A Fixed-Depth Microneedle Enhances Reproducibility and Safety for Corneal Gene Therapy.

PURPOSE: Drug delivery directly to the corneal stroma currently relies on microscopic injections that demonstrate low reproducibility and clinician-dependent variability. With use of biological drugs such as adeno-associated viral (AAV) vectors, precise and consistent drug deposition is critical to reduce concerns related to off-target transduction and the host's immune response to the viral capsid and/or transgene-derived product. Therefore, a precise corneal injection (PCI) microneedle was designed to allow accurate depth-specific injections into the corneal stroma in a macroscopic setting. METHODS: High-frequency ultrasound and confocal microscopy demonstrated the consistent ability to predetermine the precise injection depth using PCI needles of varying sizes. Next, a comparison between a standard 31-G needle and PCI needles was performed in vivo using AAV vector gene delivery. RESULTS: Intrastromal corneal injections using the PCI microneedle resulted in less vector leakage at the site of injection and fewer anterior chamber penetrations compared with a standard 31-G needle. Although reporter gene expression appeared similar when the vector was administered with either needle type, a trend toward increased vector genomes was noted in the PCI-injected corneas at the experimental conclusion. As hypothesized, corneal perforation resulted in increased detection of AAV vector genomes in nontarget tissues, highlighting the importance of consistency for biological drug applications in the cornea. CONCLUSIONS: Further development of the PCI microneedle is warranted especially for AAV corneal gene therapy and offers the potential to enhance transduction while significantly reducing safety concerns and intraclinician and interclinician injection variability.

Evaluation of equine corneal disease using spectral domain optical coherence tomography (SD-OCT).

PURPOSE: The purpose of this case series is to evaluate the use of spectral domain optical coherence tomography (SD-OCT) imaging in equine corneal disease to demonstrate the feasibility, diagnostic effectiveness, and limitations of this imaging modality. METHODS: Retrospective study: Handheld SD-OCT (Envisu, Bioptigen Inc, Morrisville, NC) was used for high-resolution imaging of horses with corneal disease presenting to the North Carolina State University Equine Ophthalmology Service from 2013 to 2018. RESULTS: Fourteen horses were included in this study, including six horses with corneal ulceration, three with stromal abscesses (SA), three with immune-mediated keratitis (IMMK), and two with ocular neoplasms. High-resolution images of the cornea were obtained using handheld SD-OCT in standing horses; however, acquiring images was time-consuming due to the inherent movement of the examiner and horse. Despite this, in horses with corneal ulcers, SA, and IMMK, SD-OCT assisted with determining location of disease in the cornea (eg, superficial, mid-stromal, endothelial) and if disruption of Descemet's membrane was present. In horses with neoplasia, the SD-OCT helped to determine whether the cornea had neoplastic invasion from anterior chamber masses. CONCLUSIONS: Results from this retrospective study suggest that handheld SD-OCT for imaging the cornea of horses is feasible and may be helpful in determining depth and extent of lesions in the cornea.