Oral fluorescein angiography in the diagnosis of paediatric optic nerve abnormalities.

OBJECTIVE: FFA is a well-established investigation for the diagnosis of optic nerve abnormalities, requiring an intravenous cannula and extended imaging acquisition time. Cannulation can present a challenge in paediatric patients and whilst oral FFA has been used for decades, it has been limited by imaging technology and unconfirmed image acquisition timings. For years, we have used a modern ultra-widefield retinal camera, and established imaging time-points to demonstrate dynamic optic nerve head changes upon ingestion of fluorescein and collected a database of oFFA images for various presentations. METHODS: Using an established protocol, optic nerve colour images were obtained, followed by oral administration of fluorescein dye. The optic nerves are then imaged at established intervals. An interpretation of oFFA tutorial was delivered to consultant ophthalmologists and trainees. Subsequently, these groups were assessed using a series of fifteen cases with the sensitivity and specificity of the test determined. RESULTS: Our study presents a series of images and descriptions for common optic nerve abnormalities in paediatric populations. In the interpretation part of the study, overall sensitivity of 76.8% in the consultant group vs 63.3% in the combined consultant + trainees and specificity of 87.5% vs 68.4% in the combined group. CONCLUSIONS: This is the first study that describes characteristic features of several common, and serious, optic nerve abnormalities specifically for oFFA interpretation in a paediatric population. It also highlights the rapid accumulation of oFFA interpretation skills in non-specialist consultant and trainee ophthalmologists such as to obtain a high diagnostic accuracy with high sensitivity and specificity.

The effect of prior long-term recellularization with keratocytes of decellularized porcine corneas implanted in a rabbit anterior lamellar keratoplasty model.

Decellularized porcine corneal scaffolds are a potential alternative to human cornea for keratoplasty. Although clinical trials have reported promising results, there can be corneal haze or scar tissue. Here, we examined if recellularizing the scaffolds with human keratocytes would result in a better outcome. Scaffolds were prepared that retained little DNA (14.89 ± 5.56 ng/mg) and demonstrated a lack of cytotoxicity by in vitro. The scaffolds were recellularized using human corneal stromal cells and cultured for between 14 in serum-supplemented media followed by a further 14 days in either serum free or serum-supplemented media. All groups showed full-depth cell penetration after 14 days. When serum was present, staining for ALDH3A1 remained weak but after serum-free culture, staining was brighter and the keratocytes adopted a native dendritic morphology with an increase (p < 0.05) of keratocan, decorin, lumican and CD34 gene expression. A rabbit anterior lamellar keratoplasty model was used to compare implanting a 250 µm thick decellularized lenticule against one that had been recellularized with human stromal cells after serum-free culture. In both groups, host rabbit epithelium covered the implants, but transparency was not restored after 3 months. Post-mortem histology showed under the epithelium, a less-compact collagen layer, which appeared to be a regenerating zone with some α-SMA staining, indicating fibrotic cells. In the posterior scaffold, ALDH1A1 staining was present in all the acellular scaffold, but in only one of the recellularized lenticules. Since there was little difference between acellular and cell-seeded scaffolds in our in vivo study, future scaffold development should use acellular controls to determine if cells are necessary.

The Use of Animal Models to Assess Engineered Corneal Tissue.

Tissue-engineered corneal constructs offer the potential of readily available corneal substitutes for transplantation. As with all medical devices and implants, these constructs require rigorous safety assessments, combined with well-described analyses of the implant's physical and biological characteristics. Although the constructs are developed in vitro, such studies are currently unable to fully emulate the complex biomechanical and biochemical conditions within living tissue, as well as the interplay between this environment and immunological factors. For these reasons, animal models remain essential to characterize such interactions. They form a stage where corneal implants can be tested for utility and survival in a living location to assess their ability to provide vision and avoid adverse event. Here, we examine the surgical considerations of animal models and we describe how the rabbit can be used for this purpose. This animal has been the routine model for ophthalmological studies and we set out methods to implant corneal constructs with this species.