[ProDigit]

My eyes are still young; and still see very well.
I merely tested on average the limits of light, where you should not go lower, or experience discomfort.
I personally replaced my LED nightstand lamp which was a 1Watt LED, to a 1,5Watt one, and the difference is noticeable! Because at 1Watt I had difficulty reading. At 1.5 I could read everything just fine.
However in relatively similar situations would suggest people to plug in a 2Watt the least.
Surely the brighter the bulb, the more comfortable the read. It goes in a curve. However, you need to double the bulb's wattage, to get only a marginal increase in comfort,until you've reached the sweet spot (that sweet spot is different from person to person).

Just like font size, I am merely stating that under a certain font size, text will become very hard to read (even for people with good eyes); does not mean that at these small sizes they are impossible to read.
The sweet spot for font size, just like brightness of reading a light are different from person to person indeed.
However, there are very few people who will want a fontsize so small, that there aren't enough pixels to display the letters completely, and you'd have to be second guessing letters because even with a magnifying glass you'd not be able to see a perfect letter (eg:imagine the letter 'e' being so small that the white dot within the 'e' has disappeared due to no pixels to display it).

Likewise with light, at a certain threshold of light intensity or lumen, even people with healthy eyes will have difficulty going any lower; and letters will start dancing on the page!

If you have a LED clip-on light above the reader you could do with 0.5Watt, but not really lower than that. (according to some wikipedia research it'd be around 150-250 Lumen you'll need for reading)

What I write are estimates you need to take with a grain of salt.

If you prefer 1000Lumen bulb over a 250, that's a personal preference indeed; but I think no one would prefer a 50lumen bulb over a 200 one for reading!