A display may have a backlight unit with a row of light-emitting diodes that emit light into the edge of a light guide plate. The light guide plate may have opposing upper and lower surfaces. Backlight may be extracted from the light guide plate using an array of bumps on the lower surface and ridges on the upper surface. Ridge density may vary as a function of location across the display. Some of the ridges may be terminated along a meandering border between regions of differing ridge density. Ridge length and endpoint location can be dithered along borders between regions and ridge widths and thicknesses may be tapered down towards the endpoints. Ridges may be patterned to reduce the density of the ridges immediately adjacent the light-emitting diodes and thereby avoid over-extraction of the light at the light-emitting diodes.