Advanced Imaging of the Equine Eye

A Mini-review on New Developments in Nanocarriers and Polymers for Ophthalmic Drug Delivery Strategies

The eye is an important and vital organ of the human body consisting of two segments - anterior and posterior segments and these segments are associated with many diseases. This review elaborates upon the various eye-related diseases with their medications and carriers used to deliver them. Delivery strategies include drugs encapsulated into liposomes, polymeric micelles of drugs, solid lipid nanoparticles, nanostructured lipid carriers, nano emulsions, and Nanosuspension used to improve penetrating properties, bioavailability, and residence time of the drugs as examples available in the literature. With regard to this, different forms of ocular drug delivery are classified and elaborated. Additionally, the possibility of addressing the physical and chemical complexities of ocular diseases and how they could be overcome with environmentally stable nanoformulations are briefly discussed. Enhanced drug delivery efficiency with various novel pharmaceuticals along with enhanced uptake by different routes/modes of drug administration. Current advancements in drug carrier systems, i.e., nanocarriers, have shown promise for improving the retention time, drug permeation and prolonging the duration of release of the drug in the ocular site. Bio-degradable polymers investigated for the preparation of nanocarriers for the entrapment of drugs and to enhance the efficacy through improved adherence of tissue in the eye, sustained release measures, enhanced bioavailability, lower toxicity, and targeted delivery is applicable. This review covers the introduction of various nanocarriers and polymers for ocular drug delivery with the purpose of enhancing the absorption, retention and bioavailability of medications in the eye.

Clinical utility, dose determination, and safety of ocular contrast-enhanced ultrasonography in horses: A pilot study

Objective

To determine efficacy of contrast‐enhanced ultrasonography (CEUS) using different sulfur hexafluoride (SF6) doses to assess blood flow and perfusion in equine eyes and to evaluate safety of SF6 in horses.

Procedures

Ocular B‐mode and contrast‐enhanced ultrasonography were performed bilaterally in nine sedated university‐owned horses. Intravenous SonoVue® bolus injections of 5, 10, 15, 20, 25, and 30 mL were administered for 2/18, 5/18, 6/18, 3/18, 1/18, and 1/18 eyes, respectively. Doses were increased based on ascending bodyweight. Each eye within one horse was examined utilizing a different dose. Qualitative blood flow and quantitative perfusion were analyzed. Heart and respiratory rates were monitored nonsedated, sedated, and during first and second minutes of CEUS.

Results

Qualitative contrast enhancement (CE) was visible in 7/9 animals. Quantitative CE was measurable bilaterally in four horses, unilaterally in three individuals, and not detected in two animals. In all horses with unilateral CE, the positive eye received the higher dose. Fifteen mL dose resulted in significantly shorter time to peak than 10 mL (P < .05). Peak intensity, maximum signal increase, and corresponding area under the curve were significantly higher for 15 and 20 mL doses compared with 10 mL (P < .05). Uveal and retinal tissues were enhanced frequently. Twenty‐five and 30 mL doses revealed no CE. Only sedation reduced heart rates significantly (P < .05). Clinically relevant changes in respiratory rates or adverse reactions following SF6 application were not observed.

Conclusions

Contrast enhancement was in most instances dose‐dependent. Fifteen mL appeared appropriate to assess equine ocular perfusion. The reliability in horses remains questionable; however, CEUS was well‐tolerated.