A histological study of rabbit corneas after transepithelial corneal crosslinking using partial epithelial photoablation or ethanol treatment

AIM: To evaluate the histological changes after transepithelial corneal crosslinking(CXL) using partial thickness excimer laser ablation or epithelial ethanol application in an experimental rabbit study.METHODS: Right eyes of twenty-four rabbits were studied. Four eyes received total epithelial debridement(group I). Four eyes received partial thickness epithelial ablation with excimer laser(group II). Twelve eyes were treated with different durations(30s and 60s) and concentrations(18% to 48%) of ethanol(group III).Riboflavin was applied for 30 min intervals along with topical proparacaine drops with benzalkonium chloride,and 370 nm irradiation was performed for 30 min, while riboflavin was instilled every 3min. Four eyes(group IV)received 48% ethanol for 30 s without riboflavin and irradiation. Eyes were collected after 24 h and examined histologically.RESULTS: All eyes in group I showed keratocyte loss in the superficial 300 μ of corneal storma. In group II, 1-4layers of epithelium were preserved and no keratocyte loss occurred. In group III, CXL after treatment with ethanol up to 24% concentration and up to 60 s revealed no keratocyte loss. CXL after treatment with 48% and higher ethanol concentrations yielded keratocyte loss in the superficial 200 μ to 300 μ of cornea.CONCLUSION: Incomplete excimer laser ablation of the epithelium or treatment with ethanol up to 24%concentration and up to 60 s duration yielded no stromal keratocyte loss. To get the same histological appearance seen in epithelial debridement group, partial thicknessexcimer laser epithelial ablation or ethanol application is not adequate for transepithelial CXL.

Safety and efficacy of photodynamic therapy using BCECF-AM compared to mitomycin C in controlling post-operative fibrosis in a rabbit model of subscleral trabeculectomy

AIM： To evaluate the safety and efficacy of cellular photoablation using BCECF-AM [2, T-bis-（2-carboxyethyl） -5-（and-6）-carboxyfluorescein, acetoxymethyl ester mixed isomersl as a method to control postoperative fibrosis in subscleral trabeculectomy （SST） compared to mitomycin C （MMC） in a rabbit model. METHODS： A comparative prospective case-control animal study was conducted. Fourteen rabbits were subjected to SST with intraoperaUve use of wound modulating agents （MMC or BCECF-AM） of the right eye （study groups I and II respectively） and SST without use of intraoperative wound modulating agents for the left eye （control group II）. Two rabbits 4 eyes were considered as control group I with no surgical intervention. BCECF-AM was injected subconjunctivally 30min before surgery followed by intraoperative illumination with diffuse blue light for 10min. Antifibrotic efficacy was established by clinical response and histological examination. Clinical response was assessed by measuring intraocular pressure （lOP） at day 1, 3, 5, 7, 14, 21 postoperatively, Success was defined by 〉20.0% reduction in lOP from the preoperative values without anti-glaucoma medications. RESULTS： The mean percentage of reduction was 35.0% in the study group I with only one eye （14.3%） had 12.5% reduction. The mean percentage of reduction was 28.0% in the study group U with two eyes （28.6%） in study group II had 14.2% reduction each. Regarding the control group II, the mean percentage of reduction was 14.3% with 64.3% eyes had 〈20.0% reduction. There was a highly statistically significant difference between each of the study groups （right eyes） and the corresponding control group II （left eyes） as regards the mean postoperative lOP values started from day 5 in both study groups and this highly significant difference remained so till the end of the follow up period. Histologically, MMC treated blebs showed thinning of conjunctival epithelium with marked reduction of the goblet cells relative to control. Marked sub-epithelial edema was seen along with variable collagen dispersion. Mild cellularity was noted in sub-epithelial tissue. BCECF-AM treated blebs showed normal conjunctival epithelial thickness with abundant goblet cells. Mild sub- epithelial edema was noted along with moderate collagen dispersion. No histological abnormality was noted in the ciliary body or the cornea in any of the studied groups. CONCLUSION： Cellular photoablation using BCECF-AM is a safe and effective wound modulating agent to control postoperative fibrosis in trabeculectomy. However MMC considered as a more potent adjuvant to trabeculectomy than BCECF-AM in promoting IOP reduction.

Branch Retinal Vein Occlusion and Its Management

The natural course of Branch Retinal Vein Occlusion is determined by the site and completeness of the occlusion, the integrity of arterial perfusion to the affected sector and the efficiency of the developing collateral circulation. Most patients with tributary vein occlusion have some capillary fall out and microvascular incompetence in the distribution of the affected retina and vision is significantly compromised in over 50% of patients who have either chronic macular oedema or ischemia involving the...