Chronic Electrical Stimulation with a Suprachoroidal Retinal Prosthesis: A Preclinical Safety and Efficacy Study
Figure 11
Retina and fibrous tissue thickness measured from histological sections.
(A) Retinal thickness (µm) was measured in retina adjacent to individual platinum stimulated electrodes, non-stimulated control electrodes, regions approximately 500 µm distal to each electrode (refer to Figure 2), as well as in matched sites from the non-implanted contralateral control eye. There was little variation in the median retinal thickness between measured regions. However, when a linear mixed model accounting for the pairing of observations was used to estimate mean differences in retinal thickness for each condition, a statistically significant difference between stimulated and control conditions was observed. This small estimated mean increase in stimulated retinal thickness (Table 6) was not regarded as being clinically relevant. (B) Fibrosis tissue thickness measurements (µm) were made in retina adjacent to stimulated electrodes, non-stimulated electrodes and in a region approximately 500 µm distal to each electrode. Measurements were repeated for the scleral and choroidal sides of the space occupied by the array. There was no fibrosis in the contralateral eye. In both panels, box plots show median (midline), 1st and 3rd quartiles (box edges), whiskers have a maximum length 1.5 times the interquartile range and open circles denote outliers. There was substantial overlap between the fibrosis distributions in the different locations measured, and between the 95% confidence intervals for the mean fibrosis thickness in each condition (Table 7). Note that the sample sizes reflect the number of unique histological measurements performed for each group. Typically, a single measurement is made at each sample or sample-adjacent site. However, in some cases, due to artifactual damage (or because the histology wasn’t retrieved), a particular site was not measured. As a result, the no-stimulation sample size was n = 7 for panel A, and n = 10 for panel B. Both of these samples are a subset of the maximum possible (i.e. n = 14) if all the samples had been retrieved with no histological artifacts.