Investigating plasticity in Retinitis Pigmentosa using retinotopic representation of the lesion projection zone

Abstract

Purpose : Retinitis Pigmentosa (RP) is a retinal disease characterized by degeneration of photoreceptors, leading to progressive, irreversible vision loss. Recent advances such as the Argus II Retinal Prosthesis System, which utilizes epiretinal microelectrodes to directly stimulate the inner retina³, allow partial sight restoration. However, clinical outcomes vary underscoring the importance of the pathology of the central visual pathway. The cross-modal activity can have a negative impact on an individual’s ability to adapt to vision restoration⁴. Functional imaging of cross-modal visual cortex response to non-visual tasks provide a cortically localized biomarker for vision loss that could account for individual variations in response to Argus implantation. We combined high resolution OCT and microperimetry imaging with retinotopically organized¹ neuroimaging, to study the relationship between RP retinal pathology and its downstream impact on the central visual pathway.

Methods : We co-registered microperimetry data in a fundus coordinate system to define the lesion defected retinal area. The cortical lesion projection zone (LPZ) was defined by fMRI in response to full-field flashing light visual stimulation. The fMRI response from each point on the cortical surface within V1-3 were projected to visual field coordinates by using the cortical template of retinotopy, which allows comparison with retinal data in a common coordinate space¹. fMRIs were acquired in response to tactile shape and roughness discrimination tasks that evoke cross-modal responses, the extent to which correlates with the severity of vision loss².

Results : We present two patients with peripheral vision loss due to RP, one from birth, another at 27. We observed a decrease in tactile evoked responses in V1, which may suggest that V1 is effectively driven by the signals evoked by the retinal stimulation. In contrast, increased tactile-evoked responses in V1 may indicate less effective visual stimulation².

Conclusions : The set of techniques introduced in this work enables characterization of the fine-scale relationship between retinal pathology and neuroimaging. The cross-modal approach may facilitate prediction of sight restoration strategies.
1 Benson 2012 Current Biology
2 Cunningham 2015 Vision Res.
3 Humayun 2012 Ophthalmology
4 Lee 2001 Nature

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Microperimetries, Blue Laser Autofluorescence, and BOLD fMRI responses in V1.