The red-spotted newt, Notophthalmus viridescens, is one of few adult vertebrate organisms that has retained the remarkable ability to regenerate a complete retina following injury or removal. The aim of this study was to develop a non-invasive method to monitor recovery of components within the retinal circuitry, in vivo, following surgical removal (retinectomy) of the adult newt retina. A novel and reproducible protocol was established for full-field electroretinography in the intact newt retina. Electroretinograms (ERGs) were measured at the corneal surface. The effects of dilation and external body temperature on the ERG amplitudes were measured as well as the reproducibility in recording ERGs in the same animal over time. Retinectomies were conducted on 15 newts, and the a- and b-wave amplitudes were measured prior to retinectomy and at various timepoints after retinectomy. Surgical removal of the retina resulted in an initial loss of ERG a- and b-waves, representing loss of photoreceptor cells and cells of the inner nuclear layer. The ERG amplitudes recovered to baseline levels by 15 weeks post-retinectomy, indicative of subsequent restoration of retinal function after regeneration.

Lens regeneration studies in the adult newt suggest that molecular aspects of lens regeneration are complete within 5 weeks of lentectomy. However, very little is known about the optical properties of the regenerated lens. In an aquatic environment, the lens accounts for almost all of the refractive power of the eye, and thus, a fully functional lens is critical. We compared the optical properties of 9- and 26-week regenerated lenses in the red spotted newt, Notophthalmus viridescens, with the original lenses removed from the same eyes. At 9 weeks, the regenerated lenses are smaller than the original lenses and are histologically immature, with a lower density of lens proteins. The 9 week lenses have greater light transmission, but significantly reduced focal length and refractive index than the original lenses. This suggests that following 9 weeks of regeneration, the lenses have not recovered the functionality of the original lens. By 26 weeks, the transmission of light in the more mature lens is reduced, but the optical parameters of the lens have recovered enough to allow functional vision.

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