Not related to collecting, but I do know someone with macular degeneration who's at the point where they can't see clearly more than a foot or two away. In good lighting conditions, you should still be able to view things fairly clearly at a really close distance. If you reach that stage of MD, when looking at a sword, I assume you would have issues viewing the full suguta or hamon, but should still be able to view parts of the blade at a time (and see the finer details like hada). That said, your case may not reach that point of severity that it impacts appreciation and evaluation.
As a side note, at the aforementioned point of severity, you can can still read up close as long as you have a magnifier (albeit slowly), are not legally allowed to drive, can recognize people by voice faster than you can by sight, will need to watch your step in case you stumble on something, and will struggle with zippers.