If you have the option to do so, this would be best done using a Regex parser such as in C#. But if you must do it in T-SQL, here is something to get you started. This is not a complete solution - it will not work correctly if you had multiple bracket-escaped items; but that can be fixed with some effort. As you can see, it is a little bit convoluted, and I disown it - i.e., no implied warranties or fitness for a particular purpose legalese
DECLARE @x VARCHAR(255) = 'GLAUCOMA , (evaluation for glaucoma, referred in by Dr x), SORE THROAT '
;WITH cte1 AS
LTRIM(RTRIM(Item)) AS Item
SELECT Item AS [data()] FROM cte1 WHERE item LIKE '(%' OR item LIKE '%)' FOR XML PATH('')
SELECT Item FROM cte1 WHERE item NOT LIKE '(%' AND item NOT LIKE '%)'
SELECT * FROM cte2;