Abstract
Purpose: :
The main objective of this study was to establish a correlation between the retinal structure and function in a rat retina model by use of a combined high speed, ultrahigh resolution optical coherence tomography (UHROCT) and full filed electroretinography (ERG) system.
Methods: :
We developed a prototype, combined UHROCT+ ERG (full field) system for simultaneous probing of retinal structure and function in rodent retinas. The UHROCT system operates in the 1060nm wavelength region, outside the spectral range of the ERG visual stimulus, and provides 3µm axial and ~5µm lateral resolution in the rat retina at an imaging rate of 46 fps. The UHROCT was combined with a commercial full field ERG system (Diagnosys LLC) for simultaneous acquisition of the OCT images and the ERG traces. UHROCT + ERG data was acquired from healthy and damaged (drug induced toxicity) rat retinas of female Long Evans rats using visual stimuli of various duration, luminance level and spectral characteristics.
Results: :
UHROCT tomograms acquired from healthy rat eyes showed clear visualization of all intra-retinal layers, the choroid and the sclera and were associated with normal ERG traces. In the retinas of drug treated animals, dose-, time- and drug type- dependent morphological changes were observed, including thinning of the nuclear layers, disruption the ILM and ELM, development of highly reflective and highly transmissive spots in the Photoreceptor and RPE layers and overall change of the optical properties (image contrast) in some of the retinal layers. ERG traces acquired simultaneously with the optical images showed reduced magnitude of the a- and b-waves and in some cases, complete loss of the ERG signal. Depending on the type of drug and the dose used, the loss of the ERG trace was temporary or permanent. The observed structural changes coincided with the elimination of the a-wave and downstream loss of function in the ERG traces.
Conclusions: :
Our preliminary results suggest a direct link between the changes in retinal morphology and functional response to visual stimuli as measured with ERG in damaged retinas. The combined UHROCT + ERG system could provide ophthalmologists with the means for deeper understanding of the origins and progression of neurodegenerative retinal diseases.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • electroretinography: non-clinical • retina