Assessment of the Biodegration of Sodium Hyaluronic Acid Implants for Non-Penetrating Deep Sclerectomy Using Ultrasound BioMicroscopy

Abstract

Purpose: : To demonstrate the use of in-vivo Ultrasound BioMicroscopy (UBM) as a useful tool in assessing the state of biodegradable implants.

Methods: : 24 NZW rabbits were implanted with Non-Perforating Deep Sclerectomy (NPDS) implants (Croma-Pharma GmbH, Austria) made of crosslinked sodium hyaluronic acid. UBM images were obtained at POD 0, 7, 14, 28, 42, 60, 92, 120, 150 and 180 using UBM (50 MHz, Sonomed VuMax). Scans were analyzed with ImageJ to obtain the implant cross-sectional areas (CSA). Mean areas and standard deviations were calculated for each POD of every rabbit and a graph created to monitor the size of the implants with time.

Results: : CSA of the implants were computed. Initial swelling of the implant following with a decrease in size was observed. In most cases, the implant started to be reabsorbed at about POD 28. UBM shows the presence of blebs, if an implant is being deformed or broken in smaller pieces. When the implant is biodegrated we can identify a scleral lake space. 10 animals were euthanized at POD 90 for histology, 1 died spontaneously at POD 7 and 13 animals are still under monthly follow-ups (now at POD 180) to assess total biodegradation. No adverse reactions were observed in any of the 24 animals demonstrating excellent biocompatibility.

Conclusions: : UBM is useful to assess the biodegradable implants’ evolution. UBM image analysis allows determination of the presence and morphological characteristics of the implant even if the implant is not clinically visible.Support: Florida Lions Eye Bank, NIH Center Grant P30-EY014801, Croma-Pharma; Research to Prevent Blindness, Henri and Flore Lesieur Foundation (JMP)

Keywords: imaging/image analysis: non-clinical • wound healing • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)