CLINICAL EVALUATION OF ELECTRICAL RESPONSES OF RETINA AND VISUAL CORTEX TO PHOTIC STIMULATION IN OPHTHALMIC DISEASES

Partial recovery of visual function in a blind patient after optogenetic therapy

Optogenetics may enable mutation-independent, circuit-specific restoration of neuronal function in neurological diseases. Retinitis pigmentosa is a neurodegenerative eye disease where loss of photoreceptors can lead to complete blindness. In a blind patient, we combined intraocular injection of an adeno-associated viral vector encoding ChrimsonR with light stimulation via engineered goggles. The goggles detect local changes in light intensity and project corresponding light pulses onto the retina in real time to activate optogenetically transduced retinal ganglion cells. The patient perceived, located, counted and touched different objects using the vector-treated eye alone while wearing the goggles. During visual perception, multichannel electroencephalographic recordings revealed object-related activity above the visual cortex. The patient could not visually detect any objects before injection with or without the goggles or after injection without the goggles. This is the first reported case of partial functional recovery in a neurodegenerative disease after optogenetic therapy.

Pattern electroretinograms and visual-evoked potentials in glaucoma and multiple sclerosis

Steady-state visual-evoked potentials and electroretinograms were simultaneously recorded in four patients with glaucoma and in five patients with multiple sclerosis. The stimuli included a homogenous field and a 2.3 cycles per degree sinusoidal grating that were counter-phase modulated at the rate of 7.5 Hz. We used narrow bandwidth spectral analysis to measure the response amplitudes and signal-to-noise ratios. Transient pattern visual-evoked potentials (1 Hz) were also measured for latency in each eye. We found abnormal pattern electroretinograms, based on the absence of a significant second harmonic component, in three of the four glaucomatous eyes although the homogenous field electroretinograms were normal. In the patients with multiple sclerosis, the pattern electroretinograms were abnormal in two eyes, but the transient visual-evoked potential latency had the highest diagnostic yield (seven of ten eyes).

Multivariate analysis of visual evoked response

The visual potentials evoked by flash are analyzed in healthy subjects in cases of retinal detachment, of optic nerve lesions, and of amblyopia by means of different statistical methods: 1. Analysis of the various features of the response, evaluated separately 2. Analysis of the interdependence between the measures of the various features The first method supplies information on the differences in 'size' of the curves in the various samples, the second method reveals differences of 'shape'. The second method has proved to be able to distinguish both normal conditions from pathologic impairment of optic structures and the different sites of the lesions.