This 7-year-old boy presented with a history of prematurity and esotropia since age 2 years. He has been wearing spectacles equal to his full cycloplegic refraction, +3.75 right eye and +2.50 left eye, for the past two years. He has also undergone amblyopia treatment with part-time occlusion of the left eye. Now, vision in both eyes is equal but he has a residual esotropia of 30 PD and a right hypertropia of 15 PD while wearing his glasses. What could be happening?