This to me is why you should not buy alone. Makers and sellers that do no answer pre-sale questions did not earn the sale. That aside the only difference I could find was the 2018 has fewer Watts in the speaker system.
This is likely to be a cost cutting move since most folk go with sound bars or receiver systems.
As to your eyesight issues I can't see any difference between these models.
Before I spend a nice chunk of change on a New TV, I wish to know what techicncal & logical justification if any, does the 2018 model 55” QLED 4K UHD 7 Series beside the higher price tag of $800.00 has over the 2017 model 55” QN55Q8C. I am an older person that has issues with my vision now and need to see w/o glare and be able to see the darkness with clarity, somthing I don’t have with my older flat screen plasma.
Also, please let me vent and say that I have been throwing money away for the last six years on a Satellite Dish from DirectTV with poor service due to windy or stormy weather in the county plus, the channel line-ups give you fewer chooses in good intelligent programming without the demeaning long commercials or brakes that rune the flow w/o cuts made to the film. It’s time for a major change!
Thanks,
Prof. GD Goldberg

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic