Loss of spatial and visual capability are very common as Alzheimer's progresses. My wife has Posterior Cortical Atrophy and has these problems early on in her Alzheimer's progression. Marks on the edges of steps are very useful to her as without them she can't tell where the edges of the steps are, particularly when going down. A staircase can look like a steep slope. Going up is easier as she can generally make out the vertical part of the step. She can't judge the height of steps so a handrail, preferably two, are very helpful to maintain balance and control when she is feeling for the next step. Once she gets into a rhythm on a regular staircase it's fine. She almost always counts the steps to keep her full concentration on the job.
Lines and colour changes on flat floors can be mistaken for steps. Black areas look like holes or deep water. Shiny floors look wet. Bright lights to one side, lots of movement or anything that twinkles make everything much more difficult. Glass doors are invisible even if they have a bar or painted line across them, unless the bar is a bright colour. Revolving doors are a huge obstacle, particularly if they are motorised and stop if you touch them.
My wife still has full awareness of herself and her condition so she can reason about all of this. This is not the case for those with the more typical form of Alzheimer's where these vision difficulties occur later in the progression.
I am all for marking the edges of steps and always having clearly visible, contrasting colour, handrails. At a railway station near us there is a pedestrian footbridge. The first and last step in each flight has a yellow edge and the others have white edges, there are good handrails and the walking surface is matt with very good grip. I think this should be a standard for all public places.
This all sounds quite understandable, but a word of caution. Once the visual and spatial areas of the brain start to get screwed up, it is virtually impossible to work out what the person sees when they look at a scene. The real kicker is that they can't describe it either as they lose the ability to recall how their vision worked before the damage.