This is an example of a typoscope.
It’s a sophisticated word for a very unsophisticated device.
Typoscopes may help reduce glare when reading. The rectangle of black card with a narrow central slit is designed to be placed over a page of text so that only about two or three lines of print can be seen within the slit area. The aim of the device is to help the person read along lines without straying up or down and to find the next line down when a line of print is completed. It also helps increase contrast by preventing scattering from the background paper. Typoscopes can be self-made by the user or carer, with a variety of sizes and slit width and heights, for use in different reading tasks
Whether tints can be of any help with disability glare is less clear. The use of a non-selective grey tint is not advised as it will reduce all parts of the light spectrum and not only those being scattered by in the eye. This will not change the retinal image contrast. Since both light and dark areas of the image will be reduced.
A tint is required that will minimise the light that is likely to be scattered. These are usually yellow, amber, brown or red tints.