eye disease
   |__refractive error
       |__hyperopia  2 rec.
           |__strabismus 2 rec.
               |__binocular vision disease(+)
               |__conjugate gaze palsy
               |__cyclotropia
               |__Duane retraction syndrome(+) 2 rec.
               |__esotropia(+)
               |__exotropia(+)
               |__hypertropia
               |__hypotropia
               |__intermittent squint
               |__internuclear ophthalmoplegia
               |__mechanical strabismus(+)
               |__monofixation syndrome
               |__paralytic squint(+)