A typical blue light therapy product such as the Philips goLITE is advertised as having the wavelength 460-485 nm, with an indicated peak wavelength of 468 nm ± 8 nm. While even exposure to normal daylight  increases the risk of such degeneration, blue light  is most likely to do this. Lipofuscin  and chronic inflammation  play roles. As far as I could tell, while the risk is still theoretical and not definitively proven in humans, it may very well exist. 
This affects older people more, as they are unable to prevent or repair everyday macular damage as younger people can.  There exist numerous controllable factors for macular degeneration and lipofuscin. Read the associated Wikipedia articles.
Persons with lighter eyes might be at a higher risk due to their limited melanin. I say "might" because they may require less therapeutic blue light to begin with than their dark eyed peers, potentially canceling the effect of eye color.
From a dietary supplementation pov, you can supplement balanced-natural-carotenes (especially beta carotene [see note 1]), xanthophylls (lutein, zeaxanthin, astaxanthin, etc.), vitamin C (at least twice daily), vitamin E (full-spectrum only), fish oil (providing omega-3s including DHA, DPA, and EPA), and also zinc with copper. [3–5]
My conclusion is to supplement all of the above [see note 2] if you use blue light therapy, and also review and prevent the other general risk factors for macular degeneration. If you're older than age 40, it may not be safe for you to try.  Finally, limit your usage, and avoid excessive usage.
Beta carotene supplementation is associated with increased mortality. I personally think this might be due to an imbalance of carotenoids caused by heavy supplementation of beta carotene, or potentially due to a difference in the stereoisomer distribution of synthetic beta carotene. Note also that alpha carotene, even though it's a half as effective source of vitamin A, is a more health promoting carotene. Various dietary carotenoids exist, and supplementation of only mostly beta carotene is likely to lead to an imbalance. I recommend using foods to obtain your carotenoids. Concurrent monounsatured fat intake is important for substantially boosting absorption of carotenes. Carrot juice and other such juices with organic extra virgin olive oil or organic avocado oil, if consumed daily, might make for a more efficient and effective source of large amounts of diverse carotenes - more than you can ever get from a pill. If, however, you are restricted to supplements only, "Solgar Advanced Carotenoid Complex" provides a balanced 1:2 ratio of natural palm-derived non-synthetic (alpha+gamma):beta carotenes.
As a general precaution, do not introduce more than one new supplement per one to two weeks. Take them daily.
Visible light and risk of age-related macular degeneration. (1990)
Do blue light filters confer protection against age-related macular degeneration? (2004)
Age-related maculopathy and the impact of blue light hazard (2006)
The role of oxidative stress in the pathogenesis of age-related macular degeneration. (2000)
Evidence for protection against age-related macular degeneration by carotenoids and antioxidant vitamins. (1995)
Retinal photodamage by endogenous and xenobiotic agents. (2010)