I've read much material on this

Anyone who undertakes these exercises might want to add changing your focus to near to very far into the routine.

The idea is it literally builds your eye muscles, which have become lazy and flabby over the years, so they can properly focus your eye.

It works.

"Rod sensitivity (the ability to see in low light) also improved significantly in those aged around 40 and over,..."

There is some research from Japan which I read more than a decade ago (haven't been able to find since). While it was specifically on color blindness, I wonder if it's related. The research confirms that rod/cone ratios isn't the sole source of color blindness. In fact a large minority of color blind people have normal rod/cone ratios but suffer from a brain/nerve affliction which prevents full processing of the color spectrum. In other words, eyes work correctly but the brain refuses to process all available information. Accordingly, light and electric stimulus therapy results in full color vision restoration. But only so long as the therapy is maintained. It falls off after 4-6 weeks without it.

This makes me wonder if the improvement is related.

"Recent advances in adapting PBM to stem cell therapy showed that stem cells and progenitor cells respond favorably to light. PBM stimulates different types of stem cells to enhance their migration, proliferation, and differentiation in vitro and in vivo."

""Photobiomodulation (PBM) is a non-thermal and non-invasive stimulating process to target using wavelengths from the red to near-infrared light spectrum (600 to 1000 nm)"

Red light is about 620-750nm.

https://www.jkslms.or.kr/journal/view.html?uid=206&vmd=Full&

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7738953/

https://www.nature.com/articles/s41598-020-77290-w

https://academic.oup.com/biomedgerontology/article/75/9/e49/5863431

Twenty-four healthy participants of both sexes were used with University College London ethical approval. They ranged from 28 to 72 years. The cutoff point between younger and older groups was >38 years, with age as the only significant variable. Different participants were used to measure rod (scotopic) thresholds and color contrast sensitivity (CCS), which were undertaken at different times. There were 12 individuals in each group. In the CCS group there were six younger (five female and one male) and six older (four female and two male) participants, and in the scotopic threshold group there were six younger (four females and two males) and six older (four female and two males) participants. 670-nm light devices were based on simple commercial DC torches with ten 670-nm LEDs mounted behind a light diffuser embedded in a tube that was 4 cm in diameter. Energies at the cornea were approximately 40 mW/cm2 which often resulted in a mild green after image for approximately 5–10 seconds. Participants were asked to use the light to illuminate their dominant eye every morning for 3 minutes and to repeat this daily for 2 weeks. These metrics were selected because they fell within the range used in a large number of animal experiments. 670-nm illumination was largely confined to the central retina comprising the peaks in rod and cone density.