Comment by graeme | Hacker News Reader

Comment by graeme | Hacker News Reader

Note that this study refers to colour vision, not myopia

> and had normal colour vision (cone function). This was assessed using a 'Chroma Test': identifying coloured letters that had very low contrast and appeared increasingly blurred, a process called colour contrast.

Using a provided LED device all 20 participants (13 female and 7 male) were exposed to three minutes of 670nm deep red light in the morning between 8am and 9am. Their colour vision was then tested again three hours post exposure and 10 of the participants were also tested one week post exposure.

On average there was a 'significant' 17% improvement in colour vision, which lasted a week in tested participants; in some older participants there was a 20% improvement, also lasting a week.

Was there a control group? I wonder whether the red light helped or people just got better at performing a test.

It looks like there was a control group:

> However, an additional control was undertaken where colour contrast thresholds were measured in the morning and then re-measured 3 h later without exposure to 670 nm. This comprised of ten subjects (six Females and four males). To determine if there were significant shifts in colour contrast sensitivities across the day that were independent of 670 nm and might undermine outcome measures for their exposure, six subjects were repeatedly tested at 0, + 3, + 6 and + 9 h (four Females and two Males).

Figure 2 shows the (lack of) effect in the no-light control group at T0 and T+3hrs. Interestingly, they don't compare to baseline like in figure 1 with the AM light group. However, Figure 4 does show a lack of training effect when repeating the same test 4 times throughout the day within the same subject.

(Also, interesting that your first response to a paper in Nature is that they don't have a control group...)

Edit: And presumably they took the design of their study into account when calculating their statistics (https://www.stat.cmu.edu/~hseltman/309/Book/chapter14.pdf). Their methods seem to imply that, but I'm not familiar with it so I'll pray the reviewers checked for that lol.

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