 week postoperatively and the logarithm of the minimum angle of resolution (logMAR) of visual acuity were not found to be significantly different between the two groups. In terms of complications, with the exception of one patient in the CXL group exhibiting loss of corneal transparency and one patient in the stromal injection group presenting with partial corneal thinning, no other forms of complications were observed. In conclusion, the present study suggested that CXL could have a beneficial impact for treating fungal corneal ulcers in the aspects of infection control, localized lesions and accelerated epithelialization. In addition, except the loss of corneal transparency, this treatment approach could be applied with reduced risks of adverse events.

Accelerated corneal collagen cross-linking in clinical management of infectious keratitis

Objective

To evaluate the clinical efficacy of corneal collagen cross-linking (CXL) in the treatment of infectious corneal diseases.

Methods

This study retrospectively analyzed the clinical efficacy of CXL in 65 eyes with infectious keratitis in Jinan Second People’s Hospital from December 2016 to June 2018. During 6 months of follow-up after CXL treatment, the results of confocal microscopy and anterior segment optical coherence tomography, as well as visual acuity and corneal biomechanical parameters, were recorded in detail.

Results

In general, the overall cure rate was 93.85%; no corneal endothelial dysfunction was encountered in any patients. After 6 months of follow-up, the visual acuity of cured patients was significantly enhanced, while corneal thickness was significantly reduced. Hyphae growth of patients with fungal keratitis was completely inhibited at 1 month postoperatively. Furthermore, corneal biomechanical parameters (i.e., central corneal thickness, deformation amplitude, and pachymetry intraocular pressure) were significantly improved after surgery, compared with baseline measurements.

Conclusion

Accelerated CXL may be an effective adjuvant treatment for infectious keratitis.

Treatment of Severe Acute Bacterial Keratitis in Rabbits Using Continuous Topical Ocular Instillation with Norvancomycin

Purpose

Efficacy of norvancomycin (NVCM) through continuous topical ocular instillation drug delivery (CTOIDD) system for treating severe acute bacterial keratitis infection with Staphylococcus aureus was investigated.

Methods

Rabbits with bacterial keratitis were treated using CTOIDD with NVCM (n=13), topical NVCM eye drops (n=11), and CTOIDD with saline (n=8). Clinical signs of keratitis in all groups were assessed consecutively for a week. Bacterial quantification of excised corneas was counted on the fourth and eighth days. Histopathologic examinations were performed to assess inflammatory cell infiltration on the eighth day.

Results

All signs of bacterial keratitis were alleviated in CTOIDD with NVCM according to criteria, and the CTOIDD-NVCM group had significantly less inflammation than CTOIDD-saline (p<0.05), and eye drop-NVCM (p<0.05). Two eyes in the eye drop-NVCM group, four eyes in the CTOIDD-saline group had corneal perforation (CP), while none of the rabbits showed CP in the CTOIDD-NVCM group. Bacterial counts were significantly less in the CTOIDD with NVCM group in comparison to the eye drop-NVCM (p<0.05), and CTOIDD-saline (p<0.05) groups. Severe inflammation and marked inflammatory cell infiltration were found in histopathologic examinations in the CTOIDD-saline and eye drop-NVCM groups, while significantly less inflammation was documented in the CTOIDD-NVCM (p<0.05) group.

Conclusion

CTOIDD with NVCM effectively reduced the severity and treated acute bacterial S. aureus keratitis infection in a rabbit model. The presented approach of CTOIDD with NVCM appears to be a promising therapeutic approach for severe acute bacterial keratitis.

Effects of hydrogen peroxide solution on the biomechanics of porcine cornea

OBJECTIVES

To determine the biomechanical changes of porcine corneas after the application of hydrogen peroxide(H₂O₂) solution.

METHODS

Fifty-five porcine eyeballs with similar sizes were divided into 11 groups based on the H₂O₂ application. The eyeballs were treated with the following concentrations of H₂O₂ solution: 1 mol/L, 500 mmol/L, 250 mmol/L, 125 mmol/L, 62.5 mmol/L, 31.25 mmol/L, 15.63 mmol/L, 7.81 mmol/L, 3.91 mmol/L, 0.9% saline, or blank. The eyeballs were immersed into the solution for 30 min. The biomechanics of each cornea in the different groups was determined soon after the indentation and tensile tests. We calculated the average Young's modulus of the different groups to determine the effects of H₂O₂ solution on porcine corneas. The comparison between the groups was conducted using ANOVA analysis. Moreover, the safety of each concentration of H₂O₂ solution on the corneal tissues was determined by histopathological examination.

RESULTS

The Young's modulus was significantly different among all the groups (p = 0.003). The modulus was the highest in the group treated with 3.91 mmol/L H₂O₂ and it was significantly different from that in the group treated with 0.9% saline or the blank group, for both the indentation and tensile tests. Histopathological examination showed that H₂O₂ at a concentration of ⩾62.5 mmol/L damaged the epithelium, stroma, or both, while H₂O₂ at a concentration ⩽31.25 mmol/L did not change the morphology of the epithelium or stroma.

CONCLUSIONS

Treatment with 3.91 mmol/L H₂O₂ solution can safely and effectively increase the biomechanical strength of the cornea.

[Application of visible longwave radiation for inactivation of microorganisms]

PURPOSE

To perform a comparative assessment of the bactericidal and fungicidal effects of various parts of the radiation spectrum (Ultraviolet A, red, green and blue).

MATERIAL AND METHODS

The study included strains of the most clinically significant microorganisms, which are the most common causes of purulent keratitis - S. aureus, P. aeruginosa and fungi C. albicans. After populating the surface of Petri dishes uniformly with microorganisms of each culture, on four out of the five specimens the central zone of the surface with a diameter of 1 cm was irradiated with light of different spectrum - from ultraviolet to red, with a total radiation energy density of 5.4 J/cm². One specimen remained as the control subject. After irradiation, scanning electron microscopy with lanthanides contrasting (SEMLC) was used to evaluate the total metabolic activity, the activity of the efflux systems and the morphological characteristics of the microorganisms.

RESULTS

The damaging effect of visible spectrum light and UVA radiation on S. aureus, P. aeruginosa and C. albicans cultures was proved by SEMLC. Green spectrum emission with a wavelength of 500 nm had the highest antimicrobial activity. It was manifested by a decrease in the overall level of metabolic activity (from 40-63 c.u. to 26-37 c.u. (S. aureus (p<0.01), P. aeruginosa (p<0.01) and C. albicans (p<0.05)), as well as a 2-fold increase in the proportion of S. aureus cells with active efflux systems.

CONCLUSION

SEMLC allows evaluation of parameters of the microorganisms` state: morphological (form and size) and functional (general metabolic activity, activation of efflux systems). Investigation of S. aureus, P. aeruginosa and C. albicans cultures using SEMLC demonstrated the antimicrobial activity of green spectrum radiation of 500 nm wavelength. This will serve as a basis for further research and development of a method of treating infectious keratitis using green light.

Research progress about the effect and prevention of blue light on eyes

In recent years, people have become increasingly attentive to light pollution influences on their eyes. In the visible spectrum, short-wave blue light with wavelength between 415 nm and 455 nm is closely related to eye light damage. This high energy blue light passes through the cornea and lens to the retina causing diseases such as dry eye, cataract, age-related macular degeneration, even stimulating the brain, inhibiting melatonin secretion, and enhancing adrenocortical hormone production, which will destroy the hormonal balance and directly affect sleep quality. Therefore, the effect of Blu-rays on ocular is becoming an important concern for the future. We describe blue light's effects on eye tissues, summarize the research on eye injury and its physical prevention and medical treatment.