Here is a recent study on age related macular (retinal) degeneration.
This study was done on humans, but the way that both dogs and humans utilize Omega-3 Fatty Acids (as related to the retina), it probably relates to dogs as well.

Omega-3 Long-Chain Polyunsaturated Fatty Acid Intake Inversely
Associated With 12-Year Progression to Advanced Age-Related Macular
Degeneration
Archives of Ophthalmology
Vol. 127, No. 1, January 2009
John Paul SanGiovanni, Elvira Agro´n, Traci E. Clemons, Emily Y. Chew
FROM ABSTRACT:
Age-related macular degeneration is a leading cause of vision loss.
Age-Related Eye Disease Study participants reporting the highest intake of omega-3 long-chain polyunsaturated fatty acids (LCPUFAs) were approximately half as likely as their peers reporting the lowest intake of these nutrients to have age-related macular degeneration at baseline or to progress across a 6-year period.

THESE AUTHORS ALSO NOTE:
The Age-Related Eye Disease Study, from which this data was obtained, is the largest longitudinal sample collected and classified with standardized methods as part of a natural history study on age-related macular degeneration.
“Participants reporting the highest baseline consumption of omega-3 LCPUFAs
were approximately 30% less likely than their peers reporting the lowest omega-3
LCPUFA consumption to develop advanced age-related macular degeneration by the end of the 12-year follow-up period.
“Omega-3 LCPUFAs and their metabolites have the capacity to act on
processes implicated in age-related macular degeneration pathogenesis.”
“Because the concentration of retinal omega-3 LCPUFAs is modifiable by and
dependent on dietary composition, these nutrients may represent an easily
implemented approach to modifying risk of age-related macular degeneration
progression.”



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