Abstract
Purpose :
Low frequency, low intensity ultrasound is being studied as a novel transcleral drug delivery method and therapy. At low frequencies (≤ 40KHz), the waves exhibit unique non-thermal effects on tissues that promote cell wall permeation and cell regeneration. This study examined the effects of low-frequency ultrasound application to the anterior segment tissues and retinal electrophysiology, when applied directly to external eyelid tissues.
Methods :
The external eyelids of 7 New Zealand White Rabbit eyes were subjected to 30-minute period exposures in-vivo of low frequency, low intensity ultrasound (BJ-NAVA, 20KHz, 0.1Wcm2). Ocular surface temperatures (Type-T Thermocouple, RS Engineering), intraocular pressure (Tono-Pen, Reichert), slit-lamp biomicroscopy, OCT (Spectralis, Hiedelberg) and electroretinogram (Roland RETI-Port/Scan 21) findings were recorded at baseline and Days 1, 3, 9 and 30 post-exposure, and compared with the contralateral control eyes for statistical differences (Prism 7, GraphPad). Corneal and retinal tissue histology was examined for cell damage and morphological changes.
Results :
Maximum mean temperatures recorded at the external lid, superior and inferior sub-tarsal ocular surfaces were 39.91 (SEM = 0.61); 39.91 (SEM = 0.26) and 40.00 (SE = 0.30) Degrees Celsius respectively. The mean IOPs measured in exposed and control eyes were 11.33 (SEM = 0.52) and 11.95 (SEM = 0.47) mmHg respectively. Anterior chamber inflammation in one rabbit eye was recorded on Day 3, which spontaneously resolved the following day. There were no recorded changes in corneal histology on staining and SEM, retinal nerve fiber layer structure and appearance on OCT, or in a-wave and b-wave amplitude and interval size on ERG.
Conclusions :
Our results support that low frequency and low intensity ultrasound exposure at 20 KHz and intensity 0.1Wcm2 for periods of up to 30 minutes produces reversible non-thermal effects and thermal effects across a safe range, and is not associated with overall changes in cell morphology or functional loss.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.