Abstract
Purpose :
Standard intravitreal injections (IVI) are performed using hypodermic (subcutaneous) needles. The inner sharp edge cuts the cells that keep stuck within the needle tip similarly to fine needle aspiration biopsy. The injection of the cellular content in the vitreous may cause vision-threatening complications. We report the study results of a new needle for IVI comparing its penetration forces and needle tip aspirates with the standard hypodermic needle.
Methods :
All experiments complied with the Guidelines of the Helsinki Declaration and the ARVO statement for use of animals in ophthalmic and visual research. The newly designed 31 gauge (G) needle (NDN) (EP 18 158 542.3 patent pending) with occluded outer orifice and side port for drug delivery was compared to a standard hypodermic 31 G needle. The penetration force was tested with positioning of the needles perpendicularly at a distance of 1 mm to a 0.4 mm thick polyurethane Testing Foil Strips PU 04 (Melab, Leonberg, Germany) and applying a velocity of 100 mm/min (three tests). The animal study of the needle aspirates was done on 10 rat eyes of 10 Wistar white outbred albino rats (age 6 months, weight 600-800 g). During IVIs instead of injection an aspiration of 0.01cc of vitreous with cut cells was performed. Aspirated material was studied to recognize the cells by their morphological characteristics and their quantity. The results were analyzed statistically according to descriptive statistics, correlation matrices and t-test methods with a p-value of <0.05 considered to be statistically significant.
Results :
The average penetration force of NDN was 32.2 % lower compared to that of a standard hypodermic needle. Cytological analysis of the needle aspirates showed presence of cellular content in each case which consisted generally of conjunctival-, ciliary body- cells, granulated proteins and vitreous body remnants. The amount of conjunctival, ciliary body epithelial cells and granulated basophilic protein sediments (result of cellular damage) in NDN tips were about 50% less compared to the standard needle (<0.05) (Tab. 1).
Conclusions :
The new needle design demonstrated a superior penetration forceas well as a significantly reduced amount of cells cut with the needle tip. The proposed new less traumatic needle design should be considered for clinical use in order to reduce IVI related complications.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.