The team that wrote the paper mentioned in Post 1 of this thread have written a follow-up paper. They hypothesize a link between light and occupation and PD [1].

"... even though the global intensity of light emitted by a computer display is relatively low compared to a fluorescent lamp, we observed that the light emitted at 706 nm by a CRT monitor was nearly one-third of the light emitted by a fluorescent lamp. Given that the average person may work or look at a computer display for hours on a daily basis, it is possible that some light could reach the substantia nigra. As a matter of fact, computer programmers tend to be diagnosed with Parkinson’s disease at a younger age compared to other patients, and risk of diagnosis in patient 50 years old or younger is greater in computer programmers".

Reference

[1] The Scientific World Journal, 2014
"Eyes as Gateways for Environmental Light to the Substantia Nigra: Relevance in Parkinson’s Disease"
Stefania Romeo,1 Daniela Di Camillo,2 Alessandra Splendiani,1 Marta Capannolo,1 Cristina Rocchi,1 Gabriella Aloisi,1 Irene Fasciani,1 Giovanni U. Corsini,3 Eugenio Scarnati,1 Luca Lozzi,2 and Roberto Maggio1
http://www.hindawi.com/journals/tswj/2014/317879/

John