If you are 18 and have had the condition for 10 years its not at all likely a tumor. You can use the search feature and archives there is a lot written here about accommodative spasm. During such spasms it will affect your ability to think and concentrate. Treatment often consists of making sure your myopic glasses are not too strong (post cycloplegic refraction), bifocals, dilute atropine. Suggest you see a neuro-ophthalmologist or a eye muscle ophthalmologist (called a pediatric or adult strabismus) eye MD