Objectively Diagnose and Monitor Treatment of Light Sensitivity

A hand-held pupillometer/electroretinogram device (RETeval, LKC) will be held in front of the subject's eye, but will not touch the eye. The device will provide a brief, a series of brief light stimuli and then record the pupil response and the elicited electrical response from the retina from a surface skin patch (electrode) placed below each eye, from the light as a measure of whether the inherent sensitivity of the eye in the retina is normal. The investigators will repeat this in the left eye. The visible light stimulus is safe and is given at an intensity experienced in normal daily light exposures. The test takes about 2 minutes per eye.

The thickness of the optic nerve and macula will also be measured inside of the eye using a special camera that forms an image of the layers of the retina without pupil dilation. The imaging is harmless and measures the structural health of the optic nerve and retinal layers. This test takes 5-10 minutes per eye.

A wrist-watch sensor device (E4, Empatica) will be place on each wrist to measure skin conductance, heart rate, skin temperature and arm movement during testing. These wrist-watch devices are being used to monitor changes in sympathetic nerve activity to light intensity, (the sympathetic nerves supply the blood vessels to the skin and heart).

The subject will sit comfortably in front of miniature combination infrared/visible light video cameras and infrared diode light source located within 1 meter to provide video recording of the face during testing with light and during darkness, described next. After the 10 minutes of dark-adapting, the subject will put his/her chin on a chin rest in front of the video cameras and a light emitting diode (LED) array give diffuse red, blue, and white stimuli over a range of intensities. None of the stimuli are as bright as a flash from a camera and are in the range of intensities normally experienced during daily activities. At the end of the test the investigators will add filters over the glasses: orange (blue-blocking) filters and neutral density filters. Subjects will grade independently, both the brightness and discomfort they feel from each light stimulus intensity.

Next, electrodes will be placed above, below and to the side of the test eye to record the electromyogram (EMG) for measuring eyelid opening and blink rate.