It’s tough to understand, but this is a basic description:
Gamma-aminobutyric acid (usually abbreviated to GABA) is an inhibitory neurotransmitter found in the nervous systems of widely divergent species. It is the chief inhibitory neurotransmitter in the central nervous system and also in the retina.
It sounds like the article is saying Propecia can affect its production.
Ha ha, just what we need, Propecia side effects in the eyes now. 
It’s no joke. Many have reported blurriness, inability to focus correctly and decreased visual acuity while on and after taking the drug.
In the Finasteride Studies section, there are studies talking about Finasteride and the use of Anti-Androgens which have been linked to these problems:
Effect of Androgen Deficiency on the Human Meibomian Gland and Ocular Surface
propeciahelp.com/forum/viewtopic.php?t=659
propeciahelp.com/forum/viewtopic.php?t=600
PAGE 7:
“Although the clinical significance is unclear, a higher incidence of cataracts (4.2%, finasteride vs. 2.5%, placebo) and diabetes (2.8%, finasteride vs. 1.7%, placebo) was observed in patients receiving finasteride.”
Propecia-associated bilateral cataract
blackwell-synergy.com/doi/ab … 04.00770.x
Here is one member’s story from another hairloss site:
propeciahelp.com/forum/viewtopic.php?t=660
In addition to all of the above, the fact that GABA is found in the eyes is very interesting. Thanks for pointing that out.