Retrograde trans-synaptic retinal ganglion cell loss following retrogeniculate lesions of human visual pathway identified using optical coherence tomography

Introduction: Retrograde trans-synaptic degeneration (RTSD) in the human visual pathway has not been well clarified. Aims 1. To confirm the RTSD in human visual pathway. 2. To study the rate of RTSD. 3. To study the pupil function in the RTSD. Methods: 1. The peripapillary retinal nerve fibre layer (RNFL) thickness measured with optical coherence tomography was compared among patients with acquired and congenital retrogeniculate lesions and normal subjects. Humphrey perimetry and brain imaging were performed. 2. A relationship between the duration of the disease and the RNFL thickness measured at a single time point was evaluated. Additionally the RNFL thickness was measured in patients with homonymous hemianopia (HH) and smaller homonymous visual field defect serially following stroke. 3. Pupil responses were measured in HH patients and normal subjects, using achromatic and chromatic stimuli localised to the blind hemifield and compared with responses obtained in the sighted hemifield. Results: 1. The overall mean RNFL thickness of the patient groups was significantly less than that of the controls. The affected sectors respected the retinotopic organization. 2. There was a negative straight line relationship between the duration of disease (log years) and the mean thickness measured at a single point in time in HH patients. In the serial measurements the mean thickness had a decreasing trend over time in all HH cases in contrast to the small visual field defect group. The thinning occurred early in the first few months after the stroke. 3. In the acquired group, pupil responses from the blind hemifield were reduced in comparison with controls to all stimuli employed. However there was a greater deficit to the chromatic stimuli than to the luminance contrast stimuli. Discussions: We showed the RTSD in patients with acquired and congenital retrogeniculate lesion by using OCT. The degeneration was correlated to the duration and occurred early after stroke. The RTSD might occur in the pupil pathway