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Damien C. Rodger, Humberto Ruiz-Garcia, Roberto Gonzalez, Rodrigo Brant, Laura Liu, Biju Thomas, Bo Lu, Ashish K. Ahuja, Mark S. Humayun, Srinivas R. Sadda; Optical Coherence Tomography and Histology Correlations for Parylene-based hESC-RPE Grafts. Invest. Ophthalmol. Vis. Sci. 2011;52(14):446.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the ability of a trained reader to localize biocompatible parylene synthetic substrates seeded with retinal pigment epithelium derived from human embryonic stem (hES-RPE) cells based on spectral-domain optical coherence tomography (SD-OCT) images after intraocular implantation when compared with post-enucleation histologic examination.
A total of fifteen Royal College of Surgeons (RCS) and Copenhagen rats were implanted with 10 µm thick parylene substrates seeded with hES-RPE at post-natal day 30-35 via a transscleral approach. SD-OCTs (Heidelberg Spectalis HRA+OCT; Heidelberg, Germany) were obtained post-operatively in vivo between post-natal days 40 and 62. The rats were then euthanized and retinal histological sections stained with H&E. Two masked graders independently assessed the placement of the parylene grafts on OCT, classifying the implant location as intraretinal, subretinal, or intrachoroidal based on the innermost layer in which the implant was noted. Graders also looked for evidence of "tilting" of the graft where the graft appeared to extend across multiple layers. Histologic graft location was also independently assessed by light microscopy and correlated with the OCT gradings.
Implants could be identified as thin hyper-reflective structures on OCT in 100% of the eyes. The two OCT graders agreed on the implant location in all cases, with nine being classified as intraretinal and six being graded as subretinal. When compared with histology, agreement with respect to innermost layer reached was 93%. When assessing for the presence of tilting of the graft on OCT, the graders agreed in 93% of cases. The combined reading of both OCT graders agreed with the histologic determination of graft tilt in 90% of cases, with nine being tilted on histology.
SD-OCT appears to be a reproducible and accurate tool for identification of the location and tilt of parylene-based hESC-RPE grafts following intraocular implantation. The relative transparency but high reflectivity of parylene on OCT facilitates its detection without compromising visualization of underlying structures. Such SD-OCT based assessment may facilitate refinement of surgical techniques for graft implantation as well as selection of optimally grafted animals for subsequent testing.
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