The four recti and two obliques control the movements of each eye. Conjugate movements are movements of both the eyes together, keeping their visual axis parallel. Strabismus is deviation of one eye away from the fixation point. Squint may be apparent, latent (heterophoria) or manifest (heterotropia). In latent squint, a tendency for deviation of the eyes is present when the fusion is broken. It is diagnosed by cover test, Maddox rod test, Maddox wing test, and by prism vergence test. Lower degrees may be corrected by exercises, surgery may be required when deviation is large. Manifest squint may be concomitant or paralytic. In concomitant squint, the deviation remains the same in all directions of gaze. It may be uniocular or alternating, both of which may be convergent or divergent. Primary deviation is equal to secondary deviation. Optical correction, occlusion, orthoptic training and operative methods are the various treatment options. In paralytic squint, deviation of the eye is caused by the paralysis of extraocular muscles. The deviation varies in different directions of gaze. An appropriate work up includes diplopia charting, Worth’s four dot test, Hess screen and synoptophore examination. A synoptophore examination tests the grades of binocular vision (simultaneous macular perception, fusion and stereopsis), suppression and retinal correspondence. A paralytic squint is treated by treating the basic underlying cause, occlusion or by surgery. Nystagmus is involuntary, symmetrical, synchronous rapid oscillatory movements of the eyes. It may be ocular, vestibular, central or congenital.