"She has poor sight."
Translation:Tá an t-amharc go dona aici.
Just because English doesn't use the article doesn't mean it isn't required in Irish. Irish uses the article plenty of times when English wouldn't, for example with abstract nouns, such as this one.
That said, it looks like it should be perfectly acceptable without the article, though the go would need to be removed. This is based on FGB's example of Tá amharc maith agam