Damage to the retina, due to trauma or disease, is usually localized. Monitoring the spatial progression of retinal dysfunction is important to the diagnosis, study, and treatment of prevalent retinal pathologies, and can be critical to early diagnosis. Non-invasive methods to measure spatial deficits in vision are therefore important, as evidenced by the widespread use of the Humphrey visual field test (HVF) and the multi- focal electroretinogram (mfERG). A new method for mapping spatial differences in retinal activity, using a conventional full-field stimulus and an array of electrodes on the cornea, is proposed here (the multi-electrode electroretinogram, meERG). This method overcomes several of the limitations imposed by the HVF and mfERG methods. In particular, it will provide direct measurement of retinal health with just a few seconds of recording time, as compared to several minutes of time required with the HVF and mfERG, thereby avoiding the long fixation times that are difficult for patients with low central vision to achieve. Further, the meERG makes a direct measurement of retinal function containing clinically-useful information;the HVF and mfERG provide indirect measures. This proposal is supported by pilot data, both experimental (in rat) and from computational 3-D finite element (FE) models. To establish the proof of concept of mapping retinal activity using meERG recording, three objectives will be met. First, a contact lens electrode array containing 13 electrodes will be fabricated. Second, the relationship between spatial variations in retinal activity and corresponding corneal potentials will be characterized. Spatially-variant retinal activity (""""""""retinal dysfunction"""""""") will be elicited using inhomogeneous illumination and focal laser damage. Third, the FE model of the rat eye will be optimized and validated based on the meERG data under several retinal dysfunction scenarios (forward problem). Once the proof of concept for meERG mapping of retinal activity has been established via the forward problem, development of the inverse problem computation would follow (beyond the scope of this R21 proposal). The inverse problem is analogous to functional mapping of brain and cardiac activity using body surface potentials, and will benefit directly from the decades of work in those areas. The meERG approach can be easily extended to human studies and the clinical setting at the UIC Department of Ophthalmology and Visual Sciences, though the potential applications in animal studies are also significant.
Damage to the retina, due to trauma or disease, is usually localized. Monitoring the spatial progression of retinal dysfunction is important to the diagnosis, study, and treatment of prevalent retinal pathologies, and can be critical to early diagnosis. A new method for mapping spatial differences in retinal activity, using a full-field stimulus and an array of electrodes on the cornea, is proposed here. This method has several advantages over existing methods.
| Krakova, Yelena; Tajalli, Hadi; Thongpang, Sanitta et al. (2014) Spatial differences in corneal electroretinogram potentials measured in rat with a contact lens electrode array. Doc Ophthalmol 129:151-66 |
