Induction of significant intraocular pressure diurnal fluctuation in rats using a modified technique of microbead occlusion

AIM: To investigate the effect of microbead iridocorneal angle occlusion on intraocular pressure (IOP) diurnal fluctuation in rat eyes. METHODS: Male Dark Agouti (DA) rats, 8-10 week old, were each given a single intracameral injection of microbeads, followed by injection of dispersive viscoelastic solution. The right eye served as the experimental eye, while the left eye served as the control. IOP was measured twice daily postoperatively for 3wk and compared between groups. At the end of 3wk, the rats were sacrificed and the eyes were harvested for histological analysis and retinal ganglion cell (RGC) counting. RESULTS: After microbead injection, experimental eyes had significantly higher dark time IOP than controls from the second week to the third week [2nd week: 22.92±1.631 mm Hg (n=5) vs 17.35±0.751 mm Hg (n=5); 3rd week: 23.59±1.494 mm Hg vs 17.73±0.592 mm Hg (n=5)], while light time IOP was comparable between groups. The fluctuation levels of IOP in the experimental eyes were 7.21±0.398 mm Hg (n=5), 9.50±1.017 mm Hg (n=5) and 10.66±0.894 mm Hg (n=5) from the first week to the third week after injection. Comparatively, they were significantly lower in the control eyes, which were 4.69±0.323 mm Hg (n=5), 2.84±1.122 mm Hg (n=5) and 4.98±0.603 mm Hg (n=5) respectively. However, at the end of 3wk, the larger fluctuations in IOP in the experimental eyes was not associated with a significant loss of RGCs. CONCLUSION: Microbead occlusion exacerbates diurnal IOP fluctuation in rats. This reported model may serve as a method of investigating the pathological effects of IOP fluctuation. A longer observation period, or repeated injections, may be needed to observe a significant change in RGC density

Comparison of electroretinographic responses between two different age groups of adult Dark Agouti rats

<b>AIM:</b> To describe and compare the differences in electroretinographic responses between two different age groups of adult Dark Agouti (DA) rats and to better understand the effect of age on retinal histology and function.<b>METHODS:</b> The electroretinographic responses of two different age groups of adult DA rats were compared. Animals were divided into younger adult DA rats 10-12wk (<i>n</i>=8) and older adult DA rats 17-19wk (<i>n</i>=8). Full field electroretinography (ERG) was recorded simultaneously from both eyes after dark adaption and light adaption and parameters including the positive scotopic threshold response (pSTR), negative scotopic threshold response (nSTR), scotopic a-wave, b-wave, photopic a-wave, b-wave and photopic negative response (PhNR) were compared between groups.<b>RESULTS:</b> The older adult rats displayed lower stimulation thresholds of the STRs (pSTR and nSTR) and higher amplitudes of pSTR, scotopic a-wave and b-wave, photopic b-wave and PhNR amplitudes, with shorter implicit times. Photopic a-wave amplitudes were however higher in the younger adult rats.<b>CONCLUSION</b>:In summary, for the rod system, photoreceptor, bipolar cell and RGC activity was enhanced in the older adult rats. For the cone system, RGC and bipolar cell activity was enhanced, while photoreceptor activity was depressed in the older adult rats. Such age-related selective modification of retinal cell function needs to be considered when conducting ophthalmic research in adult rats

ExPRESS Mini-Shunt as a Treatment Alternative for Medically Uncontrolled Steroid-Induced Glaucoma in a Pediatric Patient

This case report illustrates the use of ExPRESS mini-shunt in a pediatric glaucoma patient. We describe the management of steroid-induced glaucoma with ExPRESS mini-shunt in a 9-year-old boy with allergic keratoconjunctivitis. The intraocular pressure of both of his eyes was uncontrolled with medical and laser treatment. Both eyes were treated with ExPRESS mini-shunt and mitomycin-C. Transient overfiltration with postoperative hypotony occurred in both eyes and resolved after 2 weeks. One year postoperatively, intraocular pressure was maintained below 21 mm Hg without medication in 1 eye. Bleb needling with mitomycin-C was done to maintain filtration. The fellow eye received cataract extraction but developed bleb failure a few months afterwards. The intraocular pressure was controlled medically. To conclude, ExPRESS mini-shunt is a new surgical option in selected patients. Bleb failure developed after cataract extraction. Postoperative inflammation should be minimized. Patient selection, such as those with stable ocular condition, is important to increase surgical success

Predisposing Factors, Microbial Characteristics, and Clinical Outcome of Microbial Keratitis in a Tertiary Centre in Hong Kong: A 10-Year Experience

Purpose. To study the risk factors, microbial profile, antibiotic susceptibility pattern, and outcome for microbial keratitis over the past 10 years in a tertiary center in Hong Kong. Methods. All cases with corneal scraping performed in Queen Mary Hospital, Hong Kong from January 2004 to December 2013 were included. Clinical outcome was defined as poor if the final visual acuity (VA) was abnormal or worse than presenting VA, a major complication occurred, or therapeutic keratoplasty was required. Results. 347 scrapes were performed in the 10-year period growing 130 microorganisms (32.3% culture positive rate). Contact lens use was the commonest risk factor. The commonest isolates were coagulase-negative Staphylococcus and Pseudomonas aeruginosa. Fluoroquinolone susceptibility was tested in 47 Gram-negative bacteria with 93.6% susceptibility (100% for Pseudomonas). 90.7% of cases had good visual outcome. Multivariate logistic regression showed age (p=0.03), trauma (p=0.006), and ulcer size >3 mm (p=0.039) to be independently associated with poor outcome. Conclusion. There was no shifting trend in the isolate distribution or emergence of resistant strains in our study. Contact lens wear was the commonest risk factor, with Pseudomonas being the most frequent isolate in this group. It remained 100% susceptible to fluoroquinolones and 97% cases had good visual outcome

A Systematic Review of Potential Therapeutic Use of Lycium Barbarum Polysaccharides in Disease

Objective. To evaluate the effect of Lycium barbarum polysaccharides in the treatment and/or prevention of diseases of different etiologies and systems. Methods. We performed an Entrez PubMed literature search using keywords “lycium”, “barbarum”, “polysaccharides”, “anti-fibrotic”, “anti-apoptotic”, “anti-oxidizing”, “anti-aging”, “neuroprotection”, “metabolism”, “diabetes”, “hyperlipidemia”, “neuroprotection”, and “immunomodulation” on the 14th of August 2018, resulting in 207 papers, of which 20 were chosen after filtering for ‘English language’ and ‘published within 10 years’ as well as curation for relevance by the authors. Results. The 20 selected papers included 2 randomized control trials (1 double-blinded RCT and 1 double-blinded placebo-controlled RCT), 11 in vivo studies, 5 in vitro studies, 1 study with both in vivo and in vitro results, and 1 chemical study. There is good evidence from existing studies on the antifibrotic, antioxidizing, neuroprotective, anticancer, and anti-inflammatory effects of Lycium barbarum polysaccharides. However, there is a need for further studies in the form of large-scale clinical trials to support its use in humans. There is also significant potential for LBP as a safe and effective topical treatment in ocular surface diseases, owing to promising in vitro results and a lack of demonstrated toxic effects to corneal epithelial cells. Conclusion. Results from existing studies suggest that LBP is a promising therapeutic agent, particularly in the management of liver disease, hyperlipidemia, and diabetes. One major limitation of current research is a lack of standardization and quality control for the LBP used. The availability of research-grade LBP will inevitably promote future research in this field worldwide